The following commit has been merged into the x86/core branch of tip: Commit-ID: f9a08abb06d0abe51295479118f1f8e4a4325798 Gitweb: https://git.kernel.org/tip/f9a08abb06d0abe51295479118f1f8e4a4325798 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Tue, 08 Mar 2022 16:30:36 +01:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 08 Mar 2022 23:53:33 +01:00 x86/ibt,kexec: Disable CET on kexec Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220308154318.641454603@xxxxxxxxxxxxx --- arch/x86/include/asm/cpu.h | 3 +++ arch/x86/kernel/cpu/common.c | 6 ++++++ arch/x86/kernel/machine_kexec_64.c | 4 +++- arch/x86/kernel/relocate_kernel_64.S | 8 ++++++++ 4 files changed, 20 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index a60025f..86e5e4e 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -73,4 +73,7 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c); #else static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {} #endif + +extern __noendbr void cet_disable(void); + #endif /* _ASM_X86_CPU_H */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index db1f149..709acab 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -535,6 +535,12 @@ static __always_inline void setup_cet(struct cpuinfo_x86 *c) } } +__noendbr void cet_disable(void) +{ + if (cpu_feature_enabled(X86_FEATURE_IBT)) + wrmsrl(MSR_IA32_S_CET, 0); +} + /* * Some CPU features depend on higher CPUID levels, which may not always * be available due to CPUID level capping or broken virtualization diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index f5da4a1..566bb8e 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -27,6 +27,7 @@ #include <asm/kexec-bzimage64.h> #include <asm/setup.h> #include <asm/set_memory.h> +#include <asm/cpu.h> #ifdef CONFIG_ACPI /* @@ -310,6 +311,7 @@ void machine_kexec(struct kimage *image) /* Interrupts aren't acceptable while we reboot */ local_irq_disable(); hw_breakpoint_disable(); + cet_disable(); if (image->preserve_context) { #ifdef CONFIG_X86_IO_APIC @@ -325,7 +327,7 @@ void machine_kexec(struct kimage *image) } control_page = page_address(image->control_code_page) + PAGE_SIZE; - memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE); + __memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE); page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page); page_list[VA_CONTROL_PAGE] = (unsigned long)control_page; diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 399f075..5b65f6e 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -115,6 +115,14 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) pushq %rdx /* + * Clear X86_CR4_CET (if it was set) such that we can clear CR0_WP + * below. + */ + movq %cr4, %rax + andq $~(X86_CR4_CET), %rax + movq %rax, %cr4 + + /* * Set cr0 to a known state: * - Paging enabled * - Alignment check disabled
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