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// SPDX-License-Identifier: GPL-2.0-only
/*
* Basic VM_PFNMAP tests relying on mmap() of '/dev/mem'
*
* Copyright 2025, Red Hat, Inc.
*
* Author(s): David Hildenbrand <david@redhat.com>
*/
#define _GNU_SOURCE
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <setjmp.h>
#include <linux/mman.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include "../kselftest_harness.h"
#include "vm_util.h"
static sigjmp_buf sigjmp_buf_env;
static void signal_handler(int sig)
{
siglongjmp(sigjmp_buf_env, -EFAULT);
}
static int test_read_access(char *addr, size_t size, size_t pagesize)
{
size_t offs;
int ret;
if (signal(SIGSEGV, signal_handler) == SIG_ERR)
return -EINVAL;
ret = sigsetjmp(sigjmp_buf_env, 1);
if (!ret) {
for (offs = 0; offs < size; offs += pagesize)
/* Force a read that the compiler cannot optimize out. */
*((volatile char *)(addr + offs));
}
if (signal(SIGSEGV, signal_handler) == SIG_ERR)
return -EINVAL;
return ret;
}
FIXTURE(pfnmap)
{
size_t pagesize;
int dev_mem_fd;
char *addr1;
size_t size1;
char *addr2;
size_t size2;
};
FIXTURE_SETUP(pfnmap)
{
self->pagesize = getpagesize();
self->dev_mem_fd = open("/dev/mem", O_RDONLY);
if (self->dev_mem_fd < 0)
SKIP(return, "Cannot open '/dev/mem'\n");
/* We'll require the first two pages throughout our tests ... */
self->size1 = self->pagesize * 2;
self->addr1 = mmap(NULL, self->size1, PROT_READ, MAP_SHARED,
self->dev_mem_fd, 0);
if (self->addr1 == MAP_FAILED)
SKIP(return, "Cannot mmap '/dev/mem'\n");
/* ... and want to be able to read from them. */
if (test_read_access(self->addr1, self->size1, self->pagesize))
SKIP(return, "Cannot read-access mmap'ed '/dev/mem'\n");
self->size2 = 0;
self->addr2 = MAP_FAILED;
}
FIXTURE_TEARDOWN(pfnmap)
{
if (self->addr2 != MAP_FAILED)
munmap(self->addr2, self->size2);
if (self->addr1 != MAP_FAILED)
munmap(self->addr1, self->size1);
if (self->dev_mem_fd >= 0)
close(self->dev_mem_fd);
}
TEST_F(pfnmap, madvise_disallowed)
{
int advices[] = {
MADV_DONTNEED,
MADV_DONTNEED_LOCKED,
MADV_FREE,
MADV_WIPEONFORK,
MADV_COLD,
MADV_PAGEOUT,
MADV_POPULATE_READ,
MADV_POPULATE_WRITE,
};
int i;
/* All these advices must be rejected. */
for (i = 0; i < ARRAY_SIZE(advices); i++) {
EXPECT_LT(madvise(self->addr1, self->pagesize, advices[i]), 0);
EXPECT_EQ(errno, EINVAL);
}
}
TEST_F(pfnmap, munmap_split)
{
/*
* Unmap the first page. This munmap() call is not really expected to
* fail, but we might be able to trigger other internal issues.
*/
ASSERT_EQ(munmap(self->addr1, self->pagesize), 0);
/*
* Remap the first page while the second page is still mapped. This
* makes sure that any PAT tracking on x86 will allow for mmap()'ing
* a page again while some parts of the first mmap() are still
* around.
*/
self->size2 = self->pagesize;
self->addr2 = mmap(NULL, self->pagesize, PROT_READ, MAP_SHARED,
self->dev_mem_fd, 0);
ASSERT_NE(self->addr2, MAP_FAILED);
}
TEST_F(pfnmap, mremap_fixed)
{
char *ret;
/* Reserve a destination area. */
self->size2 = self->size1;
self->addr2 = mmap(NULL, self->size2, PROT_READ, MAP_ANON | MAP_PRIVATE,
-1, 0);
ASSERT_NE(self->addr2, MAP_FAILED);
/* mremap() over our destination. */
ret = mremap(self->addr1, self->size1, self->size2,
MREMAP_FIXED | MREMAP_MAYMOVE, self->addr2);
ASSERT_NE(ret, MAP_FAILED);
}
TEST_F(pfnmap, mremap_shrink)
{
char *ret;
/* Shrinking is expected to work. */
ret = mremap(self->addr1, self->size1, self->size1 - self->pagesize, 0);
ASSERT_NE(ret, MAP_FAILED);
}
TEST_F(pfnmap, mremap_expand)
{
/*
* Growing is not expected to work, and getting it right would
* be challenging. So this test primarily serves as an early warning
* that something that probably should never work suddenly works.
*/
self->size2 = self->size1 + self->pagesize;
self->addr2 = mremap(self->addr1, self->size1, self->size2, MREMAP_MAYMOVE);
ASSERT_EQ(self->addr2, MAP_FAILED);
}
TEST_F(pfnmap, fork)
{
pid_t pid;
int ret;
/* fork() a child and test if the child can access the pages. */
pid = fork();
ASSERT_GE(pid, 0);
if (!pid) {
EXPECT_EQ(test_read_access(self->addr1, self->size1,
self->pagesize), 0);
exit(0);
}
wait(&ret);
if (WIFEXITED(ret))
ret = WEXITSTATUS(ret);
else
ret = -EINVAL;
ASSERT_EQ(ret, 0);
}
TEST_HARNESS_MAIN
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