Hi Greg,
9 more patches against the 2018/05/23 linux-4.4.y stable branch. This gets the spectre defense of 4.4 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 (9): s390: add assembler macros for CPU alternatives s390: move expoline assembler macros to a header 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: remove indirect branch from do_softirq_own_stack s390: extend expoline to BC instructions s390: use expoline thunks in the BPF JIT
arch/s390/include/asm/alternative-asm.h | 108 ++++++++++++++++++ arch/s390/include/asm/nospec-insn.h | 193 ++++++++++++++++++++++++++++++++ arch/s390/kernel/Makefile | 1 + arch/s390/kernel/asm-offsets.c | 1 + arch/s390/kernel/base.S | 24 ++-- arch/s390/kernel/entry.S | 105 ++++------------- arch/s390/kernel/irq.c | 5 +- arch/s390/kernel/mcount.S | 14 ++- arch/s390/kernel/nospec-branch.c | 43 ++++--- arch/s390/kernel/nospec-sysfs.c | 21 ++++ arch/s390/kernel/reipl.S | 5 +- arch/s390/kernel/swsusp.S | 10 +- arch/s390/lib/mem.S | 9 +- arch/s390/net/bpf_jit.S | 16 ++- arch/s390/net/bpf_jit_comp.c | 63 ++++++++++- 15 files changed, 480 insertions(+), 138 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
[ 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 */
[ 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 | 125 ++++++++++++++++++++++++++++++++++++ arch/s390/kernel/entry.S | 105 +++++++----------------------- 2 files changed, 149 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..fcb6529de9b7 --- /dev/null +++ b/arch/s390/include/asm/nospec-insn.h @@ -0,0 +1,125 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_S390_NOSPEC_ASM_H +#define _ASM_S390_NOSPEC_ASM_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 c63730326215..5416d5d68308 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -23,6 +23,7 @@ #include <asm/vx-insn.h> #include <asm/setup.h> #include <asm/nmi.h> +#include <asm/nospec-insn.h>
__PT_R0 = __PT_GPRS __PT_R1 = __PT_GPRS + 8 @@ -225,74 +226,16 @@ _PIF_WORK = (_PIF_PER_TRAP) .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"
ENTRY(__bpon) .globl __bpon BPON - BR_R1USE_R14 + BR_EX %r14
/* * Scheduler resume function, called by switch_to @@ -322,7 +265,7 @@ 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:
@@ -388,7 +331,7 @@ 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 @@ -445,7 +388,7 @@ 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: @@ -585,7 +528,7 @@ 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 @@ -609,7 +552,7 @@ 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
/* @@ -685,7 +628,7 @@ 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 ? @@ -962,7 +905,7 @@ ENTRY(psw_idle) stpt __TIMER_IDLE_ENTER(%r2) .Lpsw_idle_lpsw: lpswe __SF_EMPTY(%r15) - BR_R1USE_R14 + BR_EX %r14 .Lpsw_idle_end:
/* @@ -1007,7 +950,7 @@ 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:
/* @@ -1054,7 +997,7 @@ 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: @@ -1227,7 +1170,7 @@ 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: @@ -1257,7 +1200,7 @@ 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: @@ -1315,7 +1258,7 @@ 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 @@ -1325,7 +1268,7 @@ 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 @@ -1342,14 +1285,14 @@ 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 @@ -1363,7 +1306,7 @@ 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 @@ -1415,17 +1358,17 @@ 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
[ 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 | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/s390/lib/mem.S b/arch/s390/lib/mem.S index c6d553e85ab1..16c5998b9792 100644 --- a/arch/s390/lib/mem.S +++ b/arch/s390/lib/mem.S @@ -5,6 +5,9 @@ */
#include <linux/linkage.h> +#include <asm/nospec-insn.h> + + GEN_BR_THUNK %r14
/* * memset implementation @@ -38,7 +41,7 @@ ENTRY(memset) .Lmemset_clear_rest: larl %r3,.Lmemset_xc ex %r4,0(%r3) - br %r14 + BR_EX %r14 .Lmemset_fill: stc %r3,0(%r2) cghi %r4,1 @@ -55,7 +58,7 @@ ENTRY(memset) .Lmemset_fill_rest: larl %r3,.Lmemset_mvc ex %r4,0(%r3) - br %r14 + BR_EX %r14 .Lmemset_xc: xc 0(1,%r1),0(%r1) .Lmemset_mvc: @@ -77,7 +80,7 @@ ENTRY(memcpy) .Lmemcpy_rest: 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)
[ 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 | 11 +++++++++++ arch/s390/kernel/asm-offsets.c | 1 + arch/s390/kernel/mcount.S | 14 +++++++++----- 3 files changed, 21 insertions(+), 5 deletions(-)
diff --git a/arch/s390/include/asm/nospec-insn.h b/arch/s390/include/asm/nospec-insn.h index fcb6529de9b7..b54d5b57cdf6 100644 --- a/arch/s390/include/asm/nospec-insn.h +++ b/arch/s390/include/asm/nospec-insn.h @@ -2,6 +2,9 @@ #ifndef _ASM_S390_NOSPEC_ASM_H #define _ASM_S390_NOSPEC_ASM_H
+#include <asm/alternative-asm.h> +#include <asm/asm-offsets.h> + #ifdef __ASSEMBLY__
#ifdef CONFIG_EXPOLINE @@ -76,13 +79,21 @@ .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 dc6c9c604543..39572281e213 100644 --- a/arch/s390/kernel/asm-offsets.c +++ b/arch/s390/kernel/asm-offsets.c @@ -170,6 +170,7 @@ int main(void) OFFSET(__LC_MACHINE_FLAGS, _lowcore, machine_flags); OFFSET(__LC_GMAP, _lowcore, gmap); OFFSET(__LC_PASTE, _lowcore, paste); + 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 e499370fbccb..6c1c7d399bf9 100644 --- a/arch/s390/kernel/mcount.S +++ b/arch/s390/kernel/mcount.S @@ -8,12 +8,16 @@ #include <linux/linkage.h> #include <asm/asm-offsets.h> #include <asm/ftrace.h> +#include <asm/nospec-insn.h> #include <asm/ptrace.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) @@ -21,7 +25,7 @@ ENTRY(ftrace_stub) #define STACK_PTREGS_PSW (STACK_PTREGS + __PT_PSW)
ENTRY(_mcount) - br %r14 + BR_EX %r14
ENTRY(ftrace_caller) .globl ftrace_regs_caller @@ -49,7 +53,7 @@ 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. @@ -64,7 +68,7 @@ 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
@@ -77,6 +81,6 @@ ENTRY(return_to_handler) aghi %r15,STACK_FRAME_OVERHEAD lgr %r14,%r2 lmg %r2,%r5,32(%r15) - br %r14 + BR_EX %r14
#endif
On Wed, May 23, 2018 at 06:21:31PM +0200, Martin Schwidefsky wrote:
[ 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 | 11 +++++++++++ arch/s390/kernel/asm-offsets.c | 1 + arch/s390/kernel/mcount.S | 14 +++++++++----- 3 files changed, 21 insertions(+), 5 deletions(-)
This patch breaks the build for 'allmodconfig' for s390, but defconfig works fine :(
The error is: LD init/built-in.o arch/s390/built-in.o: In function `__s390x_indirect_jump_r1use_r1': (.text.__s390x_indirect_jump_r1use_r1[__s390x_indirect_jump_r1use_r1]+0x2): undefined reference to `_LC_BR_R1' make: *** [Makefile:956: vmlinux] Error 1
So I'm going to drop this patch, and the rest in the series, from the 4.4.y tree. Can you please fix this up and resend the needed patches after I do the next 4.4.y kernel release?
thanks,
greg k-h
On Fri, May 25, 2018 at 03:54:20PM +0200, Greg KH wrote:
On Wed, May 23, 2018 at 06:21:31PM +0200, Martin Schwidefsky wrote:
[ 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 | 11 +++++++++++ arch/s390/kernel/asm-offsets.c | 1 + arch/s390/kernel/mcount.S | 14 +++++++++----- 3 files changed, 21 insertions(+), 5 deletions(-)
This patch breaks the build for 'allmodconfig' for s390, but defconfig works fine :(
The error is: LD init/built-in.o arch/s390/built-in.o: In function `__s390x_indirect_jump_r1use_r1': (.text.__s390x_indirect_jump_r1use_r1[__s390x_indirect_jump_r1use_r1]+0x2): undefined reference to `_LC_BR_R1' make: *** [Makefile:956: vmlinux] Error 1
So I'm going to drop this patch, and the rest in the series, from the 4.4.y tree. Can you please fix this up and resend the needed patches after I do the next 4.4.y kernel release?
Hm, it looks like everything at least boots with just this one patch removed, so I've done that. I have no idea if it boots, I'll leave that to people who have access to those types of boxes :)
thanks,
greg k-h
On Fri, 25 May 2018 16:09:13 +0200 Greg KH greg@kroah.com wrote:
On Fri, May 25, 2018 at 03:54:20PM +0200, Greg KH wrote:
On Wed, May 23, 2018 at 06:21:31PM +0200, Martin Schwidefsky wrote:
[ 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 | 11 +++++++++++ arch/s390/kernel/asm-offsets.c | 1 + arch/s390/kernel/mcount.S | 14 +++++++++----- 3 files changed, 21 insertions(+), 5 deletions(-)
This patch breaks the build for 'allmodconfig' for s390, but defconfig works fine :(
The error is: LD init/built-in.o arch/s390/built-in.o: In function `__s390x_indirect_jump_r1use_r1': (.text.__s390x_indirect_jump_r1use_r1[__s390x_indirect_jump_r1use_r1]+0x2): undefined reference to `_LC_BR_R1' make: *** [Makefile:956: vmlinux] Error 1
So I'm going to drop this patch, and the rest in the series, from the 4.4.y tree. Can you please fix this up and resend the needed patches after I do the next 4.4.y kernel release?
Hm, it looks like everything at least boots with just this one patch removed, so I've done that. I have no idea if it boots, I'll leave that to people who have access to those types of boxes :)
Uh-oh, yes. The reason is that the backport for 4.4 misses two lines from nospec-insn.h:
+_LC_BR_R1 = __LC_BR_R1 +
The compile only fails for CONFIG_MARCH_Z900=y. With a newer processor type it compiles just fine, I wonder why. Anyway I'll send a new patch.
[ 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 | 5 ++++- arch/s390/kernel/swsusp.S | 10 ++++++---- 3 files changed, 24 insertions(+), 15 deletions(-)
diff --git a/arch/s390/kernel/base.S b/arch/s390/kernel/base.S index 326f717df587..61fca549a93b 100644 --- a/arch/s390/kernel/base.S +++ b/arch/s390/kernel/base.S @@ -8,18 +8,22 @@
#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 @@ -36,10 +40,10 @@ 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 @@ -56,10 +60,10 @@ 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) @@ -116,7 +120,7 @@ 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 52aab0bd84f8..6b1b91c17b40 100644 --- a/arch/s390/kernel/reipl.S +++ b/arch/s390/kernel/reipl.S @@ -6,8 +6,11 @@
#include <linux/linkage.h> #include <asm/asm-offsets.h> +#include <asm/nospec-insn.h> #include <asm/sigp.h>
+ GEN_BR_THUNK %r14 + # # store_status # @@ -62,7 +65,7 @@ ENTRY(store_status) st %r3,__LC_PSW_SAVE_AREA-SAVE_AREA_BASE + 4(%r1) larl %r2,store_status stg %r2,__LC_PSW_SAVE_AREA-SAVE_AREA_BASE + 8(%r1) - br %r14 + BR_EX %r14
.section .bss .align 8 diff --git a/arch/s390/kernel/swsusp.S b/arch/s390/kernel/swsusp.S index 2d6b6e81f812..60a829c77378 100644 --- a/arch/s390/kernel/swsusp.S +++ b/arch/s390/kernel/swsusp.S @@ -12,6 +12,7 @@ #include <asm/ptrace.h> #include <asm/thread_info.h> #include <asm/asm-offsets.h> +#include <asm/nospec-insn.h> #include <asm/sigp.h>
/* @@ -23,6 +24,8 @@ * (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) @@ -102,7 +105,7 @@ 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. @@ -196,11 +199,10 @@ pgm_check_entry: larl %r15,init_thread_union ahi %r15,1<<(PAGE_SHIFT+THREAD_ORDER) larl %r2,.Lpanic_string - larl %r3,_sclp_print_early lghi %r1,0 sam31 sigp %r1,%r0,SIGP_SET_ARCHITECTURE - basr %r14,%r3 + brasl %r14,_sclp_print_early larl %r3,.Ldisabled_wait_31 lpsw 0(%r3) 4: @@ -266,7 +268,7 @@ 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
[ 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 8ccfbf22ecbb..c4d4d4ef5e58 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -49,6 +49,7 @@ 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) += s390_ksyms.o module.o diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 9f3b5b382743..060ec24ad0c4 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -44,24 +44,6 @@ 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"); +}
[ Upstream commit 9f18fff63cfd6f559daa1eaae60640372c65f84b ]
The inline assembly to call __do_softirq on the irq stack uses an indirect branch. This can be replaced with a normal relative branch.
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/irq.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c index f41d5208aaf7..590e9394b4dd 100644 --- a/arch/s390/kernel/irq.c +++ b/arch/s390/kernel/irq.c @@ -173,10 +173,9 @@ void do_softirq_own_stack(void) new -= STACK_FRAME_OVERHEAD; ((struct stack_frame *) new)->back_chain = old; asm volatile(" la 15,0(%0)\n" - " basr 14,%2\n" + " brasl 14,__do_softirq\n" " la 15,0(%1)\n" - : : "a" (new), "a" (old), - "a" (__do_softirq) + : : "a" (new), "a" (old) : "0", "1", "2", "3", "4", "5", "14", "cc", "memory" ); } else {
[ 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 b54d5b57cdf6..777cab993c93 100644 --- a/arch/s390/include/asm/nospec-insn.h +++ b/arch/s390/include/asm/nospec-insn.h @@ -32,10 +32,18 @@ __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 @@ -78,6 +86,23 @@ .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 @@ -98,17 +123,42 @@ 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 @@ -120,10 +170,17 @@
#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 060ec24ad0c4..d5eed651b5ab 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -94,7 +94,6 @@ 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) @@ -115,18 +114,34 @@ 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; }
[ 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 a1c917d881ec..fa716f2a95a7 100644 --- a/arch/s390/net/bpf_jit.S +++ b/arch/s390/net/bpf_jit.S @@ -8,6 +8,7 @@ */
#include <linux/linkage.h> +#include <asm/nospec-insn.h> #include "bpf_jit.h"
/* @@ -53,7 +54,7 @@ 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 */ \ @@ -63,11 +64,14 @@ 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) */ @@ -79,7 +83,7 @@ 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 @@ -89,7 +93,7 @@ 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:; \ @@ -103,7 +107,7 @@ 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) @@ -112,4 +116,4 @@ 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 1395eeb6005f..a26528afceb2 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -24,6 +24,8 @@ #include <linux/bpf.h> #include <asm/cacheflush.h> #include <asm/dis.h> +#include <asm/facility.h> +#include <asm/nospec-branch.h> #include "bpf_jit.h"
int bpf_jit_enable __read_mostly; @@ -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 */ }; @@ -248,6 +252,19 @@ 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); \ @@ -475,8 +492,45 @@ static void bpf_jit_epilogue(struct bpf_jit *jit) EMIT4(0xb9040000, REG_2, BPF_REG_0); /* Restore registers */ save_restore_regs(jit, REGS_RESTORE); + 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); + } + } }
/* @@ -980,8 +1034,13 @@ 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 (bpf_helper_changes_skb_data((void *)func)) {
On Wed, May 23, 2018 at 06:21:27PM +0200, Martin Schwidefsky wrote:
Hi Greg,
9 more patches against the 2018/05/23 linux-4.4.y stable branch. This gets the spectre defense of 4.4 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
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Martin Schwidefsky