thread-dbreg-test-pt2.c

/* $Id: thread-dbreg-test-pt2.c,v 1.7 2020/11/09 11:42:26 kostik Exp kostik $ */

#include <sys/types.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <machine/reg.h>
#include <assert.h>
#include <err.h>
#include <pthread.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>

volatile int g_val;
volatile int g_val2;

static void *
thread_func(void* foo __unused) {
	return (NULL);
}

static void
waitdbg(pid_t pid, int sig)
{
	pid_t waited;
	int nthr, ret;

	waited = waitpid(pid, &ret, 0);
	printf("wait: pid=%d, waited=%d, ret=%x\n", pid, waited, ret);
	assert(waited == pid);
	if (sig < 0) {
		assert(WIFEXITED(ret));
		return;
	}

	assert(WSTOPSIG(ret) == sig);

	nthr = ptrace(PT_GETNUMLWPS, pid, NULL, 0);
	if (nthr == -1)
		err(1, "PT_GETNUMLWPS");
	lwpid_t ids[nthr];
	ret = ptrace(PT_GETLWPLIST, pid, (caddr_t)&ids, nthr);
	if (ret == -1)
		err(1, "PT_GETLWPLIST");
	printf("threads:");
	for (int i = 0; i < nthr; i++)
		printf(" %d", ids[i]);
	printf("\n");
}

int
main(void)
{
	int ret;
	int pid = fork();
	assert(pid != -1);
	if (pid == 0) {
		pthread_t t2;

		ret = ptrace(PT_TRACE_ME, 0, NULL, 0);
		assert(ret != -1);
		// 2. wait for parent to set dbregs
		raise(SIGSTOP);

		// 4. start new thread and stop immediately afterwards
		ret = pthread_create(&t2, NULL, thread_func, NULL);
		assert(ret == 0);
		raise(SIGSTOP);
		printf("thread started\n");

		ret = pthread_join(t2, NULL);
		assert(ret == 0);
		printf("thread joined\n");
		_exit(0);
	}

	// 1. wait for the child to start
	waitdbg(pid, SIGSTOP);

	struct ptrace_lwpinfo info;
	ret = ptrace(PT_LWPINFO, pid, (caddr_t)&info, sizeof(info));
	assert(ret != -1);
	assert(info.pl_flags == PL_FLAG_SI);
	printf("tid = %d, SIGSTOP\n", info.pl_lwpid);

	// 3. set event mask & dbregs
	int ev = PTRACE_LWP;
	ret = ptrace(PT_SET_EVENT_MASK, pid, (caddr_t)&ev, sizeof(ev));
	assert(ret != -1);

	struct dbreg db;
	ret = ptrace(PT_GETDBREGS, info.pl_lwpid, (caddr_t)&db, 0);
	assert(ret != -1);

	db.dr[0] = (uintptr_t)&g_val;
	db.dr[7] = 0x303;
	ret = ptrace(PT_SETDBREGS, info.pl_lwpid, (caddr_t)&db, 0);
	assert(ret != -1);
	printf("set DR0=%p (&g_val) on tid=%d\n", (void*)db.dr[0], info.pl_lwpid);

	ret = ptrace(PT_CONTINUE, pid, (caddr_t)1, 0);
	assert(ret != -1);

	// 5. we should get SIGSTOP first, change dbregs
	waitdbg(pid, SIGSTOP);

	ret = ptrace(PT_LWPINFO, pid, (caddr_t)&info, sizeof(info));
	assert(ret != -1);
	assert(info.pl_flags == PL_FLAG_SI);
	printf("tid = %d, SIGSTOP\n", info.pl_lwpid);

	ret = ptrace(PT_GETDBREGS, info.pl_lwpid, (caddr_t)&db, 0);
	assert(ret != -1);

	db.dr[0] = (uintptr_t)&g_val2;
	db.dr[7] = 0x303;
	ret = ptrace(PT_SETDBREGS, info.pl_lwpid, (caddr_t)&db, 0);
	assert(ret != -1);
	printf("set DR0=%p (&g_val2) on tid=%d\n", (void*)db.dr[0], info.pl_lwpid);

	ret = ptrace(PT_CONTINUE, pid, (caddr_t)1, 0);
	assert(ret != -1);

	// 6. now we should get the new thread event
	waitdbg(pid, SIGTRAP);

	ret = ptrace(PT_LWPINFO, pid, (caddr_t)&info, sizeof(info));
	assert(ret != -1);
	assert(info.pl_flags & PL_FLAG_BORN);
	printf("tid = %d, SIGTRAP w/ PL_FLAG_BORN\n", info.pl_lwpid);

	ret = ptrace(PT_GETDBREGS, info.pl_lwpid, (caddr_t)&db, 0);
	assert(ret != -1);
	printf("dr0=%p, g_val=%p, g_val2=%p\n", (void*)db.dr[0], &g_val, &g_val2);

	ret = ptrace(PT_CONTINUE, pid, (caddr_t)1, 0);
	assert(ret != -1);

	// thread exited
	waitdbg(pid, SIGTRAP);

	ret = ptrace(PT_LWPINFO, pid, (caddr_t)&info, sizeof(info));
	assert(ret != -1);
	assert(info.pl_flags & PL_FLAG_EXITED);
	printf("tid = %d, SIGTRAP w/ PL_FLAG_EXITED\n", info.pl_lwpid);

	ret = ptrace(PT_CONTINUE, pid, (caddr_t)1, 0);
	assert(ret != -1);

	waitdbg(pid, -1);
}