/*-*- 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 2022 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/calls.h"
#include "libc/calls/strace.internal.h"
#include "libc/errno.h"
#include "libc/sysv/consts/pr.h"
#include "libc/sysv/errfuns.h"

static const char *DescribePrctlOperation(int x) {
  switch (x) {
    case PR_SET_NO_NEW_PRIVS:
      return "PR_SET_NO_NEW_PRIVS";
    case PR_SET_SECCOMP:
      return "PR_SET_SECCOMP";
    case PR_GET_SECCOMP:
      return "PR_GET_SECCOMP";
    default:
      return "PRCTL_???";
  }
}

/**
 * Tunes process on Linux.
 *
 * @raise ENOSYS on non-Linux.
 */
int prctl(int operation, ...) {
  int rc;
  va_list va;
  intptr_t a, b;
  register intptr_t c asm("r10");
  register intptr_t d asm("r8");
  va_start(va, operation);
  a = va_arg(va, intptr_t);
  b = va_arg(va, intptr_t);
  c = va_arg(va, intptr_t);
  d = va_arg(va, intptr_t);
  va_end(va);
  if (IsLinux()) {
    asm volatile("syscall"
                 : "=a"(rc)
                 : "0"(157), "D"(operation), "S"(a), "d"(b), "r"(c), "r"(d)
                 : "rcx", "r11", "memory");
    if (rc > -4096u) errno = -rc, rc = -1;
  } else {
    rc = enosys();
  }
  STRACE("prctl(%s, %p, %p, %p, %p) → %d% m", DescribePrctlOperation(operation),
         a, b, c, d, rc);
  return rc;
}