[libc-commits] [libc] [libc] Implement system function (PR #211672)

[Michael Jones via libc-commits]

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@@ -0,0 +1,112 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation of system for Linux.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/stdlib/system.h"
+#include "hdr/errno_macros.h"
+#include "hdr/signal_macros.h"
+#include "hdr/types/pid_t.h"
+#include "hdr/types/sigset_t.h"
+#include "src/__support/OSUtil/exit.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/execle.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/fork.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/rt_sigaction.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/rt_sigprocmask.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/wait4.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_errno.h"
+#include "src/__support/macros/config.h"
+#include "src/signal/linux/signal_utils.h"
+#include "src/unistd/environ.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(int, system, (const char *command)) {
+  if (command == nullptr)
+    return 1;
+
+  KernelSigaction sa_ign{};
+  sa_ign.sa_handler = SIG_IGN;
+
+  KernelSigaction orig_int{};
+  KernelSigaction orig_quit{};
+
+  if (auto res = linux_syscalls::rt_sigaction(SIGINT, &sa_ign, &orig_int);
+      !res.has_value()) {
+    libc_errno = res.error();
+    return -1;
+  }
+
+  if (auto res = linux_syscalls::rt_sigaction(SIGQUIT, &sa_ign, &orig_quit);
+      !res.has_value()) {
+    linux_syscalls::rt_sigaction(SIGINT, &orig_int, nullptr);
+    libc_errno = res.error();
+    return -1;
+  }
+
+  sigset_t block_mask{};
+  add_signal(block_mask, SIGCHLD);
+  sigset_t orig_mask{};
+  if (auto res =
+          linux_syscalls::rt_sigprocmask(SIG_BLOCK, &block_mask, &orig_mask);
+      !res.has_value()) {
+    linux_syscalls::rt_sigaction(SIGINT, &orig_int, nullptr);
+    linux_syscalls::rt_sigaction(SIGQUIT, &orig_quit, nullptr);
+    libc_errno = res.error();
+    return -1;
+  }
+
+  auto fork_res = linux_syscalls::fork();
+  if (!fork_res.has_value()) {
+    linux_syscalls::rt_sigaction(SIGINT, &orig_int, nullptr);
+    linux_syscalls::rt_sigaction(SIGQUIT, &orig_quit, nullptr);
+    linux_syscalls::rt_sigprocmask(SIG_SETMASK, &orig_mask, nullptr);
+    libc_errno = fork_res.error();
+    return -1;
+  }
+
+  pid_t pid = fork_res.value();
+  if (pid == 0) {
+    linux_syscalls::rt_sigaction(SIGINT, &orig_int, nullptr);
+    linux_syscalls::rt_sigaction(SIGQUIT, &orig_quit, nullptr);
+    linux_syscalls::rt_sigprocmask(SIG_SETMASK, &orig_mask, nullptr);
+
+    // Error checking isn't helpful since this is the forked process, so we
+    // can't set errno. All we can meaningfully do is exit with status 127.
+    linux_syscalls::execle("/bin/sh", "sh", "-c", command, 0, environ);
----------------
michaelrj-google wrote:

done.

https://github.com/llvm/llvm-project/pull/211672