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| author |  Peter Zijlstra <peterz@infradead.org>
| 2022-03-08 16:30:38 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org>
| 2022-03-15 10:32:40 +0100 |
| commit | fe379fa4d199abc52d5b4a256e52cf94eff685cf (patch) | |
| tree | 4466b0d16bc23c3b36f574ef17113bb3cbcfd497 /arch/x86/kernel | |
| parent | x86/alternative: Simplify int3_selftest_ip (diff) | |
| download | linux-fe379fa4d199abc52d5b4a256e52cf94eff685cf.tar.gz linux-fe379fa4d199abc52d5b4a256e52cf94eff685cf.tar.bz2 linux-fe379fa4d199abc52d5b4a256e52cf94eff685cf.zip | |
x86/ibt: Disable IBT around firmware
Assume firmware isn't IBT clean and disable it across calls.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154318.759989383@infradead.org
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/apm_32.c | 7 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 28 |
2 files changed, 35 insertions, 0 deletions
diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c index 241dda687eb9..60e330cdbd17 100644 --- a/arch/x86/kernel/apm_32.c +++ b/arch/x86/kernel/apm_32.c @@ -232,6 +232,7 @@ #include <asm/paravirt.h> #include <asm/reboot.h> #include <asm/nospec-branch.h> +#include <asm/ibt.h> #if defined(CONFIG_APM_DISPLAY_BLANK) && defined(CONFIG_VT) extern int (*console_blank_hook)(int); @@ -598,6 +599,7 @@ static long __apm_bios_call(void *_call) struct desc_struct save_desc_40; struct desc_struct *gdt; struct apm_bios_call *call = _call; + u64 ibt; cpu = get_cpu(); BUG_ON(cpu != 0); @@ -607,11 +609,13 @@ static long __apm_bios_call(void *_call) apm_irq_save(flags); firmware_restrict_branch_speculation_start(); + ibt = ibt_save(); APM_DO_SAVE_SEGS; apm_bios_call_asm(call->func, call->ebx, call->ecx, &call->eax, &call->ebx, &call->ecx, &call->edx, &call->esi); APM_DO_RESTORE_SEGS; + ibt_restore(ibt); firmware_restrict_branch_speculation_end(); apm_irq_restore(flags); gdt[0x40 / 8] = save_desc_40; @@ -676,6 +680,7 @@ static long __apm_bios_call_simple(void *_call) struct desc_struct save_desc_40; struct desc_struct *gdt; struct apm_bios_call *call = _call; + u64 ibt; cpu = get_cpu(); BUG_ON(cpu != 0); @@ -685,10 +690,12 @@ static long __apm_bios_call_simple(void *_call) apm_irq_save(flags); firmware_restrict_branch_speculation_start(); + ibt = ibt_save(); APM_DO_SAVE_SEGS; error = apm_bios_call_simple_asm(call->func, call->ebx, call->ecx, &call->eax); APM_DO_RESTORE_SEGS; + ibt_restore(ibt); firmware_restrict_branch_speculation_end(); apm_irq_restore(flags); gdt[0x40 / 8] = save_desc_40; diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 709acab25f3c..03bd73f16d74 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -517,6 +517,34 @@ static __init int setup_disable_pku(char *arg) __setup("nopku", setup_disable_pku); #endif /* CONFIG_X86_64 */ +#ifdef CONFIG_X86_KERNEL_IBT + +__noendbr u64 ibt_save(void) +{ + u64 msr = 0; + + if (cpu_feature_enabled(X86_FEATURE_IBT)) { + rdmsrl(MSR_IA32_S_CET, msr); + wrmsrl(MSR_IA32_S_CET, msr & ~CET_ENDBR_EN); + } + + return msr; +} + +__noendbr void ibt_restore(u64 save) +{ + u64 msr; + + if (cpu_feature_enabled(X86_FEATURE_IBT)) { + rdmsrl(MSR_IA32_S_CET, msr); + msr &= ~CET_ENDBR_EN; + msr |= (save & CET_ENDBR_EN); + wrmsrl(MSR_IA32_S_CET, msr); + } +} + +#endif + static __always_inline void setup_cet(struct cpuinfo_x86 *c) { u64 msr = CET_ENDBR_EN; |