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[PATCH] ARM: probes: Don't stop the machine if we're in the debugger

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If we're in kgdb then the machine is already stopped.  Trying to stop
it again will cause us to try to sleep, which is not allowed while in
kgdb.  To avoid this problem, only stop the machine when we're not in
kgdb.

Reported-by: Aapo Vienamo <avienamo@nvidia.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
 arch/arm/kernel/patch.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
index 69bda1a..abf30ec 100644
--- a/arch/arm/kernel/patch.c
+++ b/arch/arm/kernel/patch.c
@@ -1,5 +1,6 @@
 #include <linux/kernel.h>
 #include <linux/spinlock.h>
+#include <linux/kgdb.h>
 #include <linux/kprobes.h>
 #include <linux/mm.h>
 #include <linux/stop_machine.h>
@@ -124,6 +125,9 @@ void __kprobes patch_text(void *addr, unsigned int insn)
 		.insn = insn,
 	};
 
-	stop_machine(patch_text_stop_machine, &patch, NULL);
+	/* Stop machine before patching; but not if in the debugger */
+	if (unlikely(in_dbg_master()))
+		patch_text_stop_machine(&patch);
+	else
+		stop_machine(patch_text_stop_machine, &patch, NULL);
 }
-- 
2.5.0.457.gab17608

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[PATCH] ARM: probes: Don't stop the machine if we're in the debugger Douglas Anderson <dianders@chromium.org> - 2015-08-25 02:00 +0200
  Re: [PATCH] ARM: probes: Don't stop the machine if we're in the debugger Stephen Boyd <sboyd@codeaurora.org> - 2015-08-25 02:20 +0200
    Re: [PATCH] ARM: probes: Don't stop the machine if we're in the debugger Kees Cook <keescook@chromium.org> - 2015-08-25 19:00 +0200
      Re: [PATCH] ARM: probes: Don't stop the machine if we're in the debugger Doug Anderson <dianders@chromium.org> - 2015-08-25 21:50 +0200
    Re: [PATCH] ARM: probes: Don't stop the machine if we're in the debugger Doug Anderson <dianders@chromium.org> - 2015-08-26 00:10 +0200

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