Properly handle real SIGTRAPs.
* defs.h (ptrace_setoptions): Variable renamed to ptrace_setoptions_followfork. * process.c (internal_fork): Ditto. * strace.c (ptrace_setoptions_for_all): New variable. (SYSCALLTRAP): New variable. (error_msg_and_die): New function. (test_ptrace_setoptions_for_all): New function. (main): Call test_ptrace_setoptions_for_all() at init. (handle_ptrace_event): Handle PTRACE_EVENT_EXEC (by ignoring it). (trace): Check events and set ptrace options without -f too. Check WSTOPSIG(status) not for SIGTRAP, but for SYSCALLTRAP.
This commit is contained in:
Denys Vlasenko
parent
1cd5371d50
commit
3454e4b463
2
defs.h
2
defs.h
@ -504,7 +504,7 @@ typedef enum {
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extern struct tcb **tcbtab;
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extern int *qual_flags;
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extern int debug, followfork;
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extern unsigned int ptrace_setoptions;
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extern unsigned int ptrace_setoptions_followfork;
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extern int dtime, xflag, qflag;
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extern cflag_t cflag;
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extern int acolumn;
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@ -915,7 +915,7 @@ Process %u resumed (parent %d ready)\n",
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int
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internal_fork(struct tcb *tcp)
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{
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if ((ptrace_setoptions
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if ((ptrace_setoptions_followfork
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& (PTRACE_O_TRACECLONE | PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK))
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== (PTRACE_O_TRACECLONE | PTRACE_O_TRACEFORK | PTRACE_O_TRACEVFORK))
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return 0;
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157
strace.c
157
strace.c
@ -33,6 +33,7 @@
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#include "defs.h"
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#include <sys/types.h>
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#include <stdarg.h>
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#include <signal.h>
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#include <errno.h>
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#include <sys/param.h>
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@ -83,7 +84,10 @@ extern char *optarg;
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int debug = 0, followfork = 0;
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unsigned int ptrace_setoptions = 0;
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unsigned int ptrace_setoptions_followfork = 0;
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static unsigned int ptrace_setoptions_for_all = 0;
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/* Which WSTOPSIG(status) value marks syscall traps? */
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static unsigned int SYSCALLTRAP = SIGTRAP;
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int dtime = 0, xflag = 0, qflag = 0;
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cflag_t cflag = CFLAG_NONE;
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static int iflag = 0, interactive = 0, pflag_seen = 0, rflag = 0, tflag = 0;
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@ -211,6 +215,31 @@ usage: strace [-CdDffhiqrtttTvVxxy] [-a column] [-e expr] ... [-o file]\n\
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exit(exitval);
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}
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static void error_msg_and_die(const char *fmt, ...)
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#if defined __GNUC__
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__attribute__ ((noreturn, format(printf, 1, 2)))
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#endif
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;
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static void error_msg_and_die(const char *fmt, ...)
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{
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char *msg;
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va_list p;
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va_start(p, fmt);
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msg = NULL;
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vasprintf(&msg, fmt, p);
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if (msg) {
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fprintf(stderr, "%s: %s\n", progname, msg);
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free(msg);
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}
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va_end(p);
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/* TODO? cflag = 0; -- or else cleanup() may print summary */
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cleanup();
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fflush(NULL);
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_exit(1);
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}
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#ifdef SVR4
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#ifdef MIPS
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void
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@ -702,7 +731,7 @@ startup_child (char **argv)
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* and then see which options are supported by the kernel.
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*/
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static int
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test_ptrace_setoptions(void)
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test_ptrace_setoptions_followfork(void)
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{
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int pid, expected_grandchild = 0, found_grandchild = 0;
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const unsigned int test_options = PTRACE_O_TRACECLONE |
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@ -727,7 +756,7 @@ test_ptrace_setoptions(void)
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continue;
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else if (errno == ECHILD)
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break;
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perror("test_ptrace_setoptions");
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perror("test_ptrace_setoptions_followfork");
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return -1;
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}
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if (tracee_pid != pid) {
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@ -761,9 +790,91 @@ test_ptrace_setoptions(void)
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}
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}
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if (expected_grandchild && expected_grandchild == found_grandchild)
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ptrace_setoptions |= test_options;
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ptrace_setoptions_followfork |= test_options;
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return 0;
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}
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/*
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* Test whether the kernel support PTRACE_O_TRACESYSGOOD.
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* First fork a new child, call ptrace(PTRACE_SETOPTIONS) on it,
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* and then see whether it will stop with (SIGTRAP | 0x80).
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*
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* Use of this option enables correct handling of user-generated SIGTRAPs,
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* and SIGTRAPs generated by special instructions such as int3 on x86:
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* _start: .globl _start
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* int3
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* movl $42, %ebx
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* movl $1, %eax
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* int $0x80
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* (compile with: "gcc -nostartfiles -nostdlib -o int3 int3.S")
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*/
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static void
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test_ptrace_setoptions_for_all(void)
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{
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const unsigned int test_options = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEEXEC;
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int pid;
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int it_worked = 0;
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pid = fork();
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if (pid < 0)
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error_msg_and_die("fork failed");
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if (pid == 0) {
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pid = getpid();
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if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) < 0)
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/* "parent, something is deeply wrong!" */
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kill(pid, SIGKILL);
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kill(pid, SIGSTOP);
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_exit(0); /* parent should see entry into this syscall */
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}
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while (1) {
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int status, tracee_pid;
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errno = 0;
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tracee_pid = wait(&status);
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if (tracee_pid <= 0) {
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if (errno == EINTR)
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continue;
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kill(pid, SIGKILL);
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error_msg_and_die("%s: unexpected wait result %d", __func__, tracee_pid);
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}
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if (WIFEXITED(status))
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break;
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if (!WIFSTOPPED(status)) {
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kill(pid, SIGKILL);
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error_msg_and_die("%s: unexpected wait status %x", __func__, status);
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}
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if (WSTOPSIG(status) == SIGSTOP) {
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/*
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* We don't check "options aren't accepted" error.
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* If it happens, we'll never get (SIGTRAP | 0x80),
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* and thus will decide to not use the option.
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* IOW: the outcome of the test will be correct.
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*/
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ptrace(PTRACE_SETOPTIONS, pid, 0L, test_options);
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}
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if (WSTOPSIG(status) == (SIGTRAP | 0x80)) {
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it_worked = 1;
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}
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if (ptrace(PTRACE_SYSCALL, pid, 0L, 0L) < 0) {
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kill(pid, SIGKILL);
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error_msg_and_die("PTRACE_SYSCALL doesn't work");
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}
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}
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if (it_worked) {
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SYSCALLTRAP = (SIGTRAP | 0x80);
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ptrace_setoptions_for_all = test_options;
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if (debug)
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fprintf(stderr, "ptrace_setoptions_for_all = %#x\n",
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ptrace_setoptions_for_all);
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return;
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}
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fprintf(stderr,
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"Test for PTRACE_O_TRACESYSGOOD failed, giving up using this feature.\n");
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}
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#endif
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int
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@ -977,16 +1088,17 @@ main(int argc, char *argv[])
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#ifdef LINUX
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if (followfork) {
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if (test_ptrace_setoptions() < 0) {
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if (test_ptrace_setoptions_followfork() < 0) {
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fprintf(stderr,
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"Test for options supported by PTRACE_SETOPTIONS "
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"failed, giving up using this feature.\n");
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ptrace_setoptions = 0;
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ptrace_setoptions_followfork = 0;
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}
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if (debug)
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fprintf(stderr, "ptrace_setoptions = %#x\n",
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ptrace_setoptions);
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fprintf(stderr, "ptrace_setoptions_followfork = %#x\n",
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ptrace_setoptions_followfork);
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}
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test_ptrace_setoptions_for_all();
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#endif
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/* Check if they want to redirect the output. */
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@ -1751,7 +1863,7 @@ int sig;
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break;
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}
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error = ptrace_restart(PTRACE_CONT, tcp,
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WSTOPSIG(status) == SIGTRAP ? 0
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WSTOPSIG(status) == SYSCALLTRAP ? 0
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: WSTOPSIG(status));
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if (error < 0)
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break;
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@ -2408,6 +2520,11 @@ handle_ptrace_event(int status, struct tcb *tcp)
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}
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return handle_new_child(tcp, childpid, 0);
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}
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if (status >> 16 == PTRACE_EVENT_EXEC) {
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if (debug)
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fprintf(stderr, "PTRACE_EVENT_EXEC on pid %d (ignored)\n", tcp->pid);
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return 0;
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}
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return 1;
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}
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#endif
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@ -2597,7 +2714,7 @@ Process %d attached (waiting for parent)\n",
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fprintf(stderr, "pid %u stopped, [%s]\n",
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pid, signame(WSTOPSIG(status)));
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if (ptrace_setoptions && (status >> 16)) {
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if (status >> 16) {
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if (handle_ptrace_event(status, tcp) != 1)
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goto tracing;
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}
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@ -2630,16 +2747,24 @@ Process %d attached (waiting for parent)\n",
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}
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}
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#ifdef LINUX
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if (followfork && (tcp->parent == NULL) && ptrace_setoptions)
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if (ptrace(PTRACE_SETOPTIONS, tcp->pid,
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NULL, ptrace_setoptions) < 0 &&
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errno != ESRCH)
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ptrace_setoptions = 0;
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int options = ptrace_setoptions_for_all;
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if (followfork && (tcp->parent == NULL))
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options |= ptrace_setoptions_followfork;
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if (options) {
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if (debug)
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fprintf(stderr, "setting opts %x on pid %d\n", options, tcp->pid);
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if (ptrace(PTRACE_SETOPTIONS, tcp->pid, NULL, options) < 0) {
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if (errno != ESRCH) {
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/* Should never happen, really */
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error_msg_and_die("PTRACE_SETOPTIONS");
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}
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}
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}
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#endif
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goto tracing;
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}
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if (WSTOPSIG(status) != SIGTRAP) {
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if (WSTOPSIG(status) != SYSCALLTRAP) {
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if (WSTOPSIG(status) == SIGSTOP &&
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(tcp->flags & TCB_SIGTRAPPED)) {
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/*
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