Patchwork [3.5.yuz,extended,stable] Patch "mips, kgdb: fix recursive page fault with CONFIG_KPROBES" has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Nov. 15, 2012, 5:50 a.m.
Message ID <>
Download mbox | patch
Permalink /patch/199184/
State New
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Herton Ronaldo Krzesinski - Nov. 15, 2012, 5:50 a.m.
This is a note to let you know that I have just added a patch titled

    mips,kgdb: fix recursive page fault with CONFIG_KPROBES

to the linux-3.5.y-queue branch of the 3.5.yuz extended stable tree 
which can be found at:;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.yuz tree, see



From eb7ed4610e1414991c1225c0c497476fd1140487 Mon Sep 17 00:00:00 2001
From: Jason Wessel <>
Date: Fri, 10 Aug 2012 12:21:15 -0500
Subject: [PATCH] mips,kgdb: fix recursive page fault with CONFIG_KPROBES

commit f0a996eeeda214f4293e234df33b29bec003b536 upstream.

This fault was detected using the kgdb test suite on boot and it
crashes recursively due to the fact that CONFIG_KPROBES on mips adds
an extra die notifier in the page fault handler.  The crash signature
looks like this:

kgdbts:RUN bad memory access test
KGDB: re-enter exception: ALL breakpoints killed
Call Trace:
[<807b7548>] dump_stack+0x20/0x54
[<807b7548>] dump_stack+0x20/0x54

The fix for now is to have kgdb return immediately if the fault type
is DIE_PAGE_FAULT and allow the kprobe code to decide what is supposed
to happen.

Cc: Masami Hiramatsu <>
Cc: David S. Miller <>
Signed-off-by: Jason Wessel <>
Signed-off-by: Herton Ronaldo Krzesinski <>
 arch/mips/kernel/kgdb.c |    9 +++++++++
 1 file changed, 9 insertions(+)



diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
index f4546e9..23817a6 100644
--- a/arch/mips/kernel/kgdb.c
+++ b/arch/mips/kernel/kgdb.c
@@ -283,6 +283,15 @@  static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd,
 	struct pt_regs *regs = args->regs;
 	int trap = (regs->cp0_cause & 0x7c) >> 2;

+	/*
+	 * Return immediately if the kprobes fault notifier has set
+	 */
+	if (cmd == DIE_PAGE_FAULT)
+		return NOTIFY_DONE;
+#endif /* CONFIG_KPROBES */
 	/* Userspace events, ignore. */
 	if (user_mode(regs))
 		return NOTIFY_DONE;