Re: [PATCH v4 04/39] x86/cpufeatures: Enable CET CR4 bit for shadow stack
From: Borislav Petkov <bp@alien8.de>
Date: 2022-12-07 12:49:46
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linux-arch, linux-doc, linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
On Fri, Dec 02, 2022 at 04:35:31PM -0800, Rick Edgecombe wrote:
From: Yu-cheng Yu <redacted> Setting CR4.CET is a prerequisite for utilizing any CET features, most of which also require setting MSRs.
...
arch/x86/kernel/cpu/common.c | 37 ++++++++++++++++++++++++++++++------ 1 file changed, 31 insertions(+), 6 deletions(-)
Looks better. Let's get rid of the ifdeffery and simplify it even more. Diff ontop: ---
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 579f10222432..c364f3067121 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c@@ -597,12 +597,14 @@ __noendbr void ibt_restore(u64 save) #endif -#ifdef CONFIG_X86_CET static __always_inline void setup_cet(struct cpuinfo_x86 *c) { - bool kernel_ibt = HAS_KERNEL_IBT && cpu_feature_enabled(X86_FEATURE_IBT); - bool user_shstk; - u64 msr = 0; + bool kernel_ibt, user_shstk; + + if (!IS_ENABLED(CONFIG_X86_CET)) + return; + + kernel_ibt = HAS_KERNEL_IBT && cpu_feature_enabled(X86_FEATURE_IBT); /* * Enable user shadow stack only if the Linux defined user shadow stack
@@ -618,21 +620,18 @@ static __always_inline void setup_cet(struct cpuinfo_x86 *c) set_cpu_cap(c, X86_FEATURE_USER_SHSTK); if (kernel_ibt) - msr = CET_ENDBR_EN; + wrmsrl(MSR_IA32_S_CET, CET_ENDBR_EN); + else + wrmsrl(MSR_IA32_S_CET, 0); - wrmsrl(MSR_IA32_S_CET, msr); cr4_set_bits(X86_CR4_CET); if (kernel_ibt && !ibt_selftest()) { pr_err("IBT selftest: Failed!\n"); wrmsrl(MSR_IA32_S_CET, 0); setup_clear_cpu_cap(X86_FEATURE_IBT); - return; } } -#else /* CONFIG_X86_CET */ -static inline void setup_cet(struct cpuinfo_x86 *c) {} -#endif __noendbr void cet_disable(void) {
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette