This is the mail archive of the
gdb-testers@sourceware.org
mailing list for the GDB project.
[binutils-gdb] Fix PR gdb/20287 - x32 and "gdb_static_assert (sizeof (nat_siginfo_t) == sizeof (siginfo_t))"
- From: sergiodj+buildbot at sergiodj dot net
- To: gdb-testers at sourceware dot org
- Date: Tue, 26 Jul 2016 15:10:48 -0400
- Subject: [binutils-gdb] Fix PR gdb/20287 - x32 and "gdb_static_assert (sizeof (nat_siginfo_t) == sizeof (siginfo_t))"
- Authentication-results: sourceware.org; auth=none
*** TEST RESULTS FOR COMMIT 9cf12d57c58a82cfe3e6fee26d1ea55dfe49f9c4 ***
Author: Pedro Alves <palves@redhat.com>
Branch: master
Commit: 9cf12d57c58a82cfe3e6fee26d1ea55dfe49f9c4
Fix PR gdb/20287 - x32 and "gdb_static_assert (sizeof (nat_siginfo_t) == sizeof (siginfo_t))"
Building an x32 gdb trips on a static assertion:
In file included from .../src/gdb/common/common-defs.h:71:0,
from .../src/gdb/nat/amd64-linux-siginfo.c:21:
.../src/gdb/common/gdb_assert.h:26:66: error: size of array never_defined_just_used_for_checking is negative
extern int never_defined_just_used_for_checking[(expr) ? 1 : -1]
^
.../src/gdb/nat/amd64-linux-siginfo.c:113:1: note: in expansion of macro gdb_static_assert
gdb_static_assert (sizeof (nat_siginfo_t) == sizeof (siginfo_t));
^
The problem is that the way nat_siginfo_t is defined, it can only
match the host's siginfo_t object when gdb is built as a 64-bit
program.
Several bits of nat_siginfo_t are off:
- nat_siginfo_t's _pad field's definition is:
int _pad[((128 / sizeof (int)) - 4)];
while /usr/include/bits/siginfo.h has:
# define __SI_MAX_SIZE 128
# if __WORDSIZE == 64
# define __SI_PAD_SIZE ((__SI_MAX_SIZE / sizeof (int)) - 4)
# else
# define __SI_PAD_SIZE ((__SI_MAX_SIZE / sizeof (int)) - 3)
# endif
and __WORDSIZE == 32 for x32. This is what causes the size of
nat_siginfo_t to be wrong and the assertion to fail.
- the nat_clock_t type is incorrect for 64-bit. We have this:
/* For native 64-bit, clock_t in _sigchld is 64bit aligned at 4 bytes. */
typedef long __attribute__ ((__aligned__ (4))) nat_clock_t;
however, /usr/include/bits/siginfo.h has:
# if defined __x86_64__ && __WORDSIZE == 32
/* si_utime and si_stime must be 4 byte aligned for x32 to match the
kernel. We align siginfo_t to 8 bytes so that si_utime and si_stime
are actually aligned to 8 bytes since their offsets are multiple of
8 bytes. */
typedef __clock_t __attribute__ ((__aligned__ (4))) __sigchld_clock_t;
# define __SI_ALIGNMENT __attribute__ ((__aligned__ (8)))
# else
typedef __clock_t __sigchld_clock_t;
# define __SI_ALIGNMENT
# endif
So we're currently forcing 4-byte alignment on clock_t, when it
should only be so for x32, not 64-bit.
The fix:
- Leaves nat_siginfo_t strictly for the 64-bit ABI.
- Adds a new typedef for the siginfo type that ptrace uses
(ptrace_siginfo_t). An x32 gdb always gets/sets an x32 siginfo_t
type with PTRACE_GETSIGINFO/PTRACE_SETSIGINFO.
- Uses this new ptrace_siginfo_t type instead of nat_siginfo_t as the
intermediate conversion type.
gdb/ChangeLog:
2016-07-26 Pedro Alves <palves@redhat.com>
* amd64-linux-nat.c (amd64_linux_siginfo_fixup): Rename 'native'
parameter to 'ptrace'.
* nat/amd64-linux-siginfo.c (GDB_SI_SIZE): New define.
(nat_uptr_t): New an unsigned long.
(nat_clock_t): Remove attribute __aligned__.
(struct nat_timeval): Delete.
(nat_siginfo_t): Remove attribute __aligned__.
(ptrace_siginfo_t): Define.
(compat_siginfo_from_siginfo, siginfo_from_compat_siginfo)
(compat_x32_siginfo_from_siginfo)
(siginfo_from_compat_x32_siginfo): Make 'from' parameter const.
Convert through a ptrace_siginfo_t instead of a nat_siginfo_t.
Remove casts.
(amd64_linux_siginfo_fixup_common): Rename 'native' parameter to
'ptrace'. Remove static assertions.
(top level): New static assertions.
gdb/gdbserver/ChangeLog:
2016-07-26 Pedro Alves <palves@redhat.com>
* linux-x86-low.c (x86_siginfo_fixup): Rename 'native' parameter
to 'ptrace'.