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gamemode: Add function to search environment of a PID

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This function can look up arbitrary environment variables from a running
PID (given we have access permissions which should be usually true).

Signed-off-by: Kai Krakow <kai@kaishome.de>
This commit is contained in:
Kai Krakow 2018-10-03 01:21:14 +02:00
parent 47ea4514cd
commit c2344f4387
1 changed files with 38 additions and 0 deletions
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38
daemon/gamemode.c
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@ -38,6 +38,7 @@ POSSIBILITY OF SUCH DAMAGE.
#include "ioprio.h"
#include "logging.h"
#include <fcntl.h>
#include <linux/limits.h>
#include <linux/sched.h>
#include <pthread.h>
@ -45,6 +46,7 @@ POSSIBILITY OF SUCH DAMAGE.
#include <sched.h>
#include <signal.h>
#include <stdatomic.h>
#include <stdio.h>
#include <string.h>
#include <sys/param.h>
#include <sys/resource.h>
@ -673,6 +675,42 @@ GameModeContext *game_mode_context_instance()
return &instance;
}
/**
* Lookup the process environment for a specific variable or return NULL.
* Requires an open directory FD from /proc/PID.
*/
static char *game_mode_lookup_proc_env(int proc_fd, const char *var)
{
char *environ = NULL;
int fd = openat(proc_fd, "environ", O_RDONLY | O_CLOEXEC);
if (fd != -1) {
FILE *stream = fdopen(fd, "r");
if (stream) {
/* Read every \0 terminated line from the environment */
char *line = NULL;
size_t len = 0;
size_t pos = strlen(var) + 1;
while (!environ && (getdelim(&line, &len, 0, stream) != -1)) {
/* Find a match including the "=" suffix */
if ((len > pos) && (strncmp(line, var, strlen(var)) == 0) && (line[pos - 1] == '='))
environ = strndup(line + pos, len - pos);
}
free(line);
fclose(stream);
} else
close(fd);
}
/* If found variable is empty, skip it */
if (environ && !strlen(environ)) {
free(environ);
environ = NULL;
}
return environ;
}
/**
* Lookup the home directory of the user in a safe way.
*/