[lldb-dap] fix wrong assembly line number x64

[eronnen]

Fix wrong assembly line number calculation that assumes the instruction size is GetAddressByteSize() / 2

Fixes #136495

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[llvmbot]

@llvm/pr-subscribers-lldb

Author: Ely Ronnen (eronnen)

Changes

Fix wrong assembly line number calculation that assumes the instruction size is GetAddressByteSize() / 2

---

Full diff: https://github.com/llvm/llvm-project/pull/136486.diff

3 Files Affected:

• (modified) lldb/tools/lldb-dap/Handler/StackTraceRequestHandler.cpp (+2-1)
• (modified) lldb/tools/lldb-dap/JSONUtils.cpp (+16-6)
• (modified) lldb/tools/lldb-dap/JSONUtils.h (+5-2)

diff --git a/lldb/tools/lldb-dap/Handler/StackTraceRequestHandler.cpp b/lldb/tools/lldb-dap/Handler/StackTraceRequestHandler.cpp
index a58e3325af100..5d1d2835b4392 100644
--- a/lldb/tools/lldb-dap/Handler/StackTraceRequestHandler.cpp
+++ b/lldb/tools/lldb-dap/Handler/StackTraceRequestHandler.cpp
@@ -67,7 +67,8 @@ static bool FillStackFrames(DAP &dap, lldb::SBThread &thread,
       break;
     }
 
-    stack_frames.emplace_back(CreateStackFrame(frame, dap.frame_format));
+    stack_frames.emplace_back(
+        CreateStackFrame(frame, dap.frame_format, dap.target));
   }
 
   if (dap.configuration.displayExtendedBacktrace && reached_end_of_stack) {
diff --git a/lldb/tools/lldb-dap/JSONUtils.cpp b/lldb/tools/lldb-dap/JSONUtils.cpp
index 33f10c93d2ada..552fdc9439845 100644
--- a/lldb/tools/lldb-dap/JSONUtils.cpp
+++ b/lldb/tools/lldb-dap/JSONUtils.cpp
@@ -19,6 +19,8 @@
 #include "lldb/API/SBFileSpec.h"
 #include "lldb/API/SBFrame.h"
 #include "lldb/API/SBFunction.h"
+#include "lldb/API/SBInstruction.h"
+#include "lldb/API/SBInstructionList.h"
 #include "lldb/API/SBLineEntry.h"
 #include "lldb/API/SBModule.h"
 #include "lldb/API/SBQueue.h"
@@ -719,8 +721,8 @@ llvm::json::Value CreateSource(llvm::StringRef source_path) {
 //   },
 //   "required": [ "id", "name", "line", "column" ]
 // }
-llvm::json::Value CreateStackFrame(lldb::SBFrame &frame,
-                                   lldb::SBFormat &format) {
+llvm::json::Value CreateStackFrame(lldb::SBFrame &frame, lldb::SBFormat &format,
+                                   lldb::SBTarget &target) {
   llvm::json::Object object;
   int64_t frame_id = MakeDAPFrameID(frame);
   object.try_emplace("id", frame_id);
@@ -776,10 +778,18 @@ llvm::json::Value CreateStackFrame(lldb::SBFrame &frame,
 
     // Calculate the line of the current PC from the start of the current
     // symbol.
-    lldb::addr_t inst_offset = frame.GetPCAddress().GetOffset() -
-                               frame.GetSymbol().GetStartAddress().GetOffset();
-    lldb::addr_t inst_line =
-        inst_offset / (frame.GetThread().GetProcess().GetAddressByteSize() / 2);
+    lldb::SBAddress current_address = frame.GetPCAddress();
+    lldb::SBInstructionList inst_list =
+        frame.GetSymbol().GetInstructions(target);
+    size_t inst_line = 0;
+    for (size_t i = 0; i < inst_list.GetSize(); ++i) {
+      lldb::SBInstruction inst = inst_list.GetInstructionAtIndex(i);
+      if (inst.GetAddress() == current_address) {
+        inst_line = i;
+        break;
+      }
+    }
+
     // Line numbers are 1-based.
     object.try_emplace("line", inst_line + 1);
     object.try_emplace("column", 1);
diff --git a/lldb/tools/lldb-dap/JSONUtils.h b/lldb/tools/lldb-dap/JSONUtils.h
index b8c53353bf42d..ffa10743501b8 100644
--- a/lldb/tools/lldb-dap/JSONUtils.h
+++ b/lldb/tools/lldb-dap/JSONUtils.h
@@ -363,11 +363,14 @@ llvm::json::Value CreateSource(llvm::StringRef source_path);
 ///     The LLDB format to use when populating out the "StackFrame"
 ///     object.
 ///
+/// \param[in] target
+///     The LLDB target to use when populating out the "StackFrame"
+///     object.
 /// \return
 ///     A "StackFrame" JSON object with that follows the formal JSON
 ///     definition outlined by Microsoft.
-llvm::json::Value CreateStackFrame(lldb::SBFrame &frame,
-                                   lldb::SBFormat &format);
+llvm::json::Value CreateStackFrame(lldb::SBFrame &frame, lldb::SBFormat &format,
+                                   lldb::SBTarget &target);
 
 /// Create a "StackFrame" label object for a LLDB thread.
 ///

[eronnen]

Edit: improved the patch by using target.ReadInstructions in order to calculate the line number of the current instruction

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[JDevlieghere]

LGTM but I'd like to have a (x86) test that would have failed without this case.

[eronnen]

@JDevlieghere added a test that checks that line increments by exactly 1 each step

[JDevlieghere]

Thanks!

[JDevlieghere]

is this really limited to linux? It seems like this should work on at least Darwin too.

[eronnen]

seems like it should work, changing

[ashgti]

Should we explicitly step with granularity='instruction'?

[eronnen]

It should be the same because it's a function without debug symbols so each step should execute one assembly instruction

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