diff options
Diffstat (limited to 'arch/x86/entry/entry_32.S')
| -rw-r--r-- | arch/x86/entry/entry_32.S | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 50bc26949e9e..48ef7bb32c42 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -252,6 +252,23 @@ ENTRY(__switch_to_asm) END(__switch_to_asm) /* + * The unwinder expects the last frame on the stack to always be at the same + * offset from the end of the page, which allows it to validate the stack. + * Calling schedule_tail() directly would break that convention because its an + * asmlinkage function so its argument has to be pushed on the stack. This + * wrapper creates a proper "end of stack" frame header before the call. + */ +ENTRY(schedule_tail_wrapper) + FRAME_BEGIN + + pushl %eax + call schedule_tail + popl %eax + + FRAME_END + ret +ENDPROC(schedule_tail_wrapper) +/* * A newly forked process directly context switches into this address. * * eax: prev task we switched from @@ -259,24 +276,15 @@ END(__switch_to_asm) * edi: kernel thread arg */ ENTRY(ret_from_fork) - FRAME_BEGIN /* help unwinder find end of stack */ - - /* - * schedule_tail() is asmlinkage so we have to put its 'prev' argument - * on the stack. - */ - pushl %eax - call schedule_tail - popl %eax + call schedule_tail_wrapper testl %ebx, %ebx jnz 1f /* kernel threads are uncommon */ 2: /* When we fork, we trace the syscall return in the child, too. */ - leal FRAME_OFFSET(%esp), %eax + movl %esp, %eax call syscall_return_slowpath - FRAME_END jmp restore_all /* kernel thread */ |