I'm trying to run QEMU's user mode emulator as a thread in a larger program that I'm writing. I've modified the linux-user/main.c file so that the standard int main(int argc, char **argv, char **envp function is now called void *qemu_user_mode_func(void *arg). I've also added pthread_exit(NULL) to the end of that function, as is standard practice for pthreads (or so I've been told).
However, when I try to run a second thread that contains my own test function (shown below in void *test_func(void *arg)), the process exits before the second thread completes, even with a call to pthread_join(tid), which I've read blocks the calling thread until thread tid returns. Does QEMU's user mode emulation exit in such a way that would prevent pthread_join from exiting, or am I just using threads wrong?
Here's my code (not including the bulk of qemu_user_mode_func):
void *qemu_user_mode_func(void *arg)
{
thread_data_t *thread_data;
int argc;
char **argv;
char **envp;
/** QEMU's normal code **/
//return 0;
pthread_exit(NULL);
}
void *test_func(void *arg) {
struct timespec time;
time.tv_sec = 7;
time.tv_nsec = 0;
nanosleep(&time, NULL);
printf("hello, world - from a thread\n");
pthread_exit(NULL);
}
int main(int argc, char**argv, char **envp) {
//Initialize variables to create thread
int rc;
pthread_t threads[2];
thread_data_t main_args;
main_args.tid = 1;
main_args.argc = argc;
main_args.argv = argv;
main_args.envp = envp;
//Create thread
if ((rc = pthread_create(&(threads[0]), NULL, test_func, NULL))) {
fprintf(stderr, "error: pthread_create, rc: %d\n", rc);
return EXIT_FAILURE;
}
if ((rc = pthread_create(&(threads[1]), NULL, qemu_user_mode_func, (void *)&main_args))) {
fprintf(stderr, "error: pthread_create, rc: %d\n", rc);
return EXIT_FAILURE;
}
//Wait for thread to finish, then terminate process
for (rc = 0; rc < 2; rc++) {
pthread_join(threads[rc], NULL);
}
return 0;
}
EDIT: I've discovered in the void cpu_loop(CPUX86State *env) function that when the emulated program reaches its conclusion, QEMU calls syscall 231, which is sys_exit_group (as per 1). So I'm guessing this syscall is terminating the entire process that I'm running. I'd appreciate any tips on how to get around that!
