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List:       ltp-list
Subject:    Re: [LTP] Handle Bad Test Cases
From:       Mike Frysinger <vapier () gentoo ! org>
Date:       2008-10-27 8:38:28
Message-ID: 200810270438.31058.vapier () gentoo ! org
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On Monday 27 October 2008, Mike Frysinger wrote:
> On Thursday 23 October 2008, CAI Qian wrote:
> > Also, it leaves lots of processes after the test completes.
>
> that's what we call *a bug*.  fix it instead of just saying "oh it's broken
> lets forget about it".  the code already attempts to kill all of its
> children as can be seen clearly in the ptrace06.c at the end.  and it works
> fine on my x86_64 systems.

actually, i dont think this is a bug in ptrace06.  it actually looks like 
ptrace06 is doing what it was supposed to do: find bugs in the libc/kernel.  
the kernel should have enabled tracing on the child and thus halted it in the 
execve() call never allowing it to actually run.  if it did run, then either 
my understanding of ptrace is wrong, or the kernel is screwing up.  i'm 
pretty sure my ptrace code is correct.  the attached reduced test case shows 
the issue at any rate.  i'll follow up on LKML.

$ gcc -Wall ptrace-vfork-traceme.c -o ptrace-vfork-traceme
$ while ./ptrace-vfork-traceme ; do :; done
SUCCESS! :D
SUCCESS! :D
SUCCESS! :D
SUCCESS! :D
SUCCESS! :D
SUCCESS! :D
SUCCESS! :D
SUCCESS! :D
SUCCESS! :D
failure, child exited with 17: Child exited
wait() = 12275
status = 1407
        WIFEXITED = 0
        WEXITSTATUS = 5
        WIFSIGNALED = 0
        WTERMSIG = 127 (Unknown signal 127)
-mike

["signature.asc" (application/pgp-signature)]
["ptrace-vfork-traceme.c" (text/x-csrc)]

#define _GNU_SOURCE
#include <errno.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ptrace.h>
#include <sys/wait.h>

#define fail(msg, args...) \
do { \
	fprintf(stderr, "FAIL:%i: " msg "\n", __LINE__, ## args); \
	exit(1); \
} while (0)

static void child_exit(int sig)
{
	int status;
	printf("failure, child exited with %i: %s\n", sig, strsignal(sig));
	printf("wait() = %i\n", wait(&status));
	printf("status = %i\n", status);
	printf("\tWIFEXITED = %i\n", WIFEXITED(status));
	printf("\tWEXITSTATUS = %i\n", WEXITSTATUS(status));
	printf("\tWIFSIGNALED = %i\n", WIFSIGNALED(status));
	printf("\tWTERMSIG = %i (%s)\n", WTERMSIG(status), strsignal(WTERMSIG(status)));
	exit(1);
}

int main(int argc, char *argv[])
{
	long pret;
	pid_t pid;

	/* child process ... shouldnt be executed, but just in case ... */
	if (argc > 1 && !strcmp(argv[1], "child"))
		fail("kernel should have halted me...");

	pid = vfork();
	if (pid == -1)
		fail("vfork() didnt work: %m");
	else if (!pid) {
		/* do the child stuff here */
		errno = 0;
		pret = ptrace(PTRACE_TRACEME, 0, NULL, NULL);
		if (pret && errno)
			fail("ptrace(PTRACE_TRACEME) = %li: %m", pret);

		int eret = execlp(argv[0], argv[0], "child", NULL);
		fail("execlp() = %i", eret);
	}

	/* do the parent stuff here */
	signal(SIGCHLD, child_exit);

	errno = 0;
	pret = ptrace(PTRACE_PEEKUSER, pid, NULL, NULL);
	if (pret && errno)
		fail("ptrace(PTRACE_PEEKUSER, %i) = %li: %m", pid, pret);

	puts("SUCCESS! :D");

	return 0;
}


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