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Subject[PATCH] oprofile, x86: allow backtrace for 32bit apps under 64bit kernel
Date
hi,

adding support for backtrace of ia32 applications under 64bit kernels.

wbr,
jirka



Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Tom Marshall <tdm.rhbz@gmail.com>
---
arch/x86/oprofile/backtrace.c | 42 +++++++++++++++++++++++++++++++++++++++++
1 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
index 3855096..3e443ad 100644
--- a/arch/x86/oprofile/backtrace.c
+++ b/arch/x86/oprofile/backtrace.c
@@ -73,6 +73,38 @@ static struct frame_head *dump_user_backtrace(struct frame_head *head)
return bufhead[0].bp;
}

+#ifdef CONFIG_X86_64
+struct frame_head_32 {
+ __u32 ebp;
+ __u32 ret;
+} __attribute__((packed));
+
+static struct frame_head *
+dump_user_backtrace_32(struct frame_head *head)
+{
+ struct frame_head_32 bufhead_32[2];
+ unsigned long bp, ret;
+
+ /* Also check accessibility of one struct frame_head beyond */
+ if (!access_ok(VERIFY_READ, head, sizeof(bufhead_32)))
+ return NULL;
+ if (__copy_from_user_inatomic(bufhead_32, head, sizeof(bufhead_32)))
+ return NULL;
+
+ bp = bufhead_32[0].ebp;
+ ret = bufhead_32[0].ret;
+
+ oprofile_add_trace(ret);
+
+ /* frame pointers should strictly progress back up the stack
+ * (towards higher addresses) */
+ if (head >= (struct frame_head *) bp)
+ return NULL;
+
+ return (struct frame_head *) bp;
+}
+#endif
+
void
x86_backtrace(struct pt_regs * const regs, unsigned int depth)
{
@@ -86,6 +118,16 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth)
return;
}

+#ifdef CONFIG_X86_64
+ if (current && test_thread_flag(TIF_IA32)) {
+ /* User process is 32-bit */
+ head = (struct frame_head *)(regs->bp & 0xffffffff);
+ while (depth-- && head)
+ head = dump_user_backtrace_32(head);
+ return;
+ }
+#endif
+
while (depth-- && head)
head = dump_user_backtrace(head);
}
--
1.7.1


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