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authorTejun Heo <tj@kernel.org>2011-06-14 11:20:16 +0200
committerOleg Nesterov <oleg@redhat.com>2011-06-16 21:41:53 +0200
commitfca26f260c528ee51a2e451b5b200aeb528f3e09 (patch)
tree8c64ecdcece48b55e79bbb7f376a834fc99804a3 /include/linux/ptrace.h
parent3544d72a0e10d0aa1c1bd59ed77a53a59cdc12f7 (diff)
ptrace: implement PTRACE_INTERRUPT
Currently, there's no way to trap a running ptracee short of sending a signal which has various side effects. This patch implements PTRACE_INTERRUPT which traps ptracee without any signal or job control related side effect. The implementation is almost trivial. It uses the group stop trap - SIGTRAP | PTRACE_EVENT_STOP << 8. A new trap flag JOBCTL_TRAP_INTERRUPT is added, which is set on PTRACE_INTERRUPT and cleared when any trap happens. As INTERRUPT should be useable regardless of the current state of tracee, task_is_traced() test in ptrace_check_attach() is skipped for INTERRUPT. PTRACE_INTERRUPT is available iff tracee is attached with PTRACE_SEIZE. Test program follows. #define PTRACE_SEIZE 0x4206 #define PTRACE_INTERRUPT 0x4207 #define PTRACE_SEIZE_DEVEL 0x80000000 static const struct timespec ts100ms = { .tv_nsec = 100000000 }; static const struct timespec ts1s = { .tv_sec = 1 }; static const struct timespec ts3s = { .tv_sec = 3 }; int main(int argc, char **argv) { pid_t tracee; tracee = fork(); if (tracee == 0) { nanosleep(&ts100ms, NULL); while (1) { printf("tracee: alive pid=%d\n", getpid()); nanosleep(&ts1s, NULL); } } if (argc > 1) kill(tracee, SIGSTOP); nanosleep(&ts100ms, NULL); ptrace(PTRACE_SEIZE, tracee, NULL, (void *)(unsigned long)PTRACE_SEIZE_DEVEL); if (argc > 1) { waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_CONT, tracee, NULL, NULL); } nanosleep(&ts3s, NULL); printf("tracer: INTERRUPT and DETACH\n"); ptrace(PTRACE_INTERRUPT, tracee, NULL, NULL); waitid(P_PID, tracee, NULL, WSTOPPED); ptrace(PTRACE_DETACH, tracee, NULL, NULL); nanosleep(&ts3s, NULL); printf("tracer: exiting\n"); kill(tracee, SIGKILL); return 0; } When called without argument, tracee is seized from running state, interrupted and then detached back to running state. # ./test-interrupt tracee: alive pid=4546 tracee: alive pid=4546 tracee: alive pid=4546 tracer: INTERRUPT and DETACH tracee: alive pid=4546 tracee: alive pid=4546 tracee: alive pid=4546 tracer: exiting When called with argument, tracee is seized from stopped state, continued, interrupted and then detached back to stopped state. # ./test-interrupt 1 tracee: alive pid=4548 tracee: alive pid=4548 tracee: alive pid=4548 tracer: INTERRUPT and DETACH tracer: exiting Before PTRACE_INTERRUPT, once the tracee was running, there was no way to trap tracee and do PTRACE_DETACH without causing side effect. -v2: Updated to use task_set_jobctl_pending() so that it doesn't end up scheduling TRAP_STOP if child is dying which may make the child unkillable. Spotted by Oleg. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'include/linux/ptrace.h')
-rw-r--r--include/linux/ptrace.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 67ad3f15232..ad754d1e0b1 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -48,6 +48,7 @@
#define PTRACE_SETREGSET 0x4205
#define PTRACE_SEIZE 0x4206
+#define PTRACE_INTERRUPT 0x4207
/* flags in @data for PTRACE_SEIZE */
#define PTRACE_SEIZE_DEVEL 0x80000000 /* temp flag for development */