[PATCH 00/15] s390 spectre update for 4.16

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[PATCH 0/9] s390 spectre update...

[PATCH stable 4.16 00/14] powerpc...

Martin Schwidefsky

23 May 2018 23 May '18

4:22 p.m.

Hi Greg,

15 more patches against the 2018/05/23 linux-4.16.y stable branch. This gets the spectre defense of 4.16 up-to-date compared to the current upstream tree. The upstream patches to remove the indirect branches from the BPF JIT are included (these do not have a CC:stable tag).

Martin Schwidefsky (15): s390: move nobp parameter functions to nospec-branch.c s390: add automatic detection of the spectre defense s390: report spectre mitigation via syslog s390: add sysfs attributes for spectre s390: add assembler macros for CPU alternatives s390: correct nospec auto detection init order s390: correct module section names for expoline code revert s390: move expoline assembler macros to a header s390/crc32-vx: use expoline for indirect branches s390/lib: use expoline for indirect branches s390/ftrace: use expoline for indirect branches s390/kernel: use expoline for indirect branches s390: move spectre sysfs attribute code s390: extend expoline to BC instructions s390: use expoline thunks in the BPF JIT

arch/s390/Kconfig | 3 +- arch/s390/Makefile | 2 +- arch/s390/crypto/crc32be-vx.S | 5 +- arch/s390/crypto/crc32le-vx.S | 4 +- arch/s390/include/asm/alternative-asm.h | 108 ++++++++++++++++++ arch/s390/include/asm/nospec-branch.h | 7 +- arch/s390/include/asm/nospec-insn.h | 196 ++++++++++++++++++++++++++++++++ arch/s390/kernel/Makefile | 5 +- arch/s390/kernel/alternative.c | 24 +--- arch/s390/kernel/asm-offsets.c | 1 + arch/s390/kernel/base.S | 24 ++-- arch/s390/kernel/entry.S | 105 ++++------------- arch/s390/kernel/mcount.S | 14 ++- arch/s390/kernel/module.c | 15 ++- arch/s390/kernel/nospec-branch.c | 123 +++++++++++++++----- arch/s390/kernel/nospec-sysfs.c | 21 ++++ arch/s390/kernel/reipl.S | 7 +- arch/s390/kernel/setup.c | 3 + arch/s390/kernel/swsusp.S | 10 +- arch/s390/lib/mem.S | 19 ++-- arch/s390/net/bpf_jit.S | 16 ++- arch/s390/net/bpf_jit_comp.c | 63 +++++++++- 22 files changed, 587 insertions(+), 188 deletions(-) create mode 100644 arch/s390/include/asm/alternative-asm.h create mode 100644 arch/s390/include/asm/nospec-insn.h create mode 100644 arch/s390/kernel/nospec-sysfs.c

-- 2.16.3

Show replies by date

Martin Schwidefsky

23 May 23 May

4:22 p.m.

New subject: [PATCH 01/15] s390: move nobp parameter functions to nospec-branch.c

[ Upstream commit b2e2f43a01bace1a25bdbae04c9f9846882b727a ]

Keep the code for the nobp parameter handling with the code for expolines. Both are related to the spectre v2 mitigation.

Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/kernel/Makefile | 4 ++-- arch/s390/kernel/alternative.c | 23 ----------------------- arch/s390/kernel/nospec-branch.c | 27 +++++++++++++++++++++++++++ 3 files changed, 29 insertions(+), 25 deletions(-)

diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile index 7f27e3da9709..b06a6f79c1ec 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -61,11 +61,11 @@ obj-y += debug.o irq.o ipl.o dis.o diag.o vdso.o als.o obj-y += sysinfo.o jump_label.o lgr.o os_info.o machine_kexec.o pgm_check.o obj-y += runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o obj-y += entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o +obj-y += nospec-branch.o

extra-y += head.o head64.o vmlinux.lds

-obj-$(CONFIG_EXPOLINE) += nospec-branch.o -CFLAGS_REMOVE_expoline.o += $(CC_FLAGS_EXPOLINE) +CFLAGS_REMOVE_nospec-branch.o += $(CC_FLAGS_EXPOLINE)

obj-$(CONFIG_MODULES) += module.o obj-$(CONFIG_SMP) += smp.o diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c index 22476135f738..1abf4f35d059 100644 --- a/arch/s390/kernel/alternative.c +++ b/arch/s390/kernel/alternative.c @@ -15,29 +15,6 @@ static int __init disable_alternative_instructions(char *str)

early_param("noaltinstr", disable_alternative_instructions);

-static int __init nobp_setup_early(char *str) -{ - bool enabled; - int rc; - - rc = kstrtobool(str, &enabled); - if (rc) - return rc; - if (enabled && test_facility(82)) - __set_facility(82, S390_lowcore.alt_stfle_fac_list); - else - __clear_facility(82, S390_lowcore.alt_stfle_fac_list); - return 0; -} -early_param("nobp", nobp_setup_early); - -static int __init nospec_setup_early(char *str) -{ - __clear_facility(82, S390_lowcore.alt_stfle_fac_list); - return 0; -} -early_param("nospec", nospec_setup_early); - struct brcl_insn { u16 opc; s32 disp; diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 9aff72d3abda..69ce00d02d1b 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -2,6 +2,31 @@ #include <linux/module.h> #include <asm/nospec-branch.h>

+static int __init nobp_setup_early(char *str) +{ + bool enabled; + int rc; + + rc = kstrtobool(str, &enabled); + if (rc) + return rc; + if (enabled && test_facility(82)) + __set_facility(82, S390_lowcore.alt_stfle_fac_list); + else + __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + return 0; +} +early_param("nobp", nobp_setup_early); + +static int __init nospec_setup_early(char *str) +{ + __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + return 0; +} +early_param("nospec", nospec_setup_early); + +#ifdef CONFIG_EXPOLINE + int nospec_call_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); int nospec_return_disable = !IS_ENABLED(CONFIG_EXPOLINE_FULL);

@@ -98,3 +123,5 @@ void __init nospec_init_branches(void) nospec_call_revert(__nospec_call_start, __nospec_call_end); nospec_return_revert(__nospec_return_start, __nospec_return_end); } + +#endif /* CONFIG_EXPOLINE */

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 02/15] s390: add automatic detection of the spectre defense

[ Upstream commit 6e179d64126b909f0b288fa63cdbf07c531e9b1d ]

Automatically decide between nobp vs. expolines if the spectre_v2=auto kernel parameter is specified or CONFIG_EXPOLINE_AUTO=y is set.

The decision made at boot time due to CONFIG_EXPOLINE_AUTO=y being set can be overruled with the nobp, nospec and spectre_v2 kernel parameters.

Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/Kconfig | 2 +- arch/s390/Makefile | 2 +- arch/s390/include/asm/nospec-branch.h | 6 ++-- arch/s390/kernel/alternative.c | 1 + arch/s390/kernel/module.c | 11 +++--- arch/s390/kernel/nospec-branch.c | 68 +++++++++++++++++++++-------------- 6 files changed, 52 insertions(+), 38 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 6e91e0d422ea..0ad5d2a42fc6 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -576,7 +576,7 @@ choice config EXPOLINE_OFF bool "spectre_v2=off"

-config EXPOLINE_MEDIUM +config EXPOLINE_AUTO bool "spectre_v2=auto"

config EXPOLINE_FULL diff --git a/arch/s390/Makefile b/arch/s390/Makefile index 2ced3239cb84..e1bc722fba41 100644 --- a/arch/s390/Makefile +++ b/arch/s390/Makefile @@ -84,7 +84,7 @@ ifdef CONFIG_EXPOLINE CC_FLAGS_EXPOLINE += -mfunction-return=thunk CC_FLAGS_EXPOLINE += -mindirect-branch-table export CC_FLAGS_EXPOLINE - cflags-y += $(CC_FLAGS_EXPOLINE) + cflags-y += $(CC_FLAGS_EXPOLINE) -DCC_USING_EXPOLINE endif endif

diff --git a/arch/s390/include/asm/nospec-branch.h b/arch/s390/include/asm/nospec-branch.h index 7df48e5cf36f..35bf28fe4c64 100644 --- a/arch/s390/include/asm/nospec-branch.h +++ b/arch/s390/include/asm/nospec-branch.h @@ -6,12 +6,10 @@

#include <linux/types.h>

-extern int nospec_call_disable; -extern int nospec_return_disable; +extern int nospec_disable;

void nospec_init_branches(void); -void nospec_call_revert(s32 *start, s32 *end); -void nospec_return_revert(s32 *start, s32 *end); +void nospec_revert(s32 *start, s32 *end);

#endif /* __ASSEMBLY__ */

diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c index 1abf4f35d059..8e1f2aee85ef 100644 --- a/arch/s390/kernel/alternative.c +++ b/arch/s390/kernel/alternative.c @@ -2,6 +2,7 @@ #include <linux/module.h> #include <asm/alternative.h> #include <asm/facility.h> +#include <asm/nospec-branch.h>

#define MAX_PATCH_LEN (255 - 1)

diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c index 1fc6d1ff92d3..5a83be955c70 100644 --- a/arch/s390/kernel/module.c +++ b/arch/s390/kernel/module.c @@ -159,7 +159,7 @@ int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs, me->core_layout.size += me->arch.got_size; me->arch.plt_offset = me->core_layout.size; if (me->arch.plt_size) { - if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_call_disable) + if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) me->arch.plt_size += PLT_ENTRY_SIZE; me->core_layout.size += me->arch.plt_size; } @@ -318,8 +318,7 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, info->plt_offset; ip[0] = 0x0d10e310; /* basr 1,0 */ ip[1] = 0x100a0004; /* lg 1,10(1) */ - if (IS_ENABLED(CONFIG_EXPOLINE) && - !nospec_call_disable) { + if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) { unsigned int *ij; ij = me->core_layout.base + me->arch.plt_offset + @@ -440,7 +439,7 @@ int module_finalize(const Elf_Ehdr *hdr, void *aseg;

if (IS_ENABLED(CONFIG_EXPOLINE) && - !nospec_call_disable && me->arch.plt_size) { + !nospec_disable && me->arch.plt_size) { unsigned int *ij;

ij = me->core_layout.base + me->arch.plt_offset + @@ -467,11 +466,11 @@ int module_finalize(const Elf_Ehdr *hdr,

if (IS_ENABLED(CONFIG_EXPOLINE) && (!strcmp(".nospec_call_table", secname))) - nospec_call_revert(aseg, aseg + s->sh_size); + nospec_revert(aseg, aseg + s->sh_size);

if (IS_ENABLED(CONFIG_EXPOLINE) && (!strcmp(".nospec_return_table", secname))) - nospec_return_revert(aseg, aseg + s->sh_size); + nospec_revert(aseg, aseg + s->sh_size); }

jump_label_apply_nops(me); diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 69ce00d02d1b..192e633a79d8 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -10,10 +10,17 @@ static int __init nobp_setup_early(char *str) rc = kstrtobool(str, &enabled); if (rc) return rc; - if (enabled && test_facility(82)) + if (enabled && test_facility(82)) { + /* + * The user explicitely requested nobp=1, enable it and + * disable the expoline support. + */ __set_facility(82, S390_lowcore.alt_stfle_fac_list); - else + if (IS_ENABLED(CONFIG_EXPOLINE)) + nospec_disable = 1; + } else { __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + } return 0; } early_param("nobp", nobp_setup_early); @@ -27,31 +34,46 @@ early_param("nospec", nospec_setup_early);

#ifdef CONFIG_EXPOLINE

-int nospec_call_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); -int nospec_return_disable = !IS_ENABLED(CONFIG_EXPOLINE_FULL); +int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);

static int __init nospectre_v2_setup_early(char *str) { - nospec_call_disable = 1; - nospec_return_disable = 1; + nospec_disable = 1; return 0; } early_param("nospectre_v2", nospectre_v2_setup_early);

+static int __init spectre_v2_auto_early(void) +{ + if (IS_ENABLED(CC_USING_EXPOLINE)) { + /* + * The kernel has been compiled with expolines. + * Keep expolines enabled and disable nobp. + */ + nospec_disable = 0; + __clear_facility(82, S390_lowcore.alt_stfle_fac_list); + } + /* + * If the kernel has not been compiled with expolines the + * nobp setting decides what is done, this depends on the + * CONFIG_KERNEL_NP option and the nobp/nospec parameters. + */ + return 0; +} +#ifdef CONFIG_EXPOLINE_AUTO +early_initcall(spectre_v2_auto_early); +#endif + static int __init spectre_v2_setup_early(char *str) { if (str && !strncmp(str, "on", 2)) { - nospec_call_disable = 0; - nospec_return_disable = 0; - } - if (str && !strncmp(str, "off", 3)) { - nospec_call_disable = 1; - nospec_return_disable = 1; - } - if (str && !strncmp(str, "auto", 4)) { - nospec_call_disable = 0; - nospec_return_disable = 1; + nospec_disable = 0; + __clear_facility(82, S390_lowcore.alt_stfle_fac_list); } + if (str && !strncmp(str, "off", 3)) + nospec_disable = 1; + if (str && !strncmp(str, "auto", 4)) + spectre_v2_auto_early(); return 0; } early_param("spectre_v2", spectre_v2_setup_early); @@ -104,15 +126,9 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) } }

-void __init_or_module nospec_call_revert(s32 *start, s32 *end) -{ - if (nospec_call_disable) - __nospec_revert(start, end); -} - -void __init_or_module nospec_return_revert(s32 *start, s32 *end) +void __init_or_module nospec_revert(s32 *start, s32 *end) { - if (nospec_return_disable) + if (nospec_disable) __nospec_revert(start, end); }

@@ -120,8 +136,8 @@ extern s32 __nospec_call_start[], __nospec_call_end[]; extern s32 __nospec_return_start[], __nospec_return_end[]; void __init nospec_init_branches(void) { - nospec_call_revert(__nospec_call_start, __nospec_call_end); - nospec_return_revert(__nospec_return_start, __nospec_return_end); + nospec_revert(__nospec_call_start, __nospec_call_end); + nospec_revert(__nospec_return_start, __nospec_return_end); }

#endif /* CONFIG_EXPOLINE */

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 03/15] s390: report spectre mitigation via syslog

[ Upstream commit bc035599718412cfba9249aa713f90ef13f13ee9 ]

Add a boot message if either of the spectre defenses is active. The message is "Spectre V2 mitigation: execute trampolines." or "Spectre V2 mitigation: limited branch prediction."

Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/kernel/nospec-branch.c | 10 ++++++++++ 1 file changed, 10 insertions(+)

diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 192e633a79d8..adec38c5f53b 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -32,6 +32,16 @@ static int __init nospec_setup_early(char *str) } early_param("nospec", nospec_setup_early);

+static int __init nospec_report(void) +{ + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) + pr_info("Spectre V2 mitigation: execute trampolines.\n"); + if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) + pr_info("Spectre V2 mitigation: limited branch prediction.\n"); + return 0; +} +arch_initcall(nospec_report); + #ifdef CONFIG_EXPOLINE

int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 04/15] s390: add sysfs attributes for spectre

[ Upstream commit d424986f1d6b16079b3231db0314923f4f8deed1 ]

Set CONFIG_GENERIC_CPU_VULNERABILITIES and provide the two functions cpu_show_spectre_v1 and cpu_show_spectre_v2 to report the spectre mitigations.

Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/Kconfig | 1 + arch/s390/kernel/nospec-branch.c | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 0ad5d2a42fc6..c94dd09a82d1 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -120,6 +120,7 @@ config S390 select GENERIC_CLOCKEVENTS select GENERIC_CPU_AUTOPROBE select GENERIC_CPU_DEVICES if !SMP + select GENERIC_CPU_VULNERABILITIES select GENERIC_FIND_FIRST_BIT select GENERIC_SMP_IDLE_THREAD select GENERIC_TIME_VSYSCALL diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index adec38c5f53b..14867ec5f726 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/module.h> +#include <linux/device.h> #include <asm/nospec-branch.h>

static int __init nobp_setup_early(char *str) @@ -42,6 +43,24 @@ static int __init nospec_report(void) } arch_initcall(nospec_report);

+#ifdef CONFIG_SYSFS +ssize_t cpu_show_spectre_v1(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "Mitigation: __user pointer sanitization\n"); +} + +ssize_t cpu_show_spectre_v2(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) + return sprintf(buf, "Mitigation: execute trampolines\n"); + if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) + return sprintf(buf, "Mitigation: limited branch prediction.\n"); + return sprintf(buf, "Vulnerable\n"); +} +#endif + #ifdef CONFIG_EXPOLINE

int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 05/15] s390: add assembler macros for CPU alternatives

[ Upstream commit fba9eb7946251d6e420df3bdf7bc45195be7be9a ]

Add a header with macros usable in assembler files to emit alternative code sequences. It works analog to the alternatives for inline assmeblies in C files, with the same restrictions and capabilities. The syntax is

ALTERNATIVE "<default instructions sequence>", \ "<alternative instructions sequence>", \ "<features-bit>" and

ALTERNATIVE_2 "<default instructions sequence>", \ "<alternative instructions sqeuence #1>", \ "<feature-bit #1>", "<alternative instructions sqeuence #2>", \ "<feature-bit #2>"

Reviewed-by: Vasily Gorbik gor@linux.vnet.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/include/asm/alternative-asm.h | 108 ++++++++++++++++++++++++++++++++ 1 file changed, 108 insertions(+) create mode 100644 arch/s390/include/asm/alternative-asm.h

diff --git a/arch/s390/include/asm/alternative-asm.h b/arch/s390/include/asm/alternative-asm.h new file mode 100644 index 000000000000..955d620db23e --- /dev/null +++ b/arch/s390/include/asm/alternative-asm.h @@ -0,0 +1,108 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_S390_ALTERNATIVE_ASM_H +#define _ASM_S390_ALTERNATIVE_ASM_H + +#ifdef __ASSEMBLY__ + +/* + * Check the length of an instruction sequence. The length may not be larger + * than 254 bytes and it has to be divisible by 2. + */ +.macro alt_len_check start,end + .if ( \end - \start ) > 254 + .error "cpu alternatives does not support instructions blocks > 254 bytes\n" + .endif + .if ( \end - \start ) % 2 + .error "cpu alternatives instructions length is odd\n" + .endif +.endm + +/* + * Issue one struct alt_instr descriptor entry (need to put it into + * the section .altinstructions, see below). This entry contains + * enough information for the alternatives patching code to patch an + * instruction. See apply_alternatives(). + */ +.macro alt_entry orig_start, orig_end, alt_start, alt_end, feature + .long \orig_start - . + .long \alt_start - . + .word \feature + .byte \orig_end - \orig_start + .byte \alt_end - \alt_start +.endm + +/* + * Fill up @bytes with nops. The macro emits 6-byte nop instructions + * for the bulk of the area, possibly followed by a 4-byte and/or + * a 2-byte nop if the size of the area is not divisible by 6. + */ +.macro alt_pad_fill bytes + .fill ( \bytes ) / 6, 6, 0xc0040000 + .fill ( \bytes ) % 6 / 4, 4, 0x47000000 + .fill ( \bytes ) % 6 % 4 / 2, 2, 0x0700 +.endm + +/* + * Fill up @bytes with nops. If the number of bytes is larger + * than 6, emit a jg instruction to branch over all nops, then + * fill an area of size (@bytes - 6) with nop instructions. + */ +.macro alt_pad bytes + .if ( \bytes > 0 ) + .if ( \bytes > 6 ) + jg . + \bytes + alt_pad_fill \bytes - 6 + .else + alt_pad_fill \bytes + .endif + .endif +.endm + +/* + * Define an alternative between two instructions. If @feature is + * present, early code in apply_alternatives() replaces @oldinstr with + * @newinstr. ".skip" directive takes care of proper instruction padding + * in case @newinstr is longer than @oldinstr. + */ +.macro ALTERNATIVE oldinstr, newinstr, feature + .pushsection .altinstr_replacement,"ax" +770: \newinstr +771: .popsection +772: \oldinstr +773: alt_len_check 770b, 771b + alt_len_check 772b, 773b + alt_pad ( ( 771b - 770b ) - ( 773b - 772b ) ) +774: .pushsection .altinstructions,"a" + alt_entry 772b, 774b, 770b, 771b, \feature + .popsection +.endm + +/* + * Define an alternative between two instructions. If @feature is + * present, early code in apply_alternatives() replaces @oldinstr with + * @newinstr. ".skip" directive takes care of proper instruction padding + * in case @newinstr is longer than @oldinstr. + */ +.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2 + .pushsection .altinstr_replacement,"ax" +770: \newinstr1 +771: \newinstr2 +772: .popsection +773: \oldinstr +774: alt_len_check 770b, 771b + alt_len_check 771b, 772b + alt_len_check 773b, 774b + .if ( 771b - 770b > 772b - 771b ) + alt_pad ( ( 771b - 770b ) - ( 774b - 773b ) ) + .else + alt_pad ( ( 772b - 771b ) - ( 774b - 773b ) ) + .endif +775: .pushsection .altinstructions,"a" + alt_entry 773b, 775b, 770b, 771b,\feature1 + alt_entry 773b, 775b, 771b, 772b,\feature2 + .popsection +.endm + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_S390_ALTERNATIVE_ASM_H */

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 06/15] s390: correct nospec auto detection init order

[ Upstream commit 6a3d1e81a434fc311f224b8be77258bafc18ccc6 ]

With CONFIG_EXPOLINE_AUTO=y the call of spectre_v2_auto_early() via early_initcall is done *after* the early_param functions. This overwrites any settings done with the nobp/no_spectre_v2/spectre_v2 parameters. The code patching for the kernel is done after the evaluation of the early parameters but before the early_initcall is done. The end result is a kernel image that is patched correctly but the kernel modules are not.

Make sure that the nospec auto detection function is called before the early parameters are evaluated and before the code patching is done.

Fixes: 6e179d64126b ("s390: add automatic detection of the spectre defense") Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/include/asm/nospec-branch.h | 1 + arch/s390/kernel/nospec-branch.c | 8 ++------ arch/s390/kernel/setup.c | 3 +++ 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/s390/include/asm/nospec-branch.h b/arch/s390/include/asm/nospec-branch.h index 35bf28fe4c64..b4bd8c41e9d3 100644 --- a/arch/s390/include/asm/nospec-branch.h +++ b/arch/s390/include/asm/nospec-branch.h @@ -9,6 +9,7 @@ extern int nospec_disable;

void nospec_init_branches(void); +void nospec_auto_detect(void); void nospec_revert(s32 *start, s32 *end);

#endif /* __ASSEMBLY__ */ diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 14867ec5f726..f236ce8757e8 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -72,7 +72,7 @@ static int __init nospectre_v2_setup_early(char *str) } early_param("nospectre_v2", nospectre_v2_setup_early);

-static int __init spectre_v2_auto_early(void) +void __init nospec_auto_detect(void) { if (IS_ENABLED(CC_USING_EXPOLINE)) { /* @@ -87,11 +87,7 @@ static int __init spectre_v2_auto_early(void) * nobp setting decides what is done, this depends on the * CONFIG_KERNEL_NP option and the nobp/nospec parameters. */ - return 0; } -#ifdef CONFIG_EXPOLINE_AUTO -early_initcall(spectre_v2_auto_early); -#endif

static int __init spectre_v2_setup_early(char *str) { @@ -102,7 +98,7 @@ static int __init spectre_v2_setup_early(char *str) if (str && !strncmp(str, "off", 3)) nospec_disable = 1; if (str && !strncmp(str, "auto", 4)) - spectre_v2_auto_early(); + nospec_auto_detect(); return 0; } early_param("spectre_v2", spectre_v2_setup_early); diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c index ce5ff4c4d435..0786a6b53f98 100644 --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -893,6 +893,9 @@ void __init setup_arch(char **cmdline_p) init_mm.end_data = (unsigned long) &_edata; init_mm.brk = (unsigned long) &_end;

+ if (IS_ENABLED(CONFIG_EXPOLINE_AUTO)) + nospec_auto_detect(); + parse_early_param(); #ifdef CONFIG_CRASH_DUMP /* Deactivate elfcorehdr= kernel parameter */

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 07/15] s390: correct module section names for expoline code revert

[ Upstream commit 6cf09958f32b9667bb3ebadf74367c791112771b ]

The main linker script vmlinux.lds.S for the kernel image merges the expoline code patch tables into two section ".nospec_call_table" and ".nospec_return_table". This is *not* done for the modules, there the sections retain their original names as generated by gcc: ".s390_indirect_call", ".s390_return_mem" and ".s390_return_reg".

The module_finalize code has to check for the compiler generated section names, otherwise no code patching is done. This slows down the module code in case of "spectre_v2=off".

diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c index 5a83be955c70..0dc8ac8548ee 100644 --- a/arch/s390/kernel/module.c +++ b/arch/s390/kernel/module.c @@ -465,11 +465,11 @@ int module_finalize(const Elf_Ehdr *hdr, apply_alternatives(aseg, aseg + s->sh_size);

if (IS_ENABLED(CONFIG_EXPOLINE) && - (!strcmp(".nospec_call_table", secname))) + (!strncmp(".s390_indirect", secname, 14))) nospec_revert(aseg, aseg + s->sh_size);

if (IS_ENABLED(CONFIG_EXPOLINE) && - (!strcmp(".nospec_return_table", secname))) + (!strncmp(".s390_return", secname, 12))) nospec_revert(aseg, aseg + s->sh_size); }

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 08/15] s390: move expoline assembler macros to a header

[ Upstream commit 6dd85fbb87d1d6b87a3b1f02ca28d7b2abd2e7ba ]

To be able to use the expoline branches in different assembler files move the associated macros from entry.S to a new header nospec-insn.h.

While we are at it make the macros a bit nicer to use.

Cc: stable@vger.kernel.org # 4.16 Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches") Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/include/asm/nospec-insn.h | 127 ++++++++++++++++++++++++++++++++++++ arch/s390/kernel/entry.S | 105 +++++++---------------------- 2 files changed, 151 insertions(+), 81 deletions(-) create mode 100644 arch/s390/include/asm/nospec-insn.h

diff --git a/arch/s390/include/asm/nospec-insn.h b/arch/s390/include/asm/nospec-insn.h new file mode 100644 index 000000000000..440689cbcf51 --- /dev/null +++ b/arch/s390/include/asm/nospec-insn.h @@ -0,0 +1,127 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_S390_NOSPEC_ASM_H +#define _ASM_S390_NOSPEC_ASM_H + +#include <asm/dwarf.h> + +#ifdef __ASSEMBLY__ + +#ifdef CONFIG_EXPOLINE + +/* + * The expoline macros are used to create thunks in the same format + * as gcc generates them. The 'comdat' section flag makes sure that + * the various thunks are merged into a single copy. + */ + .macro __THUNK_PROLOG_NAME name + .pushsection .text.\name,"axG",@progbits,\name,comdat + .globl \name + .hidden \name + .type \name,@function +\name: + CFI_STARTPROC + .endm + + .macro __THUNK_EPILOG + CFI_ENDPROC + .popsection + .endm + + .macro __THUNK_PROLOG_BR r1,r2 + __THUNK_PROLOG_NAME __s390x_indirect_jump_r\r2()use_r\r1 + .endm + + .macro __THUNK_BR r1,r2 + jg __s390x_indirect_jump_r\r2()use_r\r1 + .endm + + .macro __THUNK_BRASL r1,r2,r3 + brasl \r1,__s390x_indirect_jump_r\r3()use_r\r2 + .endm + + .macro __DECODE_RR expand,reg,ruse + .set __decode_fail,1 + .irp r1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 + .ifc \reg,%r\r1 + .irp r2,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 + .ifc \ruse,%r\r2 + \expand \r1,\r2 + .set __decode_fail,0 + .endif + .endr + .endif + .endr + .if __decode_fail == 1 + .error "__DECODE_RR failed" + .endif + .endm + + .macro __DECODE_RRR expand,rsave,rtarget,ruse + .set __decode_fail,1 + .irp r1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 + .ifc \rsave,%r\r1 + .irp r2,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 + .ifc \rtarget,%r\r2 + .irp r3,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 + .ifc \ruse,%r\r3 + \expand \r1,\r2,\r3 + .set __decode_fail,0 + .endif + .endr + .endif + .endr + .endif + .endr + .if __decode_fail == 1 + .error "__DECODE_RRR failed" + .endif + .endm + + .macro __THUNK_EX_BR reg,ruse +#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES + exrl 0,555f + j . +#else + larl \ruse,555f + ex 0,0(\ruse) + j . +#endif +555: br \reg + .endm + + .macro GEN_BR_THUNK reg,ruse=%r1 + __DECODE_RR __THUNK_PROLOG_BR,\reg,\ruse + __THUNK_EX_BR \reg,\ruse + __THUNK_EPILOG + .endm + + .macro BR_EX reg,ruse=%r1 +557: __DECODE_RR __THUNK_BR,\reg,\ruse + .pushsection .s390_indirect_branches,"a",@progbits + .long 557b-. + .popsection + .endm + + .macro BASR_EX rsave,rtarget,ruse=%r1 +559: __DECODE_RRR __THUNK_BRASL,\rsave,\rtarget,\ruse + .pushsection .s390_indirect_branches,"a",@progbits + .long 559b-. + .popsection + .endm + +#else + .macro GEN_BR_THUNK reg,ruse=%r1 + .endm + + .macro BR_EX reg,ruse=%r1 + br \reg + .endm + + .macro BASR_EX rsave,rtarget,ruse=%r1 + basr \rsave,\rtarget + .endm +#endif + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_S390_NOSPEC_ASM_H */ diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index a5621ea6d123..d3e1a510c9c1 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -27,6 +27,7 @@ #include <asm/setup.h> #include <asm/nmi.h> #include <asm/export.h> +#include <asm/nospec-insn.h>

__PT_R0 = __PT_GPRS __PT_R1 = __PT_GPRS + 8 @@ -223,67 +224,9 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART) .popsection .endm

-#ifdef CONFIG_EXPOLINE - - .macro GEN_BR_THUNK name,reg,tmp - .section .text.\name,"axG",@progbits,\name,comdat - .globl \name - .hidden \name - .type \name,@function -\name: - CFI_STARTPROC -#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES - exrl 0,0f -#else - larl \tmp,0f - ex 0,0(\tmp) -#endif - j . -0: br \reg - CFI_ENDPROC - .endm - - GEN_BR_THUNK __s390x_indirect_jump_r1use_r9,%r9,%r1 - GEN_BR_THUNK __s390x_indirect_jump_r1use_r14,%r14,%r1 - GEN_BR_THUNK __s390x_indirect_jump_r11use_r14,%r14,%r11 - - .macro BASR_R14_R9 -0: brasl %r14,__s390x_indirect_jump_r1use_r9 - .pushsection .s390_indirect_branches,"a",@progbits - .long 0b-. - .popsection - .endm - - .macro BR_R1USE_R14 -0: jg __s390x_indirect_jump_r1use_r14 - .pushsection .s390_indirect_branches,"a",@progbits - .long 0b-. - .popsection - .endm - - .macro BR_R11USE_R14 -0: jg __s390x_indirect_jump_r11use_r14 - .pushsection .s390_indirect_branches,"a",@progbits - .long 0b-. - .popsection - .endm - -#else /* CONFIG_EXPOLINE */ - - .macro BASR_R14_R9 - basr %r14,%r9 - .endm - - .macro BR_R1USE_R14 - br %r14 - .endm - - .macro BR_R11USE_R14 - br %r14 - .endm - -#endif /* CONFIG_EXPOLINE */ - + GEN_BR_THUNK %r9 + GEN_BR_THUNK %r14 + GEN_BR_THUNK %r14,%r11

.section .kprobes.text, "ax" .Ldummy: @@ -300,7 +243,7 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART) ENTRY(__bpon) .globl __bpon BPON - BR_R1USE_R14 + BR_EX %r14

/* * Scheduler resume function, called by switch_to @@ -326,7 +269,7 @@ ENTRY(__switch_to) TSTMSK __LC_MACHINE_FLAGS,MACHINE_FLAG_LPP jz 0f .insn s,0xb2800000,__LC_LPP # set program parameter -0: BR_R1USE_R14 +0: BR_EX %r14

.L__critical_start:

@@ -393,7 +336,7 @@ sie_exit: xgr %r5,%r5 lmg %r6,%r14,__SF_GPRS(%r15) # restore kernel registers lg %r2,__SF_EMPTY+16(%r15) # return exit reason code - BR_R1USE_R14 + BR_EX %r14 .Lsie_fault: lghi %r14,-EFAULT stg %r14,__SF_EMPTY+16(%r15) # set exit reason code @@ -452,7 +395,7 @@ ENTRY(system_call) lgf %r9,0(%r8,%r10) # get system call add. TSTMSK __TI_flags(%r12),_TIF_TRACE jnz .Lsysc_tracesys - BASR_R14_R9 # call sys_xxxx + BASR_EX %r14,%r9 # call sys_xxxx stg %r2,__PT_R2(%r11) # store return value

.Lsysc_return: @@ -637,7 +580,7 @@ ENTRY(system_call) lmg %r3,%r7,__PT_R3(%r11) stg %r7,STACK_FRAME_OVERHEAD(%r15) lg %r2,__PT_ORIG_GPR2(%r11) - BASR_R14_R9 # call sys_xxx + BASR_EX %r14,%r9 # call sys_xxx stg %r2,__PT_R2(%r11) # store return value .Lsysc_tracenogo: TSTMSK __TI_flags(%r12),_TIF_TRACE @@ -661,7 +604,7 @@ ENTRY(ret_from_fork) lmg %r9,%r10,__PT_R9(%r11) # load gprs ENTRY(kernel_thread_starter) la %r2,0(%r10) - BASR_R14_R9 + BASR_EX %r14,%r9 j .Lsysc_tracenogo

/* @@ -743,7 +686,7 @@ ENTRY(pgm_check_handler) je .Lpgm_return lgf %r9,0(%r10,%r1) # load address of handler routine lgr %r2,%r11 # pass pointer to pt_regs - BASR_R14_R9 # branch to interrupt-handler + BASR_EX %r14,%r9 # branch to interrupt-handler .Lpgm_return: LOCKDEP_SYS_EXIT tm __PT_PSW+1(%r11),0x01 # returning to user ? @@ -1061,7 +1004,7 @@ ENTRY(psw_idle) stpt __TIMER_IDLE_ENTER(%r2) .Lpsw_idle_lpsw: lpswe __SF_EMPTY(%r15) - BR_R1USE_R14 + BR_EX %r14 .Lpsw_idle_end:

/* @@ -1103,7 +1046,7 @@ ENTRY(save_fpu_regs) .Lsave_fpu_regs_done: oi __LC_CPU_FLAGS+7,_CIF_FPU .Lsave_fpu_regs_exit: - BR_R1USE_R14 + BR_EX %r14 .Lsave_fpu_regs_end: EXPORT_SYMBOL(save_fpu_regs)

@@ -1149,7 +1092,7 @@ load_fpu_regs: .Lload_fpu_regs_done: ni __LC_CPU_FLAGS+7,255-_CIF_FPU .Lload_fpu_regs_exit: - BR_R1USE_R14 + BR_EX %r14 .Lload_fpu_regs_end:

.L__critical_end: @@ -1366,7 +1309,7 @@ cleanup_critical: jl 0f clg %r9,BASED(.Lcleanup_table+104) # .Lload_fpu_regs_end jl .Lcleanup_load_fpu_regs -0: BR_R11USE_R14 +0: BR_EX %r14

.align 8 .Lcleanup_table: @@ -1402,7 +1345,7 @@ cleanup_critical: ni __SIE_PROG0C+3(%r9),0xfe # no longer in SIE lctlg %c1,%c1,__LC_USER_ASCE # load primary asce larl %r9,sie_exit # skip forward to sie_exit - BR_R11USE_R14 + BR_EX %r14 #endif

.Lcleanup_system_call: @@ -1456,7 +1399,7 @@ cleanup_critical: stg %r15,56(%r11) # r15 stack pointer # set new psw address and exit larl %r9,.Lsysc_do_svc - BR_R11USE_R14 + BR_EX %r14,%r11 .Lcleanup_system_call_insn: .quad system_call .quad .Lsysc_stmg @@ -1468,7 +1411,7 @@ cleanup_critical:

.Lcleanup_sysc_tif: larl %r9,.Lsysc_tif - BR_R11USE_R14 + BR_EX %r14,%r11

.Lcleanup_sysc_restore: # check if stpt has been executed @@ -1485,14 +1428,14 @@ cleanup_critical: mvc 0(64,%r11),__PT_R8(%r9) lmg %r0,%r7,__PT_R0(%r9) 1: lmg %r8,%r9,__LC_RETURN_PSW - BR_R11USE_R14 + BR_EX %r14,%r11 .Lcleanup_sysc_restore_insn: .quad .Lsysc_exit_timer .quad .Lsysc_done - 4

.Lcleanup_io_tif: larl %r9,.Lio_tif - BR_R11USE_R14 + BR_EX %r14,%r11

.Lcleanup_io_restore: # check if stpt has been executed @@ -1506,7 +1449,7 @@ cleanup_critical: mvc 0(64,%r11),__PT_R8(%r9) lmg %r0,%r7,__PT_R0(%r9) 1: lmg %r8,%r9,__LC_RETURN_PSW - BR_R11USE_R14 + BR_EX %r14,%r11 .Lcleanup_io_restore_insn: .quad .Lio_exit_timer .quad .Lio_done - 4 @@ -1559,17 +1502,17 @@ cleanup_critical: # prepare return psw nihh %r8,0xfcfd # clear irq & wait state bits lg %r9,48(%r11) # return from psw_idle - BR_R11USE_R14 + BR_EX %r14,%r11 .Lcleanup_idle_insn: .quad .Lpsw_idle_lpsw

.Lcleanup_save_fpu_regs: larl %r9,save_fpu_regs - BR_R11USE_R14 + BR_EX %r14,%r11

.Lcleanup_load_fpu_regs: larl %r9,load_fpu_regs - BR_R11USE_R14 + BR_EX %r14,%r11

/* * Integer constants

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 09/15] s390/crc32-vx: use expoline for indirect branches

[ Upstream commit 467a3bf219cee12259182c5cb4821f88fd518a51 ]

The return from the crc32_le_vgfm_16/crc32c_le_vgfm_16 and the crc32_be_vgfm_16 functions are done with "br %r14". These are indirect branches as well and need to use execute trampolines for CONFIG_EXPOLINE=y.

Cc: stable@vger.kernel.org # 4.16 Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches") Reviewed-by: Hendrik Brueckner brueckner@linux.vnet.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/crypto/crc32be-vx.S | 5 ++++- arch/s390/crypto/crc32le-vx.S | 4 +++- 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/s390/crypto/crc32be-vx.S b/arch/s390/crypto/crc32be-vx.S index e8077f0971f8..2bf01ba44107 100644 --- a/arch/s390/crypto/crc32be-vx.S +++ b/arch/s390/crypto/crc32be-vx.S @@ -13,6 +13,7 @@ */

#include <linux/linkage.h> +#include <asm/nospec-insn.h> #include <asm/vx-insn.h>

/* Vector register range containing CRC-32 constants */ @@ -67,6 +68,8 @@

.previous

+ GEN_BR_THUNK %r14 + .text /* * The CRC-32 function(s) use these calling conventions: @@ -203,6 +206,6 @@ ENTRY(crc32_be_vgfm_16)

.Ldone: VLGVF %r2,%v2,3 - br %r14 + BR_EX %r14

.previous diff --git a/arch/s390/crypto/crc32le-vx.S b/arch/s390/crypto/crc32le-vx.S index d8c67a58c0c5..7d6f568bd3ad 100644 --- a/arch/s390/crypto/crc32le-vx.S +++ b/arch/s390/crypto/crc32le-vx.S @@ -14,6 +14,7 @@ */

#include <linux/linkage.h> +#include <asm/nospec-insn.h> #include <asm/vx-insn.h>

/* Vector register range containing CRC-32 constants */ @@ -76,6 +77,7 @@

.previous

+ GEN_BR_THUNK %r14

.text

@@ -264,6 +266,6 @@ crc32_le_vgfm_generic:

.Ldone: VLGVF %r2,%v2,2 - br %r14 + BR_EX %r14

.previous

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 10/15] s390/lib: use expoline for indirect branches

[ Upstream commit 97489e0663fa700d6e7febddc43b58df98d7bcda ]

The return from the memmove, memset, memcpy, __memset16, __memset32 and __memset64 functions are done with "br %r14". These are indirect branches as well and need to use execute trampolines for CONFIG_EXPOLINE=y.

Cc: stable@vger.kernel.org # 4.16 Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches") Reviewed-by: Hendrik Brueckner brueckner@linux.vnet.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/lib/mem.S | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/s390/lib/mem.S b/arch/s390/lib/mem.S index 495c9c4bacc7..2311f15be9cf 100644 --- a/arch/s390/lib/mem.S +++ b/arch/s390/lib/mem.S @@ -7,6 +7,9 @@

#include <linux/linkage.h> #include <asm/export.h> +#include <asm/nospec-insn.h> + + GEN_BR_THUNK %r14

/* * void *memmove(void *dest, const void *src, size_t n) @@ -33,14 +36,14 @@ ENTRY(memmove) .Lmemmove_forward_remainder: larl %r5,.Lmemmove_mvc ex %r4,0(%r5) - br %r14 + BR_EX %r14 .Lmemmove_reverse: ic %r0,0(%r4,%r3) stc %r0,0(%r4,%r1) brctg %r4,.Lmemmove_reverse ic %r0,0(%r4,%r3) stc %r0,0(%r4,%r1) - br %r14 + BR_EX %r14 .Lmemmove_mvc: mvc 0(1,%r1),0(%r3) EXPORT_SYMBOL(memmove) @@ -77,7 +80,7 @@ ENTRY(memset) .Lmemset_clear_remainder: larl %r3,.Lmemset_xc ex %r4,0(%r3) - br %r14 + BR_EX %r14 .Lmemset_fill: cghi %r4,1 lgr %r1,%r2 @@ -95,10 +98,10 @@ ENTRY(memset) stc %r3,0(%r1) larl %r5,.Lmemset_mvc ex %r4,0(%r5) - br %r14 + BR_EX %r14 .Lmemset_fill_exit: stc %r3,0(%r1) - br %r14 + BR_EX %r14 .Lmemset_xc: xc 0(1,%r1),0(%r1) .Lmemset_mvc: @@ -121,7 +124,7 @@ ENTRY(memcpy) .Lmemcpy_remainder: larl %r5,.Lmemcpy_mvc ex %r4,0(%r5) - br %r14 + BR_EX %r14 .Lmemcpy_loop: mvc 0(256,%r1),0(%r3) la %r1,256(%r1) @@ -159,10 +162,10 @@ ENTRY(__memset\bits) \insn %r3,0(%r1) larl %r5,.L__memset_mvc\bits ex %r4,0(%r5) - br %r14 + BR_EX %r14 .L__memset_exit\bits: \insn %r3,0(%r2) - br %r14 + BR_EX %r14 .L__memset_mvc\bits: mvc \bytes(1,%r1),0(%r1) .endm

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 11/15] s390/ftrace: use expoline for indirect branches

[ Upstream commit 23a4d7fd34856da8218c4cfc23dba7a6ec0a423a ]

The return from the ftrace_stub, _mcount, ftrace_caller and return_to_handler functions is done with "br %r14" and "br %r1". These are indirect branches as well and need to use execute trampolines for CONFIG_EXPOLINE=y.

The ftrace_caller function is a special case as it returns to the start of a function and may only use %r0 and %r1. For a pre z10 machine the standard execute trampoline uses a LARL + EX to do this, but this requires *two* registers in the range %r1..%r15. To get around this the 'br %r1' located in the lowcore is used, then the EX instruction does not need an address register. But the lowcore trick may only be used for pre z14 machines, with noexec=on the mapping for the first page may not contain instructions. The solution for that is an ALTERNATIVE in the expoline THUNK generated by 'GEN_BR_THUNK %r1' to switch to EXRL, this relies on the fact that a machine that supports noexec=on has EXRL as well.

Cc: stable@vger.kernel.org # 4.16 Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches") Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/include/asm/nospec-insn.h | 12 ++++++++++++ arch/s390/kernel/asm-offsets.c | 1 + arch/s390/kernel/mcount.S | 14 +++++++++----- 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/s390/include/asm/nospec-insn.h b/arch/s390/include/asm/nospec-insn.h index 440689cbcf51..7d7640e1cf90 100644 --- a/arch/s390/include/asm/nospec-insn.h +++ b/arch/s390/include/asm/nospec-insn.h @@ -2,12 +2,16 @@ #ifndef _ASM_S390_NOSPEC_ASM_H #define _ASM_S390_NOSPEC_ASM_H

+#include <asm/alternative-asm.h> +#include <asm/asm-offsets.h> #include <asm/dwarf.h>

#ifdef __ASSEMBLY__

#ifdef CONFIG_EXPOLINE

+_LC_BR_R1 = __LC_BR_R1 + /* * The expoline macros are used to create thunks in the same format * as gcc generates them. The 'comdat' section flag makes sure that @@ -78,13 +82,21 @@ .endm

.macro __THUNK_EX_BR reg,ruse + # Be very careful when adding instructions to this macro! + # The ALTERNATIVE replacement code has a .+10 which targets + # the "br \reg" after the code has been patched. #ifdef CONFIG_HAVE_MARCH_Z10_FEATURES exrl 0,555f j . #else + .ifc \reg,%r1 + ALTERNATIVE "ex %r0,_LC_BR_R1", ".insn ril,0xc60000000000,0,.+10", 35 + j . + .else larl \ruse,555f ex 0,0(\ruse) j . + .endif #endif 555: br \reg .endm diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c index 587b195b588d..3fd0b4535a71 100644 --- a/arch/s390/kernel/asm-offsets.c +++ b/arch/s390/kernel/asm-offsets.c @@ -179,6 +179,7 @@ int main(void) OFFSET(__LC_MACHINE_FLAGS, lowcore, machine_flags); OFFSET(__LC_PREEMPT_COUNT, lowcore, preempt_count); OFFSET(__LC_GMAP, lowcore, gmap); + OFFSET(__LC_BR_R1, lowcore, br_r1_trampoline); /* software defined ABI-relevant lowcore locations 0xe00 - 0xe20 */ OFFSET(__LC_DUMP_REIPL, lowcore, ipib); /* hardware defined lowcore locations 0x1000 - 0x18ff */ diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S index 82df7d80fab2..27110f3294ed 100644 --- a/arch/s390/kernel/mcount.S +++ b/arch/s390/kernel/mcount.S @@ -9,13 +9,17 @@ #include <linux/linkage.h> #include <asm/asm-offsets.h> #include <asm/ftrace.h> +#include <asm/nospec-insn.h> #include <asm/ptrace.h> #include <asm/export.h>

+ GEN_BR_THUNK %r1 + GEN_BR_THUNK %r14 + .section .kprobes.text, "ax"

ENTRY(ftrace_stub) - br %r14 + BR_EX %r14

#define STACK_FRAME_SIZE (STACK_FRAME_OVERHEAD + __PT_SIZE) #define STACK_PTREGS (STACK_FRAME_OVERHEAD) @@ -23,7 +27,7 @@ ENTRY(ftrace_stub) #define STACK_PTREGS_PSW (STACK_PTREGS + __PT_PSW)

ENTRY(_mcount) - br %r14 + BR_EX %r14

EXPORT_SYMBOL(_mcount)

@@ -53,7 +57,7 @@ ENTRY(ftrace_caller) #endif lgr %r3,%r14 la %r5,STACK_PTREGS(%r15) - basr %r14,%r1 + BASR_EX %r14,%r1 #ifdef CONFIG_FUNCTION_GRAPH_TRACER # The j instruction gets runtime patched to a nop instruction. # See ftrace_enable_ftrace_graph_caller. @@ -68,7 +72,7 @@ ftrace_graph_caller_end: #endif lg %r1,(STACK_PTREGS_PSW+8)(%r15) lmg %r2,%r15,(STACK_PTREGS_GPRS+2*8)(%r15) - br %r1 + BR_EX %r1

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

@@ -81,6 +85,6 @@ ENTRY(return_to_handler) aghi %r15,STACK_FRAME_OVERHEAD lgr %r14,%r2 lmg %r2,%r5,32(%r15) - br %r14 + BR_EX %r14

#endif

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 12/15] s390/kernel: use expoline for indirect branches

[ Upstream commit c50c84c3ac4d5db683904bdb3257798b6ef980ae ]

The assember code in arch/s390/kernel uses a few more indirect branches which need to be done with execute trampolines for CONFIG_EXPOLINE=y.

Cc: stable@vger.kernel.org # 4.16 Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches") Reviewed-by: Hendrik Brueckner brueckner@linux.vnet.ibm.com Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/kernel/base.S | 24 ++++++++++++++---------- arch/s390/kernel/reipl.S | 7 +++++-- arch/s390/kernel/swsusp.S | 10 ++++++---- 3 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/arch/s390/kernel/base.S b/arch/s390/kernel/base.S index f6c56009e822..b65874b0b412 100644 --- a/arch/s390/kernel/base.S +++ b/arch/s390/kernel/base.S @@ -9,18 +9,22 @@

#include <linux/linkage.h> #include <asm/asm-offsets.h> +#include <asm/nospec-insn.h> #include <asm/ptrace.h> #include <asm/sigp.h>

+ GEN_BR_THUNK %r9 + GEN_BR_THUNK %r14 + ENTRY(s390_base_mcck_handler) basr %r13,0 0: lg %r15,__LC_PANIC_STACK # load panic stack aghi %r15,-STACK_FRAME_OVERHEAD larl %r1,s390_base_mcck_handler_fn - lg %r1,0(%r1) - ltgr %r1,%r1 + lg %r9,0(%r1) + ltgr %r9,%r9 jz 1f - basr %r14,%r1 + BASR_EX %r14,%r9 1: la %r1,4095 lmg %r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1) lpswe __LC_MCK_OLD_PSW @@ -37,10 +41,10 @@ ENTRY(s390_base_ext_handler) basr %r13,0 0: aghi %r15,-STACK_FRAME_OVERHEAD larl %r1,s390_base_ext_handler_fn - lg %r1,0(%r1) - ltgr %r1,%r1 + lg %r9,0(%r1) + ltgr %r9,%r9 jz 1f - basr %r14,%r1 + BASR_EX %r14,%r9 1: lmg %r0,%r15,__LC_SAVE_AREA_ASYNC ni __LC_EXT_OLD_PSW+1,0xfd # clear wait state bit lpswe __LC_EXT_OLD_PSW @@ -57,10 +61,10 @@ ENTRY(s390_base_pgm_handler) basr %r13,0 0: aghi %r15,-STACK_FRAME_OVERHEAD larl %r1,s390_base_pgm_handler_fn - lg %r1,0(%r1) - ltgr %r1,%r1 + lg %r9,0(%r1) + ltgr %r9,%r9 jz 1f - basr %r14,%r1 + BASR_EX %r14,%r9 lmg %r0,%r15,__LC_SAVE_AREA_SYNC lpswe __LC_PGM_OLD_PSW 1: lpswe disabled_wait_psw-0b(%r13) @@ -117,7 +121,7 @@ ENTRY(diag308_reset) larl %r4,.Lcontinue_psw # Restore PSW flags lpswe 0(%r4) .Lcontinue: - br %r14 + BR_EX %r14 .align 16 .Lrestart_psw: .long 0x00080000,0x80000000 + .Lrestart_part2 diff --git a/arch/s390/kernel/reipl.S b/arch/s390/kernel/reipl.S index a40ebd1d29d0..8e954c102639 100644 --- a/arch/s390/kernel/reipl.S +++ b/arch/s390/kernel/reipl.S @@ -7,8 +7,11 @@

#include <linux/linkage.h> #include <asm/asm-offsets.h> +#include <asm/nospec-insn.h> #include <asm/sigp.h>

+ GEN_BR_THUNK %r9 + # # Issue "store status" for the current CPU to its prefix page # and call passed function afterwards @@ -67,9 +70,9 @@ ENTRY(store_status) st %r4,0(%r1) st %r5,4(%r1) stg %r2,8(%r1) - lgr %r1,%r2 + lgr %r9,%r2 lgr %r2,%r3 - br %r1 + BR_EX %r9

.section .bss .align 8 diff --git a/arch/s390/kernel/swsusp.S b/arch/s390/kernel/swsusp.S index e99187149f17..a049a7b9d6e8 100644 --- a/arch/s390/kernel/swsusp.S +++ b/arch/s390/kernel/swsusp.S @@ -13,6 +13,7 @@ #include <asm/ptrace.h> #include <asm/thread_info.h> #include <asm/asm-offsets.h> +#include <asm/nospec-insn.h> #include <asm/sigp.h>

/* @@ -24,6 +25,8 @@ * (see below) in the resume process. * This function runs with disabled interrupts. */ + GEN_BR_THUNK %r14 + .section .text ENTRY(swsusp_arch_suspend) stmg %r6,%r15,__SF_GPRS(%r15) @@ -103,7 +106,7 @@ ENTRY(swsusp_arch_suspend) spx 0x318(%r1) lmg %r6,%r15,STACK_FRAME_OVERHEAD + __SF_GPRS(%r15) lghi %r2,0 - br %r14 + BR_EX %r14

/* * Restore saved memory image to correct place and restore register context. @@ -197,11 +200,10 @@ pgm_check_entry: larl %r15,init_thread_union ahi %r15,1<<(PAGE_SHIFT+THREAD_SIZE_ORDER) larl %r2,.Lpanic_string - larl %r3,sclp_early_printk lghi %r1,0 sam31 sigp %r1,%r0,SIGP_SET_ARCHITECTURE - basr %r14,%r3 + brasl %r14,sclp_early_printk larl %r3,.Ldisabled_wait_31 lpsw 0(%r3) 4: @@ -267,7 +269,7 @@ restore_registers: /* Return 0 */ lmg %r6,%r15,STACK_FRAME_OVERHEAD + __SF_GPRS(%r15) lghi %r2,0 - br %r14 + BR_EX %r14

.section .data..nosave,"aw",@progbits .align 8

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 13/15] s390: move spectre sysfs attribute code

[ Upstream commit 4253b0e0627ee3461e64c2495c616f1c8f6b127b ]

The nospec-branch.c file is compiled without the gcc options to generate expoline thunks. The return branch of the sysfs show functions cpu_show_spectre_v1 and cpu_show_spectre_v2 is an indirect branch as well. These need to be compiled with expolines.

Move the sysfs functions for spectre reporting to a separate file and loose an '.' for one of the messages.

Cc: stable@vger.kernel.org # 4.16 Fixes: d424986f1d ("s390: add sysfs attributes for spectre") Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/kernel/Makefile | 1 + arch/s390/kernel/nospec-branch.c | 18 ------------------ arch/s390/kernel/nospec-sysfs.c | 21 +++++++++++++++++++++ 3 files changed, 22 insertions(+), 18 deletions(-) create mode 100644 arch/s390/kernel/nospec-sysfs.c

diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile index b06a6f79c1ec..a02bc90fe5f3 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -65,6 +65,7 @@ obj-y += nospec-branch.o

extra-y += head.o head64.o vmlinux.lds

+obj-$(CONFIG_SYSFS) += nospec-sysfs.o CFLAGS_REMOVE_nospec-branch.o += $(CC_FLAGS_EXPOLINE)

obj-$(CONFIG_MODULES) += module.o diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index f236ce8757e8..834cf29f2599 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -43,24 +43,6 @@ static int __init nospec_report(void) } arch_initcall(nospec_report);

-#ifdef CONFIG_SYSFS -ssize_t cpu_show_spectre_v1(struct device *dev, - struct device_attribute *attr, char *buf) -{ - return sprintf(buf, "Mitigation: __user pointer sanitization\n"); -} - -ssize_t cpu_show_spectre_v2(struct device *dev, - struct device_attribute *attr, char *buf) -{ - if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) - return sprintf(buf, "Mitigation: execute trampolines\n"); - if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) - return sprintf(buf, "Mitigation: limited branch prediction.\n"); - return sprintf(buf, "Vulnerable\n"); -} -#endif - #ifdef CONFIG_EXPOLINE

int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF); diff --git a/arch/s390/kernel/nospec-sysfs.c b/arch/s390/kernel/nospec-sysfs.c new file mode 100644 index 000000000000..8affad5f18cb --- /dev/null +++ b/arch/s390/kernel/nospec-sysfs.c @@ -0,0 +1,21 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/device.h> +#include <linux/cpu.h> +#include <asm/facility.h> +#include <asm/nospec-branch.h> + +ssize_t cpu_show_spectre_v1(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "Mitigation: __user pointer sanitization\n"); +} + +ssize_t cpu_show_spectre_v2(struct device *dev, + struct device_attribute *attr, char *buf) +{ + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) + return sprintf(buf, "Mitigation: execute trampolines\n"); + if (__test_facility(82, S390_lowcore.alt_stfle_fac_list)) + return sprintf(buf, "Mitigation: limited branch prediction\n"); + return sprintf(buf, "Vulnerable\n"); +}

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 14/15] s390: extend expoline to BC instructions

[ Upstream commit 6deaa3bbca804b2a3627fd685f75de64da7be535 ]

The BPF JIT uses a 'b <disp>(%r<x>)' instruction in the definition of the sk_load_word and sk_load_half functions.

Add support for branch-on-condition instructions contained in the thunk code of an expoline.

Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/include/asm/nospec-insn.h | 57 +++++++++++++++++++++++++++++++++++++ arch/s390/kernel/nospec-branch.c | 25 ++++++++++++---- 2 files changed, 77 insertions(+), 5 deletions(-)

diff --git a/arch/s390/include/asm/nospec-insn.h b/arch/s390/include/asm/nospec-insn.h index 7d7640e1cf90..a01f81186e86 100644 --- a/arch/s390/include/asm/nospec-insn.h +++ b/arch/s390/include/asm/nospec-insn.h @@ -35,10 +35,18 @@ _LC_BR_R1 = __LC_BR_R1 __THUNK_PROLOG_NAME __s390x_indirect_jump_r\r2()use_r\r1 .endm

+ .macro __THUNK_PROLOG_BC d0,r1,r2 + __THUNK_PROLOG_NAME __s390x_indirect_branch_\d0()_\r2()use_\r1 + .endm + .macro __THUNK_BR r1,r2 jg __s390x_indirect_jump_r\r2()use_r\r1 .endm

+ .macro __THUNK_BC d0,r1,r2 + jg __s390x_indirect_branch_\d0()_\r2()use_\r1 + .endm + .macro __THUNK_BRASL r1,r2,r3 brasl \r1,__s390x_indirect_jump_r\r3()use_r\r2 .endm @@ -81,6 +89,23 @@ _LC_BR_R1 = __LC_BR_R1 .endif .endm

+ .macro __DECODE_DRR expand,disp,reg,ruse + .set __decode_fail,1 + .irp r1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 + .ifc \reg,%r\r1 + .irp r2,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 + .ifc \ruse,%r\r2 + \expand \disp,\r1,\r2 + .set __decode_fail,0 + .endif + .endr + .endif + .endr + .if __decode_fail == 1 + .error "__DECODE_DRR failed" + .endif + .endm + .macro __THUNK_EX_BR reg,ruse # Be very careful when adding instructions to this macro! # The ALTERNATIVE replacement code has a .+10 which targets @@ -101,17 +126,42 @@ _LC_BR_R1 = __LC_BR_R1 555: br \reg .endm

+ .macro __THUNK_EX_BC disp,reg,ruse +#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES + exrl 0,556f + j . +#else + larl \ruse,556f + ex 0,0(\ruse) + j . +#endif +556: b \disp(\reg) + .endm + .macro GEN_BR_THUNK reg,ruse=%r1 __DECODE_RR __THUNK_PROLOG_BR,\reg,\ruse __THUNK_EX_BR \reg,\ruse __THUNK_EPILOG .endm

+ .macro GEN_B_THUNK disp,reg,ruse=%r1 + __DECODE_DRR __THUNK_PROLOG_BC,\disp,\reg,\ruse + __THUNK_EX_BC \disp,\reg,\ruse + __THUNK_EPILOG + .endm + .macro BR_EX reg,ruse=%r1 557: __DECODE_RR __THUNK_BR,\reg,\ruse .pushsection .s390_indirect_branches,"a",@progbits .long 557b-. .popsection + .endm + + .macro B_EX disp,reg,ruse=%r1 +558: __DECODE_DRR __THUNK_BC,\disp,\reg,\ruse + .pushsection .s390_indirect_branches,"a",@progbits + .long 558b-. + .popsection .endm

.macro BASR_EX rsave,rtarget,ruse=%r1 @@ -123,10 +173,17 @@ _LC_BR_R1 = __LC_BR_R1

#else .macro GEN_BR_THUNK reg,ruse=%r1 + .endm + + .macro GEN_B_THUNK disp,reg,ruse=%r1 .endm

.macro BR_EX reg,ruse=%r1 br \reg + .endm + + .macro B_EX disp,reg,ruse=%r1 + b \disp(\reg) .endm

.macro BASR_EX rsave,rtarget,ruse=%r1 diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 834cf29f2599..8ad6a7128b3a 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -93,7 +93,6 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) s32 *epo;

/* Second part of the instruction replace is always a nop */ - memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x00, 0x00 }, 4); for (epo = start; epo < end; epo++) { instr = (u8 *) epo + *epo; if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04) @@ -114,18 +113,34 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) br = thunk + (*(int *)(thunk + 2)) * 2; else continue; - if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0) + /* Check for unconditional branch 0x07f? or 0x47f???? */ + if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0) continue; + + memcpy(insnbuf + 2, (char[]) { 0x47, 0x00, 0x07, 0x00 }, 4); switch (type) { case BRCL_EXPOLINE: - /* brcl to thunk, replace with br + nop */ insnbuf[0] = br[0]; insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); + if (br[0] == 0x47) { + /* brcl to b, replace with bc + nopr */ + insnbuf[2] = br[2]; + insnbuf[3] = br[3]; + } else { + /* brcl to br, replace with bcr + nop */ + } break; case BRASL_EXPOLINE: - /* brasl to thunk, replace with basr + nop */ - insnbuf[0] = 0x0d; insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); + if (br[0] == 0x47) { + /* brasl to b, replace with bas + nopr */ + insnbuf[0] = 0x4d; + insnbuf[2] = br[2]; + insnbuf[3] = br[3]; + } else { + /* brasl to br, replace with basr + nop */ + insnbuf[0] = 0x0d; + } break; }

-- 2.16.3

Martin Schwidefsky

4:22 p.m.

New subject: [PATCH 15/15] s390: use expoline thunks in the BPF JIT

[ Upstream commit de5cb6eb514ebe241e3edeb290cb41deb380b81d ]

The BPF JIT need safe guarding against spectre v2 in the sk_load_xxx assembler stubs and the indirect branches generated by the JIT itself need to be converted to expolines.

Signed-off-by: Martin Schwidefsky schwidefsky@de.ibm.com --- arch/s390/net/bpf_jit.S | 16 ++++++----- arch/s390/net/bpf_jit_comp.c | 63 ++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 71 insertions(+), 8 deletions(-)

diff --git a/arch/s390/net/bpf_jit.S b/arch/s390/net/bpf_jit.S index 25bb4643c4f4..9f794869c1b0 100644 --- a/arch/s390/net/bpf_jit.S +++ b/arch/s390/net/bpf_jit.S @@ -9,6 +9,7 @@ */

#include <linux/linkage.h> +#include <asm/nospec-insn.h> #include "bpf_jit.h"

/* @@ -54,7 +55,7 @@ ENTRY(sk_load_##NAME##_pos); \ clg %r3,STK_OFF_HLEN(%r15); /* Offset + SIZE > hlen? */ \ jh sk_load_##NAME##_slow; \ LOAD %r14,-SIZE(%r3,%r12); /* Get data from skb */ \ - b OFF_OK(%r6); /* Return */ \ + B_EX OFF_OK,%r6; /* Return */ \ \ sk_load_##NAME##_slow:; \ lgr %r2,%r7; /* Arg1 = skb pointer */ \ @@ -64,11 +65,14 @@ sk_load_##NAME##_slow:; \ brasl %r14,skb_copy_bits; /* Get data from skb */ \ LOAD %r14,STK_OFF_TMP(%r15); /* Load from temp bufffer */ \ ltgr %r2,%r2; /* Set cc to (%r2 != 0) */ \ - br %r6; /* Return */ + BR_EX %r6; /* Return */

sk_load_common(word, 4, llgf) /* r14 = *(u32 *) (skb->data+offset) */ sk_load_common(half, 2, llgh) /* r14 = *(u16 *) (skb->data+offset) */

+ GEN_BR_THUNK %r6 + GEN_B_THUNK OFF_OK,%r6 + /* * Load 1 byte from SKB (optimized version) */ @@ -80,7 +84,7 @@ ENTRY(sk_load_byte_pos) clg %r3,STK_OFF_HLEN(%r15) # Offset >= hlen? jnl sk_load_byte_slow llgc %r14,0(%r3,%r12) # Get byte from skb - b OFF_OK(%r6) # Return OK + B_EX OFF_OK,%r6 # Return OK

sk_load_byte_slow: lgr %r2,%r7 # Arg1 = skb pointer @@ -90,7 +94,7 @@ sk_load_byte_slow: brasl %r14,skb_copy_bits # Get data from skb llgc %r14,STK_OFF_TMP(%r15) # Load result from temp buffer ltgr %r2,%r2 # Set cc to (%r2 != 0) - br %r6 # Return cc + BR_EX %r6 # Return cc

#define sk_negative_common(NAME, SIZE, LOAD) \ sk_load_##NAME##_slow_neg:; \ @@ -104,7 +108,7 @@ sk_load_##NAME##_slow_neg:; \ jz bpf_error; \ LOAD %r14,0(%r2); /* Get data from pointer */ \ xr %r3,%r3; /* Set cc to zero */ \ - br %r6; /* Return cc */ + BR_EX %r6; /* Return cc */

sk_negative_common(word, 4, llgf) sk_negative_common(half, 2, llgh) @@ -113,4 +117,4 @@ sk_negative_common(byte, 1, llgc) bpf_error: # force a return 0 from jit handler ltgr %r15,%r15 # Set condition code - br %r6 + BR_EX %r6 diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 78a19c93b380..dd2bcf0e7d00 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -25,6 +25,8 @@ #include <linux/bpf.h> #include <asm/cacheflush.h> #include <asm/dis.h> +#include <asm/facility.h> +#include <asm/nospec-branch.h> #include <asm/set_memory.h> #include "bpf_jit.h"

@@ -41,6 +43,8 @@ struct bpf_jit { int base_ip; /* Base address for literal pool */ int ret0_ip; /* Address of return 0 */ int exit_ip; /* Address of exit */ + int r1_thunk_ip; /* Address of expoline thunk for 'br %r1' */ + int r14_thunk_ip; /* Address of expoline thunk for 'br %r14' */ int tail_call_start; /* Tail call start offset */ int labels[1]; /* Labels for local jumps */ }; @@ -250,6 +254,19 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1) REG_SET_SEEN(b2); \ })

+#define EMIT6_PCREL_RILB(op, b, target) \ +({ \ + int rel = (target - jit->prg) / 2; \ + _EMIT6(op | reg_high(b) << 16 | rel >> 16, rel & 0xffff); \ + REG_SET_SEEN(b); \ +}) + +#define EMIT6_PCREL_RIL(op, target) \ +({ \ + int rel = (target - jit->prg) / 2; \ + _EMIT6(op | rel >> 16, rel & 0xffff); \ +}) + #define _EMIT6_IMM(op, imm) \ ({ \ unsigned int __imm = (imm); \ @@ -469,8 +486,45 @@ static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth) EMIT4(0xb9040000, REG_2, BPF_REG_0); /* Restore registers */ save_restore_regs(jit, REGS_RESTORE, stack_depth); + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) { + jit->r14_thunk_ip = jit->prg; + /* Generate __s390_indirect_jump_r14 thunk */ + if (test_facility(35)) { + /* exrl %r0,.+10 */ + EMIT6_PCREL_RIL(0xc6000000, jit->prg + 10); + } else { + /* larl %r1,.+14 */ + EMIT6_PCREL_RILB(0xc0000000, REG_1, jit->prg + 14); + /* ex 0,0(%r1) */ + EMIT4_DISP(0x44000000, REG_0, REG_1, 0); + } + /* j . */ + EMIT4_PCREL(0xa7f40000, 0); + } /* br %r14 */ _EMIT2(0x07fe); + + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable && + (jit->seen & SEEN_FUNC)) { + jit->r1_thunk_ip = jit->prg; + /* Generate __s390_indirect_jump_r1 thunk */ + if (test_facility(35)) { + /* exrl %r0,.+10 */ + EMIT6_PCREL_RIL(0xc6000000, jit->prg + 10); + /* j . */ + EMIT4_PCREL(0xa7f40000, 0); + /* br %r1 */ + _EMIT2(0x07f1); + } else { + /* larl %r1,.+14 */ + EMIT6_PCREL_RILB(0xc0000000, REG_1, jit->prg + 14); + /* ex 0,S390_lowcore.br_r1_tampoline */ + EMIT4_DISP(0x44000000, REG_0, REG_0, + offsetof(struct lowcore, br_r1_trampoline)); + /* j . */ + EMIT4_PCREL(0xa7f40000, 0); + } + } }

/* @@ -966,8 +1020,13 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i /* lg %w1,<d(imm)>(%l) */ EMIT6_DISP_LH(0xe3000000, 0x0004, REG_W1, REG_0, REG_L, EMIT_CONST_U64(func)); - /* basr %r14,%w1 */ - EMIT2(0x0d00, REG_14, REG_W1); + if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable) { + /* brasl %r14,__s390_indirect_jump_r1 */ + EMIT6_PCREL_RILB(0xc0050000, REG_14, jit->r1_thunk_ip); + } else { + /* basr %r14,%w1 */ + EMIT2(0x0d00, REG_14, REG_W1); + } /* lgr %b0,%r2: load return value into %b0 */ EMIT4(0xb9040000, BPF_REG_0, REG_2); if ((jit->seen & SEEN_SKB) &&

-- 2.16.3

Greg KH

5:23 p.m.

On Wed, May 23, 2018 at 06:22:16PM +0200, Martin Schwidefsky wrote:

...

Hi Greg,

15 more patches against the 2018/05/23 linux-4.16.y stable branch. This gets the spectre defense of 4.16 up-to-date compared to the current upstream tree. The upstream patches to remove the indirect branches from the BPF JIT are included (these do not have a CC:stable tag).

All now applied, thanks!

greg k-h

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Greg KH
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