Hi,
below is a small command line utility that I have been
working to allow set and forget of the PM_QOS values of
any command without the need to modify its code.
A lot of the code below deals with dropping privileges
if run setuid or under sudo. That somewhat distracts
from the simplicity of the main functionality.
I would be more than happy if a sensible home could
be found for this code.
/*
* pm-qos: run a command with pm_qos latency and throughput targets
*
* Copyright (C) 2011 Tsuru Capital LLC
* Author: Simon Horman <horms@xxxxxxxxxxxx>
*
* 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 2 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, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <stdint.h>
#include <pwd.h>
#include <grp.h>
#define PM_QOS_CPU_DMA_LATENCY_DEV "/dev/cpu_dma_latency"
#define PM_QOS_CPU_DMA_LATENCY_DEFAULT -1
#define PM_QOS_NET_LATENCY_DEV "/dev/network_latency"
#define PM_QOS_NET_LATENCY_DEFAULT -1
#define PM_QOS_NET_THROUGHPUT_DEV "/dev/network_throughput"
#define PM_QOS_NET_THROUGHPUT_DEFAULT -1
struct options {
int32_t cpu_dma_latency;
int32_t network_latency;
int32_t network_throughput;
};
#define DECLARE_OPTIONS(opt) \
struct options opt = { \
.cpu_dma_latency = PM_QOS_CPU_DMA_LATENCY_DEFAULT, \
.network_latency = PM_QOS_NET_LATENCY_DEFAULT, \
.network_throughput = PM_QOS_NET_THROUGHPUT_DEFAULT };
static void __pm_qos(const char *dev, int32_t target, const char *desc)
{
int fd;
ssize_t err;
fd = open(dev, O_RDWR);
if (fd < 0) {
switch (errno) {
case ENOENT:
fprintf(stderr, "warning: \"%s\" does not exist, "
"not setting pm_qos to target %s. "
"Kernel doesn't have pm_qos support?.\n",
dev, desc);
return;
case EACCES:
fprintf(stderr, "warning: no permissions to open "
"\"%s\" for writing, not setting pm_qos "
"to target %s. Try running as root?\n",
dev, desc);
return;
default:
fprintf(stderr, "warning: could not open \"%s\", "
"not setting pm_qos to target %s: open: %s\n",
dev, desc, strerror(errno));
return;
}
}
err = write(fd, &target, sizeof(target));
if (err < 0) {
fprintf(stderr, "warning: could not write to \"%s\", "
"not setting pm_qos to target %s: write: %s\n",
dev, desc, strerror(errno));
return;
}
if (err != sizeof(target)) {
fprintf(stderr, "warning: short write to \"%s\", "
"not setting pm_qos to target %s.\n", dev, desc);
return;
}
/* N.B: Keep fd open.
* This retains the pm_qos setting.
* See Documentation/power/pm_qos_interface.txt in the kernel
* source tree
*/
return;
}
static void pm_qos(struct options *opt)
{
if (opt->cpu_dma_latency >= 0)
__pm_qos(PM_QOS_CPU_DMA_LATENCY_DEV, opt->cpu_dma_latency,
"CPU DMA latency");
if (opt->network_latency >= 0)
__pm_qos(PM_QOS_NET_LATENCY_DEV, opt->network_latency,
"network latency");
if (opt->network_throughput >= 0)
__pm_qos(PM_QOS_NET_THROUGHPUT_DEV, opt->network_throughput,
"network throughput");
}
static void usage(const char *ident)
{
fprintf(stderr,
"usage:\n"
" %s target_cpu_dma_latency target_network_latency target_network_throughput cmd ...\n"
"\n"
" Run a command with pm_qos latency and throughput targets\n"
"\n"
" A negative value for a target indicates that a target\n"
" will not be set.\n"
"\n"
" Latency targets are in usec\n"
" Network throughput target is in kbit/s\n"
"\n",
ident);
exit (1);
}
static int32_t parse_int32(const char *str, const char *ident)
{
char *end;
long val;
errno = 0;
val = strtoll(str, &end, 10);
if ((errno == ERANGE && (val == LLONG_MAX || val == LLONG_MIN)) ||
(errno && !val)) {
perror("strtol");
usage(ident);
}
if (end == str || *end != '\0' || (int32_t)val != val)
usage(ident);
return val;
}
static uid_t parse_uid(const char *str)
{
char *end;
unsigned long val;
errno = 0;
val = strtoull(str, &end, 10);
if ((errno == ERANGE && val == ULLONG_MAX) || (errno && !val)) {
perror("strtol");
goto err;
}
if (end == str || *end != '\0' || (uid_t)val != val)
goto err;
return val;
err:
fprintf(stderr, "error: invalid SUDO_UID environment\n");
exit(1);
}
static gid_t parse_gid(const char *str)
{
char *end;
unsigned long val;
errno = 0;
val = strtoull(str, &end, 10);
if ((errno == ERANGE && val == ULLONG_MAX) || (errno && !val)) {
perror("strtol");
goto err;
}
if (end == str || *end != '\0' || (gid_t)val != val)
goto err;
return val;
err:
fprintf(stderr, "error: invalid SUDO_GID environment\n");
exit(1);
}
static void drop_privs(void)
{
const char *uid_str, *gid_str;
uid_t uid;
gid_t gid, groups[NGROUPS_MAX];
struct passwd *pwd;
int ngroups = 0;
if (geteuid())
return; /* not root, nothing to do */
if (getuid() || getgid()) { /* Running setuid or setgid */
uid = getuid();
gid = getgid();
} else { /* Running under sudo ? */
uid_str = getenv("SUDO_UID");
gid_str = getenv("SUDO_GID");
if (!uid_str && !gid_str)
return; /* not sudoed, nothing to do */
if (!uid_str || !gid_str) {
fprintf(stderr,
"error: invalid SUDO_UID/SUDO_GID \n"
"environment\n");
exit(1);
}
uid = parse_uid(uid_str);
gid = parse_gid(gid_str);
if (!uid)
return; /* Sudo run by root, nothing to do */
}
while (1) {
errno = 0;
pwd = getpwuid(uid);
if (pwd)
break;
switch (errno) {
case EINTR:
continue;
case EIO:
case ENFILE:
case ENOMEM:
case ERANGE:
perror("getpwname");
fprintf(stderr,
"error: can't lookup user %d\n", uid);
exit(1);
default:
fprintf(stderr,
"warning: can't lookup user %d, "
"not adding supplementry groups\n", uid);
break;
}
}
if (pwd) {
ngroups = NGROUPS_MAX;
if (getgrouplist(pwd->pw_name, gid, groups, &ngroups) < 0) {
fprintf(stderr,
"error: user \"%s\" is a member of too "
"many groups\n", pwd->pw_name);
exit(1);
}
if (setgroups(ngroups, groups)) {
fprintf(stderr,
"error: can't set supplementry groups\n");
exit(1);
}
}
if (setgid(gid)) {
perror("setsgid");
fprintf(stderr, "error: couldn't drop group privilages\n");
exit(1);
}
if (setuid(uid)) {
perror("setuid");
fprintf(stderr, "error: couldn't drop user privilages\n");
exit(1);
}
}
static void parse_options(int argc, char * const *argv, struct options *opt)
{
if (argc < 5)
usage(argv[0]);
opt->cpu_dma_latency = parse_int32(argv[1], argv[0]);
opt->network_latency = parse_int32(argv[2], argv[0]);
opt->network_throughput = parse_int32(argv[3], argv[0]);
}
static void cmd(int argc, char **argv)
{
memmove(argv, argv + 4, (argc - 4) * sizeof(char *));
argv[argc - 4] = NULL;
if (execvp(argv[0], argv))
perror("execp: ");
}
int main (int argc, char **argv)
{
DECLARE_OPTIONS(opt);
parse_options(argc, argv, &opt);
pm_qos(&opt);
drop_privs();
cmd(argc, argv);
return 0;
}
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