On March 6, 2025 1:33:43 PM PST, tip-bot2 for Uros Bizjak <tip-bot2@xxxxxxxxxxxxx> wrote:
>The following commit has been merged into the x86/asm branch of tip:
>
>Commit-ID: aa3942d4d12ef57f031faa2772fe410c24191e36
>Gitweb: https://git.kernel.org/tip/aa3942d4d12ef57f031faa2772fe410c24191e36
>Author: Uros Bizjak <ubizjak@xxxxxxxxx>
>AuthorDate: Thu, 06 Mar 2025 15:52:11 +01:00
>Committer: Ingo Molnar <mingo@xxxxxxxxxx>
>CommitterDate: Thu, 06 Mar 2025 22:04:48 +01:00
>
>x86/kexec: Merge x86_32 and x86_64 code using macros from <asm/asm.h>
>
>Merge common x86_32 and x86_64 code in crash_setup_regs()
>using macros from <asm/asm.h>.
>
>The compiled object files before and after the patch are unchanged.
>
>Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
>Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
>Cc: David Woodhouse <dwmw@xxxxxxxxxxxx>
>Cc: Baoquan He <bhe@xxxxxxxxxx>
>Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
>Cc: Dave Young <dyoung@xxxxxxxxxx>
>Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
>Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
>Link: https://lore.kernel.org/r/20250306145227.55819-1-ubizjak@xxxxxxxxx
>---
> arch/x86/include/asm/kexec.h | 58 +++++++++++++++--------------------
> 1 file changed, 25 insertions(+), 33 deletions(-)
>
>diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
>index 8ad1874..e3589d6 100644
>--- a/arch/x86/include/asm/kexec.h
>+++ b/arch/x86/include/asm/kexec.h
>@@ -18,6 +18,7 @@
> #include <linux/string.h>
> #include <linux/kernel.h>
>
>+#include <asm/asm.h>
> #include <asm/page.h>
> #include <asm/ptrace.h>
>
>@@ -71,41 +72,32 @@ static inline void crash_setup_regs(struct pt_regs *newregs,
> if (oldregs) {
> memcpy(newregs, oldregs, sizeof(*newregs));
> } else {
>+ asm volatile("mov %%" _ASM_BX ",%0" : "=m"(newregs->bx));
>+ asm volatile("mov %%" _ASM_CX ",%0" : "=m"(newregs->cx));
>+ asm volatile("mov %%" _ASM_DX ",%0" : "=m"(newregs->dx));
>+ asm volatile("mov %%" _ASM_SI ",%0" : "=m"(newregs->si));
>+ asm volatile("mov %%" _ASM_DI ",%0" : "=m"(newregs->di));
>+ asm volatile("mov %%" _ASM_BP ",%0" : "=m"(newregs->bp));
>+ asm volatile("mov %%" _ASM_AX ",%0" : "=m"(newregs->ax));
>+ asm volatile("mov %%" _ASM_SP ",%0" : "=m"(newregs->sp));
>+#ifdef CONFIG_X86_64
>+ asm volatile("mov %%r8,%0" : "=m"(newregs->r8));
>+ asm volatile("mov %%r9,%0" : "=m"(newregs->r9));
>+ asm volatile("mov %%r10,%0" : "=m"(newregs->r10));
>+ asm volatile("mov %%r11,%0" : "=m"(newregs->r11));
>+ asm volatile("mov %%r12,%0" : "=m"(newregs->r12));
>+ asm volatile("mov %%r13,%0" : "=m"(newregs->r13));
>+ asm volatile("mov %%r14,%0" : "=m"(newregs->r14));
>+ asm volatile("mov %%r15,%0" : "=m"(newregs->r15));
>+#endif
>+ asm volatile("mov %%ss,%k0" : "=a"(newregs->ss));
>+ asm volatile("mov %%cs,%k0" : "=a"(newregs->cs));
> #ifdef CONFIG_X86_32
>- asm volatile("movl %%ebx,%0" : "=m"(newregs->bx));
>- asm volatile("movl %%ecx,%0" : "=m"(newregs->cx));
>- asm volatile("movl %%edx,%0" : "=m"(newregs->dx));
>- asm volatile("movl %%esi,%0" : "=m"(newregs->si));
>- asm volatile("movl %%edi,%0" : "=m"(newregs->di));
>- asm volatile("movl %%ebp,%0" : "=m"(newregs->bp));
>- asm volatile("movl %%eax,%0" : "=m"(newregs->ax));
>- asm volatile("movl %%esp,%0" : "=m"(newregs->sp));
>- asm volatile("movl %%ss, %%eax;" :"=a"(newregs->ss));
>- asm volatile("movl %%cs, %%eax;" :"=a"(newregs->cs));
>- asm volatile("movl %%ds, %%eax;" :"=a"(newregs->ds));
>- asm volatile("movl %%es, %%eax;" :"=a"(newregs->es));
>- asm volatile("pushfl; popl %0" :"=m"(newregs->flags));
>-#else
>- asm volatile("movq %%rbx,%0" : "=m"(newregs->bx));
>- asm volatile("movq %%rcx,%0" : "=m"(newregs->cx));
>- asm volatile("movq %%rdx,%0" : "=m"(newregs->dx));
>- asm volatile("movq %%rsi,%0" : "=m"(newregs->si));
>- asm volatile("movq %%rdi,%0" : "=m"(newregs->di));
>- asm volatile("movq %%rbp,%0" : "=m"(newregs->bp));
>- asm volatile("movq %%rax,%0" : "=m"(newregs->ax));
>- asm volatile("movq %%rsp,%0" : "=m"(newregs->sp));
>- asm volatile("movq %%r8,%0" : "=m"(newregs->r8));
>- asm volatile("movq %%r9,%0" : "=m"(newregs->r9));
>- asm volatile("movq %%r10,%0" : "=m"(newregs->r10));
>- asm volatile("movq %%r11,%0" : "=m"(newregs->r11));
>- asm volatile("movq %%r12,%0" : "=m"(newregs->r12));
>- asm volatile("movq %%r13,%0" : "=m"(newregs->r13));
>- asm volatile("movq %%r14,%0" : "=m"(newregs->r14));
>- asm volatile("movq %%r15,%0" : "=m"(newregs->r15));
>- asm volatile("movl %%ss, %%eax;" :"=a"(newregs->ss));
>- asm volatile("movl %%cs, %%eax;" :"=a"(newregs->cs));
>- asm volatile("pushfq; popq %0" :"=m"(newregs->flags));
>+ asm volatile("mov %%ds,%k0" : "=a"(newregs->ds));
>+ asm volatile("mov %%es,%k0" : "=a"(newregs->es));
> #endif
>+ asm volatile("pushf\n\t"
>+ "pop %0" : "=m"(newregs->flags));
> newregs->ip = _THIS_IP_;
> }
> }
Incidentally, doing this in C code is obviously completely broken, especially doing it in multiple statements. You have no idea what the compiler has messed with before you get there.
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