cosmopolitan/libc/runtime/mprotect.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/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/describeflags.internal.h"
#include "libc/intrin/likely.h"
#include "libc/intrin/strace.internal.h"
#include "libc/runtime/internal.h"
#include "libc/sysv/consts/prot.h"

/**
 * Modifies restrictions on virtual memory address range.
 *
 * @param addr needs to be 4kb aligned
 * @param prot can have PROT_{NONE,READ,WRITE,EXEC,GROWSDOWN,GROWSUP}
 * @return 0 on success, or -1 w/ errno
 * @see mmap()
 */
int mprotect(void *addr, size_t size, int prot) {
  int64_t rc;
  if (prot &
      ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_GROWSDOWN | PROT_GROWSUP)) {
    errno = EINVAL;  // unix checks prot before checking size
    rc = -1;
  } else if (!size) {
    return 0;  // make new technology consistent with unix
  } else if (UNLIKELY((intptr_t)addr & 4095)) {
    errno = EINVAL;  // unix checks prot before checking size
    rc = -1;
  } else if (!IsWindows()) {
    rc = sys_mprotect(addr, size, prot);
  } else {
    rc = sys_mprotect_nt(addr, size, prot);
  }
  STRACE("mprotect(%p, %'zu, %s) → %d% m", addr, size, DescribeProtFlags(prot),
         rc);
  return rc;
}