[Lldb-commits] [lldb] c8d18cb - Reland "[lldb] [Process] Watch for fork/vfork notifications" for Linux
Michał Górny via lldb-commits
lldb-commits at lists.llvm.org
Tue Apr 13 05:47:31 PDT 2021
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
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