Commit:     bb90110dcb9e93bf79e3c988abc6cbcabd46d57f
Parent:     ee78b0a61f0514ffc3d59257fbe6863b43477829
Author:     Kawai, Hidehiro <[EMAIL PROTECTED]>
AuthorDate: Thu Jul 19 01:48:31 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Jul 19 10:04:47 2007 -0700

    coredump masking: documentation for /proc/pid/coredump_filter
    This patch adds the documentation for /proc/<pid>/coredump_filter.
    Signed-off-by: Hidehiro Kawai <[EMAIL PROTECTED]>
    Cc: Alan Cox <[EMAIL PROTECTED]>
    Cc: David Howells <[EMAIL PROTECTED]>
    Cc: Hugh Dickins <[EMAIL PROTECTED]>
    Cc: Nick Piggin <[EMAIL PROTECTED]>
    Cc: "Randy.Dunlap" <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 Documentation/filesystems/proc.txt |   38 ++++++++++++++++++++++++++++++++++++
 1 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/Documentation/filesystems/proc.txt 
index 72e247e..4a37e25 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -42,6 +42,7 @@ Table of Contents
   2.12 /proc/<pid>/oom_adj - Adjust the oom-killer score
   2.13 /proc/<pid>/oom_score - Display current oom-killer score
   2.14 /proc/<pid>/io - Display the IO accounting fields
+  2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
@@ -2184,4 +2185,41 @@ those 64-bit counters, process A could see an 
intermediate result.
 More information about this can be found within the taskstats documentation in
+2.15 /proc/<pid>/coredump_filter - Core dump filtering settings
+When a process is dumped, all anonymous memory is written to a core file as
+long as the size of the core file isn't limited. But sometimes we don't want
+to dump some memory segments, for example, huge shared memory. Conversely,
+sometimes we want to save file-backed memory segments into a core file, not
+only the individual files.
+/proc/<pid>/coredump_filter allows you to customize which memory segments
+will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
+of memory types. If a bit of the bitmask is set, memory segments of the
+corresponding memory type are dumped, otherwise they are not dumped.
+The following 4 memory types are supported:
+  - (bit 0) anonymous private memory
+  - (bit 1) anonymous shared memory
+  - (bit 2) file-backed private memory
+  - (bit 3) file-backed shared memory
+  Note that MMIO pages such as frame buffer are never dumped and vDSO pages
+  are always dumped regardless of the bitmask status.
+Default value of coredump_filter is 0x3; this means all anonymous memory
+segments are dumped.
+If you don't want to dump all shared memory segments attached to pid 1234,
+write 1 to the process's proc file.
+  $ echo 0x1 > /proc/1234/coredump_filter
+When a new process is created, the process inherits the bitmask status from its
+parent. It is useful to set up coredump_filter before the program runs.
+For example:
+  $ echo 0x7 > /proc/self/coredump_filter
+  $ ./some_program
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