[llvm-branch-commits] [lldb] [lldb] Resolve dispatch qSymbol requests by exact linkage name (PR #232696)
Karim Alweheshy via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Fri Oct 16 04:43:05 PDT 2026
https://github.com/karim-alweheshy created https://github.com/llvm/llvm-project/pull/232696
debugserver requests dispatch_queue_offsets as a C ABI data symbol. Resolve that request through exact linkage-name matching so a C++ function basename cannot satisfy it. Other qSymbol requests keep their existing matching behavior.
Depends on #232694. This PR contains only the qSymbol consumer and mock-server regressions. History checked: retain the non-Mach-O symbol-type and raw-value handling added by #200134 and #200411.
Validation: All three mock-server qSymbol tests pass with current-main LLDB built with this change over its prerequisite. On the prerequisite alone, both new cases fail by returning the C++ function address while the original case passes. Present/absent dispatch data and the unchanged generic request path are covered. Both YAML fixture variants assemble successfully.
Assisted-by: OpenAI Codex
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{"parent":"users/karim-alweheshy/lldb-exact-c-symbol-lookup","parentHead":"2888d6d184552bee1b635bbc575968b12360e79a","parentPull":232694,"trunk":"main"}
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>From aba3e072c601c59b09d5d4a8d1033df82ced7d4a Mon Sep 17 00:00:00 2001
From: Karim Alweheshy <karim.alweheshy at reddit.com>
Date: Fri, 16 Oct 2026 12:59:52 +0200
Subject: [PATCH] [lldb] Resolve dispatch qSymbol requests by exact linkage
name
Use the opt-in linkage-name lookup for dispatch_queue_offsets while preserving generic matching for other remote requests and existing address and symbol-type handling. Cover C++ basename decoys and an absent dispatch data symbol with the mock server.
Assisted-by: OpenAI Codex
---
.../GDBRemoteCommunicationClient.cpp | 8 ++-
.../gdb_remote_client/TestQSymbol.py | 61 ++++++++++++++++---
.../gdb_remote_client/test_qsymbol.yaml | 25 +++++++-
3 files changed, 84 insertions(+), 10 deletions(-)
diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
index 19b642ed3f65c5..c674641e5bcbac 100644
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
@@ -4336,8 +4336,14 @@ void GDBRemoteCommunicationClient::ServeSymbolLookups(
addr_t symbol_load_addr = LLDB_INVALID_ADDRESS;
lldb_private::SymbolContextList sc_list;
+ // debugserver uses this C ABI data symbol to decode dispatch
+ // queues. C++ basename aliases are not that runtime definition.
+ // Other remote requests retain their usual name matching.
+ const bool match_linkage_names =
+ symbol_name == "dispatch_queue_offsets";
process->GetTarget().GetImages().FindSymbolsWithNameAndType(
- ConstString(symbol_name), eSymbolTypeAny, sc_list);
+ ConstString(symbol_name), eSymbolTypeAny, sc_list,
+ match_linkage_names);
for (const SymbolContext &sc : sc_list) {
if (symbol_load_addr != LLDB_INVALID_ADDRESS)
break;
diff --git a/lldb/test/API/functionalities/gdb_remote_client/TestQSymbol.py b/lldb/test/API/functionalities/gdb_remote_client/TestQSymbol.py
index 96d6d83c203304..394c2a80d2b8c7 100644
--- a/lldb/test/API/functionalities/gdb_remote_client/TestQSymbol.py
+++ b/lldb/test/API/functionalities/gdb_remote_client/TestQSymbol.py
@@ -2,6 +2,7 @@
Test LLDB's handling of qSymbol sequences.
"""
+from pathlib import Path
from textwrap import dedent
import lldb
from lldbsuite.test.lldbtest import *
@@ -12,15 +13,19 @@
class MyResponder(MockGDBServerResponder):
- def __init__(self, test_obj):
+ def __init__(self, test_obj, wanted_symbols=None):
super().__init__()
- self.wanted_symbols = [
- "main",
- "local_address",
- "global_value",
- "local_value",
- "not_a_symbol",
- ]
+ self.wanted_symbols = (
+ wanted_symbols
+ if wanted_symbols is not None
+ else [
+ "main",
+ "local_address",
+ "global_value",
+ "local_value",
+ "not_a_symbol",
+ ]
+ )
self.last_symbol_request = None
self.symbol_results = {}
self.test_obj = test_obj
@@ -80,3 +85,43 @@ def test_qsymbol(self):
]
)
self.assertEqual(expected_results, self.server.responder.symbol_results)
+
+ @skipIfRemote
+ @skipIfLLVMTargetMissing("AArch64")
+ def test_dispatch_symbol_uses_linkage_name(self):
+ self.check_dispatch_symbol(has_dispatch_data=True)
+
+ @skipIfRemote
+ @skipIfLLVMTargetMissing("AArch64")
+ def test_missing_dispatch_symbol_rejects_cpp_basename(self):
+ self.check_dispatch_symbol(has_dispatch_data=False)
+
+ def check_dispatch_symbol(self, has_dispatch_data):
+ self.runCmd("settings set target.preload-symbols false")
+ fixture = Path(self.getSourceDir()) / "test_qsymbol.yaml"
+ if not has_dispatch_data:
+ missing = Path(self.getBuildArtifact("qsymbol-missing.yaml"))
+ missing.write_text(
+ fixture.read_text().replace(
+ "Name: dispatch_queue_offsets", "Name: unrelated_dispatch_data"
+ )
+ )
+ fixture = missing
+ target = self.createTarget(str(fixture))
+ self.server.responder = MyResponder(
+ self, ["dispatch_queue_offsets", "other_wire_request"]
+ )
+ process = self.connect(target)
+ lldbutil.expect_state_changes(
+ self, self.dbg.GetListener(), process, [lldb.eStateStopped]
+ )
+ self.assertFalse(self.server.responder.wanted_symbols)
+ # The known dispatch ABI must not resolve to the C++ function basename
+ # at 0x1008. Other requests keep their C++ basename lookup behavior.
+ self.assertEqual(
+ self.server.responder.symbol_results,
+ {
+ "dispatch_queue_offsets": 0x2000 if has_dispatch_data else None,
+ "other_wire_request": 0x1009,
+ },
+ )
diff --git a/lldb/test/API/functionalities/gdb_remote_client/test_qsymbol.yaml b/lldb/test/API/functionalities/gdb_remote_client/test_qsymbol.yaml
index 10a2cb99ea27f8..67b02a3d63e802 100644
--- a/lldb/test/API/functionalities/gdb_remote_client/test_qsymbol.yaml
+++ b/lldb/test/API/functionalities/gdb_remote_client/test_qsymbol.yaml
@@ -9,7 +9,12 @@ Sections:
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
Address: 0x1000
- Content: C0035FD6 # ret
+ Content: C0035FD6C0035FD6C0035FD6 # ret; ret; ret
+ - Name: .data
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_WRITE ]
+ Address: 0x2000
+ Content: '0000000000000000'
Symbols:
- Name: main
Type: STT_FUNC
@@ -30,4 +35,22 @@ Symbols:
Index: SHN_ABS
Value: 0x1234
Binding: STB_GLOBAL
+ - Name: _Z22dispatch_queue_offsetsv
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x1008
+ Size: 1
+ Binding: STB_GLOBAL
+ - Name: _Z18other_wire_requestv
+ Type: STT_FUNC
+ Section: .text
+ Value: 0x1009
+ Size: 1
+ Binding: STB_GLOBAL
+ - Name: dispatch_queue_offsets
+ Type: STT_OBJECT
+ Section: .data
+ Value: 0x2000
+ Size: 8
+ Binding: STB_GLOBAL
...
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