motiejus/zig

commit 27611c10f8dc6a58161699a30a573459d855aede (tree)
parent 9b1eaad13fd331c4c2135f15ab9512b9e2342ff2
Author: Alex Rønne Petersen <alex@alexrp.com>
Date:   Wed,  1 Apr 2026 11:38:06 +0200

Merge pull request 'LinuxThreadImpl fixups' (#31716) from blblack/zig:linux-thread-childtid into master

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31716
Reviewed-by: Alex Rønne Petersen <alex@alexrp.com>

Diffstat:
M
lib/std/Thread.zig
 | 
7
++++++-
M
lib/std/os/linux.zig
 | 
5
+++++

2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/lib/std/Thread.zig b/lib/std/Thread.zig
@@ -1147,6 +1147,11 @@ const LinuxThreadImpl = struct {
         /// Ported over from musl libc's pthread detached implementation:
         /// https://github.com/ifduyue/musl/search?q=__unmapself
         fn freeAndExit(self: *ThreadCompletion) noreturn {
+            // If we do not reset the child_tidptr to null here, the kernel would later write the
+            // value zero to that address, which is inside the block we're unmapping below, after
+            // our thread exits.  This can sometimes corrupt memory in other mmap blocks from
+            // unrelated concurrent threads.
+            _ = linux.set_tid_address(null);
             // If a signal were delivered between SYS_munmap and SYS_exit, any installed signal
             // handler would immediately segfault due to the stack being unmapped. To avoid this,
             // we need to mask all signals before entering the inline asm.
@@ -1484,7 +1489,7 @@ const LinuxThreadImpl = struct {
         }
 
         // Prepare the TLS segment and prepare a user_desc struct when needed on x86
-        var tls_ptr = linux.tls.prepareArea(mapped[tls_offset..]);
+        var tls_ptr = linux.tls.prepareArea(mapped[tls_offset..][0..linux.tls.area_desc.size]);
         var user_desc: if (target.cpu.arch == .x86) linux.user_desc else void = undefined;
         if (target.cpu.arch == .x86) {
             defer tls_ptr = @intFromPtr(&user_desc);
diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
@@ -1584,6 +1584,11 @@ pub fn clone2(flags: u32, child_stack_ptr: usize) usize {
     return syscall2(.clone, flags, child_stack_ptr);
 }
 
+/// This call cannot fail, and the return value is the caller's thread id
+pub fn set_tid_address(tidptr: ?*pid_t) pid_t {
+    return @intCast(@as(u32, @truncate(syscall1(.set_tid_address, @intFromPtr(tidptr)))));
+}
+
 pub fn close(fd: fd_t) usize {
     return syscall1(.close, @as(usize, @bitCast(@as(isize, fd))));
 }