[Lldb-commits] [lldb] cd64273 - [lldb/ELF] Fix IDs of synthetic eh_frame symbols

[Pavel Labath via lldb-commits]

Author: Pavel Labath
Date: 2021-04-21T11:24:43+02:00
New Revision: cd64273f5ed39ec697ff1e20a1fe25ebd3502629

URL: https://github.com/llvm/llvm-project/commit/cd64273f5ed39ec697ff1e20a1fe25ebd3502629
DIFF: https://github.com/llvm/llvm-project/commit/cd64273f5ed39ec697ff1e20a1fe25ebd3502629.diff

LOG: [lldb/ELF] Fix IDs of synthetic eh_frame symbols

The code used the total number of symbols to create a symbol ID for the
synthetic symbols. This is not correct because the IDs of real symbols
can be higher than their total number, as we do not add all symbols (and
in particular, we never add symbol zero, which is not a real symbol).

This meant we could have symbols with duplicate IDs, which caused
problems if some relocations were referring to the duplicated IDs. This
was the cause of the failure of the test D97786.

This patch fixes the code to use the ID of the highest (last) symbol
instead.

Added: 
    lldb/test/Shell/ObjectFile/ELF/eh_frame-symbols.yaml

Modified: 
    lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index f30ed427f8535..6e94ab97992a1 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -2901,8 +2901,11 @@ void ObjectFileELF::ParseUnwindSymbols(Symtab *symbol_table,
   // recalculate the index first.
   std::vector<Symbol> new_symbols;
 
-  eh_frame->ForEachFDEEntries([this, symbol_table, section_list, &new_symbols](
-      lldb::addr_t file_addr, uint32_t size, dw_offset_t) {
+  size_t num_symbols = symbol_table->GetNumSymbols();
+  uint64_t last_symbol_id =
+      num_symbols ? symbol_table->SymbolAtIndex(num_symbols - 1)->GetID() : 0;
+  eh_frame->ForEachFDEEntries([&](lldb::addr_t file_addr, uint32_t size,
+                                  dw_offset_t) {
     Symbol *symbol = symbol_table->FindSymbolAtFileAddress(file_addr);
     if (symbol) {
       if (!symbol->GetByteSizeIsValid()) {
@@ -2915,21 +2918,20 @@ void ObjectFileELF::ParseUnwindSymbols(Symtab *symbol_table,
       if (section_sp) {
         addr_t offset = file_addr - section_sp->GetFileAddress();
         const char *symbol_name = GetNextSyntheticSymbolName().GetCString();
-        uint64_t symbol_id = symbol_table->GetNumSymbols();
         Symbol eh_symbol(
-            symbol_id,       // Symbol table index.
-            symbol_name,     // Symbol name.
-            eSymbolTypeCode, // Type of this symbol.
-            true,            // Is this globally visible?
-            false,           // Is this symbol debug info?
-            false,           // Is this symbol a trampoline?
-            true,            // Is this symbol artificial?
-            section_sp,      // Section in which this symbol is defined or null.
-            offset,          // Offset in section or symbol value.
-            0,     // Size:          Don't specify the size as an FDE can
-            false, // Size is valid: cover multiple symbols.
-            false, // Contains linker annotations?
-            0);    // Symbol flags.
+            ++last_symbol_id, // Symbol table index.
+            symbol_name,      // Symbol name.
+            eSymbolTypeCode,  // Type of this symbol.
+            true,             // Is this globally visible?
+            false,            // Is this symbol debug info?
+            false,            // Is this symbol a trampoline?
+            true,             // Is this symbol artificial?
+            section_sp, // Section in which this symbol is defined or null.
+            offset,     // Offset in section or symbol value.
+            0,          // Size:          Don't specify the size as an FDE can
+            false,      // Size is valid: cover multiple symbols.
+            false,      // Contains linker annotations?
+            0);         // Symbol flags.
         new_symbols.push_back(eh_symbol);
       }
     }

diff  --git a/lldb/test/Shell/ObjectFile/ELF/eh_frame-symbols.yaml b/lldb/test/Shell/ObjectFile/ELF/eh_frame-symbols.yaml
new file mode 100644
index 0000000000000..6178a45de1b59
--- /dev/null
+++ b/lldb/test/Shell/ObjectFile/ELF/eh_frame-symbols.yaml
@@ -0,0 +1,32 @@
+# RUN: yaml2obj %s >%t
+# RUN: %lldb %t -o "image dump symtab" -b | FileCheck %s
+
+# CHECK: Index   UserID DSX Type            File Address/Value Load Address       Size               Flags      Name
+# CHECK: [    0]      1     SourceFile      0x0000000000000000                    0x0000000000000000 0x00000004 -
+# CHECK: [    1]      2  SX Code            0x0000000000201180                    0x0000000000000010 0x00000000 ___lldb_unnamed_symbol1$${{.*}}
+# CHECK: [    2]      3  SX Code            0x0000000000201190                    0x0000000000000006 0x00000000 ___lldb_unnamed_symbol2$${{.*}}
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .eh_frame
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Address:         0x200120
+    AddressAlign:    0x8
+    Content:         1400000000000000017A5200017810011B0C0708900100001C0000001C000000401000000600000000410E108602430D06410C07080000001C0000003C000000301000000600000000410E108602430D06410C070800000000000000
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x201180
+    AddressAlign:    0x10
+    Content:         554889E55DC3662E0F1F840000000000554889E55DC3
+Symbols:
+  - Name:            '-'
+    Type:            STT_FILE
+    Index:           SHN_ABS
+...