================
@@ -3895,3 +3924,103 @@ std::optional<lldb_private::DataExtractor>
ObjectFileELF::GetDynamicData() {
}
return std::nullopt;
}
+
+
+std::optional<DataExtractor>
+ObjectFileELF::GetDynsymDataFromDynamic(uint32_t &num_symbols) {
+ // Every ELF file which represents an executable or shared library has
+ // mandatory .dynamic entries. The DT_SYMTAB value contains a pointer to the
+ // symbol table, and DT_SYMENT contains the size of a symbol table entry.
+ // We then can use either the DT_HASH or DT_GNU_HASH to find the number of
+ // symbols in the symbol table as the symbol count is not stored in the
+ // .dynamic section as a key/value pair.
+ //
+ // When loading and ELF file from memory, only the program headers end up
+ // being mapped into memory, and we can find these values in the PT_DYNAMIC
+ // segment.
+ num_symbols = 0;
+ // Get the process in case this is an in memory ELF file.
+ ProcessSP process_sp(m_process_wp.lock());
+ const ELFDynamic *symtab = FindDynamicSymbol(DT_SYMTAB);
+ const ELFDynamic *syment = FindDynamicSymbol(DT_SYMENT);
+ const ELFDynamic *hash = FindDynamicSymbol(DT_HASH);
+ const ELFDynamic *gnu_hash = FindDynamicSymbol(DT_GNU_HASH);
+ // DT_SYMTAB and DT_SYMENT are mandatory.
+ if (symtab == nullptr || syment == nullptr)
+ return std::nullopt;
+ // We must have either a DT_HASH or a DT_GNU_HASH.
+ if (hash == nullptr && gnu_hash == nullptr)
+ return std::nullopt;
+ // The number of symbols in the symbol table is the number of entries in the
+ // symbol table divided by the size of each symbol table entry.
+ // We must figure out the number of symbols in the symbol table using the
+ // DT_HASH or the DT_GNU_HASH as the number of symbols isn't stored anywhere
+ // in the .dynamic section.
+
+ lldb::offset_t offset;
+ if (hash) {
+ // The DT_HASH header contains the number of symbols in the "nchain"
+ // member. The header looks like this:
+ // struct DT_HASH_HEADER {
+ // uint32_t nbucket;
+ // uint32_t nchain;
+ // };
+ if (auto data = ReadDataFromDynamic(hash, 8)) {
+ offset = 4;
+ num_symbols = data->GetU32(&offset);
+ }
+ }
+ if (num_symbols == 0 && gnu_hash) {
----------------
labath wrote:
This code is rather involved, and it would be better to have it in a helper
function. Then it could also use early returns for some of the paths. I'd
recommend something like:
```
if (std::optional<uint32_t> syms = GetNumSymbolsFromHash())
num_symbols = *syms;
else if (std::optional<uint32_t> syms = GetNumSymbolsFromDtHash())
num_symbols = *syms;
...
```
https://github.com/llvm/llvm-project/pull/112596
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