[libc-commits] [libc] [libc] Fix Darwin aarch64 fenv and sigsetjmp build support (PR #192079)

[Kacper Fiedorowicz via libc-commits]

================
@@ -0,0 +1,41 @@
+//===-- Internal Darwin implementation of sigprocmask ---------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/signal/darwin/sigprocmask_impl.h"
+
+#include "hdr/stdint_proxy.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/libc_errno.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+int sigprocmask_impl(int how, const sigset_t *__restrict set,
+                     sigset_t *__restrict oldset) {
+  uint32_t kernel_set = 0;
+  uint32_t kernel_oldset = 0;
+
+  if (set)
+    kernel_set = static_cast<uint32_t>(set->__signals[0] & 0x7FFFFFFFU);
+
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_sigprocmask, how, set ? &kernel_set : nullptr,
+      oldset ? &kernel_oldset : nullptr);
+  if (ret == 0) {
+    if (oldset)
+      oldset->__signals[0] =
+          static_cast<unsigned long>(kernel_oldset & 0x7FFFFFFFU);
+    return 0;
+  }
+
+  libc_errno = ret;
+  return -1;
+}
----------------
fenze wrote:

Done. I moved the Darwin sigprocmask syscall wrapper to `src/__support/OSUtil/darwin/syscall_wrappers/sigprocmask.h`. 
It now returns ErrorOr<int> and does not update errno. The public sigprocmask entrypoint translates an error into libc_errno and -1, while
sigsetjmp_epilogue uses the wrapper directly without mutating errno. I also pass the user
pointers to the kernel so an invalid set pointer is reported as EFAULT instead of being
dereferenced in userspace.

https://github.com/llvm/llvm-project/pull/192079