coredump: add a new elf note with siginfo of the signal

Existing PRSTATUS note contains only si_signo, si_code, si_errno fields
from the siginfo of the signal which caused core to be dumped.

There are tools which try to analyze crashes for possible security
implications, and they want to use, among other data, si_addr field from
the SIGSEGV.

This patch adds a new elf note, NT_SIGINFO, which contains the complete
siginfo_t of the signal which killed the process.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: "Jonathan M. Foote" <jmfoote@cert.org>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/compat_binfmt_elf.c b/fs/compat_binfmt_elf.c
index 112e45a..0fbcf63 100644
--- a/fs/compat_binfmt_elf.c
+++ b/fs/compat_binfmt_elf.c
@@ -38,6 +38,12 @@
 #define elf_addr_t	Elf32_Addr
 
 /*
+ * Some data types as stored in coredump.
+ */
+#define user_siginfo_t		compat_siginfo_t
+#define copy_siginfo_to_user	copy_siginfo_to_user32
+
+/*
  * The machine-dependent core note format types are defined in elfcore-compat.h,
  * which requires asm/elf.h to define compat_elf_gregset_t et al.
  */