/**
* 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 <stdio.h>
/* TODO #include <sys/types.h> */
/* TODO #include <sys/stat.h> */
/* TODO temporary contants/structs from other headers { */
#define AT_FDCWD 1
#define AT_EMPTY_PATH 1
#define AT_SYMLINK_NOFOLLOW 1
#define _CS_PATH 1
struct stat { int st_mode; };
/* } */
/**
* 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*);
va_end(args);
(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, file);
vexecat(dirfd, file, 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, file);
vexecat(dirfd, file, 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 execvpeat(dirfd, file, 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 = NULL;
int saved_errno;
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);
execve(pathname, argv, envp);
saved_errno = errno;
free(pathname);
errno = saved_errno;
return -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 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);
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 = (eacces ? EACCES : ENOENT), -1;
fail:
saved_errno = errno;
free(path);
free(pathname);
errno = saved_errno;
return -1;
}
