pexecname.c

Sun Solaris 10 中的 DTrace 组件的源代码。请参看: http://www.sun.com/software/solaris/observability.jsp

/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only.
 * See the file usr/src/LICENSING.NOTICE in this distribution or
 * http://www.opensolaris.org/license/ for details.
 */

#pragma ident	"@(#)Pexecname.c	1.3	04/03/09 SMI"

#define	__EXTENSIONS__
#include <string.h>
#undef	__EXTENSIONS__

#include <libgen.h>
#include <limits.h>
#include <stdio.h>
#include <errno.h>
#include <unistd.h>

#include "Pcontrol.h"

/*
 * Pexecname.c - Way too much code to attempt to derive the full pathname of
 * the executable file from a process handle, be it dead or alive.
 */

/*
 * Once we've computed a cwd and a relative path, we use try_exec() to
 * form an absolute path, call resolvepath() on it, and then let the
 * caller's function do the final confirmation.
 */
static int
try_exec(const char *cwd, const char *path, char *buf,
    int (*isexec)(const char *, void *), void *isdata)
{
	int i;

	if (path[0] != '/')
		(void) snprintf(buf, PATH_MAX, "%s/%s", cwd, path);
	else
		(void) strcpy(buf, path);

	dprintf("try_exec \"%s\"\n", buf);

	if ((i = resolvepath(buf, buf, PATH_MAX)) > 0) {
		buf[i] = '\0';
		return (isexec(buf, isdata));
	}

	return (0); /* resolvepath failed */
}

/*
 * The Pfindexec function contains the logic for the executable name dance.
 * The caller provides a possible executable name or likely directory (the
 * aout parameter), and a function which is responsible for doing any
 * final confirmation on the executable pathname once a possible full
 * pathname has been chosen.
 */
char *
Pfindexec(struct ps_prochandle *P, const char *aout,
    int (*isexec)(const char *, void *), void *isdata)
{
	char cwd[PATH_MAX * 2];
	char path[PATH_MAX];
	char buf[PATH_MAX];
	struct stat st;
	uintptr_t addr;
	char *p, *q;

	if (P->execname)
		return (P->execname); /* Already found */

	errno = 0; /* Set to zero so we can tell if stat() failed */

	/*
	 * First try: use the provided default value, if it is not a directory.
	 * If the aout parameter turns out to be a directory, this is
	 * interpreted as the directory to use as an alternate cwd for
	 * our subsequent attempts to locate the executable.
	 */
	if (aout != NULL && stat(aout, &st) == 0 && !S_ISDIR(st.st_mode)) {
		if (try_exec(".", aout, buf, isexec, isdata))
			goto found;
		else
			aout = ".";

	} else if (aout == NULL || errno != 0)
		aout = ".";

	/*
	 * At this point 'aout' is either "." or an alternate cwd.  We use
	 * realpath(3c) to turn this into a full pathname free of ".", "..",
	 * and symlinks.  If this fails for some reason, fall back to "."
	 */
	if (realpath(aout, cwd) == NULL)
		(void) strcpy(cwd, ".");

	/*
	 * Second try: read the string pointed to by the AT_SUN_EXECNAME
	 * auxv element, saved when the program was exec'd.  If the full
	 * pathname try_exec() forms fails, try again using just the
	 * basename appended to our cwd.
	 */
	if ((addr = Pgetauxval(P, AT_SUN_EXECNAME)) != (uintptr_t)-1L &&
	    Pread_string(P, path, sizeof (path), (off_t)addr) > 0) {

		if (try_exec(cwd, path, buf, isexec, isdata))
			goto found;

		if (strchr(path, '/') != NULL && basename(path) != NULL &&
		    try_exec(cwd, path, buf, isexec, isdata))
			goto found;
	}

	/*
	 * Third try: try using the first whitespace-separated token
	 * saved in the psinfo_t's pr_psargs (the initial value of argv[0]).
	 */
	if (Ppsinfo(P) != NULL) {
		(void) strncpy(path, P->psinfo.pr_psargs, PRARGSZ);
		path[PRARGSZ] = '\0';

		if ((p = strchr(path, ' ')) != NULL)
			*p = '\0';

		if (try_exec(cwd, path, buf, isexec, isdata))
			goto found;

		if (strchr(path, '/') != NULL && basename(path) != NULL &&
		    try_exec(cwd, path, buf, isexec, isdata))
			goto found;
	}

	/*
	 * Fourth try: read the string pointed to by argv[0] out of the
	 * stack in the process's address space.
	 */
	if (P->psinfo.pr_argv != NULL &&
	    Pread(P, &addr, sizeof (addr), P->psinfo.pr_argv) != -1 &&
	    Pread_string(P, path, sizeof (path), (off_t)addr) > 0) {

		if (try_exec(cwd, path, buf, isexec, isdata))
			goto found;

		if (strchr(path, '/') != NULL && basename(path) != NULL &&
		    try_exec(cwd, path, buf, isexec, isdata))
			goto found;
	}

	/*
	 * Fifth try: read the process's $PATH environment variable and
	 * search each directory named there for the name matching pr_fname.
	 */
	if (Pgetenv(P, "PATH", cwd, sizeof (cwd)) != NULL) {
		/*
		 * If the name from pr_psargs contains pr_fname as its
		 * leading string, then accept the name from pr_psargs
		 * because more bytes are saved there.  Otherwise use
		 * pr_fname because this gives us new information.
		 */
		(void) strncpy(path, P->psinfo.pr_psargs, PRARGSZ);
		path[PRARGSZ] = '\0';

		if ((p = strchr(path, ' ')) != NULL)
			*p = '\0';

		if (strchr(path, '/') != NULL || strncmp(path,
		    P->psinfo.pr_fname, strlen(P->psinfo.pr_fname)) != 0)
			(void) strcpy(path, P->psinfo.pr_fname);

		/*
		 * Now iterate over the $PATH elements, trying to form
		 * an executable pathname with each one.
		 */
		for (p = strtok_r(cwd, ":", &q); p != NULL;
		    p = strtok_r(NULL, ":", &q)) {

			if (*p != '/')
				continue; /* Ignore anything relative */

			if (try_exec(p, path, buf, isexec, isdata))
				goto found;
		}
	}

	errno = ENOENT;
	return (NULL);

found:
	if ((P->execname = strdup(buf)) == NULL)
		dprintf("failed to malloc; executable name is \"%s\"", buf);

	return (P->execname);
}

/*
 * Callback function for Pfindexec().  We return a match if we can stat the
 * suggested pathname and confirm its device and inode number match our
 * previous information about the /proc/<pid>/object/a.out file.
 */
static int
stat_exec(const char *path, struct stat64 *stp)
{
	struct stat64 st;

	return (stat64(path, &st) == 0 && S_ISREG(st.st_mode) &&
	    stp->st_dev == st.st_dev && stp->st_ino == st.st_ino);
}

/*
 * Return the full pathname for the executable file.  If the process handle is
 * a core file, we've already tried our best to get the executable name.
 * Otherwise, we make an attempt using Pfindexec().
 */
char *
Pexecname(struct ps_prochandle *P, char *buf, size_t buflen)
{
	if (P->execname == NULL && P->state != PS_DEAD && P->state != PS_IDLE) {
		char exec_name[PATH_MAX];
		char cwd[PATH_MAX];
		char proc_cwd[64];
		struct stat64 st;
		int ret;

		/*
		 * Try to get the path information first.
		 */
		(void) snprintf(exec_name, sizeof (exec_name),
		    "/proc/%d/path/a.out", (int)P->pid);
		if ((ret = readlink(exec_name, buf, buflen - 1)) > 0) {
			buf[ret] = '\0';
			return (buf);
		}

		/*
		 * Stat the executable file so we can compare Pfindexec's
		 * suggestions to the actual device and inode number.
		 */
		(void) snprintf(exec_name, sizeof (exec_name),
		    "/proc/%d/object/a.out", (int)P->pid);

		if (stat64(exec_name, &st) != 0 || !S_ISREG(st.st_mode))
			return (NULL);

		/*
		 * Attempt to figure out the current working directory of the
		 * target process.  This only works if the target process has
		 * not changed its current directory since it was exec'd.
		 */
		(void) snprintf(proc_cwd, sizeof (proc_cwd),
		    "/proc/%d/path/cwd", (int)P->pid);

		if ((ret = readlink(proc_cwd, cwd, PATH_MAX - 1)) > 0)
			cwd[ret] = '\0';

		(void) Pfindexec(P, ret > 0 ? cwd : NULL,
		    (int (*)(const char *, void *))stat_exec, &st);
	}

	if (P->execname != NULL) {
		(void) strncpy(buf, P->execname, buflen);
		return (buf);
	}

	return (NULL);
}