There are multiple ways to write the same code, hence the reason this
is listed as an RFC patch. I wanted to provide a working fix to
account for the case of executing 32 bit and 64 bit user space code on
a 64 bit kernel.
-----CLIP HERE-------
Allow oprofile's backtrace to work on a 32bit user space thread when
running on a 64bit kernel.
Signed-off-by: Jason Wessel <[EMAIL PROTECTED]>
---
arch/x86/oprofile/backtrace.c | 40 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 39 insertions(+), 1 deletion(-)
--- a/arch/x86/oprofile/backtrace.c
+++ b/arch/x86/oprofile/backtrace.c
@@ -52,6 +52,39 @@ struct frame_head {
unsigned long ret;
} __attribute__((packed));
+
+#if defined(CONFIG_X86_64) && defined(CONFIG_IA32_EMULATION)
+struct frame_head32 {
+ unsigned int ebp;
+ unsigned int ret;
+} __attribute__((packed));
+
+static struct frame_head *
+dump_user_backtrace32(struct frame_head * head)
+{
+ struct frame_head32 bufhead[2];
+
+ /* Also check accessibility of one struct frame_head beyond */
+ if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
+ return NULL;
+ if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
+ return NULL;
+ /* In a 32bit user space on a 64bit kernel the frame pointer and
+ * PC are not at the same place as in the 64 registers. This
+ * requires some casting and checks of the 32bit register values
+ * back to 64 pit pointers.
+ */
+ oprofile_add_trace(bufhead[0].ret);
+
+ /* frame pointers should strictly progress back up the stack
+ * (towards higher addresses) */
+ if (head >= (struct frame_head *)((unsigned long)bufhead[0].ebp))
+ return NULL;
+
+ return (struct frame_head *)((unsigned long)bufhead[0].ebp);
+}
+#endif
+
static struct frame_head *
dump_user_backtrace(struct frame_head * head)
{
@@ -85,7 +118,12 @@ x86_backtrace(struct pt_regs * const reg
&backtrace_ops, &depth);
return;
}
-
+#if defined(CONFIG_X86_64) && defined(CONFIG_IA32_EMULATION)
+ if (test_thread_flag(TIF_32BIT))
+ while (depth-- && head)
+ head = dump_user_backtrace32(head);
+ else
+#endif
while (depth-- && head)
head = dump_user_backtrace(head);
}
--
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