vdso: print fatal signals

Add the print-fatal-signals=1 boot option and the
/proc/sys/kernel/print-fatal-signals runtime switch.

This feature prints some minimal information about userspace segfaults to
the kernel console.  This is useful to find early bootup bugs where
userspace debugging is very hard.

Defaults to off.

[akpm@linux-foundation.org: Don't add new sysctl numbers]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 182c6a39d5a2..ab38322111c4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1383,6 +1383,12 @@ and is between 256 and 4096 characters. It is defined in the file
                         autoconfiguration.
                         Ranges are in pairs (memory base and size).
 
+        print-fatal-signals=
+                        [KNL] debug: print fatal signals
+                        print-fatal-signals=1: print segfault info to
+                        the kernel console.
+                        default: off.
+
         profile=        [KNL] Enable kernel profiling via /proc/profile
                         Format: [schedule,]<number>
                         Param: "schedule" - profile schedule points.