// SPDX-License-Identifier: GPL-2.0-only
/*
 * Test handling of code that might set PTE/PMD dirty in read-only VMAs.
 * Setting a PTE/PMD dirty must not accidentally set the PTE/PMD writable.
 *
 * Copyright 2023, Red Hat, Inc.
 *
 * Author(s): David Hildenbrand <david@redhat.com>
 */
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>
#include <sys/mman.h>
#include <setjmp.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <linux/userfaultfd.h>
#include <linux/mempolicy.h>

#include "kselftest.h"
#include "vm_util.h"

static size_t pagesize;
static size_t thpsize;
static int mem_fd;
static int pagemap_fd;
static sigjmp_buf env;

static void signal_handler(int sig)
{
        if (sig == SIGSEGV)
                siglongjmp(env, 1);
        siglongjmp(env, 2);
}

static void do_test_write_sigsegv(char *mem)
{
        char orig = *mem;
        int ret;

        if (signal(SIGSEGV, signal_handler) == SIG_ERR) {
                ksft_test_result_fail("signal() failed\n");
                return;
        }

        ret = sigsetjmp(env, 1);
        if (!ret)
                *mem = orig + 1;

        if (signal(SIGSEGV, SIG_DFL) == SIG_ERR)
                ksft_test_result_fail("signal() failed\n");

        ksft_test_result(ret == 1 && *mem == orig,
                         "SIGSEGV generated, page not modified\n");
}

static char *mmap_thp_range(int prot, char **_mmap_mem, size_t *_mmap_size)
{
        const size_t mmap_size = 2 * thpsize;
        char *mem, *mmap_mem;

        mmap_mem = mmap(NULL, mmap_size, prot, MAP_PRIVATE|MAP_ANON,
                        -1, 0);
        if (mmap_mem == MAP_FAILED) {
                ksft_test_result_fail("mmap() failed\n");
                return MAP_FAILED;
        }
        mem = (char *)(((uintptr_t)mmap_mem + thpsize) & ~(thpsize - 1));

        if (madvise(mem, thpsize, MADV_HUGEPAGE)) {
                ksft_test_result_skip("MADV_HUGEPAGE failed\n");
                munmap(mmap_mem, mmap_size);
                return MAP_FAILED;
        }

        *_mmap_mem = mmap_mem;
        *_mmap_size = mmap_size;
        return mem;
}

static void test_ptrace_write(void)
{
        char data = 1;
        char *mem;
        int ret;

        ksft_print_msg("[INFO] PTRACE write access\n");

        mem = mmap(NULL, pagesize, PROT_READ, MAP_PRIVATE|MAP_ANON, -1, 0);
        if (mem == MAP_FAILED) {
                ksft_test_result_fail("mmap() failed\n");
                return;
        }

        /* Fault in the shared zeropage. */
        if (*mem != 0) {
                ksft_test_result_fail("Memory not zero\n");
                goto munmap;
        }

        /*
         * Unshare the page (populating a fresh anon page that might be set
         * dirty in the PTE) in the read-only VMA using ptrace (FOLL_FORCE).
         */
        lseek(mem_fd, (uintptr_t) mem, SEEK_SET);
        ret = write(mem_fd, &data, 1);
        if (ret != 1 || *mem != data) {
                ksft_test_result_fail("write() failed\n");
                goto munmap;
        }

        do_test_write_sigsegv(mem);
munmap:
        munmap(mem, pagesize);
}

static void test_ptrace_write_thp(void)
{
        char *mem, *mmap_mem;
        size_t mmap_size;
        char data = 1;
        int ret;

        ksft_print_msg("[INFO] PTRACE write access to THP\n");

        mem = mmap_thp_range(PROT_READ, &mmap_mem, &mmap_size);
        if (mem == MAP_FAILED)
                return;

        /*
         * Write to the first subpage in the read-only VMA using
         * ptrace(FOLL_FORCE), eventually placing a fresh THP that is marked
         * dirty in the PMD.
         */
        lseek(mem_fd, (uintptr_t) mem, SEEK_SET);
        ret = write(mem_fd, &data, 1);
        if (ret != 1 || *mem != data) {
                ksft_test_result_fail("write() failed\n");
                goto munmap;
        }

        /* MM populated a THP if we got the last subpage populated as well. */
        if (!pagemap_is_populated(pagemap_fd, mem + thpsize - pagesize)) {
                ksft_test_result_skip("Did not get a THP populated\n");
                goto munmap;
        }

        do_test_write_sigsegv(mem);
munmap:
        munmap(mmap_mem, mmap_size);
}

static void test_page_migration(void)
{
        char *mem;

        ksft_print_msg("[INFO] Page migration\n");

        mem = mmap(NULL, pagesize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON,
                   -1, 0);
        if (mem == MAP_FAILED) {
                ksft_test_result_fail("mmap() failed\n");
                return;
        }

        /* Populate a fresh page and dirty it. */
        memset(mem, 1, pagesize);
        if (mprotect(mem, pagesize, PROT_READ)) {
                ksft_test_result_fail("mprotect() failed\n");
                goto munmap;
        }

        /* Trigger page migration. Might not be available or fail. */
        if (syscall(__NR_mbind, mem, pagesize, MPOL_LOCAL, NULL, 0x7fful,
                    MPOL_MF_MOVE)) {
                ksft_test_result_skip("mbind() failed\n");
                goto munmap;
        }

        do_test_write_sigsegv(mem);
munmap:
        munmap(mem, pagesize);
}

static void test_page_migration_thp(void)
{
        char *mem, *mmap_mem;
        size_t mmap_size;

        ksft_print_msg("[INFO] Page migration of THP\n");

        mem = mmap_thp_range(PROT_READ|PROT_WRITE, &mmap_mem, &mmap_size);
        if (mem == MAP_FAILED)
                return;

        /*
         * Write to the first page, which might populate a fresh anon THP
         * and dirty it.
         */
        memset(mem, 1, pagesize);
        if (mprotect(mem, thpsize, PROT_READ)) {
                ksft_test_result_fail("mprotect() failed\n");
                goto munmap;
        }

        /* MM populated a THP if we got the last subpage populated as well. */
        if (!pagemap_is_populated(pagemap_fd, mem + thpsize - pagesize)) {
                ksft_test_result_skip("Did not get a THP populated\n");
                goto munmap;
        }

        /* Trigger page migration. Might not be available or fail. */
        if (syscall(__NR_mbind, mem, thpsize, MPOL_LOCAL, NULL, 0x7fful,
                    MPOL_MF_MOVE)) {
                ksft_test_result_skip("mbind() failed\n");
                goto munmap;
        }

        do_test_write_sigsegv(mem);
munmap:
        munmap(mmap_mem, mmap_size);
}

static void test_pte_mapped_thp(void)
{
        char *mem, *mmap_mem;
        size_t mmap_size;

        ksft_print_msg("[INFO] PTE-mapping a THP\n");

        mem = mmap_thp_range(PROT_READ|PROT_WRITE, &mmap_mem, &mmap_size);
        if (mem == MAP_FAILED)
                return;

        /*
         * Write to the first page, which might populate a fresh anon THP
         * and dirty it.
         */
        memset(mem, 1, pagesize);
        if (mprotect(mem, thpsize, PROT_READ)) {
                ksft_test_result_fail("mprotect() failed\n");
                goto munmap;
        }

        /* MM populated a THP if we got the last subpage populated as well. */
        if (!pagemap_is_populated(pagemap_fd, mem + thpsize - pagesize)) {
                ksft_test_result_skip("Did not get a THP populated\n");
                goto munmap;
        }

        /* Trigger PTE-mapping the THP by mprotect'ing the last subpage. */
        if (mprotect(mem + thpsize - pagesize, pagesize,
                     PROT_READ|PROT_WRITE)) {
                ksft_test_result_fail("mprotect() failed\n");
                goto munmap;
        }

        do_test_write_sigsegv(mem);
munmap:
        munmap(mmap_mem, mmap_size);
}

#ifdef __NR_userfaultfd
static void test_uffdio_copy(void)
{
        struct uffdio_register uffdio_register;
        struct uffdio_copy uffdio_copy;
        struct uffdio_api uffdio_api;
        char *dst, *src;
        int uffd;

        ksft_print_msg("[INFO] UFFDIO_COPY\n");

        src = malloc(pagesize);
        memset(src, 1, pagesize);
        dst = mmap(NULL, pagesize, PROT_READ, MAP_PRIVATE|MAP_ANON, -1, 0);
        if (dst == MAP_FAILED) {
                ksft_test_result_fail("mmap() failed\n");
                free(src);
                return;
        }

        uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
        if (uffd < 0) {
                ksft_test_result_skip("__NR_userfaultfd failed\n");
                goto munmap;
        }

        uffdio_api.api = UFFD_API;
        uffdio_api.features = 0;
        if (ioctl(uffd, UFFDIO_API, &uffdio_api) < 0) {
                ksft_test_result_fail("UFFDIO_API failed\n");
                goto close_uffd;
        }

        uffdio_register.range.start = (unsigned long) dst;
        uffdio_register.range.len = pagesize;
        uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
        if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) {
                ksft_test_result_fail("UFFDIO_REGISTER failed\n");
                goto close_uffd;
        }

        /* Place a page in a read-only VMA, which might set the PTE dirty. */
        uffdio_copy.dst = (unsigned long) dst;
        uffdio_copy.src = (unsigned long) src;
        uffdio_copy.len = pagesize;
        uffdio_copy.mode = 0;
        if (ioctl(uffd, UFFDIO_COPY, &uffdio_copy)) {
                ksft_test_result_fail("UFFDIO_COPY failed\n");
                goto close_uffd;
        }

        do_test_write_sigsegv(dst);
close_uffd:
        close(uffd);
munmap:
        munmap(dst, pagesize);
        free(src);
}
#endif /* __NR_userfaultfd */

int main(void)
{
        int err, tests = 2;

        pagesize = getpagesize();
        thpsize = read_pmd_pagesize();
        if (thpsize) {
                ksft_print_msg("[INFO] detected THP size: %zu KiB\n",
                               thpsize / 1024);
                tests += 3;
        }
#ifdef __NR_userfaultfd
        tests += 1;
#endif /* __NR_userfaultfd */

        ksft_print_header();
        ksft_set_plan(tests);

        mem_fd = open("/proc/self/mem", O_RDWR);
        if (mem_fd < 0)
                ksft_exit_fail_msg("opening /proc/self/mem failed\n");
        pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
        if (pagemap_fd < 0)
                ksft_exit_fail_msg("opening /proc/self/pagemap failed\n");

        /*
         * On some ptrace(FOLL_FORCE) write access via /proc/self/mem in
         * read-only VMAs, the kernel may set the PTE/PMD dirty.
         */
        test_ptrace_write();
        if (thpsize)
                test_ptrace_write_thp();
        /*
         * On page migration, the kernel may set the PTE/PMD dirty when
         * remapping the page.
         */
        test_page_migration();
        if (thpsize)
                test_page_migration_thp();
        /* PTE-mapping a THP might propagate the dirty PMD bit to the PTEs. */
        if (thpsize)
                test_pte_mapped_thp();
        /* Placing a fresh page via userfaultfd may set the PTE dirty. */
#ifdef __NR_userfaultfd
        test_uffdio_copy();
#endif /* __NR_userfaultfd */

        err = ksft_get_fail_cnt();
        if (err)
                ksft_exit_fail_msg("%d out of %d tests failed\n",
                                   err, ksft_test_num());
        ksft_exit_pass();
}