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https://github.com/rui314/mold.git
synced 2024-09-11 04:55:31 +03:00
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3 Commits
b145377c39
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c6b54532e9
Author | SHA1 | Date | |
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c6b54532e9 | ||
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3936134823 | ||
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55ca05bab6 |
23
elf/main.cc
23
elf/main.cc
@ -375,11 +375,9 @@ int elf_main(int argc, char **argv) {
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<< ": " << errno_string();
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// Fork a subprocess unless --no-fork is given.
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std::function<void()> on_complete;
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#if !defined(_WIN32) && !defined(__APPLE__)
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if (ctx.arg.fork)
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on_complete = fork_child();
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fork_child();
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#endif
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acquire_global_lock();
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@ -664,8 +662,13 @@ int elf_main(int argc, char **argv) {
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// so we sort them.
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ctx.reldyn->sort(ctx);
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// Zero-clear paddings between sections
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clear_padding(ctx);
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// .note.gnu.build-id section contains a cryptographic hash of the
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// entire output file. Now that we wrote everything except build-id,
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// we can compute it.
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if (ctx.buildid) {
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compute_build_id(ctx);
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ctx.buildid->copy_buf(ctx);
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}
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// .gdb_index's contents cannot be constructed before applying
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// relocations to other debug sections. We have relocated debug
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@ -673,12 +676,6 @@ int elf_main(int argc, char **argv) {
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if (ctx.gdb_index)
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write_gdb_index(ctx);
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// .note.gnu.build-id section contains a cryptographic hash of the
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// entire output file. Now that we wrote everything except build-id,
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// we can compute it.
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if (ctx.buildid)
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ctx.buildid->write_buildid(ctx);
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t_copy.stop();
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ctx.checkpoint();
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@ -707,8 +704,8 @@ int elf_main(int argc, char **argv) {
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std::cout << std::flush;
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std::cerr << std::flush;
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if (on_complete)
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on_complete();
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if (ctx.arg.fork)
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notify_parent();
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release_global_lock();
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21
elf/mold.h
21
elf/mold.h
@ -949,9 +949,8 @@ public:
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void update_shdr(Context<E> &ctx) override;
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void copy_buf(Context<E> &ctx) override;
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void write_buildid(Context<E> &ctx);
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static constexpr i64 HEADER_SIZE = 16;
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std::vector<u8> contents;
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};
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template <typename E>
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@ -1368,7 +1367,8 @@ void print_map(Context<E> &ctx);
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// subprocess.cc
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//
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std::function<void()> fork_child();
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void fork_child();
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void notify_parent();
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template <typename E>
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[[noreturn]]
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@ -1426,11 +1426,11 @@ template <typename E> void apply_version_script(Context<E> &);
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template <typename E> void parse_symbol_version(Context<E> &);
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template <typename E> void compute_import_export(Context<E> &);
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template <typename E> void compute_address_significance(Context<E> &);
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template <typename E> void clear_padding(Context<E> &);
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template <typename E> void compute_section_headers(Context<E> &);
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template <typename E> i64 set_osec_offsets(Context<E> &);
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template <typename E> void fix_synthetic_symbols(Context<E> &);
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template <typename E> i64 compress_debug_sections(Context<E> &);
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template <typename E> void compute_build_id(Context<E> &);
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template <typename E> void write_dependency_file(Context<E> &);
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template <typename E> void show_stats(Context<E> &);
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@ -1565,7 +1565,18 @@ private:
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//
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struct BuildId {
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i64 size() const;
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i64 size() const {
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switch (kind) {
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case HEX:
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return value.size();
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case HASH:
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return hash_size;
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case UUID:
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return 16;
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default:
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unreachable();
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}
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}
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enum { NONE, HEX, HASH, UUID } kind = NONE;
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std::vector<u8> value;
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@ -1,7 +1,5 @@
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#include "mold.h"
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#include "config.h"
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#include "blake3.h"
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#include <cctype>
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#include <set>
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@ -2526,89 +2524,21 @@ void VerdefSection<E>::copy_buf(Context<E> &ctx) {
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write_vector(ctx.buf + this->shdr.sh_offset, contents);
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}
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inline i64 BuildId::size() const {
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switch (kind) {
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case HEX:
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return value.size();
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case HASH:
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return hash_size;
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case UUID:
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return 16;
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default:
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unreachable();
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}
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}
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template <typename E>
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void BuildIdSection<E>::update_shdr(Context<E> &ctx) {
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this->shdr.sh_size = HEADER_SIZE + ctx.arg.build_id.size();
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this->shdr.sh_size = ctx.arg.build_id.size() + 16; // +16 for the header
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}
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template <typename E>
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void BuildIdSection<E>::copy_buf(Context<E> &ctx) {
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U32<E> *base = (U32<E> *)(ctx.buf + this->shdr.sh_offset);
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memset(base, 0, this->shdr.sh_size);
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base[0] = 4; // Name size
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base[1] = ctx.arg.build_id.size(); // Hash size
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base[2] = NT_GNU_BUILD_ID; // Type
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memcpy(base + 3, "GNU", 4); // Name string
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}
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// BLAKE3 is a cryptographic hash function just like SHA256.
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// We use it instead of SHA256 because it's faster.
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static void blake3_hash(u8 *buf, i64 size, u8 *out) {
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blake3_hasher hasher;
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blake3_hasher_init(&hasher);
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blake3_hasher_update(&hasher, buf, size);
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blake3_hasher_finalize(&hasher, out, BLAKE3_OUT_LEN);
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}
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template <typename E>
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void BuildIdSection<E>::write_buildid(Context<E> &ctx) {
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Timer t(ctx, "build_id");
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u8 *buf = ctx.buf + this->shdr.sh_offset + HEADER_SIZE;
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switch (ctx.arg.build_id.kind) {
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case BuildId::HEX:
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write_vector(buf, ctx.arg.build_id.value);
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return;
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case BuildId::HASH: {
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i64 shard_size = 4 * 1024 * 1024;
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i64 filesize = ctx.output_file->filesize;
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i64 num_shards = align_to(filesize, shard_size) / shard_size;
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std::vector<u8> shards(num_shards * BLAKE3_OUT_LEN);
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tbb::parallel_for((i64)0, num_shards, [&](i64 i) {
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u8 *begin = ctx.buf + shard_size * i;
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u8 *end = (i == num_shards - 1) ? ctx.buf + filesize : begin + shard_size;
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blake3_hash(begin, end - begin, shards.data() + i * BLAKE3_OUT_LEN);
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#ifdef HAVE_MADVISE
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// Make the kernel page out the file contents we've just written
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// so that subsequent close(2) call will become quicker.
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if (i > 0 && ctx.output_file->is_mmapped)
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madvise(begin, end - begin, MADV_DONTNEED);
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#endif
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});
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u8 digest[BLAKE3_OUT_LEN];
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blake3_hash(shards.data(), shards.size(), digest);
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assert(ctx.arg.build_id.size() <= BLAKE3_OUT_LEN);
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memcpy(buf, digest, ctx.arg.build_id.size());
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return;
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}
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case BuildId::UUID: {
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get_random_bytes(buf, 16);
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// Indicate that this is UUIDv4 as defined by RFC4122
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buf[6] = (buf[6] & 0b0000'1111) | 0b0100'0000;
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buf[8] = (buf[8] & 0b0011'1111) | 0b1000'0000;
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return;
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}
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default:
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unreachable();
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}
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base[0] = 4; // Name size
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base[1] = ctx.arg.build_id.size(); // Hash size
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base[2] = NT_GNU_BUILD_ID; // Type
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memcpy(base + 3, "GNU", 4); // Name string
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write_vector(base + 4, contents); // Build ID
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}
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template <typename E>
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@ -1,4 +1,5 @@
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#include "mold.h"
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#include "blake3.h"
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#include <fstream>
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#include <functional>
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@ -1720,6 +1721,22 @@ void copy_chunks(Context<E> &ctx) {
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if constexpr (is_arm32<E>)
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fixup_arm_exidx_section(ctx);
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// Zero-clear paddings between chunks
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auto zero = [&](Chunk<E> *chunk, i64 next_start) {
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i64 pos = chunk->shdr.sh_offset + chunk->shdr.sh_size;
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memset(ctx.buf + pos, 0, next_start - pos);
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};
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std::vector<Chunk<E> *> chunks = ctx.chunks;
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std::erase_if(chunks, [](Chunk<E> *chunk) {
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return chunk->shdr.sh_type == SHT_NOBITS;
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});
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for (i64 i = 1; i < chunks.size(); i++)
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zero(chunks[i - 1], chunks[i]->shdr.sh_offset);
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zero(chunks.back(), ctx.output_file->filesize);
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}
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// Rewrite the leading endbr64 instruction with a nop if a function
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@ -2168,26 +2185,6 @@ void compute_address_significance(Context<E> &ctx) {
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});
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}
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template <typename E>
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void clear_padding(Context<E> &ctx) {
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Timer t(ctx, "clear_padding");
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auto zero = [&](Chunk<E> *chunk, i64 next_start) {
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i64 pos = chunk->shdr.sh_offset + chunk->shdr.sh_size;
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memset(ctx.buf + pos, 0, next_start - pos);
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};
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std::vector<Chunk<E> *> chunks = ctx.chunks;
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std::erase_if(chunks, [](Chunk<E> *chunk) {
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return chunk->shdr.sh_type == SHT_NOBITS;
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});
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for (i64 i = 1; i < chunks.size(); i++)
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zero(chunks[i - 1], chunks[i]->shdr.sh_offset);
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zero(chunks.back(), ctx.output_file->filesize);
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}
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// We want to sort output chunks in the following order.
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//
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// <ELF header>
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@ -2999,6 +2996,65 @@ i64 compress_debug_sections(Context<E> &ctx) {
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return set_osec_offsets(ctx);
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}
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// BLAKE3 is a cryptographic hash function just like SHA256.
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// We use it instead of SHA256 because it's faster.
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static void blake3_hash(u8 *buf, i64 size, u8 *out) {
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blake3_hasher hasher;
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blake3_hasher_init(&hasher);
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blake3_hasher_update(&hasher, buf, size);
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blake3_hasher_finalize(&hasher, out, BLAKE3_OUT_LEN);
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}
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template <typename E>
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void compute_build_id(Context<E> &ctx) {
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Timer t(ctx, "compute_build_id");
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switch (ctx.arg.build_id.kind) {
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case BuildId::HEX:
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ctx.buildid->contents = ctx.arg.build_id.value;
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break;
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case BuildId::HASH: {
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i64 shard_size = 4 * 1024 * 1024;
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i64 filesize = ctx.output_file->filesize;
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i64 num_shards = align_to(filesize, shard_size) / shard_size;
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std::vector<u8> shards(num_shards * BLAKE3_OUT_LEN);
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tbb::parallel_for((i64)0, num_shards, [&](i64 i) {
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u8 *begin = ctx.buf + shard_size * i;
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u8 *end = (i == num_shards - 1) ? ctx.buf + filesize : begin + shard_size;
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blake3_hash(begin, end - begin, shards.data() + i * BLAKE3_OUT_LEN);
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#ifdef HAVE_MADVISE
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// Make the kernel page out the file contents we've just written
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// so that subsequent close(2) call will become quicker.
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if (i > 0 && ctx.output_file->is_mmapped)
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madvise(begin, end - begin, MADV_DONTNEED);
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#endif
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});
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u8 buf[BLAKE3_OUT_LEN];
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blake3_hash(shards.data(), shards.size(), buf);
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assert(ctx.arg.build_id.size() <= BLAKE3_OUT_LEN);
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ctx.buildid->contents = {buf, buf + ctx.arg.build_id.size()};
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break;
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}
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case BuildId::UUID: {
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u8 buf[16];
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get_random_bytes(buf, 16);
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// Indicate that this is UUIDv4 as defined by RFC4122
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buf[6] = (buf[6] & 0b0000'1111) | 0b0100'0000;
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buf[8] = (buf[8] & 0b0011'1111) | 0b1000'0000;
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ctx.buildid->contents = {buf, buf + 16};
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break;
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}
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default:
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unreachable();
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}
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}
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// Write Makefile-style dependency rules to a file specified by
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// --dependency-file. This is analogous to the compiler's -M flag.
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template <typename E>
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@ -3134,11 +3190,11 @@ template void apply_version_script(Context<E> &);
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template void parse_symbol_version(Context<E> &);
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template void compute_import_export(Context<E> &);
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template void compute_address_significance(Context<E> &);
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template void clear_padding(Context<E> &);
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template void compute_section_headers(Context<E> &);
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template i64 set_osec_offsets(Context<E> &);
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template void fix_synthetic_symbols(Context<E> &);
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template i64 compress_debug_sections(Context<E> &);
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template void compute_build_id(Context<E> &);
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template void write_dependency_file(Context<E> &);
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template void show_stats(Context<E> &);
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|
@ -176,7 +176,6 @@ void combine_objects(Context<E> &ctx) {
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ctx.buf = ctx.output_file->buf;
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copy_chunks(ctx);
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clear_padding(ctx);
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ctx.output_file->close(ctx);
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ctx.checkpoint();
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|
@ -14,10 +14,12 @@
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namespace mold::elf {
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#ifdef MOLD_X86_64
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static int pipe_write_fd = -1;
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// Exiting from a program with large memory usage is slow --
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// it may take a few hundred milliseconds. To hide the latency,
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// we fork a child and let it do the actual linking work.
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std::function<void()> fork_child() {
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void fork_child() {
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int pipefd[2];
|
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if (pipe(pipefd) == -1) {
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perror("pipe");
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@ -50,12 +52,16 @@ std::function<void()> fork_child() {
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// Child
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close(pipefd[0]);
|
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pipe_write_fd = pipefd[1];
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}
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|
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return [=] {
|
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char buf[] = {1};
|
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[[maybe_unused]] int n = write(pipefd[1], buf, 1);
|
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assert(n == 1);
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};
|
||||
void notify_parent() {
|
||||
if (pipe_write_fd == -1)
|
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return;
|
||||
|
||||
char buf[] = {1};
|
||||
[[maybe_unused]] int n = write(pipe_write_fd, buf, 1);
|
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assert(n == 1);
|
||||
}
|
||||
#endif
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||||
|
||||
|
Loading…
Reference in New Issue
Block a user