4.4-stable review patch. If anyone has any objections, please let me know.
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From: Martin Schwidefsky schwidefsky@de.ibm.com
[ 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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(-)
--- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -742,7 +742,7 @@ choice config EXPOLINE_OFF bool "spectre_v2=off"
-config EXPOLINE_MEDIUM +config EXPOLINE_AUTO bool "spectre_v2=auto"
config EXPOLINE_FULL --- a/arch/s390/Makefile +++ b/arch/s390/Makefile @@ -83,7 +83,7 @@ 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
--- 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__ */
--- a/arch/s390/kernel/alternative.c +++ b/arch/s390/kernel/alternative.c @@ -1,6 +1,7 @@ #include <linux/module.h> #include <asm/alternative.h> #include <asm/facility.h> +#include <asm/nospec-branch.h>
#define MAX_PATCH_LEN (255 - 1)
--- a/arch/s390/kernel/module.c +++ b/arch/s390/kernel/module.c @@ -167,7 +167,7 @@ int module_frob_arch_sections(Elf_Ehdr * me->core_size += me->arch.got_size; me->arch.plt_offset = me->core_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_size += me->arch.plt_size; } @@ -326,8 +326,7 @@ static int apply_rela(Elf_Rela *rela, El 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->module_core + me->arch.plt_offset + @@ -448,7 +447,7 @@ 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->module_core + me->arch.plt_offset + @@ -475,11 +474,11 @@ 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); --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -11,10 +11,17 @@ static int __init nobp_setup_early(char 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); @@ -28,31 +35,46 @@ 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); @@ -105,15 +127,9 @@ static void __init_or_module __nospec_re } }
-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); }
@@ -121,8 +137,8 @@ extern s32 __nospec_call_start[], __nosp 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 */