[libc-commits] [libc] [libc] Implement execvpe in unistd (PR #234071)

[Aman Maurya via libc-commits]

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@@ -0,0 +1,97 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+/// Linux implementation helpers for exec.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_UNISTD_LINUX_EXEC_UTILS_H
+#define LLVM_LIBC_SRC_UNISTD_LINUX_EXEC_UTILS_H
+
+#include "hdr/errno_macros.h"
+#include "hdr/limits_macros.h"
+#include "hdr/types/size_t.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/OSUtil/linux/syscall_wrappers/execve.h"
+#include "src/__support/common.h"
+#include "src/__support/error_or.h"
+#include "src/__support/macros/config.h"
+#include "src/stdlib/environ_internal.h"
+#include "src/string/memory_utils/inline_memcpy.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace internal {
+
+// TODO: POSIX requires that if execve fails with ENOEXEC, the file is executed
+// using the system shell (as if by `sh -- file args...`). The kernel only
+// handles ELF, "#!" scripts, and binfmt_misc formats, so shebang-less scripts
+// currently fail with ENOEXEC instead of being run by /bin/sh.
+LIBC_INLINE ErrorOr<int> execvpe(cpp::string_view file, char *const argv[],
+                                 char *const envp[]) {
+  if (file.empty())
+    return Error(ENOENT);
+
+  // If there's a / in file, treat it as a path.
+  if (file.find_first_of('/') != cpp::string_view::npos)
+    return linux_syscalls::execve(file.data(), argv, envp);
+
+  // Otherwise treat file as the name of a file in a directory, search the
+  // directories listed in PATH.
+  //
+  // Per POSIX.1-2024 and Linux specifications, the search path is taken from
+  // the caller's environment (via EnvironmentManager), not from the `envp`
+  // argument passed to execvpe.
+  constexpr cpp::string_view DEFAULT_PATH = "/bin:/usr/bin";
+  const char *env_path =
+      internal::EnvironmentManager::get_instance().get("PATH");
+  cpp::string_view path_env =
+      env_path != nullptr ? cpp::string_view(env_path) : DEFAULT_PATH;
+
+  char buf[PATH_MAX];
+  bool seen_eacces = false;
+  int last_error = ENOENT;
+
+  for (size_t colon_pos = 0; colon_pos != cpp::string_view::npos;
+       path_env = path_env.substr(colon_pos + 1)) {
+    colon_pos = path_env.find_first_of(':');
+    cpp::string_view dir = path_env.substr(0, colon_pos);
+    if (dir.empty())
+      dir = ".";
+
+    if (dir.size() + 1 + file.size() >= PATH_MAX) {
+      last_error = ENAMETOOLONG;
+      continue;
+    }
+
+    inline_memcpy(buf, dir.data(), dir.size());
+    buf[dir.size()] = '/';
+    inline_memcpy(buf + dir.size() + 1, file.data(), file.size());
+    buf[dir.size() + 1 + file.size()] = '\0';
+
+    auto ret = linux_syscalls::execve(buf, argv, envp);
+    if (ret)
+      return ret;
+
+    int err = ret.error();
+    if (err == EACCES) {
+      seen_eacces = true;
+    } else if (err == ENOENT || err == ENOTDIR) {
+      last_error = err;
+    } else {
+      return Error(err);
+    }
----------------
amanmaurya92 wrote:

done

https://github.com/llvm/llvm-project/pull/234071