Re: [Crash-utility] backtrace failure on x86_64 and x86 in 2.6.33/34 kernels due to "thread_return" removal
Hi Dave,
Are these issues only for crash tools? or it occurs in kernel func-backtrace too?
And how would you fix it?
Thank you,
Dave Anderson wrote:
----- "Dave Anderson" <anderson(a)redhat.com> wrote:
> I've got a fix for x86_64 -- which have always depended on the existence of
> the "thread_return" label. But I note that x86 backtraces also are not
working,
> which I'll take a look at today.
As it turns out, the x86 backtrace failures in 2.6.33/34 are caused by a different
kprobes-related commit, which moved the system_call assembly function to the
.kprobes.text section:
commit a00e817f42663941ea0aa5f85a9d1c4f8b212839
Author: Masami Hiramatsu <mhiramat(a)redhat.com>
Date: Tue Sep 8 12:47:55 2009 -0400
kprobes/x86-32: Move irq-exit functions to kprobes section
Move irq-exit functions to .kprobes.text section to protect against
kprobes recursion.
When I ran kprobe stress test on x86-32, I found below symbols
cause unrecoverable recursive probing:
ret_from_exception
ret_from_intr
check_userspace
restore_all
restore_all_notrace
restore_nocheck
irq_return
And also, I found some interrupt/exception entry points that
cause similar problems.
This patch moves those symbols (including their container functions)
to .kprobes.text section to prevent any kprobes probing.
Signed-off-by: Masami Hiramatsu <mhiramat(a)redhat.com>
Cc: Frederic Weisbecker <fweisbec(a)gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth(a)in.ibm.com>
Cc: Jim Keniston <jkenisto(a)us.ibm.com>
Cc: Ingo Molnar <mingo(a)elte.hu>
LKML-Reference:
<20090908164755.24050.81182.stgit(a)dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec(a)gmail.com>
... [ snip ] ...
@@ -513,6 +521,10 @@ sysexit_audit:
PTGS_TO_GS_EX
ENDPROC(ia32_sysenter_target)
+/*
+ * syscall stub including irq exit should be protected against kprobes
+ */
+ .pushsection .kprobes.text, "ax"
# system call handler stub
ENTRY(system_call)
RING0_INT_FRAME # can't unwind into user space anyway
@@ -705,6 +717,10 @@ syscall_badsys:
jmp resume_userspace
END(syscall_badsys)
CFI_ENDPROC
+/*
+ * End of kprobes section
+ */
+ .popsection
I should have a fix tomorrow (if that's the only issue)...
Dave
--
Masami Hiramatsu
e-mail: mhiramat(a)redhat.com