Rewrite signal mask decoding without sigset_t

The sigset_t provided by libc is not quite convenient.
In glibc, sigset_t is an array with space for 1024 bits, which is much
more than required: all architectures supported by Linux have only 64
signals except MIPS, which has 128.
In bionic libc, LP32 sigset_t is only 4 bytes long, which is less than
necessary.

With this change, signal mask is decoded without use of intermediate
sigset_t structure, which saves us some cpu cycles in case of glibc with
its inflated sigset_t, and enables build with libcs where sigset_t is
broken.

Old implementation used to check each signal number in the given signal
mask twice using sigismember().
New implementation is based on popcount and next_set_bit() so it's
noticeably faster.

* configure.ac: Check for __builtin_popcount.
* signal.c: Ensure that NSIG >= 32.
(sprintsigmask, sprintsigmask_long, printsigmask): Remove.
(popcount32, sprintsigmask_n): New functions.
(tprintsigmask_addr, sprintsigmask_val, tprintsigmask_val): New macros.
(print_sigset_addr_len, sys_sigsetmask, sys_sigreturn, sys_siggetmask,
sys_sigsuspend, sys_sigprocmask, decode_new_sigaction): Update to use
new signal mask decoding interface.
* tests/sigaction.c (main): Add a test with almost filled signal mask.
* tests/sigaction.awk: Update.

2 files changed, 26 insertions, 8 deletions

diff --git a/tests/sigaction.awk b/tests/sigaction.awk
index 2c4eab687..5bd056865 100644
--- a/tests/sigaction.awk
+++ b/tests/sigaction.awk
@@ -8,6 +8,11 @@
 # the 1st is for any architecture with SA_RESTORER, including SPARC;
 # the 2nd is for any architecture without SA_RESTORER, including ALPHA.
 
+BEGIN {
+	lines = 5
+	fail = 0
+}
+
 # Test 1.
 NR == 1 && /^rt_sigaction\(SIGUSR2, {SIG_IGN, \[HUP INT\], SA_RESTORER\|SA_RESTART, 0x[0-9a-f]+}, {SIG_DFL, \[\], 0}, (0x[0-9a-f]+, )?(4|8|16)\) = 0$/ {next}
 NR == 1 && /^rt_sigaction\(SIGUSR2, {SIG_IGN, \[HUP INT\], SA_RESTART}, {SIG_DFL, \[\], 0}, (4|8|16)(, 0x[0-9a-f]+)?\) = 0$/ {next}
@@ -20,17 +25,26 @@ NR == 2 && /^rt_sigaction\(SIGUSR2, {0x[0-9a-f]+, \[QUIT TERM\], SA_SIGINFO}, {S
 NR == 3 && /^rt_sigaction\(SIGUSR2, {SIG_DFL, \[\], SA_RESTORER, 0x[0-9a-f]+}, {0x[0-9a-f]+, \[QUIT TERM\], SA_RESTORER\|SA_SIGINFO, 0x[0-9a-f]+}, (0x[0-9a-f]+, )?(4|8|16)\) = 0$/ {next}
 NR == 3 && /^rt_sigaction\(SIGUSR2, {SIG_DFL, \[\], 0}, {0x[0-9a-f]+, \[QUIT TERM\], SA_SIGINFO}, (4|8|16)(, 0x[0-9a-f]+)?\) = 0$/ {next}
 
+# Test 4.
+NR == 4 && /^rt_sigaction\(SIGUSR2, {SIG_DFL, ~\[HUP( ((RT|SIGRT)[^] ]+|[3-9][0-9]|1[0-9][0-9]))*\], SA_RESTORER, 0x[0-9a-f]+}, {SIG_DFL, \[\], SA_RESTORER, 0x[0-9a-f]+}, (0x[0-9a-f]+, )?(4|8|16)\) = 0$/ {next}
+NR == 4 && /^rt_sigaction\(SIGUSR2, {SIG_DFL, ~\[HUP( ((RT|SIGRT)[^] ]+|[3-9][0-9]|1[0-9][0-9]))*\], 0}, {SIG_DFL, \[\], 0}, (4|8|16)(, 0x[0-9a-f]+)?\) = 0$/ {next}
+
 # The last line.
-NR == 4 && /^\+\+\+ exited with 0 \+\+\+$/ {next}
+NR == lines && /^\+\+\+ exited with 0 \+\+\+$/ {next}
 
 {
   print "Line " NR " does not match: " $0
-  exit 1
+  fail=1
 }
 
 END {
-  if (NR != 4) {
-    print "Expected 4 lines, found " NR " line(s)."
+  if (NR != lines) {
+    print "Expected " lines " lines, found " NR " line(s)."
+    print ""
+    exit 1
+  }
+  if (fail) {
+    print ""
     exit 1
   }
 }
diff --git a/tests/sigaction.c b/tests/sigaction.c
index 82666f9e5..b5f19b561 100644
--- a/tests/sigaction.c
+++ b/tests/sigaction.c
@@ -11,26 +11,30 @@ static void handle_signal(int no)
 int
 main(void)
 {
-	struct sigaction sa, sa1, sa2, sa3;
+	struct sigaction sa, sa0;
 
 	sa.sa_handler = SIG_IGN;
 	sigemptyset(&sa.sa_mask);
 	sigaddset(&sa.sa_mask, SIGHUP);
 	sigaddset(&sa.sa_mask, SIGINT);
 	sa.sa_flags = SA_RESTART;
-	assert(!sigaction(SIGUSR2, &sa, &sa1));
+	assert(!sigaction(SIGUSR2, &sa, &sa0));
 
 	sa.sa_handler = handle_signal;
 	sigemptyset(&sa.sa_mask);
 	sigaddset(&sa.sa_mask, SIGQUIT);
 	sigaddset(&sa.sa_mask, SIGTERM);
 	sa.sa_flags = SA_SIGINFO;
-	assert(!sigaction(SIGUSR2, &sa, &sa2));
+	assert(!sigaction(SIGUSR2, &sa, &sa0));
 
 	sa.sa_handler = SIG_DFL;
 	sigemptyset(&sa.sa_mask);
 	sa.sa_flags = 0;
-	assert(!sigaction(SIGUSR2, &sa, &sa3));
+	assert(!sigaction(SIGUSR2, &sa, &sa0));
+
+	sigfillset(&sa.sa_mask);
+	sigdelset(&sa.sa_mask, SIGHUP);
+	assert(!sigaction(SIGUSR2, &sa, &sa0));
 
 	return 0;
 }