[LTP] [LTP PATCH v2 1/1] madvise11: Add test for memory allocation / Soft-offlining possible race
Richard Palethorpe
rpalethorpe@suse.de
Mon Feb 13 11:00:01 CET 2023
Hello,
william.roche@oracle.com writes:
> From: William Roche <william.roche@oracle.com>
>
> Test a possible race condition between mmap() allocating memory and
> madvise() used to Soft-offline an unrelated memory page.
> As fixed with the following kernel commit:
> d4ae9916ea29 mm: soft-offline: close the race against page allocation
>
> If everything works, restore all poisoned pages created by this test.
OK, I think there is just some LTP specific stuff left to fix and
setup/teardown issues.
>
> Signed-off-by: William Roche <william.roche@oracle.com>
> ---
> runtest/syscalls | 1 +
> testcases/kernel/syscalls/madvise/.gitignore | 1 +
> testcases/kernel/syscalls/madvise/Makefile | 3 +
> testcases/kernel/syscalls/madvise/madvise11.c | 405 ++++++++++++++++++
> 4 files changed, 410 insertions(+)
> create mode 100644 testcases/kernel/syscalls/madvise/madvise11.c
>
> diff --git a/runtest/syscalls b/runtest/syscalls
> index ae37a1192..54098c4d9 100644
> --- a/runtest/syscalls
> +++ b/runtest/syscalls
> @@ -947,6 +947,7 @@ madvise07 madvise07
> madvise08 madvise08
> madvise09 madvise09
> madvise10 madvise10
> +madvise11 madvise11
>
> newuname01 newuname01
>
> diff --git a/testcases/kernel/syscalls/madvise/.gitignore b/testcases/kernel/syscalls/madvise/.gitignore
> index f4bfdfefe..722ac3c34 100644
> --- a/testcases/kernel/syscalls/madvise/.gitignore
> +++ b/testcases/kernel/syscalls/madvise/.gitignore
> @@ -7,3 +7,4 @@
> /madvise08
> /madvise09
> /madvise10
> +/madvise11
> diff --git a/testcases/kernel/syscalls/madvise/Makefile b/testcases/kernel/syscalls/madvise/Makefile
> index 044619fb8..9664c9ae2 100644
> --- a/testcases/kernel/syscalls/madvise/Makefile
> +++ b/testcases/kernel/syscalls/madvise/Makefile
> @@ -6,3 +6,6 @@ top_srcdir ?= ../../../..
> include $(top_srcdir)/include/mk/testcases.mk
>
> include $(top_srcdir)/include/mk/generic_leaf_target.mk
> +
> +madvise11: CFLAGS += -pthread
> +
> diff --git a/testcases/kernel/syscalls/madvise/madvise11.c b/testcases/kernel/syscalls/madvise/madvise11.c
> new file mode 100644
> index 000000000..d55a69457
> --- /dev/null
> +++ b/testcases/kernel/syscalls/madvise/madvise11.c
> @@ -0,0 +1,405 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2023 Oracle and/or its affiliates.
> + */
> +
> +/*\
> + * [Description]
> + *
> + * Stress a possible race condition between memory pages allocation
> + * and soft-offline of unrelated pages as explained in the commit:
> + * d4ae9916ea29 (mm: soft-offline: close the race against page allocation)
> + *
> + * Control that soft-offlined pages get correctly replaced: with the
> + * same content and without SIGBUS generation when accessed.
> + */
> +
> +#include <errno.h>
> +#include <pthread.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <time.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +#include <sys/mman.h>
> +#include <sys/klog.h>
> +
> +#include "tst_test.h"
> +#include "tst_safe_pthread.h"
> +#include "tst_safe_stdio.h"
> +#include "lapi/mmap.h"
> +
> +#define NUM_LOOPS 5
> +#define NUM_PAGES 32
> +#define NUM_PAGES_OFFSET 5
> +
> +/* Needed module to online back memory pages */
> +#define HW_MODULE "hwpoison_inject"
> +
> +static pthread_t *thread_ids;
> +static int number_threads;
> +static int run_iterations;
> +static int maximum_pfns;
> +
> +static long pagesize;
> +static char beginning_tag[BUFSIZ];
> +static int hwpoison_probe;
> +
> +
> +static void my_yield(void)
> +{
> + static const struct timespec t0 = { 0, 0 };
> +
> + nanosleep(&t0, NULL);
> +}
> +
> +/* a SIGBUS received is a confirmation of test failure */
> +static void sigbus_handler(int signum)
> +{
> + tst_res(TFAIL, "SIGBUS Received");
Using tst_res in a signal handler is not safe although it usually
works. Possibly it will result in some confusing output on some systems.
Could we just set a global and read it later or drop it?
> + _exit(signum);
> +}
> +
> +/*
> + * Allocate a page and write a sentinel value into it.
> + */
> +static void *allocate_write(int sentinel)
> +{
> + void *p;
> + int *s;
> +
> + p = mmap(NULL, pagesize, PROT_READ|PROT_WRITE,
> + MAP_SHARED|MAP_ANONYMOUS, -1, 0);
> + if (p == MAP_FAILED) {
> + tst_brk(TBROK | TTERRNO, "mmap unexpected error");
> + return NULL;
> + }
Is this duplicating SAFE_MMAP?
I think mmap and the if statement can be replaced with it.
> + s = (int *)p;
> + *s = sentinel;
> + return p;
> +}
> +
> +/*
> + * Verify and unmap the given page.
> + */
> +static int verif_unmap(void *page, int sentinel)
> +{
> + int *s = (int *)page;
> + int ret;
> +
> + if (*s != sentinel) {
> + tst_res(TFAIL, "pid[%d]: fail: bad sentinel value seen: %d expected: %d\n", getpid(), *s, sentinel);
> + return 1;
> + }
> +
> + ret = munmap(page, pagesize);
> + if (ret == -1)
> + tst_res(TINFO | TTERRNO, "munmap unexpected error");
Same here with munmap and SAFE_MUNMAP.
> +
> + return ret;
> +}
> +
> +/*
> + * allocate_offline() - Allocate and offline test called per-thread
> + *
> + * This function does the allocation and offline by mmapping an
> + * anonymous page and offlining it.
> + */
> +static int allocate_offline(int tnum)
> +{
> + int loop;
> +
> + for (loop = 0; loop < NUM_LOOPS; loop++) {
> + long *ptrs[NUM_PAGES];
> + int num_alloc;
> + int i;
> +
> + for (num_alloc = 0; num_alloc < NUM_PAGES; num_alloc++) {
> +
> + ptrs[num_alloc] = allocate_write((tnum << NUM_PAGES_OFFSET) | num_alloc);
> + if (ptrs[num_alloc] == NULL)
> + return -1;
> +
> + if (madvise(ptrs[num_alloc], pagesize, MADV_SOFT_OFFLINE) == -1) {
> + if (errno != EINVAL)
> + tst_res(TFAIL | TERRNO, "madvise failed");
> + if (errno == EINVAL)
> + tst_res(TCONF, "madvise() didn't support MADV_SOFT_OFFLINE");
> + return errno;
> + }
> + }
> +
> + for (i = 0; i < num_alloc; i++) {
> + if (verif_unmap(ptrs[i], (tnum << NUM_PAGES_OFFSET) | i) != 0)
> + return 1;
> + }
> +
> + my_yield();
> + if (!tst_remaining_runtime()) {
> + tst_res(TINFO, "Thread [%d]: Test runtime is over, exiting", tnum);
> + break;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static void *alloc_mem(void *threadnum)
> +{
> + int err;
> + int tnum = (int)(uintptr_t)threadnum;
> +
> + /* waiting for other threads starting */
> + TST_CHECKPOINT_WAIT(0);
> +
> + err = allocate_offline(tnum);
> + tst_res(TINFO,
> + "Thread [%d] returned %d, %s.", tnum, err, (err ? "failed" : "succeeded"));
> + return (void *)(uintptr_t) (err ? -1 : 0);
> +}
> +
> +static void stress_alloc_offl(void)
> +{
> + int thread_index;
> + int thread_failure = 0;
> +
> + run_iterations++;
> +
> + for (thread_index = 0; thread_index < number_threads; thread_index++) {
> + SAFE_PTHREAD_CREATE(&thread_ids[thread_index], NULL, alloc_mem,
> + (void *)(uintptr_t)thread_index);
> + }
> +
> + TST_CHECKPOINT_WAKE2(0, number_threads);
> +
> + for (thread_index = 0; thread_index < number_threads; thread_index++) {
> + void *status;
> +
> + SAFE_PTHREAD_JOIN(thread_ids[thread_index], &status);
> + if ((intptr_t)status != 0) {
> + tst_res(TFAIL, "thread [%d] - exited with errors",
> + thread_index);
> + thread_failure++;
> + }
> + }
> +
> + if (thread_failure == 0)
> + tst_res(TPASS, "soft-offline / mmap race still clean");
> +}
> +
> +/*
> + * ------------
> + * Cleanup code:
> + * The idea is to retrieve all the pfn numbers that have been soft-offined
> + * (generating a "Soft offlining pfn 0x..." message in the kernel ring buffer)
> + * by the current test (since a "beginning_tag" message we write when starting).
> + * And to put these pages back online by writing the pfn number to the
> + * <debugfs>/hwpoison/unpoison-pfn special file.
> + * ------------
> + */
> +#define OFFLINE_PATTERN "Soft offlining pfn 0x"
> +#define OFFLINE_PATTERN_LEN sizeof(OFFLINE_PATTERN)
> +
> +/* return the pfn if the kmsg msg is a soft-offline indication*/
> +static unsigned long parse_kmsg_soft_offlined_pfn(char *line, ssize_t len)
> +{
> + char *pos;
> + unsigned long addr = 0UL;
> +
> + pos = strstr(line, OFFLINE_PATTERN);
> + if (pos == NULL)
> + return 0UL;
> +
> + pos += OFFLINE_PATTERN_LEN-1;
> + if (pos > (line + len))
> + return 0UL;
> +
> + addr = strtoul(pos, NULL, 16);
> + if ((addr == ULONG_MAX) && (errno == ERANGE))
> + return 0UL;
> +
> + return addr;
> +}
> +
> +/* return the pfns seen in kernel message log */
> +static int populate_from_klog(char *begin_tag, unsigned long *pfns, int max)
> +{
> + int found = 0, fd, beginning_tag_found = 0;
> + ssize_t sz;
> + unsigned long pfn;
> + char buf[BUFSIZ];
> +
> + fd = SAFE_OPEN("/dev/kmsg", O_RDONLY|O_NONBLOCK);
> +
> + while (found < max) {
> + sz = read(fd, buf, sizeof(buf));
> + /* kmsg returns EPIPE if record was modified while reading */
> + if (sz < 0 && errno == EPIPE)
> + continue;
> + if (sz <= 0)
> + break;
> + if (!beginning_tag_found) {
> + if (strstr(buf, begin_tag))
> + beginning_tag_found = 1;
> + continue;
> + }
> + pfn = parse_kmsg_soft_offlined_pfn(buf, sz);
> + if (pfn)
> + pfns[found++] = pfn;
> + }
> + SAFE_CLOSE(fd);
> + return found;
> +}
> +
> +/*
> + * Read the given file to search for the key.
> + * If a valuePtr is given, copy the remaining of the line right
> + * after the found key to the given location.
> + * Return 1 if the key is found.
> + */
> +static int find_in_file(char *path, char *key, char *valuePtr)
nit: we don't use camel case. Although I think this function can be
replaced, see below.
> +{
> + char line[4096];
> + char *pos = NULL;
> + int found = 0;
> + FILE *file = SAFE_FOPEN(path, "r");
> +
> + while (fgets(line, sizeof(line), file)) {
> + pos = strstr(line, key);
> + if (pos) {
> + found = 1;
> + if (valuePtr)
> + strncpy(valuePtr, pos + strlen(key),
> + line + strlen(line) - pos);
> + break;
> + }
> + }
> + SAFE_FCLOSE(file);
> + return found;
> +}
> +
> +static void unpoison_this_pfn(unsigned long pfn, int fd)
> +{
> + char pfn_str[19];
> +
> + snprintf(pfn_str, sizeof(pfn_str), "0x%lx", pfn);
> + SAFE_WRITE(0, fd, pfn_str, strlen(pfn_str));
> +}
> +
> +/* Find and open the <debugfs>/hwpoison/unpoison-pfn special file */
> +static int open_unpoison_pfn(void)
> +{
> + char *added_file_path = "/hwpoison/unpoison-pfn";
> + const char *const cmd_modprobe[] = {"modprobe", HW_MODULE, NULL};
> + char debugfs_fp[4096];
> +
> + if (!find_in_file("/proc/modules", HW_MODULE, NULL))
> + hwpoison_probe = 1;
> +
> + /* probe hwpoison only if it isn't already there */
> + if (hwpoison_probe)
> + SAFE_CMD(cmd_modprobe, NULL, NULL);
> +
> + /* debugfs mount point */
> + if (find_in_file("/etc/mtab", "debugfs ", debugfs_fp) == 0)
Scanning mtab with strstr is fragile, at the least "debugfs" can appear
in a path. Instead please use setmntent and getmntent (you can copy &
paste from tst_device or tst_cgroup). Or scanf the whole line etc.
--
Thank you,
Richard.
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