Date: Mon, 10 Dec 2018 19:39:24 +0000 (UTC) From: John Baldwin <jhb@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r341800 - in head: sys/kern tests/sys/kern Message-ID: <201812101939.wBAJdOnm016038@repo.freebsd.org>
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Author: jhb Date: Mon Dec 10 19:39:24 2018 New Revision: 341800 URL: https://svnweb.freebsd.org/changeset/base/341800 Log: Don't report stale signal information for non-signal events in ptrace_lwpinfo. Once a signal's siginfo was copied to 'td_si' as part of the signal exchange in issignal(), it was never cleared. This caused future thread events that are reported as SIGTRAP events without signal information to report the stale siginfo in 'td_si'. For example, if a debugger created a new process and used SIGSTOP to stop it after PT_ATTACH, future system call entry / exit events would set PL_FLAG_SI with the SIGSTOP siginfo in pl_siginfo. This broke 'catch syscall' in current versions of gdb as it assumed PL_FLAG_SI with SIGTRAP indicates a breakpoint or single step trap. Reviewed by: kib MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D18487 Modified: head/sys/kern/kern_sig.c head/tests/sys/kern/ptrace_test.c Modified: head/sys/kern/kern_sig.c ============================================================================== --- head/sys/kern/kern_sig.c Mon Dec 10 16:23:11 2018 (r341799) +++ head/sys/kern/kern_sig.c Mon Dec 10 19:39:24 2018 (r341800) @@ -2847,6 +2847,8 @@ issignal(struct thread *td) sig = ptracestop(td, sig, &ksi); mtx_lock(&ps->ps_mtx); + td->td_si.si_signo = 0; + /* * Keep looking if the debugger discarded or * replaced the signal. Modified: head/tests/sys/kern/ptrace_test.c ============================================================================== --- head/tests/sys/kern/ptrace_test.c Mon Dec 10 16:23:11 2018 (r341799) +++ head/tests/sys/kern/ptrace_test.c Mon Dec 10 19:39:24 2018 (r341800) @@ -3772,6 +3772,78 @@ ATF_TC_BODY(ptrace__PT_CONTINUE_different_thread, tc) } #endif +/* + * Verify that PT_LWPINFO doesn't return stale siginfo. + */ +ATF_TC_WITHOUT_HEAD(ptrace__PT_LWPINFO_stale_siginfo); +ATF_TC_BODY(ptrace__PT_LWPINFO_stale_siginfo, tc) +{ + struct ptrace_lwpinfo pl; + pid_t fpid, wpid; + int events, status; + + ATF_REQUIRE((fpid = fork()) != -1); + if (fpid == 0) { + trace_me(); + raise(SIGABRT); + exit(1); + } + + /* The first wait() should report the stop from SIGSTOP. */ + wpid = waitpid(fpid, &status, 0); + ATF_REQUIRE(wpid == fpid); + ATF_REQUIRE(WIFSTOPPED(status)); + ATF_REQUIRE(WSTOPSIG(status) == SIGSTOP); + + ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0); + + /* The next stop should report the SIGABRT in the child body. */ + wpid = waitpid(fpid, &status, 0); + ATF_REQUIRE(wpid == fpid); + ATF_REQUIRE(WIFSTOPPED(status)); + ATF_REQUIRE(WSTOPSIG(status) == SIGABRT); + + ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1); + ATF_REQUIRE(pl.pl_flags & PL_FLAG_SI); + ATF_REQUIRE(pl.pl_siginfo.si_signo == SIGABRT); + + /* + * Continue the process ignoring the signal, but enabling + * syscall traps. + */ + ATF_REQUIRE(ptrace(PT_SYSCALL, fpid, (caddr_t)1, 0) == 0); + + /* + * The next stop should report a system call entry from + * exit(). PL_FLAGS_SI should not be set. + */ + wpid = waitpid(fpid, &status, 0); + ATF_REQUIRE(wpid == fpid); + ATF_REQUIRE(WIFSTOPPED(status)); + ATF_REQUIRE(WSTOPSIG(status) == SIGTRAP); + + ATF_REQUIRE(ptrace(PT_LWPINFO, wpid, (caddr_t)&pl, sizeof(pl)) != -1); + ATF_REQUIRE(pl.pl_flags & PL_FLAG_SCE); + ATF_REQUIRE((pl.pl_flags & PL_FLAG_SI) == 0); + + /* Disable syscall tracing and continue the child to let it exit. */ + ATF_REQUIRE(ptrace(PT_GET_EVENT_MASK, fpid, (caddr_t)&events, + sizeof(events)) == 0); + events &= ~PTRACE_SYSCALL; + ATF_REQUIRE(ptrace(PT_SET_EVENT_MASK, fpid, (caddr_t)&events, + sizeof(events)) == 0); + ATF_REQUIRE(ptrace(PT_CONTINUE, fpid, (caddr_t)1, 0) == 0); + + /* The last event should be for the child process's exit. */ + wpid = waitpid(fpid, &status, 0); + ATF_REQUIRE(WIFEXITED(status)); + ATF_REQUIRE(WEXITSTATUS(status) == 1); + + wpid = wait(&status); + ATF_REQUIRE(wpid == -1); + ATF_REQUIRE(errno == ECHILD); +} + ATF_TP_ADD_TCS(tp) { @@ -3831,6 +3903,7 @@ ATF_TP_ADD_TCS(tp) #if defined(HAVE_BREAKPOINT) && defined(SKIP_BREAK) ATF_TP_ADD_TC(tp, ptrace__PT_CONTINUE_different_thread); #endif + ATF_TP_ADD_TC(tp, ptrace__PT_LWPINFO_stale_siginfo); return (atf_no_error()); }
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