Mailing List Archive

Fix x86 oprofile regression introduced by:
commit c34d1b4d165c67b966bca4aba026443d7ff161eb
[PATCH] mm: kill check_user_page_readable

That commit reorganized tests for the userspace stack walking moving all
those tests into dump_backtrace(), however, dump_backtrace() was used for
both userspace and kernel stalk walking. The result is typically no
recorded callgraph information for kernel samples.

Revive the original function as dump_kernel_backtrace() and rename the
other to dump_user_backtrace() to avoid future confusion.

Signed-off-by: Gerald Britton <gbritton@alum.mit.edu>
---
backtrace.c | 19 ++++++++++++++++---
1 files changed, 16 insertions(+), 3 deletions(-)
--- a/arch/i386/oprofile/backtrace.c 2006-02-13 19:27:40.000000000 -0500
+++ b/arch/i386/oprofile/backtrace.c 2006-02-13 19:30:32.000000000 -0500
@@ -20,7 +20,20 @@ struct frame_head {
} __attribute__((packed));

static struct frame_head *
-dump_backtrace(struct frame_head * head)
+dump_kernel_backtrace(struct frame_head * head)
+{
+ oprofile_add_trace(head->ret);
+
+ /* frame pointers should strictly progress back up the stack
+ * (towards higher addresses) */
+ if (head >= head->ebp)
+ return NULL;
+
+ return head->ebp;
+}
+
+static struct frame_head *
+dump_user_backtrace(struct frame_head * head)
{
struct frame_head bufhead[2];

@@ -105,10 +118,10 @@ x86_backtrace(struct pt_regs * const reg

if (!user_mode_vm(regs)) {
while (depth-- && valid_kernel_stack(head, regs))
- head = dump_backtrace(head);
+ head = dump_kernel_backtrace(head);
return;
}

while (depth-- && head)
- head = dump_backtrace(head);
+ head = dump_user_backtrace(head);
}
-
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