kwk updated this revision to Diff 222029.
kwk added a comment.
- Cleanup
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D67390/new/
https://reviews.llvm.org/D67390
Files:
lldb/lit/Modules/ELF/Inputs/load-from-dynsym-alone.c
lldb/lit/Modules/ELF/Inputs/load-symtab-and-dynsym.c
lldb/lit/Modules/ELF/load-from-dynsym-alone.test
lldb/lit/Modules/ELF/load-symtab-and-dynsym.test
lldb/lit/helper/toolchain.py
lldb/source/Plugins/ObjectFile/ELF/ELFHeader.cpp
lldb/source/Plugins/ObjectFile/ELF/ELFHeader.h
lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.h
Index: lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.h
===================================================================
--- lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.h
+++ lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.h
@@ -12,6 +12,8 @@
#include <stdint.h>
#include <vector>
+#include <utility>
+#include <unordered_set>
#include "lldb/Symbol/ObjectFile.h"
#include "lldb/Utility/ArchSpec.h"
@@ -55,7 +57,7 @@
/// This class provides a generic ELF (32/64 bit) reader plugin implementing
/// the ObjectFile protocol.
class ObjectFileELF : public lldb_private::ObjectFile {
-public:
+public:
// Static Functions
static void Initialize();
@@ -184,6 +186,8 @@
typedef std::map<lldb::addr_t, lldb_private::AddressClass>
FileAddressToAddressClassMap;
+
+ typedef std::unordered_set<elf::NamedELFSymbol> UniqueElfSymbolColl;
/// Version of this reader common to all plugins based on this class.
static const uint32_t m_plugin_version = 1;
@@ -278,7 +282,8 @@
/// will parse the symbols only once. Returns the number of symbols parsed.
unsigned ParseSymbolTable(lldb_private::Symtab *symbol_table,
lldb::user_id_t start_id,
- lldb_private::Section *symtab);
+ lldb_private::Section *symtab,
+ UniqueElfSymbolColl &unique_elf_symbols);
/// Helper routine for ParseSymbolTable().
unsigned ParseSymbols(lldb_private::Symtab *symbol_table,
@@ -286,7 +291,8 @@
lldb_private::SectionList *section_list,
const size_t num_symbols,
const lldb_private::DataExtractor &symtab_data,
- const lldb_private::DataExtractor &strtab_data);
+ const lldb_private::DataExtractor &strtab_data,
+ UniqueElfSymbolColl &unique_elf_symbols);
/// Scans the relocation entries and adds a set of artificial symbols to the
/// given symbol table for each PLT slot. Returns the number of symbols
Index: lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
===================================================================
--- lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -1871,7 +1871,8 @@
SectionList *section_list,
const size_t num_symbols,
const DataExtractor &symtab_data,
- const DataExtractor &strtab_data) {
+ const DataExtractor &strtab_data,
+ UniqueElfSymbolColl &unique_elf_symbols) {
ELFSymbol symbol;
lldb::offset_t offset = 0;
@@ -2196,20 +2197,28 @@
symbol_size_valid, // Symbol size is valid
has_suffix, // Contains linker annotations?
flags); // Symbol flags.
- symtab->AddSymbol(dc_symbol);
+
+ NamedELFSymbol needle(symbol);
+ needle.st_name_string = ConstString(symbol_bare);
+ if (unique_elf_symbols.find(needle) == unique_elf_symbols.end()) {
+ symtab->AddSymbol(dc_symbol);
+ unique_elf_symbols.insert(needle);
+ }
}
return i;
}
-unsigned ObjectFileELF::ParseSymbolTable(Symtab *symbol_table,
- user_id_t start_id,
- lldb_private::Section *symtab) {
+unsigned
+ObjectFileELF::ParseSymbolTable(Symtab *symbol_table, user_id_t start_id,
+ lldb_private::Section *symtab,
+ UniqueElfSymbolColl &unique_elf_symbols) {
if (symtab->GetObjectFile() != this) {
// If the symbol table section is owned by a different object file, have it
// do the parsing.
ObjectFileELF *obj_file_elf =
static_cast<ObjectFileELF *>(symtab->GetObjectFile());
- return obj_file_elf->ParseSymbolTable(symbol_table, start_id, symtab);
+ return obj_file_elf->ParseSymbolTable(symbol_table, start_id, symtab,
+ unique_elf_symbols);
}
// Get section list for this object file.
@@ -2237,7 +2246,7 @@
size_t num_symbols = symtab_data.GetByteSize() / symtab_hdr->sh_entsize;
return ParseSymbols(symbol_table, start_id, section_list, num_symbols,
- symtab_data, strtab_data);
+ symtab_data, strtab_data, unique_elf_symbols);
}
}
@@ -2405,7 +2414,7 @@
true, // Size is valid
false, // Contains linker annotations?
0); // Symbol flags.
-
+
symbol_table->AddSymbol(jump_symbol);
}
@@ -2635,6 +2644,8 @@
return module_obj_file->GetSymtab();
if (m_symtab_up == nullptr) {
+ // A unique set of ELF symbols added to the symtab
+ UniqueElfSymbolColl unique_elf_symbols({});
SectionList *section_list = module_sp->GetSectionList();
if (!section_list)
return nullptr;
@@ -2644,22 +2655,31 @@
// Sharable objects and dynamic executables usually have 2 distinct symbol
// tables, one named ".symtab", and the other ".dynsym". The dynsym is a
- // smaller version of the symtab that only contains global symbols. The
- // information found in the dynsym is therefore also found in the symtab,
- // while the reverse is not necessarily true.
+ // smaller version of the symtab that only contains global symbols.
+ // Information in the dynsym section is *usually* also found in the symtab,
+ // but this is not required as symtab entries can be removed after linking.
+ // The minidebuginfo format makes use of this facility to create smaller
+ // symbol tables.
Section *symtab =
section_list->FindSectionByType(eSectionTypeELFSymbolTable, true).get();
- if (!symtab) {
- // The symtab section is non-allocable and can be stripped, so if it
- // doesn't exist then use the dynsym section which should always be
- // there.
- symtab =
- section_list->FindSectionByType(eSectionTypeELFDynamicSymbols, true)
- .get();
- }
if (symtab) {
m_symtab_up.reset(new Symtab(symtab->GetObjectFile()));
- symbol_id += ParseSymbolTable(m_symtab_up.get(), symbol_id, symtab);
+ symbol_id += ParseSymbolTable(m_symtab_up.get(), symbol_id, symtab,
+ unique_elf_symbols);
+ }
+
+ // The symtab section is non-allocable and can be stripped, while the dynsym
+ // section which should always be always be there. If both exist we load
+ // both to support the minidebuginfo case. Otherwise we just load the dynsym
+ // section.
+ Section *dynsym =
+ section_list->FindSectionByType(eSectionTypeELFDynamicSymbols, true)
+ .get();
+ if (dynsym) {
+ if (!m_symtab_up)
+ m_symtab_up.reset(new Symtab(dynsym->GetObjectFile()));
+ symbol_id += ParseSymbolTable(m_symtab_up.get(), symbol_id, dynsym,
+ unique_elf_symbols);
}
// DT_JMPREL
Index: lldb/source/Plugins/ObjectFile/ELF/ELFHeader.h
===================================================================
--- lldb/source/Plugins/ObjectFile/ELF/ELFHeader.h
+++ lldb/source/Plugins/ObjectFile/ELF/ELFHeader.h
@@ -24,6 +24,8 @@
#include "lldb/lldb-enumerations.h"
#include "lldb/lldb-types.h"
+#include "lldb/Utility/ConstString.h"
+#include "llvm/ADT/Hashing.h"
namespace lldb_private {
class DataExtractor;
@@ -230,6 +232,8 @@
elf_half st_shndx; ///< Section to which this symbol applies.
ELFSymbol();
+
+ ELFSymbol(const ELFSymbol &other);
/// Returns the binding attribute of the st_info member.
unsigned char getBinding() const { return st_info >> 4; }
@@ -269,6 +273,26 @@
void Dump(lldb_private::Stream *s, uint32_t idx,
const lldb_private::DataExtractor *strtab_data,
const lldb_private::SectionList *section_list);
+
+ bool operator==(const ELFSymbol &rhs) const {
+ return st_info == rhs.st_info && st_name == rhs.st_name &&
+ st_size == rhs.st_size && st_other == rhs.st_other &&
+ st_shndx == rhs.st_shndx && st_value == rhs.st_value;
+ }
+};
+
+// A NamedELFSymbol is an ELFSymbol that, alongside it's name index, stores the
+// name of the symbol as a string and only uses that for comparison instead of
+// the name index which could differ depending on which section the symbol is
+// defined in (e.g. .strtab or .dynstr).
+struct NamedELFSymbol : ELFSymbol {
+ lldb_private::ConstString st_name_string; ///< Actual name of the ELF symbol
+
+ NamedELFSymbol();
+
+ NamedELFSymbol(const ELFSymbol & sym);
+
+ bool operator==(const NamedELFSymbol &rhs) const;
};
/// \class ELFDynamic
@@ -391,4 +415,33 @@
} // End namespace elf.
+namespace std {
+
+// Define specializations of the std::hash struct for ELFSymbol and
+// NamedELFSymbol so they can be used in an std::unordered_map
+
+template <> struct hash<elf::ELFSymbol> {
+ std::size_t operator()(const elf::ELFSymbol &s) const noexcept {
+ std::size_t h1 = std::hash<elf::elf_addr>()(s.st_value);
+ std::size_t h2 = std::hash<elf::elf_xword>()(s.st_size);
+ std::size_t h3 = std::hash<elf::elf_word>()(s.st_name);
+ std::size_t h4 = std::hash<unsigned char>()(s.st_info);
+ std::size_t h5 = std::hash<unsigned char>()(s.st_other);
+ std::size_t h6 = std::hash<elf::elf_half>()(s.st_shndx);
+ return llvm::hash_combine(h1, h2, h3, h4, h5, h6);
+ }
+};
+
+template <> struct hash<elf::NamedELFSymbol> {
+ std::size_t operator()(const elf::NamedELFSymbol &s) const noexcept {
+ elf::ELFSymbol tmp = s;
+ // ignore the name when hashing the ELFSymbol
+ tmp.st_name = 0;
+ std::size_t h1 = std::hash<elf::ELFSymbol>()(tmp);
+ std::size_t h2 = std::hash<const char *>()(s.st_name_string.AsCString());
+ return llvm::hash_combine(h1, h2);
+ }
+};
+} // namespace std
+
#endif // #ifndef liblldb_ELFHeader_h_
Index: lldb/source/Plugins/ObjectFile/ELF/ELFHeader.cpp
===================================================================
--- lldb/source/Plugins/ObjectFile/ELF/ELFHeader.cpp
+++ lldb/source/Plugins/ObjectFile/ELF/ELFHeader.cpp
@@ -250,6 +250,11 @@
ELFSymbol::ELFSymbol() { memset(this, 0, sizeof(ELFSymbol)); }
+ELFSymbol::ELFSymbol(const ELFSymbol &other)
+ : st_value(other.st_value), st_size(other.st_size), st_name(other.st_name),
+ st_info(other.st_info), st_other(other.st_other),
+ st_shndx(other.st_shndx) {}
+
#define ENUM_TO_CSTR(e) \
case e: \
return #e
@@ -353,6 +358,21 @@
return true;
}
+// NamedELFSymbol
+
+NamedELFSymbol::NamedELFSymbol() : ELFSymbol() {}
+
+NamedELFSymbol::NamedELFSymbol(const ELFSymbol &other) : ELFSymbol(other) {}
+
+bool NamedELFSymbol::operator==(const NamedELFSymbol &rhs) const {
+ NamedELFSymbol r = rhs;
+ // Always ignore the name index when comparing the symbols
+ // and instead compare the symbol name itself.
+ r.st_name = st_name;
+ return elf::ELFSymbol::operator==(r) &&
+ st_name_string == rhs.st_name_string;
+}
+
// ELFProgramHeader
ELFProgramHeader::ELFProgramHeader() {
Index: lldb/lit/helper/toolchain.py
===================================================================
--- lldb/lit/helper/toolchain.py
+++ lldb/lit/helper/toolchain.py
@@ -126,6 +126,6 @@
support_tools = ['yaml2obj', 'obj2yaml', 'llvm-pdbutil',
'llvm-mc', 'llvm-readobj', 'llvm-objdump',
- 'llvm-objcopy', 'lli']
+ 'llvm-objcopy', 'lli', 'llvm-strip']
additional_tool_dirs += [config.lldb_tools_dir, config.llvm_tools_dir]
llvm_config.add_tool_substitutions(support_tools, additional_tool_dirs)
Index: lldb/lit/Modules/ELF/load-symtab-and-dynsym.test
===================================================================
--- /dev/null
+++ lldb/lit/Modules/ELF/load-symtab-and-dynsym.test
@@ -0,0 +1,48 @@
+# REQUIRES: system-linux
+
+# This test ensures that we will load .dynsym even if there's a .symtab section.
+# We do this by compiling a small C program with two functions and we direct the
+# linker where to put the symbols so that in the end the layout is as follows:
+#
+# Symbol table '.dynsym' contains 4 entries:
+# Num: Value Size Type Bind Vis Ndx Name
+# 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
+# 1: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.2.5
+# 2: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
+# 3: 0000000000401120 13 FUNC GLOBAL DEFAULT 10 functionInDynsym
+#
+# Symbol table '.symtab' contains 2 entries:
+# Num: Value Size Type Bind Vis Ndx Name
+# 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
+# 1: 0000000000401110 15 FUNC GLOBAL DEFAULT 10 functionInSymtab
+
+# We want to keep the symbol "functionInDynsym" in the .dynsym section and not
+# have it put the default .symtab section.
+# RUN: echo "{functionInDynsym;};" > %T/dynmic-symbols.txt
+# RUN: %clang -Wl,--dynamic-list=%T/dynmic-symbols.txt -g -o %t.binary %p/Inputs/load-symtab-and-dynsym.c
+
+# Remove not needed symbols
+# RUN: echo "functionInSymtab" > %t.keep_symbols
+# RUN: echo "functionInDynsym" >> %t.keep_symbols
+# RUN: llvm-objcopy --strip-all --remove-section .gdb_index --remove-section .comment --keep-symbols=%t.keep_symbols %t.binary
+
+# Remove functionInDynsym symbol from .symtab (will leave symbol in .dynsym intact)
+# RUN: llvm-strip --strip-symbol=functionInDynsym %t.binary
+
+# RUN: %lldb -b -o 'b functionInSymtab' -o 'b functionInDynsym' -o 'run' -o 'continue' %t.binary | FileCheck %s
+
+# CHECK: (lldb) b functionInSymtab
+# CHECK-NEXT: Breakpoint 1: where = {{.*}}.binary`functionInSymtab, address = 0x{{.*}}
+
+# CHECK: (lldb) b functionInDynsym
+# CHECK-NEXT: Breakpoint 2: where = {{.*}}.binary`functionInDynsym, address = 0x{{.*}}
+
+# CHECK: (lldb) run
+# CHECK-NEXT: Process {{.*}} stopped
+# CHECK-NEXT: * thread #1, name = 'load-symtab-and', stop reason = breakpoint 1.1
+
+# CHECK: (lldb) continue
+# CHECK-NEXT: Process {{.*}} resuming
+# CHECK-NEXT: Process {{.*}} stopped
+# CHECK-NEXT: * thread #1, name = 'load-symtab-and', stop reason = breakpoint 2.1
+
Index: lldb/lit/Modules/ELF/load-from-dynsym-alone.test
===================================================================
--- /dev/null
+++ lldb/lit/Modules/ELF/load-from-dynsym-alone.test
@@ -0,0 +1,33 @@
+# REQUIRES: system-linux
+
+# This test ensures that we will load .dynsym even if there's no .symtab section.
+# We do this by compiling a small C program with a function and we direct the
+# linker where to put the symbols so that in the end the layout is as follows:
+#
+# Symbol table '.dynsym' contains 4 entries:
+# Num: Value Size Type Bind Vis Ndx Name
+# 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
+# 1: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.2.5
+# 2: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
+# 3: 0000000000401110 13 FUNC GLOBAL DEFAULT 10 functionInDynsym
+
+# We want to keep the symbol "functionInDynsym" in the .dynsym section and not
+# have it put the default .symtab section.
+# RUN: echo "{functionInDynsym;};" > %T/dynmic-symbols.txt
+# RUN: %clang -Wl,--dynamic-list=%T/dynmic-symbols.txt -g -o %t.binary %p/Inputs/load-from-dynsym-alone.c
+
+# Remove not needed symbols
+# RUN: echo "functionInDynsym" > %t.keep_symbols
+# RUN: llvm-objcopy --strip-all --remove-section .gdb_index --remove-section .comment --keep-symbols=%t.keep_symbols %t.binary
+
+# Remove functionInDynsym symbol from .symtab (will leave symbol in .dynsym intact)
+# RUN: llvm-strip --strip-symbol=functionInDynsym %t.binary
+
+# RUN: %lldb -b -o 'b functionInDynsym' -o 'run' -o 'continue' %t.binary | FileCheck %s
+
+# CHECK: (lldb) b functionInDynsym
+# CHECK-NEXT: Breakpoint 1: where = {{.*}}.binary`functionInDynsym, address = 0x{{.*}}
+
+# CHECK: (lldb) run
+# CHECK-NEXT: Process {{.*}} stopped
+# CHECK-NEXT: * thread #1, name = 'load-from-dynsy', stop reason = breakpoint 1.1
Index: lldb/lit/Modules/ELF/Inputs/load-symtab-and-dynsym.c
===================================================================
--- /dev/null
+++ lldb/lit/Modules/ELF/Inputs/load-symtab-and-dynsym.c
@@ -0,0 +1,12 @@
+// This function will be embedded within the .symtab section of the
+// .gnu_debugdata section.
+int functionInSymtab(int num) { return num * 4; }
+
+// This function will be embedded within the .dynsym section of the main binary.
+int functionInDynsym(int num) { return num * 3; }
+
+int main(int argc, char *argv[]) {
+ int x = functionInSymtab(argc);
+ int y = functionInDynsym(x);
+ return y;
+}
Index: lldb/lit/Modules/ELF/Inputs/load-from-dynsym-alone.c
===================================================================
--- /dev/null
+++ lldb/lit/Modules/ELF/Inputs/load-from-dynsym-alone.c
@@ -0,0 +1,7 @@
+// This function will be embedded within the .dynsym section of the main binary.
+int functionInDynsym(int num) { return num * 3; }
+
+int main(int argc, char *argv[]) {
+ int y = functionInDynsym(argc);
+ return y;
+}
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