mgorny updated this revision to Diff 333064.
mgorny retitled this revision from "[lldb] [Process/Linux] Watch for fork
notifications" to "[lldb] [Process/Linux] Watch for fork/vfork notifications".
mgorny edited the summary of this revision.
mgorny added a comment.
Included `vfork()`. Still have to look into other `clone()` variants, then
other platforms.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D98822/new/
https://reviews.llvm.org/D98822
Files:
lldb/include/lldb/Host/common/NativeProcessProtocol.h
lldb/source/Host/common/NativeProcessProtocol.cpp
lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
lldb/source/Plugins/Process/Linux/NativeProcessLinux.h
lldb/test/Shell/Subprocess/Inputs/fork.c
lldb/test/Shell/Subprocess/Inputs/vfork.c
lldb/test/Shell/Subprocess/fork-follow-parent-softbp.test
lldb/test/Shell/Subprocess/fork-follow-parent-wp.test
lldb/test/Shell/Subprocess/fork-follow-parent.test
lldb/test/Shell/Subprocess/vfork-follow-parent-softbp.test
lldb/test/Shell/Subprocess/vfork-follow-parent.test
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
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/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/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-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/Inputs/vfork.c
===================================================================
--- /dev/null
+++ lldb/test/Shell/Subprocess/Inputs/vfork.c
@@ -0,0 +1,37 @@
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <assert.h>
+#include <stdio.h>
+#include <unistd.h>
+
+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/Inputs/fork.c
===================================================================
--- /dev/null
+++ lldb/test/Shell/Subprocess/Inputs/fork.c
@@ -0,0 +1,36 @@
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <assert.h>
+#include <stdio.h>
+#include <unistd.h>
+
+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/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 +248,24 @@
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<lldb::pid_t, llvm::Optional<CloneInfo>> m_pending_pid_map;
+
+ // Software breakpoints saved for the duration of vfork().
+ llvm::SmallVector<std::pair<lldb::addr_t, size_t>, 8> m_saved_breakpoints;
+
+ // 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
Index: lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
===================================================================
--- lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
+++ lldb/source/Plugins/Process/Linux/NativeProcessLinux.cpp
@@ -383,14 +383,22 @@
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 +452,7 @@
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 +516,24 @@
}
}
-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 +541,15 @@
}
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,
@@ -580,10 +576,12 @@
"pid {0} received thread creation event but "
"GetEventMessage failed so we don't know the new 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 +647,38 @@
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 error = ReaddSoftwareBreakpoints(m_saved_breakpoints);
+ if (error) {
+ LLDB_LOG_ERROR(log, std::move(error),
+ "failed to restore breakpoints after vfork: {0}");
+ SetState(StateType::eStateInvalid);
+ return;
+ }
+ m_saved_breakpoints.clear();
+ 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 +888,92 @@
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;
+ }
+
+ // 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: {
+ 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;
+ }
+ 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;
+ auto bp = child_process.RemoveAllSoftwareBreakpoints();
+ if (!bp) {
+ LLDB_LOG_ERROR(log, std::move(bp.takeError()),
+ "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
+ auto bp = RemoveAllSoftwareBreakpoints();
+ if (!bp) {
+ LLDB_LOG_ERROR(log, std::move(bp.takeError()),
+ "failed to remove breakpoints from vforked process {1}: {0}",
+ child_pid);
+ SetState(StateType::eStateInvalid);
+ return true;
+ }
+ m_saved_breakpoints.append(bp.get());
+ 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/source/Host/common/NativeProcessProtocol.cpp
===================================================================
--- lldb/source/Host/common/NativeProcessProtocol.cpp
+++ lldb/source/Host/common/NativeProcessProtocol.cpp
@@ -642,6 +642,30 @@
return RemoveSoftwareBreakpoint(addr);
}
+llvm::Expected<llvm::SmallVector<std::pair<lldb::addr_t, size_t>, 8>>
+NativeProcessProtocol::RemoveAllSoftwareBreakpoints() {
+ llvm::SmallVector<std::pair<lldb::addr_t, size_t>, 8> breakpoints;
+
+ while (!m_software_breakpoints.empty()) {
+ auto& bp = *m_software_breakpoints.begin();
+ breakpoints.emplace_back(bp.first, bp.second.saved_opcodes.size());
+ Status ret = RemoveSoftwareBreakpoint(bp.first);
+ if (ret.Fail())
+ return ret.ToError();
+ }
+
+ return breakpoints;
+}
+
+llvm::Error NativeProcessProtocol::ReaddSoftwareBreakpoints(llvm::ArrayRef<std::pair<lldb::addr_t, size_t>> breakpoints) {
+ for (auto& x : breakpoints) {
+ Status ret = SetSoftwareBreakpoint(x.first, x.second);
+ if (ret.Fail())
+ return ret.ToError();
+ }
+ return llvm::Error::success();
+}
+
Status NativeProcessProtocol::ReadMemoryWithoutTrap(lldb::addr_t addr,
void *buf, size_t size,
size_t &bytes_read) {
Index: lldb/include/lldb/Host/common/NativeProcessProtocol.h
===================================================================
--- lldb/include/lldb/Host/common/NativeProcessProtocol.h
+++ lldb/include/lldb/Host/common/NativeProcessProtocol.h
@@ -142,6 +142,14 @@
virtual Status RemoveBreakpoint(lldb::addr_t addr, bool hardware = false);
+ // Remove all software breakpoints and return a vector of breakpoint data
+ // that can be used to readd them.
+ virtual llvm::Expected<llvm::SmallVector<std::pair<lldb::addr_t, size_t>, 8>>
+ RemoveAllSoftwareBreakpoints();
+
+ virtual llvm::Error ReaddSoftwareBreakpoints(
+ llvm::ArrayRef<std::pair<lldb::addr_t, size_t>> breakpoints);
+
// Hardware Breakpoint functions
virtual const HardwareBreakpointMap &GetHardwareBreakpointMap() const;
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