Author: Michał Górny Date: 2021-04-13T14:38:31+02:00 New Revision: c8d18cba4e2f63f2135749ef87d09e7f4f405712
URL: https://github.com/llvm/llvm-project/commit/c8d18cba4e2f63f2135749ef87d09e7f4f405712 DIFF: https://github.com/llvm/llvm-project/commit/c8d18cba4e2f63f2135749ef87d09e7f4f405712.diff LOG: Reland "[lldb] [Process] Watch for fork/vfork notifications" for Linux Big thanks to Pavel Labath for figuring out my mistake. Differential Revision: https://reviews.llvm.org/D98822 Added: lldb/include/lldb/Host/linux/Host.h Modified: lldb/source/Host/linux/Host.cpp lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp lldb/source/Plugins/Process/Linux/NativeProcessLinux.h lldb/test/Shell/Subprocess/clone-follow-parent-wp.test Removed: ################################################################################ diff --git a/lldb/include/lldb/Host/linux/Host.h b/lldb/include/lldb/Host/linux/Host.h new file mode 100644 index 0000000000000..409a9fc9b3220 --- /dev/null +++ b/lldb/include/lldb/Host/linux/Host.h @@ -0,0 +1,22 @@ +//===-- Host.h --------------------------------------------------*- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +#ifndef LLDB_HOST_LINUX_HOST_H +#define LLDB_HOST_LINUX_HOST_H + +#include "lldb/lldb-types.h" +#include "llvm/ADT/Optional.h" + +namespace lldb_private { + +// Get PID (i.e. the primary thread ID) corresponding to the specified TID. +llvm::Optional<lldb::pid_t> getPIDForTID(lldb::pid_t tid); + +} // namespace lldb_private + +#endif // #ifndef LLDB_HOST_LINUX_HOST_H diff --git a/lldb/source/Host/linux/Host.cpp b/lldb/source/Host/linux/Host.cpp index 520a00df35f6d..334634a357f57 100644 --- a/lldb/source/Host/linux/Host.cpp +++ b/lldb/source/Host/linux/Host.cpp @@ -27,6 +27,7 @@ #include "lldb/Host/FileSystem.h" #include "lldb/Host/Host.h" #include "lldb/Host/HostInfo.h" +#include "lldb/Host/linux/Host.h" #include "lldb/Host/linux/Support.h" #include "lldb/Utility/DataExtractor.h" @@ -53,7 +54,8 @@ class ProcessLaunchInfo; } static bool GetStatusInfo(::pid_t Pid, ProcessInstanceInfo &ProcessInfo, - ProcessState &State, ::pid_t &TracerPid) { + ProcessState &State, ::pid_t &TracerPid, + ::pid_t &Tgid) { Log *log = GetLogIfAllCategoriesSet(LIBLLDB_LOG_HOST); auto BufferOrError = getProcFile(Pid, "status"); @@ -107,6 +109,9 @@ static bool GetStatusInfo(::pid_t Pid, ProcessInstanceInfo &ProcessInfo, } else if (Line.consume_front("TracerPid:")) { Line = Line.ltrim(); Line.consumeInteger(10, TracerPid); + } else if (Line.consume_front("Tgid:")) { + Line = Line.ltrim(); + Line.consumeInteger(10, Tgid); } } return true; @@ -204,6 +209,7 @@ static void GetProcessEnviron(::pid_t pid, ProcessInstanceInfo &process_info) { static bool GetProcessAndStatInfo(::pid_t pid, ProcessInstanceInfo &process_info, ProcessState &State, ::pid_t &tracerpid) { + ::pid_t tgid; tracerpid = 0; process_info.Clear(); @@ -214,7 +220,7 @@ static bool GetProcessAndStatInfo(::pid_t pid, GetProcessEnviron(pid, process_info); // Get User and Group IDs and get tracer pid. - if (!GetStatusInfo(pid, process_info, State, tracerpid)) + if (!GetStatusInfo(pid, process_info, State, tracerpid, tgid)) return false; return true; @@ -308,3 +314,14 @@ Environment Host::GetEnvironment() { return Environment(environ); } Status Host::ShellExpandArguments(ProcessLaunchInfo &launch_info) { return Status("unimplemented"); } + +llvm::Optional<lldb::pid_t> lldb_private::getPIDForTID(lldb::pid_t tid) { + ::pid_t tracerpid, tgid = LLDB_INVALID_PROCESS_ID; + ProcessInstanceInfo process_info; + ProcessState state; + + if (!GetStatusInfo(tid, process_info, state, tracerpid, tgid) || + tgid == LLDB_INVALID_PROCESS_ID) + return llvm::None; + return tgid; +} diff --git a/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp b/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp index 5a876ce5befec..40ba5e2e604b2 100644 --- a/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp +++ b/lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp @@ -30,6 +30,7 @@ #include "lldb/Host/PseudoTerminal.h" #include "lldb/Host/ThreadLauncher.h" #include "lldb/Host/common/NativeRegisterContext.h" +#include "lldb/Host/linux/Host.h" #include "lldb/Host/linux/Ptrace.h" #include "lldb/Host/linux/Uio.h" #include "lldb/Host/posix/ProcessLauncherPosixFork.h" @@ -383,14 +384,22 @@ Status NativeProcessLinux::SetDefaultPtraceOpts(lldb::pid_t pid) { ptrace_opts |= PTRACE_O_TRACEEXIT; // Have the tracer trace threads which spawn in the inferior process. - // TODO: if we want to support tracing the inferiors' child, add the - // appropriate ptrace flags here (PTRACE_O_TRACEFORK, PTRACE_O_TRACEVFORK) ptrace_opts |= PTRACE_O_TRACECLONE; // Have the tracer notify us before execve returns (needed to disable legacy // SIGTRAP generation) ptrace_opts |= PTRACE_O_TRACEEXEC; + // Have the tracer trace forked children. + ptrace_opts |= PTRACE_O_TRACEFORK; + + // Have the tracer trace vforks. + ptrace_opts |= PTRACE_O_TRACEVFORK; + + // Have the tracer trace vfork-done in order to restore breakpoints after + // the child finishes sharing memory. + ptrace_opts |= PTRACE_O_TRACEVFORKDONE; + return PtraceWrapper(PTRACE_SETOPTIONS, pid, nullptr, (void *)ptrace_opts); } @@ -444,8 +453,7 @@ void NativeProcessLinux::MonitorCallback(lldb::pid_t pid, bool exited, LLDB_LOG(log, "tid {0}, si_code: {1}, si_pid: {2}", pid, info.si_code, info.si_pid); - NativeThreadLinux &thread = AddThread(pid, /*resume*/ true); - ThreadWasCreated(thread); + MonitorClone(pid, llvm::None); return; } @@ -509,29 +517,24 @@ void NativeProcessLinux::MonitorCallback(lldb::pid_t pid, bool exited, } } -void NativeProcessLinux::WaitForNewThread(::pid_t tid) { +void NativeProcessLinux::WaitForCloneNotification(::pid_t pid) { Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_PROCESS)); - if (GetThreadByID(tid)) { - // We are already tracking the thread - we got the event on the new thread - // (see MonitorSignal) before this one. We are done. - return; - } - - // The thread is not tracked yet, let's wait for it to appear. + // The PID is not tracked yet, let's wait for it to appear. int status = -1; LLDB_LOG(log, - "received thread creation event for tid {0}. tid not tracked " - "yet, waiting for thread to appear...", - tid); - ::pid_t wait_pid = llvm::sys::RetryAfterSignal(-1, ::waitpid, tid, &status, __WALL); - // Since we are waiting on a specific tid, this must be the creation event. + "received clone event for pid {0}. pid not tracked yet, " + "waiting for it to appear...", + pid); + ::pid_t wait_pid = + llvm::sys::RetryAfterSignal(-1, ::waitpid, pid, &status, __WALL); + // Since we are waiting on a specific pid, this must be the creation event. // But let's do some checks just in case. - if (wait_pid != tid) { + if (wait_pid != pid) { LLDB_LOG(log, - "waiting for tid {0} failed. Assuming the thread has " + "waiting for pid {0} failed. Assuming the pid has " "disappeared in the meantime", - tid); + pid); // The only way I know of this could happen is if the whole process was // SIGKILLed in the mean time. In any case, we can't do anything about that // now. @@ -539,17 +542,15 @@ void NativeProcessLinux::WaitForNewThread(::pid_t tid) { } if (WIFEXITED(status)) { LLDB_LOG(log, - "waiting for tid {0} returned an 'exited' event. Not " - "tracking the thread.", - tid); + "waiting for pid {0} returned an 'exited' event. Not " + "tracking it.", + pid); // Also a very improbable event. + m_pending_pid_map.erase(pid); return; } - LLDB_LOG(log, "pid = {0}: tracking new thread tid {1}", GetID(), tid); - NativeThreadLinux &new_thread = AddThread(tid, /*resume*/ true); - - ThreadWasCreated(new_thread); + MonitorClone(pid, llvm::None); } void NativeProcessLinux::MonitorSIGTRAP(const siginfo_t &info, @@ -560,26 +561,26 @@ void NativeProcessLinux::MonitorSIGTRAP(const siginfo_t &info, assert(info.si_signo == SIGTRAP && "Unexpected child signal!"); switch (info.si_code) { - // TODO: these two cases are required if we want to support tracing of the - // inferiors' children. We'd need this to debug a monitor. case (SIGTRAP | - // (PTRACE_EVENT_FORK << 8)): case (SIGTRAP | (PTRACE_EVENT_VFORK << 8)): - + case (SIGTRAP | (PTRACE_EVENT_FORK << 8)): + case (SIGTRAP | (PTRACE_EVENT_VFORK << 8)): case (SIGTRAP | (PTRACE_EVENT_CLONE << 8)): { - // This is the notification on the parent thread which informs us of new - // thread creation. We don't want to do anything with the parent thread so - // we just resume it. In case we want to implement "break on thread - // creation" functionality, we would need to stop here. + // This can either mean a new thread or a new process spawned via + // clone(2) without SIGCHLD or CLONE_VFORK flag. Note that clone(2) + // can also cause PTRACE_EVENT_FORK and PTRACE_EVENT_VFORK if one + // of these flags are passed. unsigned long event_message = 0; if (GetEventMessage(thread.GetID(), &event_message).Fail()) { LLDB_LOG(log, - "pid {0} received thread creation event but " - "GetEventMessage failed so we don't know the new tid", + "pid {0} received clone() event but GetEventMessage failed " + "so we don't know the new pid/tid", thread.GetID()); - } else - WaitForNewThread(event_message); + ResumeThread(thread, thread.GetState(), LLDB_INVALID_SIGNAL_NUMBER); + } else { + if (!MonitorClone(event_message, {{(info.si_code >> 8), thread.GetID()}})) + WaitForCloneNotification(event_message); + } - ResumeThread(thread, thread.GetState(), LLDB_INVALID_SIGNAL_NUMBER); break; } @@ -645,6 +646,11 @@ void NativeProcessLinux::MonitorSIGTRAP(const siginfo_t &info, break; } + case (SIGTRAP | (PTRACE_EVENT_VFORK_DONE << 8)): { + ResumeThread(thread, thread.GetState(), LLDB_INVALID_SIGNAL_NUMBER); + break; + } + case 0: case TRAP_TRACE: // We receive this on single stepping. case TRAP_HWBKPT: // We receive this on watchpoint hit @@ -854,6 +860,77 @@ void NativeProcessLinux::MonitorSignal(const siginfo_t &info, StopRunningThreads(thread.GetID()); } +bool NativeProcessLinux::MonitorClone( + lldb::pid_t child_pid, + llvm::Optional<NativeProcessLinux::CloneInfo> clone_info) { + Log *log(ProcessPOSIXLog::GetLogIfAllCategoriesSet(POSIX_LOG_PROCESS)); + LLDB_LOG(log, "clone, child_pid={0}, clone info?={1}", child_pid, + clone_info.hasValue()); + + auto find_it = m_pending_pid_map.find(child_pid); + if (find_it == m_pending_pid_map.end()) { + // not in the map, so this is the first signal for the PID + m_pending_pid_map.insert({child_pid, clone_info}); + return false; + } + m_pending_pid_map.erase(find_it); + + // second signal for the pid + assert(clone_info.hasValue() != find_it->second.hasValue()); + if (!clone_info) { + // child signal does not indicate the event, so grab the one stored + // earlier + clone_info = find_it->second; + } + + LLDB_LOG(log, "second signal for child_pid={0}, parent_tid={1}, event={2}", + child_pid, clone_info->parent_tid, clone_info->event); + + auto *parent_thread = GetThreadByID(clone_info->parent_tid); + assert(parent_thread); + + switch (clone_info->event) { + case PTRACE_EVENT_CLONE: { + // PTRACE_EVENT_CLONE can either mean a new thread or a new process. + // Try to grab the new process' PGID to figure out which one it is. + // If PGID is the same as the PID, then it's a new process. Otherwise, + // it's a thread. + auto tgid_ret = getPIDForTID(child_pid); + if (tgid_ret != child_pid) { + // A new thread should have PGID matching our process' PID. + assert(!tgid_ret || tgid_ret.getValue() == GetID()); + + NativeThreadLinux &child_thread = AddThread(child_pid, /*resume*/ true); + ThreadWasCreated(child_thread); + + // Resume the parent. + ResumeThread(*parent_thread, parent_thread->GetState(), + LLDB_INVALID_SIGNAL_NUMBER); + break; + } + } + LLVM_FALLTHROUGH; + case PTRACE_EVENT_FORK: + case PTRACE_EVENT_VFORK: { + MainLoop unused_loop; + NativeProcessLinux child_process{static_cast<::pid_t>(child_pid), + m_terminal_fd, + m_delegate, + m_arch, + unused_loop, + {static_cast<::pid_t>(child_pid)}}; + child_process.Detach(); + ResumeThread(*parent_thread, parent_thread->GetState(), + LLDB_INVALID_SIGNAL_NUMBER); + break; + } + default: + llvm_unreachable("unknown clone_info.event"); + } + + return true; +} + bool NativeProcessLinux::SupportHardwareSingleStepping() const { if (m_arch.GetMachine() == llvm::Triple::arm || m_arch.IsMIPS()) return false; diff --git a/lldb/source/Plugins/Process/Linux/NativeProcessLinux.h b/lldb/source/Plugins/Process/Linux/NativeProcessLinux.h index 77905a193c2b7..86f6a1c27e5a4 100644 --- a/lldb/source/Plugins/Process/Linux/NativeProcessLinux.h +++ b/lldb/source/Plugins/Process/Linux/NativeProcessLinux.h @@ -157,7 +157,7 @@ class NativeProcessLinux : public NativeProcessELF, void MonitorCallback(lldb::pid_t pid, bool exited, WaitStatus status); - void WaitForNewThread(::pid_t tid); + void WaitForCloneNotification(::pid_t pid); void MonitorSIGTRAP(const siginfo_t &info, NativeThreadLinux &thread); @@ -234,6 +234,21 @@ class NativeProcessLinux : public NativeProcessELF, /// Manages Intel PT process and thread traces. IntelPTManager m_intel_pt_manager; + + struct CloneInfo { + int event; + lldb::tid_t parent_tid; + }; + + // Map of child processes that have been signaled once, and we are + // waiting for the second signal. + llvm::DenseMap<lldb::pid_t, llvm::Optional<CloneInfo>> m_pending_pid_map; + + // Handle a clone()-like event. If received by parent, clone_info contains + // additional info. Returns true if the event is handled, or false if it + // is pending second notification. + bool MonitorClone(lldb::pid_t child_pid, + llvm::Optional<CloneInfo> clone_info); }; } // namespace process_linux diff --git a/lldb/test/Shell/Subprocess/clone-follow-parent-wp.test b/lldb/test/Shell/Subprocess/clone-follow-parent-wp.test index 19fa7d6f1a32a..67d94af3ca105 100644 --- a/lldb/test/Shell/Subprocess/clone-follow-parent-wp.test +++ b/lldb/test/Shell/Subprocess/clone-follow-parent-wp.test @@ -1,4 +1,4 @@ -# REQUIRES: native && system-netbsd && dbregs-set +# REQUIRES: native && (system-linux || system-netbsd) && dbregs-set # clone() tests fails on arm64 Linux, PR #49899 # UNSUPPORTED: system-linux && target-aarch64 # RUN: %clangxx_host -g %p/Inputs/fork.cpp -DTEST_CLONE -o %t _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits