Index: lldb/include/lldb/Host/common/NativeProcessProtocol.h =================================================================== --- lldb/include/lldb/Host/common/NativeProcessProtocol.h +++ lldb/include/lldb/Host/common/NativeProcessProtocol.h @@ -472,6 +472,16 @@ NativeThreadProtocol *GetThreadByIDUnlocked(lldb::tid_t tid); + // Software breakpoints saved for the duration of vfork(). + llvm::SmallVector, 8> m_saved_breakpoints; + + // Disable all current software breakpoints and store them for reenabling + // later. + llvm::Error DisableSoftwareBreakpoints(); + + // Reenable all software breakpoints (undo DisableSoftwareBreakpoints()). + llvm::Error EnableSoftwareBreakpoints(); + private: void SynchronouslyNotifyProcessStateChanged(lldb::StateType state); llvm::Expected Index: lldb/include/lldb/Host/linux/Host.h =================================================================== --- /dev/null +++ lldb/include/lldb/Host/linux/Host.h @@ -0,0 +1,23 @@ +//===-- 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 "llvm/ADT/Optional.h" + +#include "lldb/lldb-types.h" + +namespace lldb_private { + +// Get PID (i.e. the primary thread ID) corresponding to the specified TID. +llvm::Optional getPIDForTID(lldb::pid_t tid); + +} // namespace lldb_private + +#endif // #ifndef LLDB_HOST_LINUX_HOST_H Index: lldb/source/Host/common/NativeProcessProtocol.cpp =================================================================== --- lldb/source/Host/common/NativeProcessProtocol.cpp +++ lldb/source/Host/common/NativeProcessProtocol.cpp @@ -760,4 +760,26 @@ // Default implementation does nothing. } +llvm::Error NativeProcessProtocol::DisableSoftwareBreakpoints() { + while (!m_software_breakpoints.empty()) { + auto &bp = *m_software_breakpoints.begin(); + m_saved_breakpoints.emplace_back(bp.first, bp.second.saved_opcodes.size()); + Status ret = RemoveSoftwareBreakpoint(bp.first); + if (ret.Fail()) + return ret.ToError(); + } + + return llvm::Error::success(); +} + +llvm::Error NativeProcessProtocol::EnableSoftwareBreakpoints() { + for (auto it = m_saved_breakpoints.begin(); it != m_saved_breakpoints.end(); + it = m_saved_breakpoints.erase(it)) { + Status ret = SetSoftwareBreakpoint(it->first, it->second); + if (ret.Fail()) + return ret.ToError(); + } + return llvm::Error::success(); +} + NativeProcessProtocol::Factory::~Factory() = default; Index: lldb/source/Host/linux/Host.cpp =================================================================== --- lldb/source/Host/linux/Host.cpp +++ 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 @@ } 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 @@ } 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 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 @@ 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 +314,13 @@ Status Host::ShellExpandArguments(ProcessLaunchInfo &launch_info) { return Status("unimplemented"); } + +llvm::Optional 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 == 0) + return llvm::None; + return tgid; +} Index: lldb/source/Plugins/Process/Linux/NativeProcessLinux.h =================================================================== --- lldb/source/Plugins/Process/Linux/NativeProcessLinux.h +++ lldb/source/Plugins/Process/Linux/NativeProcessLinux.h @@ -158,7 +158,7 @@ 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); @@ -248,6 +248,21 @@ lldb::user_id_t m_pt_proces_trace_id = LLDB_INVALID_UID; TraceOptions m_pt_process_trace_config; + + struct CloneInfo { + uint32_t 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> 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 clone_info); }; } // namespace process_linux Index: lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp =================================================================== --- lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp +++ 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 @@ 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); } @@ -444,11 +453,7 @@ LLDB_LOG(log, "tid {0}, si_code: {1}, si_pid: {2}", pid, info.si_code, info.si_pid); - NativeThreadLinux &thread = AddThread(pid); - - // Resume the newly created thread. - ResumeThread(thread, eStateRunning, LLDB_INVALID_SIGNAL_NUMBER); - ThreadWasCreated(thread); + MonitorClone(pid, llvm::None); return; } @@ -512,29 +517,24 @@ } } -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. @@ -542,18 +542,15 @@ } 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); - - ResumeThread(new_thread, eStateRunning, LLDB_INVALID_SIGNAL_NUMBER); - ThreadWasCreated(new_thread); + MonitorClone(pid, llvm::None); } void NativeProcessLinux::MonitorSIGTRAP(const siginfo_t &info, @@ -564,26 +561,24 @@ 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_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, {{PTRACE_EVENT_CLONE, thread.GetID()}})) + WaitForCloneNotification(event_message); + } - ResumeThread(thread, thread.GetState(), LLDB_INVALID_SIGNAL_NUMBER); break; } @@ -649,6 +644,39 @@ break; } + case (SIGTRAP | (PTRACE_EVENT_FORK << 8)): { + unsigned long data = 0; + if (GetEventMessage(thread.GetID(), &data).Fail()) + data = 0; + + if (!MonitorClone(data, {{PTRACE_EVENT_FORK, thread.GetID()}})) + WaitForCloneNotification(data); + break; + } + + case (SIGTRAP | (PTRACE_EVENT_VFORK << 8)): { + unsigned long data = 0; + if (GetEventMessage(thread.GetID(), &data).Fail()) + data = 0; + + if (!MonitorClone(data, {{PTRACE_EVENT_VFORK, thread.GetID()}})) + WaitForCloneNotification(data); + break; + } + + case (SIGTRAP | (PTRACE_EVENT_VFORK_DONE << 8)): { + // restore breakpoints + llvm::Error bp_err = EnableSoftwareBreakpoints(); + if (bp_err) { + LLDB_LOG_ERROR(log, std::move(bp_err), + "failed to restore breakpoints after vfork: {0}"); + SetState(StateType::eStateInvalid); + return; + } + 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 @@ -858,6 +886,102 @@ StopRunningThreads(thread.GetID()); } +bool NativeProcessLinux::MonitorClone( + lldb::pid_t child_pid, + llvm::Optional 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; + } + + // 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 pgid_ret = getPIDForTID(child_pid); + if (!pgid_ret || pgid_ret.getValue() != child_pid) { + // A new thread should have PGID matching our process' PID. + assert(!pgid_ret || pgid_ret.getValue() == clone_info->parent_tid); + + NativeThreadLinux &child_thread = AddThread(child_pid); + // Resume the newly created thread. + ResumeThread(child_thread, eStateRunning, LLDB_INVALID_SIGNAL_NUMBER); + ThreadWasCreated(child_thread); + + // Resume the parent. + ResumeThread(*parent_thread, parent_thread->GetState(), + LLDB_INVALID_SIGNAL_NUMBER); + break; + } + } + // fallthrough + case PTRACE_EVENT_FORK: { + MainLoop unused_loop; + NativeProcessLinux child_process{child_pid, m_terminal_fd, *m_delegates[0], + m_arch, unused_loop, {child_pid}}; + child_process.m_software_breakpoints = m_software_breakpoints; + llvm::Error bp_err = child_process.DisableSoftwareBreakpoints(); + if (bp_err) { + LLDB_LOG_ERROR(log, std::move(bp_err), + "failed to remove breakpoints from forked process {1}: {0}", + child_pid); + SetState(StateType::eStateInvalid); + return true; + } + child_process.Detach(); + ResumeThread(*parent_thread, parent_thread->GetState(), + LLDB_INVALID_SIGNAL_NUMBER); + break; + } + case PTRACE_EVENT_VFORK: { + MainLoop unused_loop; + NativeProcessLinux child_process{child_pid, m_terminal_fd, *m_delegates[0], + m_arch, unused_loop, {child_pid}}; + // vfork shares memory with the parent, so we need to temporarily remove + // breakpoints + llvm::Error bp_err = DisableSoftwareBreakpoints(); + if (bp_err) { + LLDB_LOG_ERROR(log, std::move(bp_err), + "failed to remove breakpoints from vforked process {1}: {0}", + child_pid); + SetState(StateType::eStateInvalid); + return true; + } + child_process.Detach(); + ResumeThread(*parent_thread, parent_thread->GetState(), + LLDB_INVALID_SIGNAL_NUMBER); + break; + } + default: + assert(false && "unknown clone_info.event"); + } + + m_pending_pid_map.erase(child_pid); + return true; +} + bool NativeProcessLinux::SupportHardwareSingleStepping() const { if (m_arch.GetMachine() == llvm::Triple::arm || m_arch.IsMIPS()) return false; Index: lldb/test/Shell/Subprocess/Inputs/fork.c =================================================================== --- /dev/null +++ lldb/test/Shell/Subprocess/Inputs/fork.c @@ -0,0 +1,36 @@ +#include +#include +#include +#include +#include + +int g_val = 0; + +void parent_func() { + g_val = 1; + printf("function run in parent\n"); +} + +void child_func() { + g_val = 2; + printf("function run in child\n"); +} + +int main() { + pid_t pid = fork(); + assert(pid != -1); + + if (pid == 0) { + child_func(); + _exit(0); + } + + parent_func(); + int status; + pid_t waited = waitpid(pid, &status, 0); + assert(waited == pid); + assert(WIFEXITED(status)); + printf("child exited: %d\n", WEXITSTATUS(status)); + + return 0; +} Index: lldb/test/Shell/Subprocess/Inputs/vfork.c =================================================================== --- /dev/null +++ lldb/test/Shell/Subprocess/Inputs/vfork.c @@ -0,0 +1,37 @@ +#include +#include +#include +#include +#include + +int g_val = 0; + +void parent_func() { + g_val = 1; + printf("function run in parent\n"); +} + +void child_func() { + // do something relatively safe + volatile int val = 0; + ++val; +} + +int main() { + pid_t pid = vfork(); + assert(pid != -1); + + if (pid == 0) { + child_func(); + _exit(0); + } + + parent_func(); + int status; + pid_t waited = waitpid(pid, &status, 0); + assert(waited == pid); + assert(WIFEXITED(status)); + printf("child exited: %d\n", WEXITSTATUS(status)); + + return 0; +} Index: lldb/test/Shell/Subprocess/fork-follow-parent-softbp.test =================================================================== --- /dev/null +++ lldb/test/Shell/Subprocess/fork-follow-parent-softbp.test @@ -0,0 +1,12 @@ +# REQUIRES: native +# RUN: %clang_host %p/Inputs/fork.c -o %t +# RUN: %lldb -b -s %s %t | FileCheck %s +b parent_func +b child_func +process launch +# CHECK: function run in child +# CHECK-NOT: function run in parent +# CHECK: stop reason = breakpoint +continue +# CHECK: function run in parent +# CHECK: child exited: 0 Index: lldb/test/Shell/Subprocess/fork-follow-parent-wp.test =================================================================== --- /dev/null +++ lldb/test/Shell/Subprocess/fork-follow-parent-wp.test @@ -0,0 +1,13 @@ +# REQUIRES: native && (target-x86 || target-x86_64 || target-aarch64) && dbregs-set +# RUN: %clang_host -g %p/Inputs/fork.c -o %t +# RUN: %lldb -b -s %s %t | FileCheck %s +process launch -s +watchpoint set variable -w write g_val +# CHECK: Watchpoint created: +continue +# CHECK: function run in child +# CHECK-NOT: function run in parent +# CHECK: stop reason = watchpoint +continue +# CHECK: function run in parent +# CHECK: child exited: 0 Index: lldb/test/Shell/Subprocess/fork-follow-parent.test =================================================================== --- /dev/null +++ lldb/test/Shell/Subprocess/fork-follow-parent.test @@ -0,0 +1,11 @@ +# REQUIRES: native +# RUN: %clang_host %p/Inputs/fork.c -o %t +# RUN: %lldb -b -s %s %t | FileCheck %s +b parent_func +process launch +# CHECK: function run in child +# CHECK-NOT: function run in parent +# CHECK: stop reason = breakpoint +continue +# CHECK: function run in parent +# CHECK: child exited: 0 Index: lldb/test/Shell/Subprocess/vfork-follow-parent-softbp.test =================================================================== --- /dev/null +++ lldb/test/Shell/Subprocess/vfork-follow-parent-softbp.test @@ -0,0 +1,11 @@ +# REQUIRES: native +# RUN: %clang_host %p/Inputs/vfork.c -o %t +# RUN: %lldb -b -s %s %t | FileCheck %s +b parent_func +b child_func +process launch +# CHECK-NOT: function run in parent +# CHECK: stop reason = breakpoint +continue +# CHECK: function run in parent +# CHECK: child exited: 0 Index: lldb/test/Shell/Subprocess/vfork-follow-parent.test =================================================================== --- /dev/null +++ lldb/test/Shell/Subprocess/vfork-follow-parent.test @@ -0,0 +1,10 @@ +# REQUIRES: native +# RUN: %clang_host %p/Inputs/vfork.c -o %t +# RUN: %lldb -b -s %s %t | FileCheck %s +b parent_func +process launch +# CHECK-NOT: function run in parent +# CHECK: stop reason = breakpoint +continue +# CHECK: function run in parent +# CHECK: child exited: 0