cosmopolitan/libc/intrin/maps.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 2024 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/intrin/maps.h"
#include "ape/sections.internal.h"
#include "libc/dce.h"
#include "libc/intrin/dll.h"
#include "libc/intrin/maps.h"
#include "libc/runtime/runtime.h"
#include "libc/runtime/stack.h"
#include "libc/sysv/consts/auxv.h"
#include "libc/sysv/consts/prot.h"

#ifdef __x86_64__
__static_yoink("_init_maps");
#endif

struct Maps __maps;

void __maps_add(struct Map *map) {
  tree_insert(&__maps.maps, &map->tree, __maps_compare);
  ++__maps.count;
}

static void __maps_adder(struct Map *map, int pagesz) {
  __maps.pages += ((map->size + pagesz - 1) & -pagesz) / pagesz;
  __maps_add(map);
}

void __maps_stack(char *stackaddr, int pagesz, int guardsize, size_t stacksize,
                  int stackprot, intptr_t stackhand) {
  __maps.stack.addr = stackaddr + guardsize;
  __maps.stack.size = stacksize - guardsize;
  __maps.stack.prot = stackprot;
  __maps.stack.hand = -1;
  __maps_adder(&__maps.stack, pagesz);
  if (guardsize) {
    __maps.guard.addr = stackaddr;
    __maps.guard.size = guardsize;
    __maps.guard.prot = PROT_NONE;
    __maps.guard.hand = stackhand;
    __maps_adder(&__maps.guard, pagesz);
  }
}

void __maps_init(void) {
  int pagesz = __pagesize;

  // record _start() stack mapping
  if (!IsWindows()) {
    struct AddrSize stack;
    stack = __get_main_stack();
    __maps_stack(stack.addr, pagesz, 0, stack.size, (uintptr_t)ape_stack_prot,
                 0);
  }

  // record .text and .data mappings
  static struct Map text, data;
  text.addr = (char *)__executable_start;
  text.size = _etext - __executable_start;
  text.prot = PROT_READ | PROT_EXEC;
  uintptr_t ds = ((uintptr_t)_etext + pagesz - 1) & -pagesz;
  if (ds < (uintptr_t)_end) {
    data.addr = (char *)ds;
    data.size = (uintptr_t)_end - ds;
    data.prot = PROT_READ | PROT_WRITE;
    __maps_adder(&data, pagesz);
  }
  __maps_adder(&text, pagesz);
}

privileged bool __maps_lock(void) {
  struct CosmoTib *tib;
  if (!__tls_enabled)
    return false;
  tib = __get_tls_privileged();
  if (atomic_fetch_add_explicit(&tib->tib_relock_maps, 1, memory_order_relaxed))
    return true;
  int backoff = 0;
  while (atomic_exchange_explicit(&__maps.lock, 1, memory_order_acquire)) {
    if (backoff < 7) {
      volatile int i;
      for (i = 0; i != 1 << backoff; i++) {
      }
      backoff++;
    } else {
      // STRACE("pthread_delay_np(__maps)");
#if defined(__GNUC__) && defined(__aarch64__)
      __asm__ volatile("yield");
#elif defined(__GNUC__) && (defined(__x86_64__) || defined(__i386__))
      __asm__ volatile("pause");
#endif
    }
  }
  return false;
}

privileged void __maps_unlock(void) {
  struct CosmoTib *tib;
  if (!__tls_enabled)
    return;
  tib = __get_tls_privileged();
  if (atomic_fetch_sub_explicit(&tib->tib_relock_maps, 1,
                                memory_order_relaxed) == 1)
    atomic_store_explicit(&__maps.lock, 0, memory_order_release);
}