coredump: add new %P variable in core_pattern

Add a new %P variable to be used in core_pattern.  This variable contains
the global PID (PID in the init namespace) as %p contains the PID in the
current namespace which isn't always what we want.

The main use for this is to make it easier to handle crashes that happened
within a container.  With that new variables it's possible to have the
crashes dumped into the container or forwarded to the host with the right
PID (from the host's point of view).

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Reported-by: Hans Feldt <hans.feldt@ericsson.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Andy Whitcroft <apw@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index ab7d16efa96b..9d4c1d18ad44 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -182,6 +182,7 @@ core_pattern is used to specify a core dumpfile pattern name.
         %<NUL>  '%' is dropped
         %%      output one '%'
         %p      pid
+        %P      global pid (init PID namespace)
         %u      uid
         %g      gid
         %d      dump mode, matches PR_SET_DUMPABLE and
diff --git a/fs/coredump.c b/fs/coredump.c
index 72f816d6cad9..9bdeca12ae0e 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -190,6 +190,11 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm)
                                 err = cn_printf(cn, "%d",
                                               task_tgid_vnr(current));
                                 break;
+                        /* global pid */
+                        case 'P':
+                                err = cn_printf(cn, "%d",
+                                              task_tgid_nr(current));
+                                break;
                         /* uid */
                         case 'u':
                                 err = cn_printf(cn, "%d", cred->uid);