cosmopolitan/libc/runtime/getsymboltable.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/atomic.h"
#include "libc/calls/calls.h"
#include "libc/cosmo.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/kprintf.h"
#include "libc/intrin/promises.internal.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/symbols.internal.h"
#include "libc/sysv/consts/map.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/prot.h"

__static_yoink("__get_symbol");

struct SymbolTableLoader __symtab;

static struct SymbolTable *GetSymbolTableFromZip(void) {
  int fd;
  struct SymbolTable *res = 0;
  if ((fd = open("/zip/.symtab." _ARCH_NAME, O_RDONLY)) != -1 ||
      (fd = open("/zip/.symtab", O_RDONLY)) != -1) {
    void *map;
    ssize_t size;
    if ((size = lseek(fd, 0, SEEK_END)) != -1 &&
        (map = mmap(0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0)) !=
            MAP_FAILED) {
      res = map;
    }
    close(fd);
  }
  return res;
}

static struct SymbolTable *GetSymbolTableFromElf(void) {
  const char *path;
  if ((path = FindDebugBinary())) {
    return OpenSymbolTable(path);
  } else {
    return 0;
  }
}

static void GetSymbolTableInit(void) {
  if (!PLEDGED(RPATH)) return;
  int e = errno;
  if ((__symtab.st = GetSymbolTableFromZip())) {
    __symtab.st->names =
        (uint32_t *)((char *)__symtab.st + __symtab.st->names_offset);
    __symtab.st->name_base =
        (char *)((char *)__symtab.st + __symtab.st->name_base_offset);
  }
  if (!__symtab.st) {
    __symtab.st = GetSymbolTableFromElf();
  }
  errno = e;
}

/**
 * Returns symbol table singleton.
 *
 * This uses multiple strategies to find the symbol table. The first
 * strategy, depends on whether or not the following is linked:
 *
 *     __static_yoink("zipos");
 *
 * In that case, the symbol table may be read from `/zip/.symtab.ARCH`
 * or `/zip/.symtab` which are generated by `o//tool/build/symtab.com`
 * or `o//tool/build/apelink.com`.
 *
 * The second strategy is to look for the ELF executable for the current
 * program. If you're running a .com binary, it'll look for the .com.dbg
 * file. If it's running the .com.dbg or .elf file, then it'll just read
 * the symbols from itself. In other cases, you can explicitly specify a
 * debug symbol binary via the `COMDBG` environment variable.
 *
 * When using pledge() security, it's recommended that this function get
 * called *before* calling pledge() if it lacks the rpath promise, so it
 * can load the symbols into memory before the filesystem goes away.
 *
 * @return symbol table, or NULL if not found
 */
struct SymbolTable *GetSymbolTable(void) {
  cosmo_once(&__symtab.once, GetSymbolTableInit);
  return __symtab.st;
}