Fix a recursion that could happen when creating the first frame in

an unwind because RegisterContextLLDB::InitializeZerothFrame() would
create a minimal stack frame to fetch the pc value of the current
instruction.  This proved fragile when another section of code was
trying to create the first stack frame and UnwindLLDB called
RegisterContextLLDB which tried to create its minimal stack frame.

Instead, get the live RegisterContext, retrieve the pc value from
the registers, and create an Address object from that.

llvm-svn: 151714

1 files changed, 45 insertions, 13 deletions

diff --git a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
index 03de3d1355c..d9ff61b1815 100644
--- a/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
+++ b/lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp
@@ -86,27 +86,59 @@ void
 RegisterContextLLDB::InitializeZerothFrame()
 {
     ExecutionContext exe_ctx(m_thread.shared_from_this());
-    StackFrameSP frame_sp (m_thread.GetStackFrameAtIndex (0));
-    exe_ctx.SetFrameSP (frame_sp);
+    RegisterContextSP reg_ctx_sp = m_thread.GetRegisterContext();
 
     LogSP log(GetLogIfAllCategoriesSet (LIBLLDB_LOG_UNWIND));
 
-    if (m_thread.GetRegisterContext() == NULL)
+    if (reg_ctx_sp.get() == NULL)
     {
         m_frame_type = eNotAValidFrame;
         return;
     }
-    m_sym_ctx = frame_sp->GetSymbolContext (eSymbolContextFunction | eSymbolContextSymbol);
-    
+
+    addr_t current_pc = reg_ctx_sp->GetPC();
+
+    if (current_pc == LLDB_INVALID_ADDRESS)
+    {
+        m_frame_type = eNotAValidFrame;
+        return;
+    }
+
+    Process *process = exe_ctx.GetProcessPtr();
+
+    // Let ABIs fixup code addresses to make sure they are valid. In ARM ABIs
+    // this will strip bit zero in case we read a PC from memory or from the LR.
+    // (which would be a no-op in frame 0 where we get it from the register set,
+    // but still a good idea to make the call here for other ABIs that may exist.)
+    ABI *abi = process->GetABI().get();
+    if (abi)
+        current_pc = abi->FixCodeAddress(current_pc);
+
+    // Initialize m_current_pc, an Address object, based on current_pc, an addr_t.
+    process->GetTarget().GetSectionLoadList().ResolveLoadAddress (current_pc, m_current_pc);
+
+    // If we don't have a Module for some reason, we're not going to find symbol/function information - just
+    // stick in some reasonable defaults and hope we can unwind past this frame.
+    ModuleSP pc_module_sp (m_current_pc.GetModule());
+    if (!m_current_pc.IsValid() || !pc_module_sp)
+    {
+        if (log)
+        {
+            log->Printf("%*sFrame %u using architectural default unwind method",
+                        m_frame_number < 100 ? m_frame_number : 100, "", m_frame_number);
+        }
+    }
+
     // We require that eSymbolContextSymbol be successfully filled in or this context is of no use to us.
-    if ((m_sym_ctx.GetResolvedMask() & eSymbolContextSymbol) == eSymbolContextSymbol)
+    if (pc_module_sp.get()
+        && (pc_module_sp->ResolveSymbolContextForAddress (m_current_pc, eSymbolContextFunction| eSymbolContextSymbol, m_sym_ctx) & eSymbolContextSymbol) == eSymbolContextSymbol)
+    {
         m_sym_ctx_valid = true;
+    }
 
     AddressRange addr_range;
     m_sym_ctx.GetAddressRange (eSymbolContextFunction | eSymbolContextSymbol, 0, false, addr_range);
     
-    m_current_pc = frame_sp->GetFrameCodeAddress();
-
     static ConstString g_sigtramp_name ("_sigtramp");
     if ((m_sym_ctx.function && m_sym_ctx.function->GetName() == g_sigtramp_name) ||
         (m_sym_ctx.symbol   && m_sym_ctx.symbol->GetName()   == g_sigtramp_name))
@@ -124,17 +156,17 @@ RegisterContextLLDB::InitializeZerothFrame()
     if (addr_range.GetBaseAddress().IsValid())
     {
         m_start_pc = addr_range.GetBaseAddress();
-        if (frame_sp->GetFrameCodeAddress().GetSection() == m_start_pc.GetSection())
+        if (m_current_pc.GetSection() == m_start_pc.GetSection())
         {
-            m_current_offset = frame_sp->GetFrameCodeAddress().GetOffset() - m_start_pc.GetOffset();
+            m_current_offset = m_current_pc.GetOffset() - m_start_pc.GetOffset();
         }
-        else if (frame_sp->GetFrameCodeAddress().GetModule() == m_start_pc.GetModule())
+        else if (m_current_pc.GetModule() == m_start_pc.GetModule())
         {
             // This means that whatever symbol we kicked up isn't really correct
-            // as no should cross section boundaries... We really should NULL out
+            // --- we should not cross section boundaries ... We really should NULL out
             // the function/symbol in this case unless there is a bad assumption
             // here due to inlined functions?
-            m_current_offset = frame_sp->GetFrameCodeAddress().GetFileAddress() - m_start_pc.GetFileAddress();
+            m_current_offset = m_current_pc.GetFileAddress() - m_start_pc.GetFileAddress();
         }
         m_current_offset_backed_up_one = m_current_offset;
     }