diff --git a/lib/std/os.zig b/lib/std/os.zig index 18513f2eca..d32618a82f 100644 --- a/lib/std/os.zig +++ b/lib/std/os.zig @@ -250,6 +250,15 @@ pub var argv: [][*:0]u8 = if (builtin.link_libc) undefined else switch (builtin. else => undefined, }; +/// Atomic to guard correct program teardown in abort() +var abort_entered = impl: { + if (builtin.single_threaded) { + break :impl {}; + } else { + break :impl std.atomic.Atomic(bool).init(false); + } +}; + /// To obtain errno, call this function with the return value of the /// system function call. For some systems this will obtain the value directly /// from the return code; for others it will use a thread-local errno variable. @@ -442,6 +451,7 @@ fn getRandomBytesDevURandom(buf: []u8) !void { /// Causes abnormal process termination. /// If linking against libc, this calls the abort() libc function. Otherwise /// it raises SIGABRT followed by SIGKILL and finally lo +/// assume: Current signal handler for SIGABRT does **not call abort**. pub fn abort() noreturn { @setCold(true); // MSVCRT abort() sometimes opens a popup window which is undesirable, so @@ -454,11 +464,48 @@ pub fn abort() noreturn { windows.kernel32.ExitProcess(3); } if (!builtin.link_libc and builtin.os.tag == .linux) { + // Linux man page wants to first "unblock SIG.ABRT", but this is a footgun + // for user-defined signal handlers that want to restore some state in + // some program sections and crash in others + + // user installed SIGABRT handler is run, if installed raise(SIG.ABRT) catch {}; - // TODO the rest of the implementation of abort() from musl libc here + // disable all signal handlers + sigprocmask(SIG.BLOCK, &linux.all_mask, null); + // ensure teardown by one thread + if (!builtin.single_threaded) { + while (abort_entered.compareAndSwap(false, true, .SeqCst, .SeqCst)) |_| {} + } + + // install default handler to terminate + const sigact = Sigaction{ + .handler = .{ .sigaction = SIG.DFL }, + .mask = undefined, + .flags = undefined, + .restorer = undefined, + }; + sigaction(SIG.ABRT, &sigact, null) catch unreachable; + + // make sure we have a pending SIGABRT queued + const tid = std.Thread.getCurrentId(); + _ = linux.tkill(@intCast(i32, tid), SIG.ABRT); + + // SIG.ABRT signal will run default handler + const sigabrtmask: linux.sigset_t = [_]u32{0} ** 31 ++ [_]u32{1 << (SIG.ABRT - 1)}; + sigprocmask(SIG.UNBLOCK, &sigabrtmask, null); // [32]u32 + + // Beyond this point should be unreachable + + // abnormal termination without using signal handler + const nullptr: *allowzero volatile u8 = @intToPtr(*allowzero volatile u8, 0); + nullptr.* = 0; + + // try SIGKILL, which is no abnormal termination as defined by POSIX and ISO C raise(SIG.KILL) catch {}; + + // pid 1 might not be signalled in some containers exit(127); } if (builtin.os.tag == .uefi) { @@ -485,13 +532,13 @@ pub fn raise(sig: u8) RaiseError!void { if (builtin.os.tag == .linux) { var set: sigset_t = undefined; // block application signals - _ = linux.sigprocmask(SIG.BLOCK, &linux.app_mask, &set); + sigprocmask(SIG.BLOCK, &linux.app_mask, &set); const tid = linux.gettid(); const rc = linux.tkill(tid, sig); // restore signal mask - _ = linux.sigprocmask(SIG.SETMASK, &set, null); + sigprocmask(SIG.SETMASK, &set, null); switch (errno(rc)) { .SUCCESS => return, @@ -5441,6 +5488,17 @@ pub fn sigaction(sig: u6, noalias act: ?*const Sigaction, noalias oact: ?*Sigact } } +/// Set the thread signal mask +/// Invalid masks are checked in Debug and ReleaseFast +pub fn sigprocmask(flags: u32, noalias set: ?*const sigset_t, noalias oldset: ?*sigset_t) void { + switch (errno(system.sigprocmask(flags, set, oldset))) { + .SUCCESS => return, + .FAULT => unreachable, + .INVAL => unreachable, // main purpose: debug InvalidValue error + else => unreachable, + } +} + pub const FutimensError = error{ /// times is NULL, or both tv_nsec values are UTIME_NOW, and either: /// * the effective user ID of the caller does not match the owner