add execat functions

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 507 insertions, 0 deletions

diff --git a/src/unistd/execat.c b/src/unistd/execat.c
new file mode 100644
index 0000000..d80d24b
--- /dev/null
+++ b/src/unistd/execat.c
@@ -0,0 +1,507 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <unistd.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <alloca.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+
+
+/**
+ * The current environment variables.
+ */
+extern char** environ;
+
+
+
+/**
+ * Common code for the `execl*at` functions.
+ * 
+ * @param   dirfd       The first argument of said functions.
+ * @param   file        The second argument of said functions.
+ * @param   argv        The rest of the arguments of said functions;
+ *                      may conclude `envp`.
+ * @param   fetch_envp  Whether `argv` includes `envp`.
+ * @param   use_path    Whether $PATH may be used.
+ * 
+ * @throws              Any error specified for execve(2).
+ */
+static void vexecat(int dirfd, const char* file, va_list argv, int fetch_envp, int use_path)
+{
+  char* const* envp = environ;
+  size_t n = 0, i;
+  va_list args;
+  char** argv_;
+  int flags;
+  
+  va_copy(args, argv);
+  while (n++, va_arg(args, char*) != NULL)
+    break;
+  
+  if (fetch_envp)
+    envp = va_arg(args, char* const*);
+  flags = va_arg(args, int);
+  
+  argv_ = alloca(n * sizeof(char*));
+  for (i = 0; i < n; i++)
+    argv_[i] = va_arg(argv, char*);
+  
+  (void)(use_path ? execvpeat : execveat)(dirfd, file, argv_, envp, flags);
+}
+
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   path   The pathname of the file to execute.
+ * @param   ...    The arguments with which to execute the file.
+ *                 The arguments should have the type `const char*`.
+ *                 As a slibc extension, it can be empty.
+ *                 This list shall be terminated by a `NULL` sentinel.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `path` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `path` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execlat(int dirfd, const char* path, ... /*, NULL, int flags */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexecat(dirfd, path, argv, 0, 0);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   file   The pathname of the file to execute,
+ *                 or the filename of a file in $PATH,
+ *                 to execute. If $PATH is not set, the current
+ *                 working directory (yes, you read that right,)
+ *                 and a default value for $PATH will be used.
+ * @param   ...    The arguments with which to execute the file.
+ *                 The arguments should have the type `const char*`.
+ *                 As a slibc extension, it can be empty.
+ *                 This list shall be terminated by a `NULL` sentinel.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `file` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `file` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execlpat(int dirfd, const char* file, ... /*, NULL, int flags */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexecat(dirfd, path, argv, 0, 1);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   path   The pathname of the file to execute.
+ * @param   ...    The arguments with which to execute the file.
+ *                 The arguments should have the type `const char*`.
+ *                 As a slibc extension, it can be empty.
+ *                 This list shall be terminated by a `NULL` sentinel.
+ * @param   envp   The list of environment variables the new program shall
+ *                 have set. Each element shall be formatted $name=$value.
+ *                 This list shall be `NULL`-terminated. The behaviour
+ *                 is system-dependant if this argument is `NULL`.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `path` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `path` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execleat(int dirfd, const char* path, ... /*, NULL, char* const[] envp, int flags */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexecat(dirfd, path, argv, 1, 0);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   file   The pathname of the file to execute,
+ *                 or the filename of a file in $PATH,
+ *                 to execute. If $PATH is not set, the current
+ *                 working directory (yes, you read that right,)
+ *                 and a default value for $PATH will be used.
+ * @param   ...    The arguments with which to execute the file.
+ *                 The arguments should have the type `const char*`.
+ *                 As a slibc extension, it can be empty.
+ *                 This list shall be terminated by a `NULL` sentinel.
+ * @param   envp   The list of environment variables the new program shall
+ *                 have set. Each element shall be formatted $name=$value.
+ *                 This list shall be `NULL`-terminated. The behaviour
+ *                 is system-dependant if this argument is `NULL`.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `file` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `file` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execlpeat(int dirfd, const char* file, ... /*, NULL, char* const[] envp, int flags */)
+{
+  int saved_errno;
+  va_list argv;
+  va_start(argv, path);
+  vexecat(dirfd, path, argv, 1, 1);
+  saved_errno = errno;
+  va_end(argv);
+  return errno = saved_errno, -1;
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   path   The pathname of the file to execute.
+ * @param   argv   The arguments with which to execute the file.
+ *                 This parameter should really have the type
+ *                 `const char* const[]`, but that probably not
+ *                 so because compiles take issue with casts
+ *                 adding const to any pointer in the type
+ *                 except the outmost pointer. This list shall
+ *                 be `NULL`-terminated. The behaviour is
+ *                 system-dependant if this argument is `NULL`.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `path` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `path` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execvat(int dirfd, const char* path, char* const argv[], int flags)
+{
+  return execveat(dirfd, path, argv, environ, flags);
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   file   The pathname of the file to execute,
+ *                 or the filename of a file in $PATH,
+ *                 to execute. If $PATH is not set, the current
+ *                 working directory (yes, you read that right,)
+ *                 and a default value for $PATH will be used.
+ * @param   argv   The arguments with which to execute the file.
+ *                 This parameter should really have the type
+ *                 `const char* const[]`, but that probably not
+ *                 so because compiles take issue with casts
+ *                 adding const to any pointer in the type
+ *                 except the outmost pointer. This list shall
+ *                 be `NULL`-terminated. The behaviour is
+ *                 system-dependant if this argument is `NULL`.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `file` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `file` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execvpat(int dirfd, const char* file, char* const argv[], int flags)
+{
+  return execvpe(dirfd, path, argv, environ, flags);
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   path   The pathname of the file to execute.
+ * @param   argv   The arguments with which to execute the file.
+ *                 This parameter should really have the type
+ *                 `const char* const[]`, but that probably not
+ *                 so because compiles take issue with casts
+ *                 adding const to any pointer in the type
+ *                 except the outmost pointer. This list shall
+ *                 be `NULL`-terminated. The behaviour is
+ *                 system-dependant if this argument is `NULL`.
+ * @param   envp   The list of environment variables the new program shall
+ *                 have set. Each element shall be formatted $name=$value.
+ *                 This list shall be `NULL`-terminated. The behaviour
+ *                 is system-dependant if this argument is `NULL`.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `path` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `path` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execveat(int dirfd, const char* path, char* const argv[], char* const envp[], int flags)
+{
+/* TODO use linux system call if available */
+  struct stat attr;
+  char* pathname;
+  
+  if (*path == '/')
+    return execve(path, argv, envp);
+  
+  if ((dirfd == AT_FDCWD) && (flags & AT_EMPTY_PATH) && !*path)
+    return errno = EISDIR, -1;
+  
+  if ((dirfd == AT_FDCWD) && (flags & AT_SYMLINK_NOFOLLOW))
+    {
+      if (lstat(path, &attr))
+	return -1;
+      if (S_IFLNK(attr.st_mode))
+	return errno = ELOOP, -1;
+    }
+  
+  pathname = malloc(sizeof("/dev/fd//") + (3 * sizeof(int) + strlen(path)) * sizeof(char));
+  if (pathname == NULL)
+    return -1;
+  
+  sprintf(pathname, "/dev/fd/%i%s%s", dirfd, *path ? "/" : "", path);
+  return execve(pathname, argv, envp);
+}
+
+
+/**
+ * Replace the current process image with a new process image.
+ * 
+ * This is a slibc extension.
+ * 
+ * @param   dirfd  File descriptor for a directory (opened with
+ *                 with the open(2) `O_PATH` flag,) that will
+ *                 act as the current working directory.
+ *                 If `AT_FDCWD`, the current working directory
+ *                 will be used.
+ * @param   file   The pathname of the file to execute,
+ *                 or the filename of a file in $PATH,
+ *                 to execute. If $PATH is not set, the current
+ *                 working directory (yes, you read that right,)
+ *                 and a default value for $PATH will be used.
+ * @param   argv   The arguments with which to execute the file.
+ *                 This parameter should really have the type
+ *                 `const char* const[]`, but that probably not
+ *                 so because compiles take issue with casts
+ *                 adding const to any pointer in the type
+ *                 except the outmost pointer. This list shall
+ *                 be `NULL`-terminated. The behaviour is
+ *                 system-dependant if this argument is `NULL`.
+ * @param   envp   The list of environment variables the new program shall
+ *                 have set. Each element shall be formatted $name=$value.
+ *                 This list shall be `NULL`-terminated. The behaviour
+ *                 is system-dependant if this argument is `NULL`.
+ * @param   flags  Bit mask that can include zero or more of the
+ *                 following flags:
+ *                   AT_EMPTY_PATH:
+ *                     If `file` is an empty string, operate on the
+ *                     file (not directory) referred to by `dirfd`.
+ *                   AT_SYMLINK_NOFOLLOW:
+ *                     If `file` is relative is a symbolic link,
+ *                     fail with `errno` set to `ELOOP`.
+ * @return         This function does not return on success,
+ *                 on error, -1 is returned and `errno` is
+ *                 set to describe the error.
+ * 
+ * @throws         Any error specified for execveat(2).
+ */
+int execvpeat(int dirfd, const char* file, char* const argv[], char* const envp[], int flags)
+{
+  char* path = NULL;
+  char* pathname = NULL;
+  char* p;
+  char* q;
+  size_t len = 0;
+  int eacces = 0;
+  int saved_errno;
+  
+  if (strchr(file, '/') || !*file)
+    return execveat(dirfd, file, argv, envp, flags);
+  
+  if (!*file)
+    return errno = ENOENT, -1;
+  
+  path = getenv(PATH);
+  if (path == NULL)
+    {
+      execveat(dirfd, file, argv, envp, flags);
+      if      (errno == EACCES)  eacces = 1;
+      else if (errno != ENOENT)  goto fail;
+      
+      if ((len = confstr(_CS_PATH, NULL, 0)))
+	{
+	  path = malloc(len * sizeof(char));
+	  if (path == NULL)
+	    goto fail;
+	  if (!confstr(_CS_PATH, path, len))
+	    free(path), path = NULL;
+	}
+      if (path == NULL)
+	path = strdup("/usr/local/bin:/bin:/usr/bin");
+    }
+  else
+    path = strdup(path);
+  if (path == NULL)
+    goto fail;
+  
+  pathname = malloc((strlen(path) + strlen(file) + 2) * sizeof(char));
+  if (pathname == NULL)
+    goto fail;
+  
+  for (p = path; *p; p = q + 1)
+    {
+      if (p == (q = strchr(p, ':')))
+	continue;
+      *q = '\0';
+      
+      stpcpy(stpcpy(stpcpy(pathname, p), "/"), file);
+      
+      execve(pathname, argv, envp);
+      if      (errno == EACCES)  eacces = 1;
+      else if (errno != ENOENT)  goto fail;
+    }
+  
+  free(path);
+  free(pathname);
+  return errno = (eaccess ? EACCES : ENOENT), -1;
+  
+ fail:
+  saved_errno = errno;
+  free(path);
+  free(pathname);
+  errno = saved_errno;
+  return -1;
+}
+