mirror of
https://github.com/jart/cosmopolitan.git
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b01282e23e
This reduces the virtual memory usage of Emacs for me by 30%. We now have a simpler implementation that uses read(), rather mmap()ing the whole executable.
104 lines
4.4 KiB
C
104 lines
4.4 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/atomic.h"
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#include "libc/calls/calls.h"
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#include "libc/cosmo.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/intrin/kprintf.h"
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#include "libc/intrin/promises.internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/symbols.internal.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/o.h"
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#include "libc/sysv/consts/prot.h"
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__static_yoink("__get_symbol");
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struct SymbolTableLoader __symtab;
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static struct SymbolTable *GetSymbolTableFromZip(void) {
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int fd;
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struct SymbolTable *res = 0;
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if ((fd = open("/zip/.symtab." _ARCH_NAME, O_RDONLY)) != -1 ||
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(fd = open("/zip/.symtab", O_RDONLY)) != -1) {
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void *map;
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ssize_t size;
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if ((size = lseek(fd, 0, SEEK_END)) != -1 &&
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(map = mmap(0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0)) !=
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MAP_FAILED) {
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res = map;
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}
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close(fd);
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}
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return res;
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}
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static struct SymbolTable *GetSymbolTableFromElf(void) {
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const char *path;
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if ((path = FindDebugBinary())) {
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return OpenSymbolTable(path);
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} else {
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return 0;
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}
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}
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static void GetSymbolTableInit(void) {
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if (!PLEDGED(RPATH)) return;
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int e = errno;
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if ((__symtab.st = GetSymbolTableFromZip())) {
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__symtab.st->names =
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(uint32_t *)((char *)__symtab.st + __symtab.st->names_offset);
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__symtab.st->name_base =
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(char *)((char *)__symtab.st + __symtab.st->name_base_offset);
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}
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if (!__symtab.st) {
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__symtab.st = GetSymbolTableFromElf();
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}
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errno = e;
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}
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/**
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* Returns symbol table singleton.
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*
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* This uses multiple strategies to find the symbol table. The first
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* strategy, depends on whether or not the following is linked:
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*
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* __static_yoink("zipos");
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*
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* In that case, the symbol table may be read from `/zip/.symtab.ARCH`
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* or `/zip/.symtab` which are generated by `o//tool/build/symtab.com`
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* or `o//tool/build/apelink.com`.
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*
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* The second strategy is to look for the ELF executable for the current
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* program. If you're running a .com binary, it'll look for the .com.dbg
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* file. If it's running the .com.dbg or .elf file, then it'll just read
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* the symbols from itself. In other cases, you can explicitly specify a
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* debug symbol binary via the `COMDBG` environment variable.
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*
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* When using pledge() security, it's recommended that this function get
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* called *before* calling pledge() if it lacks the rpath promise, so it
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* can load the symbols into memory before the filesystem goes away.
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*
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* @return symbol table, or NULL if not found
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*/
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struct SymbolTable *GetSymbolTable(void) {
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cosmo_once(&__symtab.once, GetSymbolTableInit);
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return __symtab.st;
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}
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