[PATCH 3/4] ELF/BFD: Handle both variants of the 64-bit Linux core PRPSINFO note

Maciej W. Rozycki
2017-09-23T00:04:52Z

Fix commit 70a38d42c5b3 ("New entry points for writing Linux NT_PRPSINFO
notes."), <https://sourceware.org/ml/binutils/2013-02/msg00023.html>,
and handle both variants of the 64-bit Linux core PRPSINFO note across
all targets.

The 64-bit Linux core PRPSINFO note matches the 64-bit kernel structure,
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)

where the individual data types of most members are the same across all
64-bit Linux ports, with the exception of `__kernel_uid_t' and
`__kernel_gid_t'. These are defined in <asm-generic/posix_types.h> as
32-bit `unsigned int' by default, however overridden as 16-bit `unsigned
short' in port-specific <asm/posix_types.h> for the SuperH target.

The default is already handled, as from the commit referred. Add the
other variant then and provide a backend flag to switch between the two
cases possible, with the 32-bit one being the default and the 16-bit one
explicitly selected. Set the flag in the SuperH target backend. This
arrangement is analogous to how the 32-bit Linux core PRPSINFO note is
handled.

bfd/
* elf-bfd.h (elf_backend_data): Add `linux_prpsinfo64_ugid16'
member.
* elf-linux-core.h (elf_external_linux_prpsinfo64): Rename to...
(elf_external_linux_prpsinfo64_ugid32): ... this.
(swap_linux_prpsinfo32_out): Rename to...
(swap_linux_prpsinfo32_ugid32_out): ... this.
(elf_external_linux_prpsinfo64_ugid16): New structure.
(swap_linux_prpsinfo64_ugid16_out): New function.
* elfxx-target.h [!elf_backend_linux_prpsinfo64_ugid16]
(elf_backend_linux_prpsinfo64_ugid16): Define.
(elfNN_bed): Initialize `linux_prpsinfo64_ugid16' member.
* elf.c (elfcore_write_linux_prpsinfo64): Handle both variants
of the 64-bit Linux core PRPSINFO note.
* elf64-sh64.c (elf_backend_linux_prpsinfo64_ugid16): Define.
---
bfd/elf-bfd.h | 4 +++
bfd/elf-linux-core.h | 68 +++++++++++++++++++++++++++++++++++++++++++++++----
bfd/elf.c | 21 ++++++++++++---
bfd/elf64-sh64.c | 2 +
bfd/elfxx-target.h | 6 +++-
5 files changed, 90 insertions(+), 11 deletions(-)

gdb-elf-linux-core-prpsinfo64-ugid.diff
Index: binutils/bfd/elf-bfd.h
===================================================================
--- binutils.orig/bfd/elf-bfd.h 2017-09-20 13:03:18.000000000 +0100
+++ binutils/bfd/elf-bfd.h 2017-09-20 13:06:49.534308157 +0100
@@ -1556,6 +1556,10 @@ struct elf_backend_data
/* True if the 32-bit Linux PRPSINFO structure's `pr_uid' and `pr_gid'
members use a 16-bit data type. */
unsigned linux_prpsinfo32_ugid16 : 1;
+
+ /* True if the 64-bit Linux PRPSINFO structure's `pr_uid' and `pr_gid'
+ members use a 16-bit data type. */
+ unsigned linux_prpsinfo64_ugid16 : 1;
};

/* Information about reloc sections associated with a bfd_elf_section_data
Index: binutils/bfd/elf-linux-core.h
===================================================================
--- binutils.orig/bfd/elf-linux-core.h 2017-09-20 13:03:18.000000000 +0100
+++ binutils/bfd/elf-linux-core.h 2017-09-20 13:15:40.694234169 +0100
@@ -129,10 +129,14 @@ swap_linux_prpsinfo32_ugid16_out
ABI-defined, thus we choose to use char arrays here in order to
avoid dealing with different types in different architectures.

+ This is the variant for targets which use a 32-bit data type for
+ UID and GID, as most Linux ports do. The SH64 port uses a 16-bit
+ data type instead; see below for the alternative variant.
+
This structure will ultimately be written in the corefile's note
section, as the PRPSINFO. */

-struct elf_external_linux_prpsinfo64
+struct elf_external_linux_prpsinfo64_ugid32
{
char pr_state; /* Numeric process state. */
char pr_sname; /* Char for pr_state. */
@@ -151,12 +155,13 @@ struct elf_external_linux_prpsinfo64
};

/* Helper function to copy an elf_internal_linux_prpsinfo in host
- endian to an elf_external_linux_prpsinfo64 in target endian. */
+ endian to an elf_external_linux_prpsinfo64_ugid32 in target endian. */

static inline void
-swap_linux_prpsinfo64_out (bfd *obfd,
- const struct elf_internal_linux_prpsinfo *from,
- struct elf_external_linux_prpsinfo64 *to)
+swap_linux_prpsinfo64_ugid32_out
+ (bfd *obfd,
+ const struct elf_internal_linux_prpsinfo *from,
+ struct elf_external_linux_prpsinfo64_ugid32 *to)
{
bfd_put_8 (obfd, from->pr_state, &to->pr_state);
bfd_put_8 (obfd, from->pr_sname, &to->pr_sname);
@@ -173,4 +178,57 @@ swap_linux_prpsinfo64_out (bfd *obfd,
strncpy (to->pr_psargs, from->pr_psargs, sizeof (to->pr_psargs));
}

+/* External 64-bit structure for PRPSINFO. This structure is
+ ABI-defined, thus we choose to use char arrays here in order to
+ avoid dealing with different types in different architectures.
+
+ This is the variant for the SH64 port which uses a 16-bit data
+ type for UID and GID. Most Linux ports use a 32-bit data type
+ instead; see above for the alternative variant.
+
+ This structure will ultimately be written in the corefile's note
+ section, as the PRPSINFO. */
+
+struct elf_external_linux_prpsinfo64_ugid16
+ {
+ char pr_state; /* Numeric process state. */
+ char pr_sname; /* Char for pr_state. */
+ char pr_zomb; /* Zombie. */
+ char pr_nice; /* Nice val. */
+ char gap[4];
+ char pr_flag[8]; /* Flags. */
+ char pr_uid[2];
+ char pr_gid[2];
+ char pr_pid[4];
+ char pr_ppid[4];
+ char pr_pgrp[4];
+ char pr_sid[4];
+ char pr_fname[16]; /* Filename of executable. */
+ char pr_psargs[80]; /* Initial part of arg list. */
+ };
+
+/* Helper function to copy an elf_internal_linux_prpsinfo in host
+ endian to an elf_external_linux_prpsinfo64_ugid16 in target endian. */
+
+static inline void
+swap_linux_prpsinfo64_ugid16_out
+ (bfd *obfd,
+ const struct elf_internal_linux_prpsinfo *from,
+ struct elf_external_linux_prpsinfo64_ugid16 *to)
+{
+ bfd_put_8 (obfd, from->pr_state, &to->pr_state);
+ bfd_put_8 (obfd, from->pr_sname, &to->pr_sname);
+ bfd_put_8 (obfd, from->pr_zomb, &to->pr_zomb);
+ bfd_put_8 (obfd, from->pr_nice, &to->pr_nice);
+ bfd_put_64 (obfd, from->pr_flag, to->pr_flag);
+ bfd_put_16 (obfd, from->pr_uid, to->pr_uid);
+ bfd_put_16 (obfd, from->pr_gid, to->pr_gid);
+ bfd_put_32 (obfd, from->pr_pid, to->pr_pid);
+ bfd_put_32 (obfd, from->pr_ppid, to->pr_ppid);
+ bfd_put_32 (obfd, from->pr_pgrp, to->pr_pgrp);
+ bfd_put_32 (obfd, from->pr_sid, to->pr_sid);
+ strncpy (to->pr_fname, from->pr_fname, sizeof (to->pr_fname));
+ strncpy (to->pr_psargs, from->pr_psargs, sizeof (to->pr_psargs));
+}
+
#endif
Index: binutils/bfd/elf.c
===================================================================
--- binutils.orig/bfd/elf.c 2017-09-20 13:03:18.000000000 +0100
+++ binutils/bfd/elf.c 2017-09-20 13:18:25.396554524 +0100
@@ -10470,11 +10470,22 @@ elfcore_write_linux_prpsinfo64
(bfd *abfd, char *buf, int *bufsiz,
const struct elf_internal_linux_prpsinfo *prpsinfo)
{
- struct elf_external_linux_prpsinfo64 data;
-
- swap_linux_prpsinfo64_out (abfd, prpsinfo, &data);
- return elfcore_write_note (abfd, buf, bufsiz,
- "CORE", NT_PRPSINFO, &data, sizeof (data));
+ if (get_elf_backend_data (abfd)->linux_prpsinfo64_ugid16)
+ {
+ struct elf_external_linux_prpsinfo64_ugid16 data;
+
+ swap_linux_prpsinfo64_ugid16_out (abfd, prpsinfo, &data);
+ return elfcore_write_note (abfd, buf, bufsiz,
+ "CORE", NT_PRPSINFO, &data, sizeof (data));
+ }
+ else
+ {
+ struct elf_external_linux_prpsinfo64_ugid32 data;
+
+ swap_linux_prpsinfo64_ugid32_out (abfd, prpsinfo, &data);
+ return elfcore_write_note (abfd, buf, bufsiz,
+ "CORE", NT_PRPSINFO, &data, sizeof (data));
+ }
}

char *
Index: binutils/bfd/elf64-sh64.c
===================================================================
--- binutils.orig/bfd/elf64-sh64.c 2017-08-02 13:13:26.000000000 +0100
+++ binutils/bfd/elf64-sh64.c 2017-09-20 13:19:29.748292419 +0100
@@ -3944,6 +3944,8 @@ static const struct bfd_elf_special_sect
#define elf_backend_got_header_size 24
#define elf_backend_dtrel_excludes_plt 1

+#define elf_backend_linux_prpsinfo64_ugid16 TRUE
+
#include "elf64-target.h"

/* NetBSD support. */
Index: binutils/bfd/elfxx-target.h
===================================================================
--- binutils.orig/bfd/elfxx-target.h 2017-09-20 13:03:18.000000000 +0100
+++ binutils/bfd/elfxx-target.h 2017-09-20 13:20:49.220803426 +0100
@@ -135,6 +135,9 @@
#ifndef elf_backend_linux_prpsinfo32_ugid16
#define elf_backend_linux_prpsinfo32_ugid16 FALSE
#endif
+#ifndef elf_backend_linux_prpsinfo64_ugid16
+#define elf_backend_linux_prpsinfo64_ugid16 FALSE
+#endif
#ifndef elf_backend_stack_align
#define elf_backend_stack_align 16
#endif
@@ -895,7 +898,8 @@ static struct elf_backend_data elfNN_bed
elf_backend_caches_rawsize,
elf_backend_extern_protected_data,
elf_backend_always_renumber_dynsyms,
- elf_backend_linux_prpsinfo32_ugid16
+ elf_backend_linux_prpsinfo32_ugid16,
+ elf_backend_linux_prpsinfo64_ugid16
};

/* Forward declaration for use when initialising alternative_target field. */