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mold/fix-gdb-index.patch

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From c90801e62906f454eb3d478683cd54bce5d8d7b3 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Sat, 16 Apr 2022 13:18:09 +0800
Subject: [PATCH] [ELF] Make --gdb-index work for compressed input debug
sections
Previously, --gdb-index tries to read bogus compressed data from
input sections if input debug sections are compressed.
Fixes https://github.com/rui314/mold/issues/431
---
elf/arch-riscv64.cc | 4 ++--
elf/input-files.cc | 10 ++--------
elf/input-sections.cc | 44 +++++++++++++++++++++++++------------------
elf/mold.h | 14 ++++++--------
elf/output-chunks.cc | 2 ++
test/elf/gdb-index.sh | 21 +++++++++++++--------
6 files changed, 51 insertions(+), 44 deletions(-)
diff --git a/elf/arch-riscv64.cc b/elf/arch-riscv64.cc
index aa5d7b1c..955407f2 100644
--- a/elf/arch-riscv64.cc
+++ b/elf/arch-riscv64.cc
@@ -490,8 +490,8 @@ template <>
void InputSection<E>::copy_contents_riscv(Context<E> &ctx, u8 *buf) {
// A non-alloc section isn't relaxed, so just copy it as one big chunk.
if (!(shdr().sh_flags & SHF_ALLOC)) {
- if (is_compressed())
- uncompress(ctx, buf);
+ if (compressed)
+ uncompress_to(ctx, buf);
else
memcpy(buf, contents.data(), contents.size());
return;
diff --git a/elf/input-files.cc b/elf/input-files.cc
index 6980e21a..d44216af 100644
--- a/elf/input-files.cc
+++ b/elf/input-files.cc
@@ -524,16 +524,10 @@ split_section(Context<E> &ctx, InputSection<E> &sec) {
sec.shdr().sh_flags);
rec->p2align = sec.p2align;
- std::string_view data = sec.contents;
-
// If thes section contents are compressed, uncompress them.
- if (sec.is_compressed()) {
- u8 *buf = new u8[sec.sh_size];
- sec.uncompress(ctx, buf);
- data = {(char *)buf, sec.sh_size};
- ctx.string_pool.emplace_back(buf);
- }
+ sec.uncompress(ctx);
+ std::string_view data = sec.contents;
const char *begin = data.data();
u64 entsize = sec.shdr().sh_entsize;
HyperLogLog estimator;
diff --git a/elf/input-sections.cc b/elf/input-sections.cc
index cfe1c570..81663cdb 100644
--- a/elf/input-sections.cc
+++ b/elf/input-sections.cc
@@ -38,8 +38,6 @@ InputSection<E>::InputSection(Context<E> &ctx, ObjectFile<E> &file,
if (shndx < file.elf_sections.size())
contents = {(char *)file.mf->data + shdr().sh_offset, shdr().sh_size};
- bool compressed;
-
if (name.starts_with(".zdebug")) {
sh_size = *(ubig64 *)&contents[4];
p2align = to_p2align(shdr().sh_addralign);
@@ -55,28 +53,37 @@ InputSection<E>::InputSection(Context<E> &ctx, ObjectFile<E> &file,
compressed = false;
}
- // Uncompress early if the relocation is REL-type so that we can read
- // addends from section contents. If RELA-type, we don't need to do this
- // because addends are in relocations.
- if (compressed && E::is_rel) {
- u8 *buf = new u8[sh_size];
- uncompress(ctx, buf);
- contents = {(char *)buf, sh_size};
- ctx.string_pool.emplace_back(buf);
- }
+ // Sections may have been compressed. We usually uncompress them
+ // directly into the mmap'ed output file, but we want to uncompress
+ // early for REL-type ELF types to read relocation addends from
+ // section contents. For RELA-type, we don't need to do this because
+ // addends are in relocations.
+ if (E::is_rel)
+ uncompress(ctx);
output_section =
OutputSection<E>::get_instance(ctx, name, shdr().sh_type, shdr().sh_flags);
}
template <typename E>
-bool InputSection<E>::is_compressed() {
- return !E::is_rel &&
- (name().starts_with(".zdebug") || (shdr().sh_flags & SHF_COMPRESSED));
+void InputSection<E>::uncompress(Context<E> &ctx) {
+ if (!compressed || uncompressed)
+ return;
+
+ u8 *buf = new u8[sh_size];
+ uncompress_to(ctx, buf);
+ contents = {(char *)buf, sh_size};
+ ctx.string_pool.emplace_back(buf);
+ uncompressed = true;
}
template <typename E>
-void InputSection<E>::uncompress(Context<E> &ctx, u8 *buf) {
+void InputSection<E>::uncompress_to(Context<E> &ctx, u8 *buf) {
+ if (!compressed || uncompressed) {
+ memcpy(buf, contents.data(), contents.size());
+ return;
+ }
+
auto do_uncompress = [&](std::string_view data) {
unsigned long size = sh_size;
if (::uncompress(buf, &size, (u8 *)data.data(), data.size()) != Z_OK)
@@ -100,7 +107,8 @@ void InputSection<E>::uncompress(Context<E> &ctx, u8 *buf) {
ElfChdr<E> &hdr = *(ElfChdr<E> *)&contents[0];
if (hdr.ch_type != ELFCOMPRESS_ZLIB)
- Fatal(ctx) << *this << ": unsupported compression type";
+ Fatal(ctx) << *this << ": unsupported compression type: 0x"
+ << std::hex << hdr.ch_type;
do_uncompress(contents.substr(sizeof(ElfChdr<E>)));
}
@@ -213,8 +221,8 @@ void InputSection<E>::write_to(Context<E> &ctx, u8 *buf) {
// Copy data
if constexpr (std::is_same_v<E, RISCV64>) {
copy_contents_riscv(ctx, buf);
- } else if (is_compressed()) {
- uncompress(ctx, buf);
+ } else if (compressed) {
+ uncompress_to(ctx, buf);
} else {
memcpy(buf, contents.data(), contents.size());
}
diff --git a/elf/mold.h b/elf/mold.h
index b36446cb..d38fec9a 100644
--- a/elf/mold.h
+++ b/elf/mold.h
@@ -266,8 +266,8 @@ class InputSection {
InputSection(Context<E> &ctx, ObjectFile<E> &file, std::string_view name,
i64 shndx);
- bool is_compressed();
- void uncompress(Context<E> &ctx, u8 *buf);
+ void uncompress(Context<E> &ctx);
+ void uncompress_to(Context<E> &ctx, u8 *buf);
void scan_relocations(Context<E> &ctx);
void write_to(Context<E> &ctx, u8 *buf);
void apply_reloc_alloc(Context<E> &ctx, u8 *base);
@@ -307,10 +307,12 @@ class InputSection {
// For COMDAT de-duplication and garbage collection
std::atomic_bool is_alive = true;
- bool killed_by_icf = false;
-
u8 p2align = 0;
+ u8 compressed : 1 = false;
+ u8 uncompressed : 1 = false;
+ u8 killed_by_icf : 1 = false;
+
private:
typedef enum : u8 { NONE, ERROR, COPYREL, PLT, CPLT, DYNREL, BASEREL } Action;
@@ -1142,10 +1144,6 @@ class ObjectFile : public InputFile<E> {
const ElfSym<E> &esym, i64 symidx);
void merge_visibility(Context<E> &ctx, Symbol<E> &sym, u8 visibility);
- std::pair<std::string_view, const ElfShdr<E> *>
- uncompress_contents(Context<E> &ctx, const ElfShdr<E> &shdr,
- std::string_view name);
-
bool has_common_symbol = false;
std::string_view symbol_strtab;
diff --git a/elf/output-chunks.cc b/elf/output-chunks.cc
index abb278ef..315172bb 100644
--- a/elf/output-chunks.cc
+++ b/elf/output-chunks.cc
@@ -2407,6 +2407,7 @@ void GdbIndexSection<E>::write_address_areas(Context<E> &ctx) {
template <typename E>
std::vector<std::string_view>
GdbIndexSection<E>::read_compunits(Context<E> &ctx, ObjectFile<E> &file) {
+ file.debug_info->uncompress(ctx);
std::string_view data = file.debug_info->contents;
std::vector<std::string_view> vec;
@@ -2444,6 +2445,7 @@ GdbIndexSection<E>::read_pubnames(Context<E> &ctx, ObjectFile<E> &file) {
};
auto read = [&](InputSection<E> &isec) {
+ isec.uncompress(ctx);
std::string_view contents = isec.contents;
while (!contents.empty()) {
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