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9cf12d57c5
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'.
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README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.