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Add ability to print file descriptor paths and filter by those paths

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* pathtrace.c: New file, implements matching syscall arguments to
user-specified file paths.
* Makefile.am (strace_SOURCES): Add pathtrace.c.
* defs.h (TCB_FILTERED, filtered): New defines.
(getfdpath, pathtrace_select, pathtrace_match, show_fd_path,
tracing_paths): New declarations.
* strace.c (show_fd_path, tracing_paths): New global variables.
(usage, main): Implement handling of -y and -P options.
* strace.1: Add descriptions of -y and -P options.
* syscall.c (trace_syscall_entering): Add path matching logic to the
print/noprint decision and set the TCB_FILTERED bit appropriately.
(trace_syscall_exiting): Use filtered() macro that checks the
TCB_FILTERED bit to determine print/noprint status.
* util.c (printfd): Use getfdpath().
This commit is contained in:
Grant Edwards 2011-04-07 20:25:40 +00:00 committed by Dmitry V. Levin
parent 4cee0af77b
commit 8a08277d13
7 changed files with 451 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Makefile.am
View File

@ -18,7 +18,7 @@ AM_CPPFLAGS = -I$(srcdir)/$(OS)/$(ARCH) -I$(srcdir)/$(OS) -I$(builddir)/$(OS)
strace_SOURCES = strace.c syscall.c count.c util.c desc.c file.c ipc.c \
io.c ioctl.c mem.c net.c process.c bjm.c quota.c \
resource.c signal.c sock.c system.c term.c time.c \
proc.c scsi.c stream.c block.c
proc.c scsi.c stream.c block.c pathtrace.c
noinst_HEADERS = defs.h
EXTRA_DIST = $(man_MANS) errnoent.sh signalent.sh syscallent.sh ioctlsort.c \

10
defs.h
View File

@ -401,6 +401,7 @@ struct tcb {
#define TCB_SIGTRAPPED 00200 /* Process wanted to block SIGTRAP */
#define TCB_FOLLOWFORK 00400 /* Process should have forks followed */
#define TCB_REPRINT 01000 /* We should reprint this syscall on exit */
#define TCB_FILTERED 02000 /* This system call has been filtered out */
#ifdef LINUX
/* x86 does not need TCB_WAITEXECVE.
* It can detect execve's SIGTRAP by looking at eax/rax.
@ -410,7 +411,7 @@ struct tcb {
|| defined(POWERPC) || defined(IA64) || defined(HPPA) \
|| defined(SH) || defined(SH64) || defined(S390) || defined(S390X) \
|| defined(ARM) || defined(MIPS) || defined(BFIN) || defined(TILE)
# define TCB_WAITEXECVE 02000 /* ignore SIGTRAP after exceve */
# define TCB_WAITEXECVE 04000 /* ignore SIGTRAP after exceve */
# endif
# define TCB_CLONE_THREAD 010000 /* CLONE_THREAD set in creating syscall */
# define TCB_GROUP_EXITING 020000 /* TCB_EXITING was exit_group, not _exit */
@ -452,6 +453,7 @@ struct tcb {
#define syserror(tcp) ((tcp)->u_error != 0)
#define verbose(tcp) (qual_flags[(tcp)->scno] & QUAL_VERBOSE)
#define abbrev(tcp) (qual_flags[(tcp)->scno] & QUAL_ABBREV)
#define filtered(tcp) ((tcp)->flags & TCB_FILTERED)
struct xlat {
int val;
@ -553,6 +555,7 @@ extern void sprint_timespec(char *, struct tcb *, long);
#ifdef HAVE_SIGINFO_T
extern void printsiginfo(siginfo_t *, int);
#endif
extern const char *getfdpath(struct tcb *, int);
extern void printfd(struct tcb *, int);
extern void printsock(struct tcb *, long, int);
extern void print_sock_optmgmt(struct tcb *, long, int);
@ -574,6 +577,9 @@ extern void tprint_open_modes(mode_t);
extern const char *sprint_open_modes(mode_t);
extern int is_restart_error(struct tcb *);
extern int pathtrace_select(const char *);
extern int pathtrace_match(struct tcb *);
extern int change_syscall(struct tcb *, int);
extern int internal_fork(struct tcb *);
extern int internal_exec(struct tcb *);
@ -706,3 +712,5 @@ extern long ia32;
#endif
extern int not_failing_only;
extern int show_fd_path;
extern int tracing_paths;

390
pathtrace.c Normal file
View File

@ -0,0 +1,390 @@
/*
* Copyright (c) 2011, Comtrol Corp.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include "defs.h"
#include <ctype.h>
#include <limits.h>
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#ifdef HAVE_SYS_POLL_H
#include <sys/poll.h>
#endif
#include "syscall.h"
#define NumElem(a) ((int)((sizeof (a))/((sizeof (a)[0]))))
#define MAXSELECTED 256 /* max number of "selected" paths */
static const char *selected[MAXSELECTED]; /* paths selected for tracing */
/*
* Return true if specified path matches one that we're tracing.
*/
static int
pathmatch(const char *path)
{
int i;
for (i = 0; i < NumElem(selected); ++i)
{
if (selected[i] == NULL)
return 0;
if (!strcmp(path, selected[i]))
return 1;
}
return 0;
}
/*
* Return true if specified path (in user-space) matches.
*/
static int
upathmatch(struct tcb *tcp, unsigned long upath)
{
char path[PATH_MAX + 1];
return umovestr(tcp, upath, sizeof path, path) == 0 &&
pathmatch(path);
}
/*
* Return true if specified fd maps to a path we're tracing.
*/
static int
fdmatch(struct tcb *tcp, int fd)
{
const char *path = getfdpath(tcp, fd);
return path && pathmatch(path);
}
/*
* Add a path to the set we're tracing.
* Secifying NULL will delete all paths.
*/
static int
storepath(const char *path)
{
int i;
if (path == NULL)
{
for (i = 0; i < NumElem(selected); ++i)
if (selected[i])
{
free((char *) selected[i]);
selected[i] = NULL;
}
return 0;
}
for (i = 0; i < NumElem(selected); ++i)
if (!selected[i])
{
selected[i] = path;
return 0;
}
fprintf(stderr, "Max trace paths exceeded, only using first %d\n",
NumElem(selected));
return -1;
}
/*
* Get path associated with fd.
*/
const char *getfdpath(struct tcb *tcp, int fd)
{
#ifdef LINUX
static char path[PATH_MAX+1];
char linkpath[64];
ssize_t n;
if (fd < 0)
return NULL;
snprintf(linkpath, sizeof linkpath, "/proc/%d/fd/%d", tcp->pid, fd);
n = readlink(linkpath, path, (sizeof path) - 1);
if (n <= 0)
return NULL;
path[n] = '\0';
return path;
#else
return NULL;
#endif
}
/*
* Add a path to the set we're tracing. Also add the canonicalized
* version of the path. Secifying NULL will delete all paths.
*/
int
pathtrace_select(const char *path)
{
char *rpath;
if (path == NULL)
return storepath(path);
if (storepath(path))
return -1;
rpath = realpath(path, NULL);
if (rpath == NULL)
return 0;
/* if realpath and specified path are same, we're done */
if (!strcmp(path, rpath))
{
free(rpath);
return 0;
}
fprintf(stderr, "Requested path '%s' resolved into '%s'\n",
path, rpath);
return storepath(rpath);
}
/*
* Return true if syscall accesses a selected path
* (or if no paths have been specified for tracing).
*/
int
pathtrace_match(struct tcb *tcp)
{
const struct sysent *s;
if (selected[0] == NULL)
return 1;
s = &sysent[tcp->scno];
if (!(s->sys_flags & (TRACE_FILE | TRACE_DESC)))
return 0;
/*
* Check for special cases where we need to do something
* other than test arg[0].
*/
#ifdef LINUX
if (s->sys_func == sys_dup2 ||
s->sys_func == sys_dup3 ||
s->sys_func == sys_sendfile ||
s->sys_func == sys_sendfile64 ||
!strcmp(s->sys_name, "tee"))
{
/* fd, fd */
return fdmatch(tcp, tcp->u_arg[0]) ||
fdmatch(tcp, tcp->u_arg[1]);
}
if (s->sys_func == sys_inotify_add_watch ||
s->sys_func == sys_faccessat ||
s->sys_func == sys_fchmodat ||
s->sys_func == sys_futimesat ||
s->sys_func == sys_mkdirat ||
s->sys_func == sys_unlinkat ||
s->sys_func == sys_newfstatat ||
s->sys_func == sys_mknodat ||
s->sys_func == sys_openat ||
s->sys_func == sys_readlinkat ||
s->sys_func == sys_utimensat ||
s->sys_func == sys_fchownat ||
s->sys_func == sys_pipe2)
{
/* fd, path */
return fdmatch(tcp, tcp->u_arg[0]) ||
upathmatch(tcp, tcp->u_arg[1]);
}
if (s->sys_func == sys_link ||
s->sys_func == sys_pivotroot ||
s->sys_func == sys_rename ||
s->sys_func == sys_symlink ||
s->sys_func == sys_mount)
{
/* path, path */
return upathmatch(tcp, tcp->u_arg[0]) ||
upathmatch(tcp, tcp->u_arg[1]);
}
if (s->sys_func == sys_renameat ||
s->sys_func == sys_linkat)
{
/* fd, path, fd, path */
return fdmatch(tcp, tcp->u_arg[0]) ||
fdmatch(tcp, tcp->u_arg[2]) ||
upathmatch(tcp, tcp->u_arg[1]) ||
upathmatch(tcp, tcp->u_arg[3]);
}
if (s->sys_func == sys_old_mmap || s->sys_func == sys_mmap)
{
/* x, x, x, x, fd */
return fdmatch(tcp, tcp->u_arg[4]);
}
if (s->sys_func == sys_symlinkat)
{
/* path, fd, path */
return fdmatch(tcp, tcp->u_arg[1]) ||
upathmatch(tcp, tcp->u_arg[0]) ||
upathmatch(tcp, tcp->u_arg[2]);
}
if (!strcmp(s->sys_name, "splice"))
{
/* fd, x, fd, x, x */
return fdmatch(tcp, tcp->u_arg[0]) ||
fdmatch(tcp, tcp->u_arg[2]);
}
if (s->sys_func == sys_epoll_ctl)
{
/* x, x, fd, x */
return fdmatch(tcp, tcp->u_arg[2]);
}
if (s->sys_func == sys_select ||
s->sys_func == sys_oldselect ||
s->sys_func == sys_pselect6)
{
int i, j, nfds;
long *args, oldargs[5];
unsigned fdsize;
fd_set *fds;
if (s->sys_func == sys_oldselect)
{
if (umoven(tcp, tcp->u_arg[0], sizeof oldargs,
(char*) oldargs) < 0)
{
fprintf(stderr, "umoven() failed\n");
return 0;
}
args = oldargs;
} else
args = tcp->u_arg;
nfds = args[0];
fdsize = ((((nfds + 7) / 8) + sizeof(long) - 1)
& -sizeof(long));
fds = malloc(fdsize);
if (fds == NULL)
{
fprintf(stderr, "out of memory\n");
return 0;
}
for (i = 1; i <= 3; ++i)
{
if (args[i] == 0)
continue;
if (umoven(tcp, args[i], fdsize, (char *) fds) < 0)
{
fprintf(stderr, "umoven() failed\n");
continue;
}
for (j = 0; j < nfds; ++j)
if (FD_ISSET(j, fds) && fdmatch(tcp, j))
{
free(fds);
return 1;
}
}
free(fds);
return 0;
}
if (s->sys_func == sys_poll ||
s->sys_func == sys_ppoll)
{
struct pollfd fds;
unsigned nfds;
unsigned long start, cur, end;
start = tcp->u_arg[0];
nfds = tcp->u_arg[1];
end = start + sizeof(fds) * nfds;
if (nfds == 0 || end < start)
return 0;
for (cur = start; cur < end; cur += sizeof(fds))
if ((umoven(tcp, cur, sizeof fds, (char *) &fds) == 0)
&& fdmatch(tcp, fds.fd))
return 1;
return 0;
}
if (s->sys_func == printargs ||
s->sys_func == sys_pipe ||
s->sys_func == sys_pipe2 ||
s->sys_func == sys_eventfd2 ||
s->sys_func == sys_eventfd ||
s->sys_func == sys_inotify_init1 ||
s->sys_func == sys_timerfd_create ||
s->sys_func == sys_timerfd_settime ||
s->sys_func == sys_timerfd_gettime ||
s->sys_func == sys_epoll_create ||
!strcmp(s->sys_name, "fanotify_init"))
{
/*
* These have TRACE_FILE or TRACE_DESCRIPTOR set, but they
* don't have any file descriptor or path args to test.
*/
return 0;
}
#else
#warning "path tracing only using arg[0]"
#endif
/*
* Our fallback position for calls that haven't already
* been handled is to just check arg[0].
*/
if (s->sys_flags & TRACE_FILE)
return upathmatch(tcp, tcp->u_arg[0]);
if (s->sys_flags & TRACE_DESC)
return fdmatch(tcp, tcp->u_arg[0]);
return 0;
}

16
strace.1
View File

@ -43,7 +43,7 @@ strace \- trace system calls and signals
.SH SYNOPSIS
.B strace
[
.B \-CdDffhiqrtttTvxx
.B \-CdDffhiqrtttTvxxy
]
[
.BI \-a column
@ -60,6 +60,10 @@ strace \- trace system calls and signals
]
\&...
[
.BI \-P path
]
\&...
[
.BI \-s strsize
]
[
@ -358,6 +362,9 @@ Print all non-ASCII strings in hexadecimal string format.
.B \-xx
Print all strings in hexadecimal string format.
.TP
.B \-y
Print paths associated with file descriptor arguments.
.TP
.BI "\-a " column
Align return values in a specific column (default column 40).
.TP
@ -549,6 +556,13 @@ options can be used to attach to up to 32 processes in addition to
.B \-p
option is given).
.TP
.BI "\-P " path
Trace only system calls accessing
.I path.
Multiple
.B \-P
options can be used to specify up to 256 paths.
.TP
.BI "\-s " strsize
Specify the maximum string size to print (the default is 32). Note
that filenames are not considered strings and are always printed in

26
strace.c
View File

@ -104,6 +104,12 @@ static bool daemonized_tracer = 0;
/* Sometimes we want to print only succeeding syscalls. */
int not_failing_only = 0;
/* Show path associated with fd arguments */
int show_fd_path = 0;
/* are we filtering traces based on paths? */
int tracing_paths = 0;
static int exit_code = 0;
static int strace_child = 0;
@ -169,9 +175,9 @@ FILE *ofp;
int exitval;
{
fprintf(ofp, "\
usage: strace [-CdDffhiqrtttTvVxx] [-a column] [-e expr] ... [-o file]\n\
usage: strace [-CdDffhiqrtttTvVxxy] [-a column] [-e expr] ... [-o file]\n\
[-p pid] ... [-s strsize] [-u username] [-E var=val] ...\n\
[command [arg ...]]\n\
[-P path] [command [arg ...]]\n\
or: strace -c [-D] [-e expr] ... [-O overhead] [-S sortby] [-E var=val] ...\n\
[command [arg ...]]\n\
-c -- count time, calls, and errors for each syscall and report summary\n\
@ -184,6 +190,7 @@ usage: strace [-CdDffhiqrtttTvVxx] [-a column] [-e expr] ... [-o file]\n\
-T -- print time spent in each syscall, -V -- print version\n\
-v -- verbose mode: print unabbreviated argv, stat, termio[s], etc. args\n\
-x -- print non-ascii strings in hex, -xx -- print all strings in hex\n\
-y -- print paths associated with file descriptor arguments\n\
-a column -- alignment COLUMN for printing syscall results (default %d)\n\
-e expr -- a qualifying expression: option=[!]all or option=[!]val1[,val2]...\n\
options: trace, abbrev, verbose, raw, signal, read, or write\n\
@ -196,6 +203,7 @@ usage: strace [-CdDffhiqrtttTvVxx] [-a column] [-e expr] ... [-o file]\n\
-u username -- run command as username handling setuid and/or setgid\n\
-E var=val -- put var=val in the environment for command\n\
-E var -- remove var from the environment for command\n\
-P path -- trace accesses to path\n\
" /* this is broken, so don't document it
-z -- print only succeeding syscalls\n\
*/
@ -792,11 +800,11 @@ main(int argc, char *argv[])
qualify("verbose=all");
qualify("signal=all");
while ((c = getopt(argc, argv,
"+cCdfFhiqrtTvVxz"
"+cCdfFhiqrtTvVxyz"
#ifndef USE_PROCFS
"D"
#endif
"a:e:o:O:p:s:S:u:E:")) != EOF) {
"a:e:o:O:p:s:S:u:E:P:")) != EOF) {
switch (c) {
case 'c':
if (cflag == CFLAG_BOTH) {
@ -850,6 +858,9 @@ main(int argc, char *argv[])
case 'x':
xflag++;
break;
case 'y':
show_fd_path = 1;
break;
case 'v':
qualify("abbrev=none");
break;
@ -886,6 +897,13 @@ main(int argc, char *argv[])
tcp->flags |= TCB_ATTACHED;
pflag_seen++;
break;
case 'P':
tracing_paths = 1;
if (pathtrace_select(optarg)) {
fprintf(stderr,"%s : failed to select path '%s'\n", progname, optarg);
exit(1);
}
break;
case 's':
max_strlen = atoi(optarg);
if (max_strlen < 0) {

12
syscall.c
View File

@ -2422,8 +2422,7 @@ trace_syscall_exiting(struct tcb *tcp)
if (res == 1)
internal_syscall(tcp);
if (res == 1 && tcp->scno >= 0 && tcp->scno < nsyscalls &&
!(qual_flags[tcp->scno] & QUAL_TRACE)) {
if (res == 1 && filtered(tcp)) {
tcp->flags &= ~TCB_INSYSCALL;
return 0;
}
@ -2688,11 +2687,16 @@ trace_syscall_entering(struct tcb *tcp)
}
internal_syscall(tcp);
if (tcp->scno >=0 && tcp->scno < nsyscalls && !(qual_flags[tcp->scno] & QUAL_TRACE)) {
tcp->flags |= TCB_INSYSCALL;
if ((tcp->scno >= 0 && tcp->scno < nsyscalls &&
!(qual_flags[tcp->scno] & QUAL_TRACE)) ||
(tracing_paths && !pathtrace_match(tcp))) {
tcp->flags |= TCB_INSYSCALL | TCB_FILTERED;
return 0;
}
tcp->flags &= ~TCB_FILTERED;
if (cflag == CFLAG_ONLY_STATS) {
tcp->flags |= TCB_INSYSCALL;
gettimeofday(&tcp->etime, NULL);

7
util.c
View File

@ -418,7 +418,12 @@ printnum_int(struct tcb *tcp, long addr, const char *fmt)
void
printfd(struct tcb *tcp, int fd)
{
tprintf("%d", fd);
const char *p;
if (show_fd_path && (p = getfdpath(tcp, fd)))
tprintf("%d<%s>", fd, p);
else
tprintf("%d", fd);
}
void