cosmopolitan/libc/runtime/zipos-get.c

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et 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/calls/metalfile.internal.h"
#include "libc/calls/struct/stat.h"
#include "libc/cosmo.h"
#include "libc/fmt/conv.h"
#include "libc/intrin/cmpxchg.h"
#include "libc/intrin/promises.internal.h"
#include "libc/intrin/strace.internal.h"
#include "libc/macros.internal.h"
#include "libc/mem/alg.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/zipos.internal.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/auxv.h"
#include "libc/sysv/consts/f.h"
#include "libc/sysv/consts/map.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/posix.h"
#include "libc/sysv/consts/prot.h"
#include "libc/thread/thread.h"
#include "libc/zip.internal.h"

#ifdef __x86_64__
__static_yoink(APE_COM_NAME);
#endif

static struct Zipos __zipos;
static atomic_uint __zipos_once;

static void __zipos_dismiss(uint8_t *map, const uint8_t *cdir, long pg) {
  uint64_t i, n, c, ef, lf, mo, lo, hi;

  // determine the byte range of zip file content (excluding central dir)
  c = GetZipCdirOffset(cdir);
  n = GetZipCdirRecords(cdir);
  for (lo = c, hi = i = 0; i < n; ++i, c += ZIP_CFILE_HDRSIZE(map + c)) {
    lf = GetZipCfileOffset(map + c);
    if (lf < lo)
      lo = lf;
    ef = lf + ZIP_LFILE_HDRSIZE(map + lf) + GetZipLfileCompressedSize(map + lf);
    if (ef > hi)
      hi = ef;
  }

  // unmap the executable portion beneath the local files
  mo = ROUNDDOWN(lo, __granularity());
  if (mo)
    munmap(map, mo);

  // this is supposed to reduce our rss usage but does it really?
  lo = ROUNDDOWN(lo, pg);
  hi = MIN(ROUNDUP(hi, pg), ROUNDDOWN(c, pg));
  if (hi > lo) {
    posix_madvise(map + lo, hi - lo, POSIX_MADV_DONTNEED);
  }
}

static int __zipos_compare_names(const void *a, const void *b, void *c) {
  const size_t *x = (const size_t *)a;
  const size_t *y = (const size_t *)b;
  struct Zipos *z = (struct Zipos *)c;
  int xn = ZIP_CFILE_NAMESIZE(z->map + *x);
  int yn = ZIP_CFILE_NAMESIZE(z->map + *y);
  int n = MIN(xn, yn);
  if (n) {
    int res =
        memcmp(ZIP_CFILE_NAME(z->map + *x), ZIP_CFILE_NAME(z->map + *y), n);
    if (res)
      return res;
  }
  return xn - yn;  // xn and yn are 16-bit
}

// creates binary searchable array of file offsets to cdir records
static void __zipos_generate_index(struct Zipos *zipos) {
  size_t c, i;
  zipos->records = GetZipCdirRecords(zipos->cdir);
  zipos->index = _mapanon(zipos->records * sizeof(size_t));
  for (i = 0, c = GetZipCdirOffset(zipos->cdir); i < zipos->records;
       ++i, c += ZIP_CFILE_HDRSIZE(zipos->map + c)) {
    zipos->index[i] = c;
  }
  // smoothsort() isn't the fastest algorithm, but it guarantees
  // o(nlogn) won't smash the stack and doesn't depend on malloc
  smoothsort_r(zipos->index, zipos->records, sizeof(size_t),
               __zipos_compare_names, zipos);
}

static void __zipos_init(void) {
  char *endptr;
  const char *s;
  struct stat st;
  int x, fd, err, msg;
  uint8_t *map, *cdir;
  const char *progpath;
  if (!(s = getenv("COSMOPOLITAN_DISABLE_ZIPOS"))) {
    // this environment variable may be a filename or file descriptor
    if ((progpath = getenv("COSMOPOLITAN_INIT_ZIPOS")) &&
        (x = strtol(progpath, &endptr, 10)) >= 0 && !*endptr) {
      fd = x;
    } else {
      fd = -1;
    }
    if (fd != -1 || PLEDGED(RPATH)) {
      if (fd == -1) {
        if (!progpath) {
          progpath = GetProgramExecutableName();
        }
        fd = open(progpath, O_RDONLY);
      }
      if (fd != -1) {
        if (!fstat(fd, &st) && (map = mmap(0, st.st_size, PROT_READ, MAP_SHARED,
                                           fd, 0)) != MAP_FAILED) {
          if ((cdir = GetZipEocd(map, st.st_size, &err))) {
            long pagesz = getauxval(AT_PAGESZ);
            __zipos_dismiss(map, cdir, pagesz);
            __zipos.map = map;
            __zipos.cdir = cdir;
            __zipos.dev = st.st_ino;
            __zipos.pagesz = pagesz;
            __zipos_generate_index(&__zipos);
            msg = kZipOk;
          } else {
            munmap(map, st.st_size);
            msg = !cdir ? err : kZipErrorRaceCondition;
          }
        } else {
          msg = kZipErrorMapFailed;
        }
        close(fd);
      } else {
        msg = kZipErrorOpenFailed;
      }
    } else {
      msg = -666;
    }
  } else {
    progpath = 0;
    msg = -777;
  }
  STRACE("__zipos_get(%#s) → %d% m", progpath, msg);
}

/**
 * Returns pointer to zip central directory of current executable.
 * @asyncsignalsafe
 */
struct Zipos *__zipos_get(void) {
  cosmo_once(&__zipos_once, __zipos_init);
  return __zipos.cdir ? &__zipos : 0;
}