Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[sfrench/cifs-2.6.git] / arch / x86 / kernel / unwind_frame.c

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 478d15dbaee41b251c8bb28b59183e2b6c733326..08339262b666e56f2623406a10c42f3184c83e29 100644 (file)
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -82,19 +82,43 @@ static size_t regs_size(struct pt_regs *regs)
        return sizeof(*regs);
 }
 
+#ifdef CONFIG_X86_32
+#define GCC_REALIGN_WORDS 3
+#else
+#define GCC_REALIGN_WORDS 1
+#endif
+
 static bool is_last_task_frame(struct unwind_state *state)
 {
-       unsigned long bp = (unsigned long)state->bp;
-       unsigned long regs = (unsigned long)task_pt_regs(state->task);
+       unsigned long *last_bp = (unsigned long *)task_pt_regs(state->task) - 2;
+       unsigned long *aligned_bp = last_bp - GCC_REALIGN_WORDS;
 
        /*
         * We have to check for the last task frame at two different locations
         * because gcc can occasionally decide to realign the stack pointer and
-        * change the offset of the stack frame by a word in the prologue of a
-        * function called by head/entry code.
+        * change the offset of the stack frame in the prologue of a function
+        * called by head/entry code.  Examples:
+        *
+        * <start_secondary>:
+        *      push   %edi
+        *      lea    0x8(%esp),%edi
+        *      and    $0xfffffff8,%esp
+        *      pushl  -0x4(%edi)
+        *      push   %ebp
+        *      mov    %esp,%ebp
+        *
+        * <x86_64_start_kernel>:
+        *      lea    0x8(%rsp),%r10
+        *      and    $0xfffffffffffffff0,%rsp
+        *      pushq  -0x8(%r10)
+        *      push   %rbp
+        *      mov    %rsp,%rbp
+        *
+        * Note that after aligning the stack, it pushes a duplicate copy of
+        * the return address before pushing the frame pointer.
         */
-       return bp == regs - FRAME_HEADER_SIZE ||
-              bp == regs - FRAME_HEADER_SIZE - sizeof(long);
+       return (state->bp == last_bp ||
+               (state->bp == aligned_bp && *(aligned_bp+1) == *(last_bp+1)));
 }
 
 /*