[compiler-rt] compiler-rt: sanitizer_common: use close_range() instead of looping (PR #114442)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Kyle Evans (kevans91)

<details>
<summary>Changes</summary>

_SC_OPEN_MAX is quite high on FreeBSD, which makes this close() loop a quite obvious problem when attempting to do any kind of debugging in a process that uses StartSubprocess.  Switch to using close_range(2) instead to close them all in a single syscall and dramatically reduce the runtime and syscall trace noise

Linux has an equivalent syscall, but I do not have the capacity to test that it works there, so this is limited to SANITIZER_FREEBSD for the time being.

---
Full diff: https://github.com/llvm/llvm-project/pull/114442.diff


3 Files Affected:

- (modified) compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp (+5) 
- (modified) compiler-rt/lib/sanitizer_common/sanitizer_posix.h (+3) 
- (modified) compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp (+4) 


``````````diff
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
index 33107eb0b42993..8b1850f85010cf 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
@@ -256,6 +256,11 @@ int internal_madvise(uptr addr, uptr length, int advice) {
   return internal_syscall(SYSCALL(madvise), addr, length, advice);
 }
 
+#    if SANITIZER_FREEBSD
+uptr internal_close_range(fd_t lowfd, fd_t highfd, int flags) {
+  return internal_syscall(SYSCALL(close_range), lowfd, highfd, flags);
+}
+#    endif
 uptr internal_close(fd_t fd) { return internal_syscall(SYSCALL(close), fd); }
 
 uptr internal_open(const char *filename, int flags) {
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_posix.h b/compiler-rt/lib/sanitizer_common/sanitizer_posix.h
index 1f0795caa420c7..b5491c540dc083 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_posix.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_posix.h
@@ -28,6 +28,9 @@ namespace __sanitizer {
 // Don't use directly, use __sanitizer::OpenFile() instead.
 uptr internal_open(const char *filename, int flags);
 uptr internal_open(const char *filename, int flags, u32 mode);
+#  if SANITIZER_FREEBSD
+uptr internal_close_range(fd_t lowfd, fd_t highfd, int flags);
+#  endif
 uptr internal_close(fd_t fd);
 
 uptr internal_read(fd_t fd, void *buf, uptr count);
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp
index 7ee2319456d23e..894998090b01b3 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_posix_libcdep.cpp
@@ -543,7 +543,11 @@ pid_t StartSubprocess(const char *program, const char *const argv[],
       internal_close(stderr_fd);
     }
 
+#  if SANITIZER_FREEBSD
+    internal_close_range(3, ~0U, 0);
+#  else
     for (int fd = sysconf(_SC_OPEN_MAX); fd > 2; fd--) internal_close(fd);
+#  endif
 
     internal_execve(program, const_cast<char **>(&argv[0]),
                     const_cast<char *const *>(envp));

``````````

</details>


https://github.com/llvm/llvm-project/pull/114442