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1b132d55e2
The posix_spawn on sparc issues invalid sigprocmask calls:
rt_sigprocmask(0xffe5e15c /* SIG_??? */, ~[], 0xffe5e1dc, 8) = -1 EINVAL (Invalid argument)
Which make support/tst-support_capture_subprocess fails with random
output (due the child signal being wrongly captured by the parent).
Tracking the culprit it seems to be a wrong code generation in the
INTERNAL_SYSCALL due the automatic sigset_t used on
__libc_signal_block_all:
return INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_BLOCK, &SIGALL_SET,
set, _NSIG / 8);
Where SIGALL_SET is defined as:
((__sigset_t) { .__val = {[0 ... _SIGSET_NWORDS-1 ] = -1 } })
Building the expanded __libc_signal_block_all on sparc64 with recent
compiler (gcc 8.3.1 and 9.1.1):
#include <signal>
int
_libc_signal_block_all (sigset_t *set)
{
INTERNAL_SYSCALL_DECL (err);
return INTERNAL_SYSCALL (rt_sigprocmask, err, 4, SIG_BLOCK, &SIGALL_SET,
set, _NSIG / 8);
}
The first argument (SIG_BLOCK) is not correctly set on 'o0' register:
__libc_signal_block_all:
save %sp, -304, %sp
add %fp, 1919, %o0
mov 128, %o2
sethi %hi(.LC0), %o1
call memcpy, 0
or %o1, %lo(.LC0), %o1
add %fp, 1919, %o1
mov %i0, %o2
mov 8, %o3
mov 103, %g1
ta 0x6d;
bcc,pt %xcc, 1f
mov 0, %g1
sub %g0, %o0, %o0
mov 1, %g1
1: sra %o0, 0, %i0
return %i7+8
nop
Where if SIGALL_SET is defined a const object, gcc correctly sets the
expected kernel argument in correct register:
sethi %hi(.LC0), %o1
call memcpy, 0
or %o1, %lo(.LC0), %o1
-> mov 1, %o0
add %fp, 1919, %o1
Another possible fix is use a static const object. Although there
should not be a difference between a const compound literal and a static
const object, the gcc C99 status page [1] has a note stating that this
optimization is not implemented:
"const-qualified compound literals could share storage with each
other and with string literals, but currently don't.".
This patch fixes it by moving both sigset_t that represent the
signal sets to static const data object. It generates slight better
code where the object reference is used directly instead of a stack
allocation plus the content materialization.
Checked on x86_64-linux-gnu, i686-linux-gnu, and sparc64-linux-gnu.
[1] https://gcc.gnu.org/c99status.html
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