detach(): Reorganize code. Logic is the same.
* strace.c (detach): Use goto's instead of excessive nesting. Drop sigstop_expected and interrupt_done variables. Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko
parent
a2de9dacec
commit
e2567d54dd
257
strace.c
257
strace.c
@ -733,7 +733,7 @@ static void
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detach(struct tcb *tcp)
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{
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int error;
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int status, sigstop_expected, interrupt_done;
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int status;
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if (tcp->flags & TCB_BPTSET)
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clearbpt(tcp);
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@ -748,142 +748,145 @@ detach(struct tcb *tcp)
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# define PTRACE_DETACH PTRACE_SUNDETACH
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#endif
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error = 0;
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sigstop_expected = 0;
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interrupt_done = 0;
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if (tcp->flags & TCB_ATTACHED) {
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/*
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* We attached but possibly didn't see the expected SIGSTOP.
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* We must catch exactly one as otherwise the detached process
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* would be left stopped (process state T).
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*/
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sigstop_expected = (tcp->flags & TCB_IGNORE_ONE_SIGSTOP);
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if (sigstop_expected)
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goto wait_loop;
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error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
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if (error == 0) {
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/* On a clear day, you can see forever. */
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}
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else if (errno != ESRCH) {
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/* Shouldn't happen. */
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perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
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}
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else
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/* ESRCH: process is either not stopped or doesn't exist. */
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if (my_tkill(tcp->pid, 0) < 0) {
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if (errno != ESRCH)
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/* Shouldn't happen. */
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perror_msg("detach: tkill(%u,0)", tcp->pid);
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/* else: process doesn't exist. */
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}
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else
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/* Process is not stopped. */
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if (!sigstop_expected) {
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/* We need to stop it. */
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if (use_seize) {
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/*
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* With SEIZE, tracee can be in group-stop already.
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* In this state sending it another SIGSTOP does nothing.
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* Need to use INTERRUPT.
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* Testcase: trying to ^C a "strace -p <stopped_process>".
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*/
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error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
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if (!error)
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interrupt_done = 1;
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else if (errno != ESRCH)
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perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
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}
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else {
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error = my_tkill(tcp->pid, SIGSTOP);
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if (!error)
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sigstop_expected = 1;
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else if (errno != ESRCH)
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perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
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}
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}
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}
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if (!(tcp->flags & TCB_ATTACHED))
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goto drop;
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/* We attached but possibly didn't see the expected SIGSTOP.
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* We must catch exactly one as otherwise the detached process
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* would be left stopped (process state T).
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*/
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if (tcp->flags & TCB_IGNORE_ONE_SIGSTOP)
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goto wait_loop;
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error = ptrace(PTRACE_DETACH, tcp->pid, 0, 0);
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if (!error) {
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/* On a clear day, you can see forever. */
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goto drop;
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}
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if (errno != ESRCH) {
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/* Shouldn't happen. */
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perror_msg("detach: ptrace(PTRACE_DETACH,%u)", tcp->pid);
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goto drop;
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}
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/* ESRCH: process is either not stopped or doesn't exist. */
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if (my_tkill(tcp->pid, 0) < 0) {
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if (errno != ESRCH)
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/* Shouldn't happen. */
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perror_msg("detach: tkill(%u,0)", tcp->pid);
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/* else: process doesn't exist. */
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goto drop;
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}
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/* Process is not stopped, need to stop it. */
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if (use_seize) {
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/*
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* With SEIZE, tracee can be in group-stop already.
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* In this state sending it another SIGSTOP does nothing.
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* Need to use INTERRUPT.
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* Testcase: trying to ^C a "strace -p <stopped_process>".
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*/
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error = ptrace(PTRACE_INTERRUPT, tcp->pid, 0, 0);
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if (!error)
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goto wait_loop;
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if (errno != ESRCH)
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perror_msg("detach: ptrace(PTRACE_INTERRUPT,%u)", tcp->pid);
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}
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else {
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error = my_tkill(tcp->pid, SIGSTOP);
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if (!error)
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goto wait_loop;
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if (errno != ESRCH)
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perror_msg("detach: tkill(%u,SIGSTOP)", tcp->pid);
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}
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/* Either process doesn't exist, or some weird error. */
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goto drop;
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if (sigstop_expected || interrupt_done) {
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wait_loop:
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for (;;) {
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int sig;
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if (waitpid(tcp->pid, &status, __WALL) < 0) {
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if (errno == EINTR)
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continue;
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/* We end up here in three cases:
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* 1. We sent PTRACE_INTERRUPT (use_seize case)
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* 2. We sent SIGSTOP (!use_seize)
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* 3. Attach SIGSTOP was already pending (TCB_IGNORE_ONE_SIGSTOP set)
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*/
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for (;;) {
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int sig;
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if (waitpid(tcp->pid, &status, __WALL) < 0) {
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if (errno == EINTR)
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continue;
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/*
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* if (errno == ECHILD) break;
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* ^^^ WRONG! We expect this PID to exist,
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* and want to emit a message otherwise:
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*/
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perror_msg("detach: waitpid(%u)", tcp->pid);
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break;
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}
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if (!WIFSTOPPED(status)) {
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/*
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* Tracee exited or was killed by signal.
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* We shouldn't normally reach this place:
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* we don't want to consume exit status.
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* Consider "strace -p PID" being ^C-ed:
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* we want merely to detach from PID.
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*
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* However, we _can_ end up here if tracee
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* was SIGKILLed.
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*/
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break;
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}
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sig = WSTOPSIG(status);
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if (debug_flag)
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fprintf(stderr, "detach wait: event:%d sig:%d\n",
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(unsigned)status >> 16, sig);
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if (use_seize) {
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unsigned event = (unsigned)status >> 16;
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if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
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/*
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* if (errno == ECHILD) break;
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* ^^^ WRONG! We expect this PID to exist,
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* and want to emit a message otherwise:
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* sig == SIGTRAP: PTRACE_INTERRUPT stop.
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* sig == other: process was already stopped
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* with this stopping sig (see tests/detach-stopped).
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* Looks like re-injecting this sig is not necessary
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* in DETACH for the tracee to remain stopped.
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*/
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perror_msg("detach: waitpid(%u)", tcp->pid);
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break;
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}
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if (!WIFSTOPPED(status)) {
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/*
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* Tracee exited or was killed by signal.
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* We shouldn't normally reach this place:
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* we don't want to consume exit status.
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* Consider "strace -p PID" being ^C-ed:
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* we want merely to detach from PID.
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*
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* However, we _can_ end up here if tracee
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* was SIGKILLed.
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*/
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break;
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}
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sig = WSTOPSIG(status);
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if (debug_flag)
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fprintf(stderr, "detach wait: event:%d sig:%d\n",
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(unsigned)status >> 16, sig);
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if (sigstop_expected && sig == SIGSTOP) {
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/* Detach, suppressing SIGSTOP */
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ptrace_restart(PTRACE_DETACH, tcp, 0);
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break;
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}
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if (interrupt_done) {
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unsigned event = (unsigned)status >> 16;
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if (event == PTRACE_EVENT_STOP /*&& sig == SIGTRAP*/) {
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/*
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* sig == SIGTRAP: PTRACE_INTERRUPT stop.
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* sig == other: process was already stopped
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* with this stopping sig (see tests/detach-stopped).
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* Looks like re-injecting this sig is not necessary
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* in DETACH for the tracee to remain stopped.
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*/
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sig = 0;
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}
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/*
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* PTRACE_INTERRUPT is not guaranteed to produce
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* the above event if other ptrace-stop is pending.
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* See tests/detach-sleeping testcase:
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* strace got SIGINT while tracee is sleeping.
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* We sent PTRACE_INTERRUPT.
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* We see syscall exit, not PTRACE_INTERRUPT stop.
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* We won't get PTRACE_INTERRUPT stop
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* if we would CONT now. Need to DETACH.
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*/
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if (sig == syscall_trap_sig)
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sig = 0;
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/* else: not sure in which case we can be here.
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* Signal stop? Inject it while detaching.
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*/
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ptrace_restart(PTRACE_DETACH, tcp, sig);
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break;
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sig = 0;
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}
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/*
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* PTRACE_INTERRUPT is not guaranteed to produce
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* the above event if other ptrace-stop is pending.
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* See tests/detach-sleeping testcase:
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* strace got SIGINT while tracee is sleeping.
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* We sent PTRACE_INTERRUPT.
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* We see syscall exit, not PTRACE_INTERRUPT stop.
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* We won't get PTRACE_INTERRUPT stop
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* if we would CONT now. Need to DETACH.
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*/
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if (sig == syscall_trap_sig)
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sig = 0;
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/* Can't detach just yet, may need to wait for SIGSTOP */
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error = ptrace_restart(PTRACE_CONT, tcp, sig);
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if (error < 0) {
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/* Should not happen.
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* Note: ptrace_restart returns 0 on ESRCH, so it's not it.
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* ptrace_restart already emitted error message.
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*/
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break;
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}
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/* else: not sure in which case we can be here.
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* Signal stop? Inject it while detaching.
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*/
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ptrace_restart(PTRACE_DETACH, tcp, sig);
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break;
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}
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/* Note: this check has to be after use_seize check */
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/* (else, in use_seize case SIGSTOP will be mistreated) */
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if (sig == SIGSTOP) {
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/* Detach, suppressing SIGSTOP */
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ptrace_restart(PTRACE_DETACH, tcp, 0);
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break;
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}
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if (sig == syscall_trap_sig)
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sig = 0;
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/* Can't detach just yet, may need to wait for SIGSTOP */
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error = ptrace_restart(PTRACE_CONT, tcp, sig);
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if (error < 0) {
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/* Should not happen.
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* Note: ptrace_restart returns 0 on ESRCH, so it's not it.
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* ptrace_restart already emitted error message.
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*/
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break;
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}
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}
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drop:
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if (!qflag && (tcp->flags & TCB_ATTACHED))
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fprintf(stderr, "Process %u detached\n", tcp->pid);
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