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Tue, 8 Mar 2022 16:54:39 +0100 (CET) Message-ID: <20220308154318.641454603@infradead.org> User-Agent: quilt/0.66 Date: Tue, 08 Mar 2022 16:30:36 +0100 From: Peter Zijlstra To: x86@kernel.org, joao@overdrivepizza.com, hjl.tools@gmail.com, jpoimboe@redhat.com, andrew.cooper3@citrix.com Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, ndesaulniers@google.com, keescook@chromium.org, samitolvanen@google.com, mark.rutland@arm.com, alyssa.milburn@intel.com, mbenes@suse.cz, rostedt@goodmis.org, mhiramat@kernel.org, alexei.starovoitov@gmail.com Subject: [PATCH v4 25/45] x86/ibt,kexec: Disable CET on kexec References: <20220308153011.021123062@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Peter Zijlstra (Intel) --- 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(-) --- 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_x #else static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {} #endif + +extern __noendbr void cet_disable(void); + #endif /* _ASM_X86_CPU_H */ --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -612,6 +612,12 @@ static __always_inline void setup_cet(st } } +__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 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -27,6 +27,7 @@ #include #include #include +#include #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; --- 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_ma 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