mirror of
https://github.com/rui314/mold.git
synced 2024-09-11 13:06:59 +03:00
150 lines
4.3 KiB
C++
150 lines
4.3 KiB
C++
#include "common.h"
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#include <fcntl.h>
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#include <filesystem>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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namespace mold {
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inline u32 get_umask() {
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u32 orig_umask = umask(0);
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umask(orig_umask);
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return orig_umask;
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}
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template <typename Context>
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static std::pair<i64, char *>
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open_or_create_file(Context &ctx, std::string path, i64 filesize, i64 perm) {
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std::string tmpl = filepath(path).parent_path() / ".mold-XXXXXX";
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char *path2 = (char *)save_string(ctx, tmpl).data();
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i64 fd = mkstemp(path2);
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if (fd == -1)
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Fatal(ctx) << "cannot open " << path2 << ": " << errno_string();
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// Reuse an existing file if exists and writable because on Linux,
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// writing to an existing file is much faster than creating a fresh
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// file and writing to it.
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if (ctx.overwrite_output_file && rename(path.c_str(), path2) == 0) {
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::close(fd);
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fd = ::open(path2, O_RDWR | O_CREAT, perm);
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if (fd != -1 && !ftruncate(fd, filesize) && !fchmod(fd, perm & ~get_umask()))
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return {fd, path2};
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unlink(path2);
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fd = ::open(path2, O_RDWR | O_CREAT, perm);
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if (fd == -1)
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Fatal(ctx) << "cannot open " << path2 << ": " << errno_string();
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}
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if (fchmod(fd, (perm & ~get_umask())) == -1)
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Fatal(ctx) << "fchmod failed: " << errno_string();
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#ifdef __linux__
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if (fallocate(fd, 0, 0, filesize) == 0)
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return {fd, path2};
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#endif
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if (ftruncate(fd, filesize) == -1)
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Fatal(ctx) << "ftruncate failed: " << errno_string();
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return {fd, path2};
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}
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template <typename Context>
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class MemoryMappedOutputFile : public OutputFile<Context> {
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public:
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MemoryMappedOutputFile(Context &ctx, std::string path, i64 filesize, i64 perm)
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: OutputFile<Context>(path, filesize, true) {
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std::tie(this->fd, output_tmpfile) =
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open_or_create_file(ctx, path, filesize, perm);
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this->buf = (u8 *)mmap(nullptr, filesize, PROT_READ | PROT_WRITE,
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MAP_SHARED, this->fd, 0);
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if (this->buf == MAP_FAILED)
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Fatal(ctx) << path << ": mmap failed: " << errno_string();
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mold::output_buffer_start = this->buf;
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mold::output_buffer_end = this->buf + filesize;
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}
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~MemoryMappedOutputFile() {
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if (fd2 != -1)
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::close(fd2);
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}
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void close(Context &ctx) override {
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Timer t(ctx, "close_file");
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if (!this->is_unmapped)
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munmap(this->buf, this->filesize);
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if (this->buf2.empty()) {
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::close(this->fd);
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} else {
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FILE *out = fdopen(this->fd, "w");
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fseek(out, 0, SEEK_END);
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fwrite(&this->buf2[0], this->buf2.size(), 1, out);
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fclose(out);
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}
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// If an output file already exists, open a file and then remove it.
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// This is the fastest way to unlink a file, as it does not make the
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// system to immediately release disk blocks occupied by the file.
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fd2 = ::open(this->path.c_str(), O_RDONLY);
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if (fd2 != -1)
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unlink(this->path.c_str());
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if (rename(output_tmpfile, this->path.c_str()) == -1)
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Fatal(ctx) << this->path << ": rename failed: " << errno_string();
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output_tmpfile = nullptr;
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}
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private:
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int fd2 = -1;
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};
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template <typename Context>
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std::unique_ptr<OutputFile<Context>>
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OutputFile<Context>::open(Context &ctx, std::string path, i64 filesize, i64 perm) {
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Timer t(ctx, "open_file");
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if (path.starts_with('/') && !ctx.arg.chroot.empty())
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path = ctx.arg.chroot + "/" + path_clean(path);
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bool is_special = false;
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if (path == "-") {
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is_special = true;
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} else {
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struct stat st;
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if (stat(path.c_str(), &st) == 0 && (st.st_mode & S_IFMT) != S_IFREG)
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is_special = true;
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}
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OutputFile<Context> *file;
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if (is_special)
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file = new MallocOutputFile(ctx, path, filesize, perm);
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else
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file = new MemoryMappedOutputFile(ctx, path, filesize, perm);
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#ifdef MADV_HUGEPAGE
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// Enable transparent huge page for an output memory-mapped file.
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// On Linux, it has an effect only on tmpfs mounted with `huge=advise`,
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// but it can make the linker ~10% faster. You can try it by creating
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// a tmpfs with the following commands
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//
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// $ mkdir tmp
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// $ sudo mount -t tmpfs -o size=2G,huge=advise none tmp
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//
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// and then specifying a path under the directory as an output file.
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madvise(file->buf, filesize, MADV_HUGEPAGE);
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#endif
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if (ctx.arg.filler != -1)
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memset(file->buf, ctx.arg.filler, filesize);
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return std::unique_ptr<OutputFile>(file);
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}
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} // namespace mold
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