elf coredump: add extended numbering support

The current ELF dumper implementation can produce broken corefiles if
program headers exceed 65535.  This number is determined by the number of
vmas which the process have.  In particular, some extreme programs may use
more than 65535 vmas.  (If you google max_map_count, you can find some
users facing this problem.) This kind of program never be able to generate
correct coredumps.

This patch implements ``extended numbering'' that uses sh_info field of
the first section header instead of e_phnum field in order to represent
upto 4294967295 vmas.

This is supported by
AMD64-ABI(http://www.x86-64.org/documentation.html) and
Solaris(http://docs.sun.com/app/docs/doc/817-1984/).
Of course, we are preparing patches for gdb and binutils.

Signed-off-by: Daisuke HATAYAMA <d.hatayama@jp.fujitsu.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Greg Ungerer <gerg@snapgear.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 1 deletions

diff --git a/include/linux/elf.h b/include/linux/elf.h
index ccde3fd45f36..597858418051 100644
--- a/include/linux/elf.h
+++ b/include/linux/elf.h
@@ -50,6 +50,28 @@ typedef __s64	Elf64_Sxword;
 
 #define PT_GNU_STACK    (PT_LOOS + 0x474e551)
 
+/*
+ * Extended Numbering
+ *
+ * If the real number of program header table entries is larger than
+ * or equal to PN_XNUM(0xffff), it is set to sh_info field of the
+ * section header at index 0, and PN_XNUM is set to e_phnum
+ * field. Otherwise, the section header at index 0 is zero
+ * initialized, if it exists.
+ *
+ * Specifications are available in:
+ *
+ * - Sun microsystems: Linker and Libraries.
+ *   Part No: 817-1984-17, September 2008.
+ *   URL: http://docs.sun.com/app/docs/doc/817-1984
+ *
+ * - System V ABI AMD64 Architecture Processor Supplement
+ *   Draft Version 0.99.,
+ *   May 11, 2009.
+ *   URL: http://www.x86-64.org/
+ */
+#define PN_XNUM 0xffff
+
 /* These constants define the different elf file types */
 #define ET_NONE   0
 #define ET_REL    1
@@ -286,7 +308,7 @@ typedef struct elf64_phdr {
 #define SHN_COMMON      0xfff2
 #define SHN_HIRESERVE   0xffff
  
-typedef struct {
+typedef struct elf32_shdr {
   Elf32_Word    sh_name;
   Elf32_Word    sh_type;
   Elf32_Word    sh_flags;
@@ -394,6 +416,7 @@ typedef struct elf64_note {
 extern Elf32_Dyn _DYNAMIC [];
 #define elfhdr          elf32_hdr
 #define elf_phdr        elf32_phdr
+#define elf_shdr        elf32_shdr
 #define elf_note        elf32_note
 #define elf_addr_t      Elf32_Off
 #define Elf_Half        Elf32_Half
@@ -403,6 +426,7 @@ extern Elf32_Dyn _DYNAMIC [];
 extern Elf64_Dyn _DYNAMIC [];
 #define elfhdr          elf64_hdr
 #define elf_phdr        elf64_phdr
+#define elf_shdr        elf64_shdr
 #define elf_note        elf64_note
 #define elf_addr_t      Elf64_Off
 #define Elf_Half        Elf64_Half