/**
* slibc — Yet another C library
* Copyright © 2015, 2016 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 <stdio.h>
/**
* The directory where all the process's file descriptors are available.
*/
#if defined(_LINUX_)
# define FD_PATH "/proc/self/fd" /* /dev/fd works but it is a symbolic link. */
#else
# define FD_PATH "/dev/fd"
#endif
/**
* The current environment variables.
*
* @since Always.
*/
extern char** environ;
/**
* Common code for the `fexecl*` functions.
*
* @param fd The first argument of said functions.
* @param argv The rest of the arguments of said functions;
* may conclude `envp`.
* @param fetch_envp Whether `argv` includes `envp`.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
static void vfexec(int fd, va_list argv, int fetch_envp)
{
char* const* envp = environ;
size_t n = 0, i;
va_list args;
char** argv_;
va_copy(args, argv);
while (n++, va_arg(args, char*) != NULL)
break;
if (fetch_envp)
envp = va_arg(args, char* const*);
argv_ = alloca(n * sizeof(char*));
for (i = 0; i < n; i++)
argv_[i] = va_arg(argv, char*);
va_end(args);
fexecve(fd, argv_, envp);
}
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param fd File descriptor for 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.
* @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 execve(2).
*
* @since Always.
*/
int fexecl(int fd, ... /*, NULL */)
{
int saved_errno;
va_list argv;
va_start(argv, fd);
vfexec(fd, argv, 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 fd File descriptor for 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`.
* @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 execve(2).
*
* @since Always.
*/
int fexecle(int fd, ... /*, NULL, char* const envp[] */)
{
int saved_errno;
va_list argv;
va_start(argv, fd);
vfexec(fd, argv, 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 fd File descriptor for 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`.
* @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 execve(2).
*
* @since Always.
*/
int fexecv(int fd, char* const argv[])
{
return fexecve(fd, argv, environ);
}
/**
* Replace the current process image with a new process image.
*
* @param fd File descriptor for 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`.
* @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 execve(2).
*
* @since Always.
*/
int fexecve(int fd, char* const argv[], char* const envp[])
{
char pathname[sizeof(FD_PATH "//") + 3 * sizeof(int)];
int saved_errno;
sprintf(pathname, FD_PATH "/%i/", fd);
execve(pathname, argv, envp);
saved_errno = errno;
if (access(FD_PATH "/", X_OK))
saved_errno = ENOSYS;
errno = saved_errno == ENOENT ? EBADF : saved_errno;
return -1;
}
