xserver/os/backtrace.c

/*
 * Copyright 2008 Red Hat, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software")
 * to deal in the software without restriction, including without limitation
 * on the rights to use, copy, modify, merge, publish, distribute, sub
 * license, and/or sell copies of the Software, and to permit persons to whom
 * them Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTIBILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES, OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT, OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifdef HAVE_DIX_CONFIG_H
#include <dix-config.h>
#endif

#include "os.h"
#include "misc.h"

#ifdef HAVE_BACKTRACE
#include <execinfo.h>

void xorg_backtrace(void)
{
    void *array[32]; /* deeper nesting than this means something's wrong */
    int size, i;
    char **strings;
    ErrorF("\nBacktrace:\n");
    size = backtrace(array, 32);
    strings = backtrace_symbols(array, size);
    for (i = 0; i < size; i++)
        ErrorF("%d: %s\n", i, strings[i]);
    free(strings);
}

#else /* not glibc or glibc < 2.1 */

# if defined(sun) && defined(__SVR4)
#  define HAVE_PSTACK
# endif

# if defined(HAVE_WALKCONTEXT) /* Solaris 9 & later */

# include <ucontext.h>
# include <signal.h>
# include <dlfcn.h>
# include <sys/elf.h>

#ifdef _LP64
# define ElfSym Elf64_Sym
#else
# define ElfSym Elf32_Sym
#endif

/* Called for each frame on the stack to print it's contents */
static int xorg_backtrace_frame(uintptr_t pc, int signo, void *arg)
{
    Dl_info dlinfo;
    ElfSym *dlsym;
    char header[32];
    int depth = *((int *) arg);

    if (signo) {
	char signame[SIG2STR_MAX];

	if (sig2str(signo, signame) != 0) {
	    strcpy(signame, "unknown");
	}

	ErrorF("** Signal %d (%s)\n", signo, signame);
    }

    snprintf(header, sizeof(header), "%d: 0x%lx", depth, pc);
    *((int *) arg) = depth + 1;

    /* Ask system dynamic loader for info on the address */
    if (dladdr1((void *) pc, &dlinfo, (void **) &dlsym, RTLD_DL_SYMENT)) {
	unsigned long offset = pc - (uintptr_t) dlinfo.dli_saddr;
	const char *symname;
	
	if (offset < dlsym->st_size) { /* inside a function */
	    symname = dlinfo.dli_sname;
	} else { /* found which file it was in, but not which function */
	    symname = "<section start>";
	    offset = pc - (uintptr_t)dlinfo.dli_fbase;
	}
	ErrorF("%s: %s:%s+0x%lx\n", header, dlinfo.dli_fname,
	       symname, offset);

    } else {
	/* Couldn't find symbol info from system dynamic loader, should
	 * probably poke elfloader here, but haven't written that code yet,
	 * so we just print the pc.
	 */
	ErrorF("%s\n", header);
    }

    return 0;
}
# endif /* HAVE_WALKCONTEXT */

# ifdef HAVE_PSTACK
static int xorg_backtrace_pstack(void) {
    pid_t kidpid;
    int pipefd[2];

    if (pipe(pipefd) != 0) {
	return -1;
    }

    kidpid = fork1();

    if (kidpid == -1) {
	/* ERROR */
	return -1;
    } else if (kidpid == 0) {
	/* CHILD */
	char parent[16];
	
	seteuid(0);
	close(STDIN_FILENO);
	close(STDOUT_FILENO);
	dup2(pipefd[1],STDOUT_FILENO);
	closefrom(STDERR_FILENO);

	snprintf(parent, sizeof(parent), "%d", getppid());
	execle("/usr/bin/pstack", "pstack", parent, NULL);
	exit(1);
    } else {
	/* PARENT */
	char btline[256];
	int kidstat;
	int bytesread;
	int done = 0;
	
	close(pipefd[1]);

	while (!done) {
	    bytesread = read(pipefd[0], btline, sizeof(btline) - 1);

	    if (bytesread > 0) {
		btline[bytesread] = 0;
		ErrorF("%s", btline);
	    }
	    else if ((bytesread < 0) ||
		     ((errno != EINTR) && (errno != EAGAIN)))
		done = 1;
	}
	close(pipefd[0]);
	waitpid(kidpid, &kidstat, 0);
	if (kidstat != 0)
	    return -1;
    }
    return 0;
}
# endif /* HAVE_PSTACK */


# if defined(HAVE_PSTACK) || defined(HAVE_WALKCONTEXT)

void xorg_backtrace(void) {

    ErrorF("\nBacktrace:\n");

#  ifdef HAVE_PSTACK
/* First try fork/exec of pstack - otherwise fall back to walkcontext
   pstack is preferred since it can print names of non-exported functions */

    if (xorg_backtrace_pstack() < 0)
#  endif	
    {
#  ifdef HAVE_WALKCONTEXT
	ucontext_t u;
	int depth = 1;
	
	if (getcontext(&u) == 0)
	    walkcontext(&u, xorg_backtrace_frame, &depth);
	else
#  endif
	    Error("Failed to get backtrace info");
    }
    ErrorF("\n");	
}

# else

/* Default fallback if we can't find any way to get a backtrace */
void xorg_backtrace(void) { return; }

# endif
#endif