// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (c) 2018 Jan Stancek. All rights reserved.
*/
/*
* Test: Spawn 2 threads. First thread maps, writes and unmaps
* an area. Second thread tries to read from it. Second thread
* races against first thread. There is no synchronization
* between threads, but each mmap/munmap increases a counter
* that is checked to determine when has read occurred. If a read
* hit SIGSEGV in between mmap/munmap it is a failure. If a read
* between mmap/munmap worked, then its value must match expected
* value.
*/
#include <errno.h>
#include <float.h>
#include <pthread.h>
#include <sched.h>
#include <setjmp.h>
#include <stdio.h>
#include <stdlib.h>
#include "tst_test.h"
#include "tst_safe_pthread.h"
#define DISTANT_MMAP_SIZE (64*1024*1024)
#define TEST_FILENAME "ashfile"
/* seconds remaining before reaching timeout */
#define STOP_THRESHOLD 10
#define PROGRESS_SEC 3
static int file_size = 1024;
static int num_iter = 5000;
static float exec_time = 0.05; /* default is 3 min */
static void *distant_area;
static char *str_exec_time;
static jmp_buf jmpbuf;
static volatile unsigned char *map_address;
static unsigned long page_sz;
static unsigned long mapped_sigsegv_count;
static unsigned long map_count;
static unsigned long threads_spawned;
static unsigned long data_matched;
static unsigned long repeated_reads;
/* sequence id for each map/unmap performed */
static int mapcnt, unmapcnt;
/* stored sequence id before making read attempt */
static int br_map, br_unmap;
static struct tst_option options[] = {
{"x:", &str_exec_time, "Exec time (hours)"},
{NULL, NULL, NULL}
};
/* compare "before read" counters with "after read" counters */
static inline int was_area_mapped(int br_m, int br_u, int ar_m, int ar_u)
{
return (br_m == ar_m && br_u == ar_u && br_m > br_u);
}
static void sig_handler(int signal, siginfo_t *info,
LTP_ATTRIBUTE_UNUSED void *ut)
{
int ar_m, ar_u;
switch (signal) {
case SIGSEGV:
/* if we hit SIGSEGV between map/unmap, something is wrong */
ar_u = tst_atomic_load(&unmapcnt);
ar_m = tst_atomic_load(&mapcnt);
if (was_area_mapped(br_map, br_unmap, ar_m, ar_u)) {
tst_res(TFAIL, "got sigsegv while mapped");
_exit(TFAIL);
}
mapped_sigsegv_count++;
longjmp(jmpbuf, 1);
break;
default:
tst_res(TFAIL, "Unexpected signal - %d, addr: %p, exiting\n",
signal, info->si_addr);
_exit(TBROK);
}
}
void *map_write_unmap(void *ptr)
{
int *fd = ptr;
void *tmp;
int i, j;
for (i = 0; i < num_iter; i++) {
map_address = SAFE_MMAP(distant_area,
(size_t) file_size, PROT_WRITE | PROT_READ,
MAP_SHARED, *fd, 0);
tst_atomic_inc(&mapcnt);
for (j = 0; j < file_size; j++)
map_address[j] = 'b';
tmp = (void *)map_address;
tst_atomic_inc(&unmapcnt);
SAFE_MUNMAP(tmp, file_size);
map_count++;
}
return NULL;
}
void *read_mem(LTP_ATTRIBUTE_UNUSED void *ptr)
{
volatile int i; /* longjmp could clobber i */
int j, ar_map, ar_unmap;
unsigned char c;
for (i = 0; i < num_iter; i++) {
if (setjmp(jmpbuf) == 1)
continue;
for (j = 0; j < file_size; j++) {
read_again:
br_map = tst_atomic_load(&mapcnt);
br_unmap = tst_atomic_load(&unmapcnt);
c = map_address[j];
ar_unmap = tst_atomic_load(&unmapcnt);
ar_map = tst_atomic_load(&mapcnt);
/*
* Read above is racing against munmap and mmap
* in other thread. While the address might be valid
* the mapping could be in various stages of being
* 'ready'. We only check the value, if we can be sure
* read hapenned in between single mmap and munmap as
* observed by first thread.
*/
if (was_area_mapped(br_map, br_unmap, ar_map,
ar_unmap)) {
switch (c) {
case 'a':
repeated_reads++;
goto read_again;
case 'b':
data_matched++;
break;
default:
tst_res(TFAIL, "value[%d] is %c", j, c);
break;
}
}
}
}
return NULL;
}
int mkfile(int size)
{
int fd, i;
fd = SAFE_OPEN(TEST_FILENAME, O_RDWR | O_CREAT, 0600);
SAFE_UNLINK(TEST_FILENAME);
for (i = 0; i < size; i++)
SAFE_WRITE(1, fd, "a", 1);
SAFE_WRITE(1, fd, "\0", 1);
if (fsync(fd) == -1)
tst_brk(TBROK | TERRNO, "fsync()");
return fd;
}
static void setup(void)
{
struct sigaction sigptr;
page_sz = getpagesize();
/*
* Used as hint for mmap thread, so it doesn't interfere
* with other potential (temporary) mappings from libc
*/
distant_area = SAFE_MMAP(0, DISTANT_MMAP_SIZE, PROT_WRITE | PROT_READ,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
SAFE_MUNMAP(distant_area, (size_t)DISTANT_MMAP_SIZE);
distant_area += DISTANT_MMAP_SIZE / 2;
if (tst_parse_float(str_exec_time, &exec_time, 0, FLT_MAX)) {
tst_brk(TBROK, "Invalid number for exec_time '%s'",
str_exec_time);
}
sigptr.sa_sigaction = sig_handler;
sigemptyset(&sigptr.sa_mask);
sigptr.sa_flags = SA_SIGINFO | SA_NODEFER;
SAFE_SIGACTION(SIGSEGV, &sigptr, NULL);
tst_set_timeout((int)(exec_time * 3600));
}
static void run(void)
{
pthread_t thid[2];
int remaining = tst_timeout_remaining();
int elapsed = 0;
while (tst_timeout_remaining() > STOP_THRESHOLD) {
int fd = mkfile(file_size);
tst_atomic_store(0, &mapcnt);
tst_atomic_store(0, &unmapcnt);
SAFE_PTHREAD_CREATE(&thid[0], NULL, map_write_unmap, &fd);
SAFE_PTHREAD_CREATE(&thid[1], NULL, read_mem, &fd);
threads_spawned += 2;
SAFE_PTHREAD_JOIN(thid[0], NULL);
SAFE_PTHREAD_JOIN(thid[1], NULL);
close(fd);
if (remaining - tst_timeout_remaining() > PROGRESS_SEC) {
remaining = tst_timeout_remaining();
elapsed += PROGRESS_SEC;
tst_res(TINFO, "[%d] mapped: %lu, sigsegv hit: %lu, "
"threads spawned: %lu", elapsed, map_count,
mapped_sigsegv_count, threads_spawned);
tst_res(TINFO, "[%d] repeated_reads: %ld, "
"data_matched: %lu", elapsed, repeated_reads,
data_matched);
}
}
tst_res(TPASS, "System survived.");
}
static struct tst_test test = {
.test_all = run,
.setup = setup,
.options = options,
.needs_tmpdir = 1,
};