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[PATCH] OProfile: fixed x86_64 incorrect kernel call graphs

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Fix the problem in kernel 2.6.15.1 (and early versions) that OProfile on
x86_64 does not correctly collect the stack traces for kernel functions.

The original code in valid_kernel_stack() in arch/i386/oprofile/backtrace.c
assumes that the frame pointer (headaddr) should be greater than stack
(i.e., regs).

This assumption is wrong for x86_64 because NMIs in x86_64 use a seperate
stack different from the kernel stack.  Therefore, the variable stack now
points to some location on the NMI stack, which turns out to be at a higher
address than the frame pointer (headaddr) on the kernel stack.  The correct
comparison here should be between headaddr and regs->rsp for x86_64.

Signed-off-by: Tong Li <tong.n.li@intel.com>
Cc: John Levon <levon@movementarian.org>
Cc: Philippe Elie <phil.el@wanadoo.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Tong Li 2006-02-03 03:04:09 -08:00 committed by Linus Torvalds
parent 8145916996
commit 23332c2e9d
1 changed files with 17 additions and 2 deletions
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19
arch/i386/oprofile/backtrace.c
View file

@ -49,7 +49,9 @@ dump_backtrace(struct frame_head * head)
* | stack |
* --------------- saved regs->ebp value if valid (frame_head address)
* . .
* --------------- struct pt_regs stored on stack (struct pt_regs *)
* --------------- saved regs->rsp value if x86_64
* | |
* --------------- struct pt_regs * stored on stack if 32-bit
* | |
* . .
* | |
@ -57,13 +59,26 @@ dump_backtrace(struct frame_head * head)
* | |
* | | \/ Lower addresses
*
* Thus, &pt_regs <-> stack base restricts the valid(ish) ebp values
* Thus, regs (or regs->rsp for x86_64) <-> stack base restricts the
* valid(ish) ebp values. Note: (1) for x86_64, NMI and several other
* exceptions use special stacks, maintained by the interrupt stack table
* (IST). These stacks are set up in trap_init() in
* arch/x86_64/kernel/traps.c. Thus, for x86_64, regs now does not point
* to the kernel stack; instead, it points to some location on the NMI
* stack. On the other hand, regs->rsp is the stack pointer saved when the
* NMI occurred. (2) For 32-bit, regs->esp is not valid because the
* processor does not save %esp on the kernel stack when interrupts occur
* in the kernel mode.
*/
#ifdef CONFIG_FRAME_POINTER
static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
{
unsigned long headaddr = (unsigned long)head;
#ifdef CONFIG_X86_64
unsigned long stack = (unsigned long)regs->rsp;
#else
unsigned long stack = (unsigned long)regs;
#endif
unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
return headaddr > stack && headaddr < stack_base;