From 83ba3740bf51347307494d013099e392c310e32b Mon Sep 17 00:00:00 2001
From: Pavel Labath <pavel@labath.sk>
Date: Fri, 7 Feb 2025 12:52:21 +0100
Subject: [lldb] Clear cached unwind plans when adding symbols (#125839)

PR #86603 broke unwinding in for unwind info added via "target symbols
add". #86770 attempted to fix this, but the fix was only partial -- it
accepted new sources of unwind information, but didn't take into account
that the symbol file can alter what lldb percieves as function
boundaries.

A stripped file will not contain information about private
(non-exported) symbols, which will make the public symbols appear very
large. If lldb tries to unwind from such a function before symbols are
added, then the cached unwind plan will prevent new (correct) unwind
plans from being created.

target-symbols-add-unwind.test might have caught this, were it not for
the fact that the "image show-unwind" command does *not* use cached
unwind information (it recomputes it from scratch).

The changes in this patch come in three pieces:
- Clear cached unwind plans when adding symbols. Since the symbol
boundaries can change, we cannot trust anything we've computed
previously.
- Add a flag to "image show-unwind" to display the cached unwind
information (mainly for the use in the test, but I think it's also
generally useful).
- Rewrite the test to better and more reliably simulate the real-world
scenario: I've swapped the running process for a core (minidump) file so
it can run anywhere; used the caching version of the show-unwind
command; and swapped C for assembly to better control the placement of
symbols
---
 lldb/source/Commands/CommandObjectTarget.cpp | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

(limited to 'lldb/source/Commands/CommandObjectTarget.cpp')

diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index d0092c2..da50fe0 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -3474,6 +3474,17 @@ public:
         m_type = eLookupTypeFunctionOrSymbol;
         break;
 
+      case 'c':
+        bool value, success;
+        value = OptionArgParser::ToBoolean(option_arg, false, &success);
+        if (success) {
+          m_cached = value;
+        } else {
+          return Status::FromErrorStringWithFormatv(
+              "invalid boolean value '%s' passed for -c option", option_arg);
+        }
+        break;
+
       default:
         llvm_unreachable("Unimplemented option");
       }
@@ -3485,6 +3496,7 @@ public:
       m_type = eLookupTypeInvalid;
       m_str.clear();
       m_addr = LLDB_INVALID_ADDRESS;
+      m_cached = false;
     }
 
     llvm::ArrayRef<OptionDefinition> GetDefinitions() override {
@@ -3497,6 +3509,7 @@ public:
                                      // parsing options
     std::string m_str; // Holds name lookup
     lldb::addr_t m_addr = LLDB_INVALID_ADDRESS; // Holds the address to lookup
+    bool m_cached = true;
   };
 
   CommandObjectTargetModulesShowUnwind(CommandInterpreter &interpreter)
@@ -3583,9 +3596,12 @@ protected:
       if (abi)
         start_addr = abi->FixCodeAddress(start_addr);
 
-      FuncUnwindersSP func_unwinders_sp(
-          sc.module_sp->GetUnwindTable()
-              .GetUncachedFuncUnwindersContainingAddress(start_addr, sc));
+      UnwindTable &uw_table = sc.module_sp->GetUnwindTable();
+      FuncUnwindersSP func_unwinders_sp =
+          m_options.m_cached
+              ? uw_table.GetFuncUnwindersContainingAddress(start_addr, sc)
+              : uw_table.GetUncachedFuncUnwindersContainingAddress(start_addr,
+                                                                   sc);
       if (!func_unwinders_sp)
         continue;
 
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