helper.c
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/*
* Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sched.h>
#include <linux/limits.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <kern_util.h>
#include <os.h>
#include <um_malloc.h>
struct helper_data {
void (*pre_exec)(void*);
void *pre_data;
char **argv;
int fd;
char *buf;
};
static int helper_child(void *arg)
{
struct helper_data *data = arg;
char **argv = data->argv;
int err, ret;
if (data->pre_exec != NULL)
(*data->pre_exec)(data->pre_data);
err = execvp_noalloc(data->buf, argv[0], argv);
/* If the exec succeeds, we don't get here */
CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
return 0;
}
/* Returns either the pid of the child process we run or -E* on failure. */
int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
{
struct helper_data data;
unsigned long stack, sp;
int pid, fds[2], ret, n;
stack = alloc_stack(0, __cant_sleep());
if (stack == 0)
return -ENOMEM;
ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
if (ret < 0) {
ret = -errno;
printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
errno);
goto out_free;
}
ret = os_set_exec_close(fds[1]);
if (ret < 0) {
printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
"ret = %d\n", -ret);
goto out_close;
}
sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
data.pre_exec = pre_exec;
data.pre_data = pre_data;
data.argv = argv;
data.fd = fds[1];
data.buf = __cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
if (pid < 0) {
ret = -errno;
printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
errno);
goto out_free2;
}
close(fds[1]);
fds[1] = -1;
/*
* Read the errno value from the child, if the exec failed, or get 0 if
* the exec succeeded because the pipe fd was set as close-on-exec.
*/
n = read(fds[0], &ret, sizeof(ret));
if (n == 0) {
ret = pid;
} else {
if (n < 0) {
n = -errno;
printk(UM_KERN_ERR "run_helper : read on pipe failed, "
"ret = %d\n", -n);
ret = n;
}
CATCH_EINTR(waitpid(pid, NULL, __WCLONE));
}
out_free2:
kfree(data.buf);
out_close:
if (fds[1] != -1)
close(fds[1]);
close(fds[0]);
out_free:
free_stack(stack, 0);
return ret;
}
int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
unsigned long *stack_out)
{
unsigned long stack, sp;
int pid, status, err;
stack = alloc_stack(0, __cant_sleep());
if (stack == 0)
return -ENOMEM;
sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
pid = clone(proc, (void *) sp, flags, arg);
if (pid < 0) {
err = -errno;
printk(UM_KERN_ERR "run_helper_thread : clone failed, "
"errno = %d\n", errno);
return err;
}
if (stack_out == NULL) {
CATCH_EINTR(pid = waitpid(pid, &status, __WCLONE));
if (pid < 0) {
err = -errno;
printk(UM_KERN_ERR "run_helper_thread - wait failed, "
"errno = %d\n", errno);
pid = err;
}
if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
printk(UM_KERN_ERR "run_helper_thread - thread "
"returned status 0x%x\n", status);
free_stack(stack, 0);
} else
*stack_out = stack;
return pid;
}
int helper_wait(int pid)
{
int ret, status;
int wflags = __WCLONE;
CATCH_EINTR(ret = waitpid(pid, &status, wflags));
if (ret < 0) {
printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
"errno = %d\n", pid, errno);
return -errno;
} else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
printk(UM_KERN_ERR "helper_wait : process %d exited with "
"status 0x%x\n", pid, status);
return -ECHILD;
} else
return 0;
}