Merge tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc

[karo-tx-linux.git] / arch / x86 / entry / entry_32.S

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 50bc26949e9edf75cc5978f8a08a4273bf489aec..48ef7bb32c4269331ceb2332b8e6bf5faffcb3de 100644 (file)
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -251,6 +251,23 @@ ENTRY(__switch_to_asm)
        jmp     __switch_to
 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.
  *
@@ -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 */