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overhaul implementation-internal signal protections

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the new approach relies on the fact that the only ways to create
sigset_t objects without invoking UB are to use the sig*set()
functions, or from the masks returned by sigprocmask, sigaction, etc.
or in the ucontext_t argument to a signal handler. thus, as long as
sigfillset and sigaddset avoid adding the "protected" signals, there
is no way the application will ever obtain a sigset_t including these
bits, and thus no need to add the overhead of checking/clearing them
when sigprocmask or sigaction is called.

note that the old code actually *failed* to remove the bits from
sa_mask when sigaction was called.

the new implementations are also significantly smaller, simpler, and
faster due to ignoring the useless "GNU HURD signals" 65-1024, which
are not used and, if there's any sanity in the world, never will be
used.
This commit is contained in:
Rich Felker
2011-05-07 23:23:58 -04:00
parent 77f15d108e
commit 99b8a25e94
13 changed files with 32 additions and 50 deletions
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5
src/thread/__rsyscall.c
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@ -56,8 +56,7 @@ int __rsyscall(int nr, long a, long b, long c, long d, long e, long f)
while ((i=rs.blocks))
__wait(&rs.blocks, 0, i, 1);
sigfillset(&set);
__libc_sigprocmask(SIG_BLOCK, &set, &set);
__syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1}, &set, 8);
if (!rs.init) {
struct sigaction sa = {
@ -88,7 +87,7 @@ int __rsyscall(int nr, long a, long b, long c, long d, long e, long f)
}
/* Handle any lingering signals with no-op */
__libc_sigprocmask(SIG_UNBLOCK, &set, &set);
__syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, &set, 8);
/* Resume other threads' signal handlers and wait for them */
rs.hold = 0;