diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index 9af927e59d49745757dd1bf07ad148df0db5a006..9de7f1e1dede7f6e6ebdc66e5f63756a173cdc0a 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -84,13 +84,13 @@ ENTRY(entry_SYSENTER_compat) pushq %rdx /* pt_regs->dx */ pushq %rcx /* pt_regs->cx */ pushq $-ENOSYS /* pt_regs->ax */ - pushq $0 /* pt_regs->r8 = 0 */ + pushq %r8 /* pt_regs->r8 */ xorl %r8d, %r8d /* nospec r8 */ - pushq $0 /* pt_regs->r9 = 0 */ + pushq %r9 /* pt_regs->r9 */ xorl %r9d, %r9d /* nospec r9 */ - pushq $0 /* pt_regs->r10 = 0 */ + pushq %r10 /* pt_regs->r10 */ xorl %r10d, %r10d /* nospec r10 */ - pushq $0 /* pt_regs->r11 = 0 */ + pushq %r11 /* pt_regs->r11 */ xorl %r11d, %r11d /* nospec r11 */ pushq %rbx /* pt_regs->rbx */ xorl %ebx, %ebx /* nospec rbx */ diff --git a/tools/testing/selftests/x86/test_syscall_vdso.c b/tools/testing/selftests/x86/test_syscall_vdso.c index 40370354d4c11e48f9404eccfbda1b5bf03cd682..c9c3281077bca413b9164547c9a3da9a2a061103 100644 --- a/tools/testing/selftests/x86/test_syscall_vdso.c +++ b/tools/testing/selftests/x86/test_syscall_vdso.c @@ -100,12 +100,19 @@ asm ( " shl $32, %r8\n" " orq $0x7f7f7f7f, %r8\n" " movq %r8, %r9\n" - " movq %r8, %r10\n" - " movq %r8, %r11\n" - " movq %r8, %r12\n" - " movq %r8, %r13\n" - " movq %r8, %r14\n" - " movq %r8, %r15\n" + " incq %r9\n" + " movq %r9, %r10\n" + " incq %r10\n" + " movq %r10, %r11\n" + " incq %r11\n" + " movq %r11, %r12\n" + " incq %r12\n" + " movq %r12, %r13\n" + " incq %r13\n" + " movq %r13, %r14\n" + " incq %r14\n" + " movq %r14, %r15\n" + " incq %r15\n" " ret\n" " .code32\n" " .popsection\n" @@ -128,12 +135,13 @@ int check_regs64(void) int err = 0; int num = 8; uint64_t *r64 = ®s64.r8; + uint64_t expected = 0x7f7f7f7f7f7f7f7fULL; if (!kernel_is_64bit) return 0; do { - if (*r64 == 0x7f7f7f7f7f7f7f7fULL) + if (*r64 == expected++) continue; /* register did not change */ if (syscall_addr != (long)&int80) { /* @@ -147,18 +155,17 @@ int check_regs64(void) continue; } } else { - /* INT80 syscall entrypoint can be used by + /* + * INT80 syscall entrypoint can be used by * 64-bit programs too, unlike SYSCALL/SYSENTER. * Therefore it must preserve R12+ * (they are callee-saved registers in 64-bit C ABI). * - * This was probably historically not intended, - * but R8..11 are clobbered (cleared to 0). - * IOW: they are the only registers which aren't - * preserved across INT80 syscall. + * Starting in Linux 4.17 (and any kernel that + * backports the change), R8..11 are preserved. + * Historically (and probably unintentionally), they + * were clobbered or zeroed. */ - if (*r64 == 0 && num <= 11) - continue; } printf("[FAIL]\tR%d has changed:%016llx\n", num, *r64); err++;