[lldb] Correctly resolve (discontinuous) function offsets when disassembling

[labath]

We need to iterate through the all symbol context ranges returned by (since #126505) SymbolContext::GetAddressRange. This also includes a fix to print the function offsets as signed values.

I've also wanted to check that the addresses which are in the middle of the function do not resolve to the function, but that's not entirely the case right now. This appears to be a separate issue though, so I've just left a TODO for now.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Pavel Labath (labath)

Changes

We need to iterate through the all symbol context ranges returned by (since #126505) SymbolContext::GetAddressRange. This also includes a fix to print the function offsets as signed values.

I've also wanted to check that the addresses which are in the middle of the function do not resolve to the function, but that's not entirely the case right now. This appears to be a separate issue though, so I've just left a TODO for now.

---

Full diff: https://github.com/llvm/llvm-project/pull/126925.diff

3 Files Affected:

• (modified) lldb/source/Plugins/Disassembler/LLVMC/DisassemblerLLVMC.cpp (+8-4)
• (modified) lldb/source/Symbol/SymbolContext.cpp (+9-5)
• (modified) lldb/test/Shell/Commands/command-disassemble.s (+8-5)

diff --git a/lldb/source/Plugins/Disassembler/LLVMC/DisassemblerLLVMC.cpp b/lldb/source/Plugins/Disassembler/LLVMC/DisassemblerLLVMC.cpp
index 76f2db086476f..a77155f6bf41e 100644
--- a/lldb/source/Plugins/Disassembler/LLVMC/DisassemblerLLVMC.cpp
+++ b/lldb/source/Plugins/Disassembler/LLVMC/DisassemblerLLVMC.cpp
@@ -31,6 +31,7 @@
 
 #include "lldb/Core/Address.h"
 #include "lldb/Core/Module.h"
+#include "lldb/Symbol/Function.h"
 #include "lldb/Symbol/SymbolContext.h"
 #include "lldb/Target/ExecutionContext.h"
 #include "lldb/Target/Process.h"
@@ -1806,10 +1807,13 @@ const char *DisassemblerLLVMC::SymbolLookup(uint64_t value, uint64_t *type_ptr,
         bool format_omitting_current_func_name = false;
         if (sym_ctx.symbol || sym_ctx.function) {
           AddressRange range;
-          if (sym_ctx.GetAddressRange(resolve_scope, 0, false, range) &&
-              range.GetBaseAddress().IsValid() &&
-              range.ContainsLoadAddress(value_so_addr, target)) {
-            format_omitting_current_func_name = true;
+          for (uint32_t idx = 0;
+               sym_ctx.GetAddressRange(resolve_scope, idx, false, range);
+               ++idx) {
+            if (range.ContainsLoadAddress(value_so_addr, target)) {
+              format_omitting_current_func_name = true;
+              break;
+            }
           }
         }
 
diff --git a/lldb/source/Symbol/SymbolContext.cpp b/lldb/source/Symbol/SymbolContext.cpp
index 4725df52ff559..183947a694363 100644
--- a/lldb/source/Symbol/SymbolContext.cpp
+++ b/lldb/source/Symbol/SymbolContext.cpp
@@ -104,15 +104,19 @@ bool SymbolContext::DumpStopContext(
 
     if (addr_t file_addr = addr.GetFileAddress();
         file_addr != LLDB_INVALID_ADDRESS) {
-      const addr_t function_offset =
-          file_addr - function->GetAddress().GetFileAddress();
+      // Avoiding signed arithmetic due to UB in -INT_MAX.
+      const char sign =
+          file_addr >= function->GetAddress().GetFileAddress() ? '+' : '-';
+      addr_t offset = file_addr - function->GetAddress().GetFileAddress();
+      if (sign == '-')
+        offset = -offset;
       if (!show_function_name) {
         // Print +offset even if offset is 0
         dumped_something = true;
-        s->Printf("+%" PRIu64 ">", function_offset);
-      } else if (function_offset) {
+        s->Format("{0}{1}>", sign, offset);
+      } else if (offset) {
         dumped_something = true;
-        s->Printf(" + %" PRIu64, function_offset);
+        s->Format(" {0} {1}", sign, offset);
       }
     }
 
diff --git a/lldb/test/Shell/Commands/command-disassemble.s b/lldb/test/Shell/Commands/command-disassemble.s
index 951d96cefd4b9..eb84a9ce39d4a 100644
--- a/lldb/test/Shell/Commands/command-disassemble.s
+++ b/lldb/test/Shell/Commands/command-disassemble.s
@@ -84,7 +84,7 @@
 # CHECK-NEXT: command-disassemble.s.tmp[0x2044] <+0>: int    $0x32
 # CHECK-NEXT: warning: Not disassembling a function because it is very large [0x0000000000002046-0x0000000000004046). To disassemble specify an instruction count limit, start/stop addresses or use the --force option.
 # CHECK-NEXT: (lldb) disassemble --name case3
-# CHECK-NEXT: error: Not disassembling a function because it is very large [0x0000000000006046-0x0000000000007046)[0x0000000000009046-0x000000000000a046). To disassemble specify an instruction count limit, start/stop addresses or use the --force option.
+# CHECK-NEXT: error: Not disassembling a function because it is very large [0x0000000000006046-0x0000000000007046)[0x0000000000009046-0x000000000000a050). To disassemble specify an instruction count limit, start/stop addresses or use the --force option.
 # CHECK-NEXT: Not disassembling a function because it is very large [0x0000000000004046-0x0000000000006046). To disassemble specify an instruction count limit, start/stop addresses or use the --force option.
 # CHECK-NEXT: (lldb) disassemble --name case3 --count 3
 # CHECK-NEXT: command-disassemble.s.tmp`n2::case3:
@@ -93,9 +93,10 @@
 # CHECK-NEXT: command-disassemble.s.tmp[0x604a] <-12284>: int    $0x2a
 # CHECK-EMPTY:
 # CHECK-NEXT: command-disassemble.s.tmp`n2::case3:
-# CHECK-NEXT: command-disassemble.s.tmp[0x9046] <+0>: int    $0x2a
-# CHECK-NEXT: command-disassemble.s.tmp[0x9048] <+2>: int    $0x2a
-# CHECK-NEXT: command-disassemble.s.tmp[0x904a] <+4>: int    $0x2a
+# CHECK-NEXT: command-disassemble.s.tmp[0x9046] <+0>: jmp 0x6046 ; <-12288>
+## FIXME: This should resolve to `middle_of_case3`
+# CHECK-NEXT: command-disassemble.s.tmp[0x904b] <+5>: jmp 0x7046 ; n2::case3 - 8192
+# CHECK-NEXT: command-disassemble.s.tmp[0x9050] <+10>: int    $0x2a
 # CHECK-EMPTY:
 # CHECK-NEXT: command-disassemble.s.tmp`n1::case3:
 # CHECK-NEXT: command-disassemble.s.tmp[0x4046] <+0>: int    $0x2a
@@ -171,12 +172,14 @@ _ZN2n15case3Ev:
         .endr
 .L_ZN2n25case3Ev.__part.1_end:
 
-.Lpadding:
+middle_of_case3:
         .rept 0x1000
         int $42
         .endr
 
 _ZN2n25case3Ev:
+        jmp .L_ZN2n25case3Ev.__part.1
+        jmp middle_of_case3
         .rept 0x800
         int $42
         .endr

[jasonmolenda]

This looks straightforward.

[DavidSpickett]

LGTM