diff options
Diffstat (limited to 'arch/x86/entry')
| -rw-r--r-- | arch/x86/entry/calling.h | 20 | ||||
| -rw-r--r-- | arch/x86/entry/entry_32.S | 33 | ||||
| -rw-r--r-- | arch/x86/entry/entry_64.S | 10 |
3 files changed, 56 insertions, 7 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 38dcdfa2be55..05ed3d393da7 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -192,6 +192,26 @@ For 32-bit we have the following conventions - kernel is built with .byte 0xf1 .endm +/* + * This is a sneaky trick to help the unwinder find pt_regs on the stack. The + * frame pointer is replaced with an encoded pointer to pt_regs. The encoding + * is just setting the LSB, which makes it an invalid stack address and is also + * a signal to the unwinder that it's a pt_regs pointer in disguise. + * + * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts + * the original rbp. + */ +.macro ENCODE_FRAME_POINTER ptregs_offset=0 +#ifdef CONFIG_FRAME_POINTER + .if \ptregs_offset + leaq \ptregs_offset(%rsp), %rbp + .else + mov %rsp, %rbp + .endif + orq $0x1, %rbp +#endif +.endm + #endif /* CONFIG_X86_64 */ /* diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 22251055c5b7..acc0c6f36f3f 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -176,6 +176,22 @@ SET_KERNEL_GS %edx .endm +/* + * This is a sneaky trick to help the unwinder find pt_regs on the stack. The + * frame pointer is replaced with an encoded pointer to pt_regs. The encoding + * is just setting the LSB, which makes it an invalid stack address and is also + * a signal to the unwinder that it's a pt_regs pointer in disguise. + * + * NOTE: This macro must be used *after* SAVE_ALL because it corrupts the + * original rbp. + */ +.macro ENCODE_FRAME_POINTER +#ifdef CONFIG_FRAME_POINTER + mov %esp, %ebp + orl $0x1, %ebp +#endif +.endm + .macro RESTORE_INT_REGS popl %ebx popl %ecx @@ -641,6 +657,7 @@ common_interrupt: ASM_CLAC addl $-0x80, (%esp) /* Adjust vector into the [-256, -1] range */ SAVE_ALL + ENCODE_FRAME_POINTER TRACE_IRQS_OFF movl %esp, %eax call do_IRQ @@ -652,6 +669,7 @@ ENTRY(name) \ ASM_CLAC; \ pushl $~(nr); \ SAVE_ALL; \ + ENCODE_FRAME_POINTER; \ TRACE_IRQS_OFF \ movl %esp, %eax; \ call fn; \ @@ -786,6 +804,7 @@ END(spurious_interrupt_bug) ENTRY(xen_hypervisor_callback) pushl $-1 /* orig_ax = -1 => not a system call */ SAVE_ALL + ENCODE_FRAME_POINTER TRACE_IRQS_OFF /* @@ -840,6 +859,7 @@ ENTRY(xen_failsafe_callback) jmp iret_exc 5: pushl $-1 /* orig_ax = -1 => not a system call */ SAVE_ALL + ENCODE_FRAME_POINTER jmp ret_from_exception .section .fixup, "ax" @@ -1067,6 +1087,7 @@ common_exception: pushl %edx pushl %ecx pushl %ebx + ENCODE_FRAME_POINTER cld movl $(__KERNEL_PERCPU), %ecx movl %ecx, %fs @@ -1099,6 +1120,7 @@ ENTRY(debug) ASM_CLAC pushl $-1 # mark this as an int SAVE_ALL + ENCODE_FRAME_POINTER xorl %edx, %edx # error code 0 movl %esp, %eax # pt_regs pointer @@ -1114,11 +1136,11 @@ ENTRY(debug) .Ldebug_from_sysenter_stack: /* We're on the SYSENTER stack. Switch off. */ - movl %esp, %ebp + movl %esp, %ebx movl PER_CPU_VAR(cpu_current_top_of_stack), %esp TRACE_IRQS_OFF call do_debug - movl %ebp, %esp + movl %ebx, %esp jmp ret_from_exception END(debug) @@ -1141,6 +1163,7 @@ ENTRY(nmi) pushl %eax # pt_regs->orig_ax SAVE_ALL + ENCODE_FRAME_POINTER xorl %edx, %edx # zero error code movl %esp, %eax # pt_regs pointer @@ -1159,10 +1182,10 @@ ENTRY(nmi) * We're on the SYSENTER stack. Switch off. No one (not even debug) * is using the thread stack right now, so it's safe for us to use it. */ - movl %esp, %ebp + movl %esp, %ebx movl PER_CPU_VAR(cpu_current_top_of_stack), %esp call do_nmi - movl %ebp, %esp + movl %ebx, %esp jmp .Lrestore_all_notrace #ifdef CONFIG_X86_ESPFIX32 @@ -1179,6 +1202,7 @@ ENTRY(nmi) .endr pushl %eax SAVE_ALL + ENCODE_FRAME_POINTER FIXUP_ESPFIX_STACK # %eax == %esp xorl %edx, %edx # zero error code call do_nmi @@ -1192,6 +1216,7 @@ ENTRY(int3) ASM_CLAC pushl $-1 # mark this as an int SAVE_ALL + ENCODE_FRAME_POINTER TRACE_IRQS_OFF xorl %edx, %edx # zero error code movl %esp, %eax # pt_regs pointer diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index ef766a358b37..65fad8a63cd0 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -469,6 +469,7 @@ END(irq_entries_start) ALLOC_PT_GPREGS_ON_STACK SAVE_C_REGS SAVE_EXTRA_REGS + ENCODE_FRAME_POINTER testb $3, CS(%rsp) jz 1f @@ -985,6 +986,7 @@ ENTRY(xen_failsafe_callback) ALLOC_PT_GPREGS_ON_STACK SAVE_C_REGS SAVE_EXTRA_REGS + ENCODE_FRAME_POINTER jmp error_exit END(xen_failsafe_callback) @@ -1028,6 +1030,7 @@ ENTRY(paranoid_entry) cld SAVE_C_REGS 8 SAVE_EXTRA_REGS 8 + ENCODE_FRAME_POINTER 8 movl $1, %ebx movl $MSR_GS_BASE, %ecx rdmsr @@ -1075,6 +1078,7 @@ ENTRY(error_entry) cld SAVE_C_REGS 8 SAVE_EXTRA_REGS 8 + ENCODE_FRAME_POINTER 8 xorl %ebx, %ebx testb $3, CS+8(%rsp) jz .Lerror_kernelspace @@ -1257,6 +1261,7 @@ ENTRY(nmi) pushq %r13 /* pt_regs->r13 */ pushq %r14 /* pt_regs->r14 */ pushq %r15 /* pt_regs->r15 */ + ENCODE_FRAME_POINTER /* * At this point we no longer need to worry about stack damage @@ -1270,11 +1275,10 @@ ENTRY(nmi) /* * Return back to user mode. We must *not* do the normal exit - * work, because we don't want to enable interrupts. Fortunately, - * do_nmi doesn't modify pt_regs. + * work, because we don't want to enable interrupts. */ SWAPGS - jmp restore_c_regs_and_iret + jmp restore_regs_and_iret .Lnmi_from_kernel: /* |