authorgravatar for pat.github@tullmann.orgPat Tullmann <pat.github@tullmann.org> 2025-04-07 22:21:03-07:00
committergravatar for alex@alexrp.comAlex Rønne Petersen <alex@alexrp.com> 2025-04-10 23:49:44+02:00
log4b63f94b4ecf282c259c24a09d6c4ab7490b6cab
treef003b1365d4138476c415be6d9a1739f237ef60b
parenta9ff2d56ceccd545c9659b8c2768dbeeaa25dca4

Fix sigaddset/sigdelset bit-fiddling math

The code was using u32 and usize interchangably, which doesn't work on 64-bit systems. This: `pub const sigset_t = [1024 / 32]u32;` is not consistent with this: `const shift = @as(u5, @intCast(s & (usize_bits - 1)));` However, normal signal numbers are less than 31, so the bad math doesn't matter much. Also, despite support for 1024 signals in the set, only setting signals between 1 and NSIG (which is mostly 65, but sometimes 128) is defined. The existing tests only exercised signal numbers in the first 31 bits so they didn't trip over this: The C library `sigaddset` will return `EINVAL` if given an out of bounds signal number. I made the Zig code just silently ignore any out of bounds signal numbers. Moved all the `sigset` related declarations next to each in the source, too. The `filled_sigset` seems non-standard to me. I think it is meant to be used like `empty_sigset`, but it only contains 31 set signals, which seems wrong (should be 64 or 128, aka `NSIG`). It's also unused. The oddly named but similar `all_mask` is used (by posix.zig) but sets all 1024 bits (which I understood to be undefined behavior but seems to work just fine). For comparison the musl `sigfillset` fills in 65 bits or 128 bits.

2 files changed, 62 insertions(+), 41 deletions(-)

lib/std/os/linux.zig+31-23
...@@ -1786,25 +1786,41 @@ pub fn sigaction(sig: u6, noalias act: ?*const Sigaction, noalias oact: ?*Sigact...@@ -1786,25 +1786,41 @@ pub fn sigaction(sig: u6, noalias act: ?*const Sigaction, noalias oact: ?*Sigact
17861786
1787const usize_bits = @typeInfo(usize).int.bits;1787const usize_bits = @typeInfo(usize).int.bits;
17881788
1789pub fn sigaddset(set: *sigset_t, sig: u6) void {1789pub const sigset_t = [1024 / 32]u32;
1790 const s = sig - 1;1790
1791 // shift in musl: s&8*sizeof *set->__bits-11791const sigset_len = @typeInfo(sigset_t).array.len;
1792 const shift = @as(u5, @intCast(s & (usize_bits - 1)));1792
1793 const val = @as(u32, @intCast(1)) << shift;1793/// Empty set to initialize sigset_t instances from.
1794 (set.*)[@as(usize, @intCast(s)) / usize_bits] |= val;1794pub const empty_sigset: sigset_t = [_]u32{0} ** sigset_len;
1795
1796pub const filled_sigset: sigset_t = [_]u32{0x7fff_ffff} ++ [_]u32{0} ** (sigset_len - 1);
1797
1798pub const all_mask: sigset_t = [_]u32{0xffff_ffff} ** sigset_len;
1799
1800fn sigset_bit_index(sig: usize) struct { word: usize, mask: u32 } {
1801 assert(sig > 0);
1802 assert(sig < NSIG);
1803 const bit = sig - 1;
1804 const shift = @as(u5, @truncate(bit % 32));
1805 return .{
1806 .word = bit / 32,
1807 .mask = @as(u32, 1) << shift,
1808 };
1795}1809}
17961810
1797pub fn sigdelset(set: *sigset_t, sig: u6) void {1811pub fn sigaddset(set: *sigset_t, sig: usize) void {
1798 const s = sig - 1;1812 const index = sigset_bit_index(sig);
1799 // shift in musl: s&8*sizeof *set->__bits-11813 (set.*)[index.word] |= index.mask;
1800 const shift = @as(u5, @intCast(s & (usize_bits - 1)));
1801 const val = @as(u32, @intCast(1)) << shift;
1802 (set.*)[@as(usize, @intCast(s)) / usize_bits] ^= val;
1803}1814}
18041815
1805pub fn sigismember(set: *const sigset_t, sig: u6) bool {1816pub fn sigdelset(set: *sigset_t, sig: usize) void {
1806 const s = sig - 1;1817 const index = sigset_bit_index(sig);
1807 return ((set.*)[@as(usize, @intCast(s)) / usize_bits] & (@as(usize, @intCast(1)) << @intCast(s & (usize_bits - 1)))) != 0;1818 (set.*)[index.word] ^= index.mask;
1819}
1820
1821pub fn sigismember(set: *const sigset_t, sig: usize) bool {
1822 const index = sigset_bit_index(sig);
1823 return ((set.*)[index.word] & index.mask) != 0;
1808}1824}
18091825
1810pub fn getsockname(fd: i32, noalias addr: *sockaddr, noalias len: *socklen_t) usize {1826pub fn getsockname(fd: i32, noalias addr: *sockaddr, noalias len: *socklen_t) usize {
...@@ -5402,10 +5418,6 @@ pub const TFD = switch (native_arch) {...@@ -5402,10 +5418,6 @@ pub const TFD = switch (native_arch) {
5402/// As signal numbers are sequential, NSIG is one greater than the largest defined signal number.5418/// As signal numbers are sequential, NSIG is one greater than the largest defined signal number.
5403pub const NSIG = if (is_mips) 128 else 65;5419pub const NSIG = if (is_mips) 128 else 65;
54045420
5405pub const sigset_t = [1024 / 32]u32;
5406
5407pub const all_mask: sigset_t = [_]u32{0xffffffff} ** @typeInfo(sigset_t).array.len;
5408
5409const k_sigaction_funcs = struct {5421const k_sigaction_funcs = struct {
5410 const handler = ?*align(1) const fn (i32) callconv(.c) void;5422 const handler = ?*align(1) const fn (i32) callconv(.c) void;
5411 const restorer = *const fn () callconv(.c) void;5423 const restorer = *const fn () callconv(.c) void;
...@@ -5446,10 +5458,6 @@ pub const Sigaction = extern struct {...@@ -5446,10 +5458,6 @@ pub const Sigaction = extern struct {
5446 restorer: ?*const fn () callconv(.c) void = null,5458 restorer: ?*const fn () callconv(.c) void = null,
5447};5459};
54485460
5449const sigset_len = @typeInfo(sigset_t).array.len;
5450pub const empty_sigset = [_]u32{0} ** sigset_len;
5451pub const filled_sigset = [_]u32{(1 << (31 & (usize_bits - 1))) - 1} ++ [_]u32{0} ** (sigset_len - 1);
5452
5453pub const SFD = struct {5461pub const SFD = struct {
5454 pub const CLOEXEC = 1 << @bitOffsetOf(O, "CLOEXEC");5462 pub const CLOEXEC = 1 << @bitOffsetOf(O, "CLOEXEC");
5455 pub const NONBLOCK = 1 << @bitOffsetOf(O, "NONBLOCK");5463 pub const NONBLOCK = 1 << @bitOffsetOf(O, "NONBLOCK");
lib/std/os/linux/test.zig+31-18
...@@ -128,28 +128,41 @@ test "fadvise" {...@@ -128,28 +128,41 @@ test "fadvise" {
128test "sigset_t" {128test "sigset_t" {
129 var sigset = linux.empty_sigset;129 var sigset = linux.empty_sigset;
130130
131 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR1), false);131 // See that none are set, then set each one, see that they're all set, then
132 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR2), false);132 // remove them all, and then see that none are set.
133133 for (1..linux.NSIG) |i| {
134 linux.sigaddset(&sigset, linux.SIG.USR1);134 try expectEqual(linux.sigismember(&sigset, @truncate(i)), false);
135135 }
136 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR1), true);136 for (1..linux.NSIG) |i| {
137 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR2), false);137 linux.sigaddset(&sigset, @truncate(i));
138138 }
139 linux.sigaddset(&sigset, linux.SIG.USR2);139 for (1..linux.NSIG) |i| {
140140 try expectEqual(linux.sigismember(&sigset, @truncate(i)), true);
141 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR1), true);141 try expectEqual(linux.sigismember(&linux.empty_sigset, @truncate(i)), false);
142 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR2), true);142 }
143 for (1..linux.NSIG) |i| {
144 linux.sigdelset(&sigset, @truncate(i));
145 }
146 for (1..linux.NSIG) |i| {
147 try expectEqual(linux.sigismember(&sigset, @truncate(i)), false);
148 }
143149
144 linux.sigdelset(&sigset, linux.SIG.USR1);150 linux.sigaddset(&sigset, 1);
151 try expectEqual(sigset[0], 1);
152 try expectEqual(sigset[1], 0);
145153
146 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR1), false);154 linux.sigaddset(&sigset, 31);
147 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR2), true);155 try expectEqual(sigset[0], 0x4000_0001);
156 try expectEqual(sigset[1], 0);
148157
149 linux.sigdelset(&sigset, linux.SIG.USR2);158 linux.sigaddset(&sigset, 36);
159 try expectEqual(sigset[0], 0x4000_0001);
160 try expectEqual(sigset[1], 0x8);
150161
151 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR1), false);162 linux.sigaddset(&sigset, 64);
152 try expectEqual(linux.sigismember(&sigset, linux.SIG.USR2), false);163 try expectEqual(sigset[0], 0x4000_0001);
164 try expectEqual(sigset[1], 0x8000_0008);
165 try expectEqual(sigset[2], 0);
153}166}
154167
155test {168test {