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/*
* Copyright (c) 2014 Google Inc.
*
* Permission to use, copy, modify, and 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 <sys/mman.h>
#include <sys/wait.h>
#include <assert.h>
#include <err.h>
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#define CHECK(x) assert(x)
#define CHECK_EQ(a, b) assert((a) == (b))
#define CHECK_NE(a, b) assert((a) != (b))
#define CHECK_GE(a, b) assert((a) >= (b))
#define CHECK_LE(a, b) assert((a) <= (b))
/* Test arc4random_buf(3) instead of arc4random(3). */
static int flagbuf;
/* Initialize arc4random(3) before forking. */
static int flagprefork;
enum {
N = 4096
};
typedef struct {
uint32_t x[N];
} Buf;
static int
isfullbuf(const Buf *buf)
{
size_t i;
for (i = 0; i < N; i++)
if (buf->x[i])
return (1);
return (0);
}
static void
fillbuf(Buf *buf)
{
if (flagbuf) {
arc4random_buf(buf->x, sizeof(buf->x));
} else {
size_t i;
for (i = 0; i < N; i++)
buf->x[i] = arc4random();
}
}
static void
usage()
{
errx(1, "usage: arc4random-fork [-bp]");
}
static pid_t
safewaitpid(pid_t pid, int *status, int options)
{
pid_t ret;
do {
ret = waitpid(pid, status, options);
} while (ret == -1 && errno == EINTR);
return (ret);
}
int
main(int argc, char *argv[])
{
int opt, status;
Buf *bufparent, *bufchildone, *bufchildtwo;
pid_t pidone, pidtwo;
size_t i, countone = 0, counttwo = 0, countkids = 0;
/* Ensure SIGCHLD isn't set to SIG_IGN. */
const struct sigaction sa = {
.sa_handler = SIG_DFL,
};
CHECK_EQ(0, sigaction(SIGCHLD, &sa, NULL));
while ((opt = getopt(argc, argv, "bp")) != -1) {
switch (opt) {
case 'b':
flagbuf = 1;
break;
case 'p':
flagprefork = 1;
break;
default:
usage();
}
}
if (flagprefork)
arc4random();
bufparent = mmap(NULL, sizeof(Buf), PROT_READ|PROT_WRITE,
MAP_ANON|MAP_PRIVATE, -1, 0);
CHECK_NE(MAP_FAILED, bufparent);
bufchildone = mmap(NULL, sizeof(Buf), PROT_READ|PROT_WRITE,
MAP_ANON|MAP_SHARED, -1, 0);
CHECK_NE(MAP_FAILED, bufchildone);
bufchildtwo = mmap(NULL, sizeof(Buf), PROT_READ|PROT_WRITE,
MAP_ANON|MAP_SHARED, -1, 0);
CHECK_NE(MAP_FAILED, bufchildtwo);
pidone = fork();
CHECK_GE(pidone, 0);
if (pidone == 0) {
fillbuf(bufchildone);
_exit(0);
}
pidtwo = fork();
CHECK_GE(pidtwo, 0);
if (pidtwo == 0) {
fillbuf(bufchildtwo);
_exit(0);
}
fillbuf(bufparent);
CHECK_EQ(pidone, safewaitpid(pidone, &status, 0));
CHECK(WIFEXITED(status));
CHECK_EQ(0, WEXITSTATUS(status));
CHECK_EQ(pidtwo, safewaitpid(pidtwo, &status, 0));
CHECK(WIFEXITED(status));
CHECK_EQ(0, WEXITSTATUS(status));
CHECK(isfullbuf(bufchildone));
CHECK(isfullbuf(bufchildtwo));
for (i = 0; i < N; i++) {
countone += bufparent->x[i] == bufchildone->x[i];
counttwo += bufparent->x[i] == bufchildtwo->x[i];
countkids += bufchildone->x[i] == bufchildtwo->x[i];
}
/*
* These checks are inherently probabilistic and theoretically risk
* flaking, but there's less than a 1 in 2^40 chance of more than
* one pairwise match between two vectors of 4096 32-bit integers.
*/
CHECK_LE(countone, 1);
CHECK_LE(counttwo, 1);
CHECK_LE(countkids, 1);
return (0);
}
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