Add setting to require hardware breakpoints.

When debugging read-only memory we cannot use software breakpoint. We
already have support for hardware breakpoints and users can specify them
with `-H`. However, there's no option to force LLDB to use hardware
breakpoints internally, for example while stepping.

This patch adds a setting target.require-hardware-breakpoint that forces
LLDB to always use hardware breakpoints. Because hardware breakpoints
are a limited resource and can fail to resolve, this patch also extends
error handling in thread plans, where breakpoints are used for stepping.

Differential revision: https://reviews.llvm.org/D54221

llvm-svn: 346920

1 files changed, 12 insertions, 1 deletions

diff --git a/lldb/source/Target/ThreadPlanStepInstruction.cpp b/lldb/source/Target/ThreadPlanStepInstruction.cpp
index b2cecf3a121..7707454c979 100644
--- a/lldb/source/Target/ThreadPlanStepInstruction.cpp
+++ b/lldb/source/Target/ThreadPlanStepInstruction.cpp
@@ -53,11 +53,19 @@ void ThreadPlanStepInstruction::SetUpState() {
 
 void ThreadPlanStepInstruction::GetDescription(Stream *s,
                                                lldb::DescriptionLevel level) {
+  auto PrintFailureIfAny = [&]() {
+    if (m_status.Success())
+      return;
+    s->Printf(" failed (%s)", m_status.AsCString());
+  };
+
   if (level == lldb::eDescriptionLevelBrief) {
     if (m_step_over)
       s->Printf("instruction step over");
     else
       s->Printf("instruction step into");
+
+    PrintFailureIfAny();
   } else {
     s->Printf("Stepping one instruction past ");
     s->Address(m_instruction_addr, sizeof(addr_t));
@@ -68,6 +76,8 @@ void ThreadPlanStepInstruction::GetDescription(Stream *s,
       s->Printf(" stepping over calls");
     else
       s->Printf(" stepping into calls");
+
+    PrintFailureIfAny();
   }
 }
 
@@ -188,7 +198,8 @@ bool ThreadPlanStepInstruction::ShouldStop(Event *event_ptr) {
           // for now it is safer to run others.
           const bool stop_others = false;
           m_thread.QueueThreadPlanForStepOutNoShouldStop(
-              false, nullptr, true, stop_others, eVoteNo, eVoteNoOpinion, 0);
+              false, nullptr, true, stop_others, eVoteNo, eVoteNoOpinion, 0,
+              m_status);
           return false;
         } else {
           if (log) {