[PATCH 1/4] ELF/BFD: Fix padding in `elf_external_linux_prpsinfo64'

Maciej W. Rozycki
2017-09-23T00:03:19Z

Fix commit 70a38d42c5b3 ("New entry points for writing Linux NT_PRPSINFO
notes."), <https://sourceware.org/ml/binutils/2013-02/msg00023.html>,
and move the padding of the `elf_external_linux_prpsinfo64' structure to
match the corresponding 64-bit Linux kernel `elf_prpsinfo' structure.

The 64-bit kernel structure is defined as follows:

(gdb) ptype struct elf_prpsinfo
type = struct elf_prpsinfo {
char pr_state;
char pr_sname;
char pr_zomb;
char pr_nice;
unsigned long pr_flag;
__kernel_uid_t pr_uid;
__kernel_gid_t pr_gid;
pid_t pr_pid;
pid_t pr_ppid;
pid_t pr_pgrp;
pid_t pr_sid;
char pr_fname[16];
char pr_psargs[80];
}
(gdb) print /x &((struct elf_prpsinfo *)0)->pr_nice
$1 = 0x3
(gdb) print /x &((struct elf_prpsinfo *)0)->pr_flag
$2 = 0x8
(gdb) print /x &((struct elf_prpsinfo *)0)->pr_uid
$3 = 0x10
(gdb) print sizeof(((struct elf_prpsinfo *)0)->pr_flag)
$4 = 8
(gdb)

with implicit padding present before the `pr_flag' member, to correctly
align it to a multiple of 8. Conversely `elf_external_linux_prpsinfo64'
has padding after its `pr_flag' member:

(top-gdb) ptype struct elf_external_linux_prpsinfo64
type = struct elf_external_linux_prpsinfo64 {
char pr_state;
char pr_sname;
char pr_zomb;
char pr_nice;
char pr_flag[8];
char gap[4];
char pr_uid[4];
char pr_gid[4];
char pr_pid[4];
char pr_ppid[4];
char pr_pgrp[4];
char pr_sid[4];
char pr_fname[16];
char pr_psargs[80];
}
(top-gdb) print /x &((struct elf_external_linux_prpsinfo64 *)0)->pr_nice
$1 = 0x3
(top-gdb) print /x &((struct elf_external_linux_prpsinfo64 *)0)->pr_flag
$2 = 0x4
(top-gdb) print /x &((struct elf_external_linux_prpsinfo64 *)0)->pr_uid
$3 = 0x10
(top-gdb)

and consequently `pr_flag' is misplaced. Move `gap' ahead of `pr_flag'
then.

bfd/
* elf-linux-core.h (elf_external_linux_prpsinfo64): Move the
`gap' member ahead of `pr_flag'.
---
bfd/elf-linux-core.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: binutils/bfd/elf-linux-core.h
===================================================================
--- binutils.orig/bfd/elf-linux-core.h 2017-07-31 09:18:48.000000000 +0100
+++ binutils/bfd/elf-linux-core.h 2017-09-19 15:49:09.859093825 +0100
@@ -85,8 +85,8 @@ struct elf_external_linux_prpsinfo64
char pr_sname; /* Char for pr_state. */
char pr_zomb; /* Zombie. */
char pr_nice; /* Nice val. */
- char pr_flag[8]; /* Flags. */
char gap[4];
+ char pr_flag[8]; /* Flags. */
char pr_uid[4];
char pr_gid[4];
char pr_pid[4];