/**
* mds — A micro-display server
* Copyright © 2014 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 "util.h"
#include "config.h"
#include "macros.h"
#include <alloca.h>
#include <stdlib.h>
#include <unistd.h>
#include <limits.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <errno.h>
#include <ctype.h>
#include <time.h>
#include <sys/wait.h>
/**
* The content of `/proc/self/exe`, when
* `prepare_reexec` was invoked.
*/
static char self_exe[PATH_MAX] = {0};
/**
* Convert a client ID string into a client ID integer
*
* @param str The client ID string
* @return The client ID integer
*/
uint64_t parse_client_id(const char* str)
{
char client_words[22];
char* client_high;
char* client_low;
uint64_t client;
strcpy(client_high = client_words, str);
client_low = rawmemchr(client_words, ':');
*client_low++ = '\0';
client = atou64(client_high) << 32;
client |= atou64(client_low);
return client;
}
/**
* Read an environment variable, but handle it as undefined if empty
*
* @param var The environment variable's name
* @return The environment variable's value, `NULL` if empty or not defined
*/
char* getenv_nonempty(const char* var)
{
char* rc = getenv(var);
if ((rc == NULL) || (*rc == '\0'))
return NULL;
return rc;
}
/**
* Prepare the server so that it can reexec into
* a newer version of the executed file.
*
* This is required for two reasons:
* 1: We cannot use argv[0] as PATH-resolution may
* cause it to reexec into another pathname, and
* maybe to wrong program. Additionally argv[0]
* may not even refer to the program, and chdir
* could also hinter its use.
* 2: The kernel appends ` (deleted)` to
* `/proc/self/exe` once it has been removed,
* so it cannot be replaced.
*
* The function will should be called immediately, it
* will store the content of `/proc/self/exe`.
*
* @return Zero on success, -1 on error
*/
int prepare_reexec(void)
{
ssize_t len;
len = readlink(SELF_EXE, self_exe, (sizeof(self_exe) / sizeof(char)) - 1);
if (len < 0)
return -1;
/* ‘readlink() does not append a null byte to buf.’ */
self_exe[len] = '\0';
return 0;
}
/**
* Re-exec the server.
* This function only returns on failure.
*
* If `prepare_reexec` failed or has not been called,
* `argv[0]` will be used as a fallback.
*
* @param argc The number of elements in `argv`
* @param argv The command line arguments
* @param reexeced Whether the server has previously been re-exec:ed
*/
void reexec_server(int argc, char** argv, int reexeced)
{
char** reexec_args;
char** reexec_args_;
int i;
/* Re-exec the server. */
reexec_args = alloca(((size_t)argc + 2) * sizeof(char*));
reexec_args_ = reexec_args;
if (reexeced == 0)
{
*reexec_args_++ = *argv;
*reexec_args_ = strdup("--re-exec");
if (*reexec_args_ == NULL)
return;
for (i = 1; i < argc; i++)
reexec_args_[i] = argv[i];
}
else /* Don't let the --re-exec:s accumulate. */
*reexec_args_ = *argv;
for (i = 1; i < argc; i++)
reexec_args_[i] = argv[i];
reexec_args_[argc] = NULL;
execv(self_exe[0] ? self_exe : argv[0], reexec_args);
}
/**
* Set up a signal trap.
* This function should only be used for common mds
* signals and signals that does not require and
* special settings. This function may choose to add
* additional behaviour depending on the signal, such
* as blocking other signals.
*
* @param signo The signal to trap
* @param function The function to run when the signal is caught
* @return Zero on success, -1 on error
*/
int xsigaction(int signo, void (*function)(int signo))
{
struct sigaction action;
sigset_t sigset;
sigemptyset(&sigset);
action.sa_handler = function;
action.sa_mask = sigset;
action.sa_flags = 0;
return sigaction(signo, &action, NULL);
}
/**
* Send a message over a socket
*
* @param socket The file descriptor of the socket
* @param message The message to send
* @param length The length of the message
* @return The number of bytes that have been sent (even on error)
*/
size_t send_message(int socket, const char* message, size_t length)
{
size_t block_size = length;
size_t sent = 0;
ssize_t just_sent;
errno = 0;
while (length > 0)
if ((just_sent = send(socket, message + sent, min(block_size, length), MSG_NOSIGNAL)) < 0)
{
if (errno == EMSGSIZE)
{
block_size >>= 1;
if (block_size == 0)
return sent;
}
else
return sent;
}
else
{
sent += (size_t)just_sent;
length -= (size_t)just_sent;
}
return sent;
}
/**
* A version of `atoi` that is strict about the syntax and bounds
*
* @param str The text to parse
* @param value Slot in which to store the value
* @param min The minimum accepted value
* @param max The maximum accepted value
* @return Zero on success, -1 on syntax error
*/
int strict_atoi(const char* str, int* value, int min, int max)
{
long long int r;
char* endptr;
r = strtoll(str, &endptr, 10);
if ((*str == '\0') || isspace(*str) ||
(endptr - str != (ssize_t)strlen(str)) ||
(r < (long long int)min) ||
(r > (long long int)max))
return -1;
*value = (int)r;
return 0;
}
/**
* Send a buffer into a file and ignore interruptions
*
* @param fd The file descriptor
* @param buffer The buffer
* @param length The length of the buffer
* @return Zero on success, -1 on error
*/
int full_write(int fd, const char* buffer, size_t length)
{
ssize_t wrote;
while (length > 0)
{
errno = 0;
wrote = write(fd, buffer, length);
if (errno && (errno != EINTR))
return -1;
length -= (size_t)max(wrote, 0);
buffer += (size_t)max(wrote, 0);
}
return 0;
}
/**
* Read a file completely and ignore interruptions
*
* @param fd The file descriptor
* @param length Output parameter for the length of the file, may be `NULL`
* @return The content of the file, you will need to free it. `NULL` on error.
*/
char* full_read(int fd, size_t* length)
{
size_t buffer_size = 8 << 10;
size_t buffer_ptr = 0;
char* buffer;
ssize_t got;
if (length != NULL)
*length = 0;
/* Allocate buffer for data. */
if (xmalloc(buffer, buffer_size, char))
return NULL;
/* Read the file. */
for (;;)
{
/* Grow buffer if it is too small. */
if (buffer_size == buffer_ptr)
{
char* old_buf = buffer;
if (xrealloc(buffer, buffer_size <<= 1, char))
{
free(old_buf);
return NULL;
}
}
/* Read from the file into the buffer. */
got = read(fd, buffer + buffer_ptr, buffer_size - buffer_ptr);
if ((got < 0) && (errno != EINTR))
{
free(buffer);
return NULL;
}
if (got == 0)
break;
buffer_ptr += (size_t)got;
}
if (length != NULL)
*length = buffer_ptr;
return buffer;
}
/**
* Check whether a string begins with a specific string,
* where neither of the strings are necessarily NUL-terminated
*
* @param haystack The string that should start with the other string
* @param needle The string the first string should start with
* @param haystack_n The length of `haystack`
* @param needle_n The length of `needle`
* @return Whether the `haystack` begins with `needle`
*/
int startswith_n(const char* haystack, const char* needle, size_t haystack_n, size_t needle_n)
{
size_t i;
if (haystack_n < needle_n)
return 0;
for (i = 0; i < needle_n; i++)
if (haystack[i] != needle[i])
return 0;
return 1;
}
/**
* Wrapper around `waitpid` that never returns on an interruption unless
* it is interrupted 100 times within the same second
*
* @param pid See description of `pid` in the documentation for `waitpid`
* @param status See description of `status` in the documentation for `waitpid`
* @param options See description of `options` in the documentation for `waitpid`
* @return See the documentation for `waitpid`
*/
pid_t uninterruptable_waitpid(pid_t pid, int* restrict status, int options)
{
struct timespec time_start;
struct timespec time_intr;
int intr_count = 0, have_time;
pid_t rc;
have_time = (monotone(&time_start) >= 0);
rewait:
rc = waitpid(pid, status, options);
if (rc == (pid_t)-1)
{
if (errno != EINTR)
goto fail;
if (have_time && (monotone(&time_intr) >= 0))
if (time_start.tv_sec != time_intr.tv_sec)
intr_count = 0;
if (intr_count++ < 100)
goto rewait;
/* Don't let the CPU catch fire! */
errno = EINTR;
}
fail:
return rc;
}
