[Lldb-commits] [lldb] r219371 - POSIX dynamic loader: add more logging around launch/attach, fix breakpoint handling on entry callback.

[Todd Fiala]

Author: tfiala
Date: Wed Oct  8 19:11:43 2014
New Revision: 219371

URL: http://llvm.org/viewvc/llvm-project?rev=219371&view=rev
Log:
POSIX dynamic loader: add more logging around launch/attach, fix breakpoint handling on entry callback.

This change adds some logging around dynamic loader handling.
It also fixes an issue where the dynamic loader entry breakpoint can end
up being re-inserted, showing the wrong (i.e. software breakpoint) instruction
at the stop location when a backtrace is displayed at program startup.

I discussed with Jim Ingham a few weeks back.  Essentially the
one-hit breakpoints need to make it back to public state handling before
the software breakpoint gets cleared.  The flow I was hitting was that
the breakpoint would get set, it would get hit, it would get cleared to
step over, then it would get reapplied, when we never wanted it reapplied.
Stops at the beginning of execution would then show backtraces with
software breakpoint instructions in it, erroneously.  This change fixes it.
There might be a more elegant way to do this, or a flow change somewhere else
to avoid, but it does fix an issue I experienced in startup breakpoint handling.

Modified:
    lldb/trunk/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp

Modified: lldb/trunk/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp?rev=219371&r1=219370&r2=219371&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp (original)
+++ lldb/trunk/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp Wed Oct  8 19:11:43 2014
@@ -181,6 +181,10 @@ DynamicLoaderPOSIXDYLD::DidAttach()
 void
 DynamicLoaderPOSIXDYLD::DidLaunch()
 {
+    Log *log (GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));
+    if (log)
+        log->Printf ("DynamicLoaderPOSIXDYLD::%s()", __FUNCTION__);
+
     ModuleSP executable;
     addr_t load_offset;
 
@@ -194,7 +198,11 @@ DynamicLoaderPOSIXDYLD::DidLaunch()
         ModuleList module_list;
         module_list.Append(executable);
         UpdateLoadedSections(executable, LLDB_INVALID_ADDRESS, load_offset);
+
+        if (log)
+            log->Printf ("DynamicLoaderPOSIXDYLD::%s about to call ProbeEntry()", __FUNCTION__);
         ProbeEntry();
+
         m_process->GetTarget().ModulesDidLoad(module_list);
     }
 }
@@ -247,13 +255,15 @@ DynamicLoaderPOSIXDYLD::ProbeEntry()
     }
 
     if (log)
-        if (log)
-            log->Printf ("DynamicLoaderPOSIXDYLD::%s pid %" PRIu64 " GetEntryPoint() returned address 0x%" PRIx64 ", setting entry breakpoint", __FUNCTION__, m_process ? m_process->GetID () : LLDB_INVALID_PROCESS_ID, entry);
+        log->Printf ("DynamicLoaderPOSIXDYLD::%s pid %" PRIu64 " GetEntryPoint() returned address 0x%" PRIx64 ", setting entry breakpoint", __FUNCTION__, m_process ? m_process->GetID () : LLDB_INVALID_PROCESS_ID, entry);
 
 
     Breakpoint *const entry_break = m_process->GetTarget().CreateBreakpoint(entry, true, false).get();
     entry_break->SetCallback(EntryBreakpointHit, this, true);
     entry_break->SetBreakpointKind("shared-library-event");
+
+    // Shoudn't hit this more than once.
+    entry_break->SetOneShot (true);
 }
 
 // The runtime linker has run and initialized the rendezvous structure once the
@@ -277,6 +287,31 @@ DynamicLoaderPOSIXDYLD::EntryBreakpointH
     if (log)
         log->Printf ("DynamicLoaderPOSIXDYLD::%s called for pid %" PRIu64, __FUNCTION__, dyld_instance->m_process ? dyld_instance->m_process->GetID () : LLDB_INVALID_PROCESS_ID);
 
+    // Disable the breakpoint --- if a stop happens right after this, which we've seen on occasion, we don't
+    // want the breakpoint stepping thread-plan logic to show a breakpoint instruction at the disassembled
+    // entry point to the program.  Disabling it prevents it.  (One-shot is not enough - one-shot removal logic
+    // only happens after the breakpoint goes public, which wasn't happening in our scenario).
+    if (dyld_instance->m_process)
+    {
+        BreakpointSP breakpoint_sp = dyld_instance->m_process->GetTarget().GetBreakpointByID (break_id);
+        if (breakpoint_sp)
+        {
+            if (log)
+                log->Printf ("DynamicLoaderPOSIXDYLD::%s pid %" PRIu64 " disabling breakpoint id %" PRIu64, __FUNCTION__, dyld_instance->m_process->GetID (), break_id);
+            breakpoint_sp->SetEnabled (false);
+        }
+        else
+        {
+            if (log)
+                log->Printf ("DynamicLoaderPOSIXDYLD::%s pid %" PRIu64 " failed to find breakpoint for breakpoint id %" PRIu64, __FUNCTION__, dyld_instance->m_process->GetID (), break_id);
+        }
+    }
+    else
+    {
+        if (log)
+            log->Printf ("DynamicLoaderPOSIXDYLD::%s breakpoint id %" PRIu64 " no Process instance!  Cannot disable breakpoint", __FUNCTION__, break_id);
+    }
+
     dyld_instance->LoadAllCurrentModules();
     dyld_instance->SetRendezvousBreakpoint();
     return false; // Continue running.