[LTP] [PATCH 09/29] Hugetlb: Migrating libhugetlbfs fork-cow
Cyril Hrubis
chrubis@suse.cz
Mon Oct 17 15:45:03 CEST 2022
Hi!
> Migrating the libhugetlbfs/testcases/fork-cow.c test
>
> Test Description: This checks copy-on-write semantics, specifically the
> semantics of a MAP_PRIVATE mapping across a fork(). Some versions of the
> powerpc kernel had a bug in huge_ptep_set_wrprotect() which would fail to
> flush the hash table after setting the write protect bit in the parent's
> page tables, thus allowing the parent to pollute the child's mapping.
>
> Signed-off-by: Tarun Sahu <tsahu@linux.ibm.com>
> ---
> runtest/hugetlb | 2 +
> testcases/kernel/mem/.gitignore | 1 +
> .../kernel/mem/hugetlb/hugefork/Makefile | 10 +
> .../kernel/mem/hugetlb/hugefork/hugefork01.c | 220 ++++++++++++++++++
> 4 files changed, 233 insertions(+)
> create mode 100644 testcases/kernel/mem/hugetlb/hugefork/Makefile
> create mode 100644 testcases/kernel/mem/hugetlb/hugefork/hugefork01.c
>
> diff --git a/runtest/hugetlb b/runtest/hugetlb
> index ec1fc2515..4c16e1e7c 100644
> --- a/runtest/hugetlb
> +++ b/runtest/hugetlb
> @@ -1,6 +1,8 @@
> hugefallocate01 hugefallocate01
> hugefallocate02 hugefallocate02
>
> +hugefork01 hugefork01
> +
> hugemmap01 hugemmap01
> hugemmap02 hugemmap02
> hugemmap04 hugemmap04
> diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
> index c0906f3d3..adea760c7 100644
> --- a/testcases/kernel/mem/.gitignore
> +++ b/testcases/kernel/mem/.gitignore
> @@ -1,6 +1,7 @@
> /cpuset/cpuset01
> /hugetlb/hugefallocate/hugefallocate01
> /hugetlb/hugefallocate/hugefallocate02
> +/hugetlb/hugefork/hugefork01
> /hugetlb/hugemmap/hugemmap01
> /hugetlb/hugemmap/hugemmap02
> /hugetlb/hugemmap/hugemmap04
> diff --git a/testcases/kernel/mem/hugetlb/hugefork/Makefile b/testcases/kernel/mem/hugetlb/hugefork/Makefile
> new file mode 100644
> index 000000000..77ebb0aef
> --- /dev/null
> +++ b/testcases/kernel/mem/hugetlb/hugefork/Makefile
> @@ -0,0 +1,10 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +# Copyright (C) 2009, Cisco Systems Inc.
> +# Ngie Cooper, July 2009
> +
> +top_srcdir ?= ../../../../..
> +
> +include $(top_srcdir)/include/mk/testcases.mk
> +include $(abs_srcdir)/../Makefile.inc
> +include $(top_srcdir)/include/mk/generic_leaf_target.mk
> +
> diff --git a/testcases/kernel/mem/hugetlb/hugefork/hugefork01.c b/testcases/kernel/mem/hugetlb/hugefork/hugefork01.c
> new file mode 100644
> index 000000000..096ff0c4d
> --- /dev/null
> +++ b/testcases/kernel/mem/hugetlb/hugefork/hugefork01.c
> @@ -0,0 +1,220 @@
> +// SPDX-License-Identifier: LGPL-2.1-or-later
> +/*
> + * Copyright (C) 2008 David Gibson, IBM Corporation.
> + *
> + * Test Name: fork COW
> + *
> + * Test Description: This checks copy-on-write semantics, specifically the
> + * semantics of a MAP_PRIVATE mapping across a fork(). Some versions of the
> + * powerpc kernel had a bug in huge_ptep_set_wrprotect() which would fail to
> + * flush the hash table after setting the write protect bit in the parent's
> + * page tables, thus allowing the parent to pollute the child's mapping.
> + *
> + * HISTORY
> + * Written by David Gibson
> + *
> + */
> +
> +#define _GNU_SOURCE
> +
> +
> +#include <sys/shm.h>
> +#include <sys/wait.h>
> +#include <sys/mman.h>
> +#include <errno.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <sys/mount.h>
> +#include <limits.h>
> +#include <sys/param.h>
> +#include <sys/types.h>
> +
> +#include "hugetlb.h"
> +
> +#define RANDOM_CONSTANT 0x1234ABCD
> +#define OTHER_CONSTANT 0xfeef5678
> +
> +static int fd = -1;
> +static char hfile[MAXPATHLEN];
> +static long hpage_size;
> +static char *verbose;
> +
> +/*
> + * The parent uses this to check if the child terminated badly.
> + */
> +static void sigchld_handler(int signum, siginfo_t *si, void *uc)
> +{
> + (void)signum;
> + (void)uc;
> + if (WEXITSTATUS(si->si_status) != 0) {
> + tst_res(TFAIL, "Child failed: %d", WEXITSTATUS(si->si_status));
> + goto fail;
> + }
> + if (WIFSIGNALED(si->si_status)) {
> + tst_res(TFAIL, "Child recived signal %s",
> + strsignal(WTERMSIG(si->si_status)));
> + goto fail;
> + }
> + return;
> +fail:
> + tst_brk(TBROK, "Once failed, No point in continuing the test");
You cannot call tst_* functions from a signal handler, these are not
async-signal-safe.
The only sensible thing to use the value filled in by the waitpid() call
instead.
> +}
> +
> +static void run_test(void)
> +{
> + int status;
> + void *syncarea;
> + volatile unsigned int *p;
> + volatile unsigned int *trigger, *child_readback;
> + int parent_readback;
> + pid_t pid;
> + struct sigaction sa = {
> + .sa_sigaction = sigchld_handler,
> + .sa_flags = SA_SIGINFO,
> + };
> +
> + /* Get a shared normal page for synchronization */
> + if (verbose)
> + tst_res(TINFO, "Mapping synchronization area..");
> + syncarea = SAFE_MMAP(NULL, getpagesize(), PROT_READ|PROT_WRITE,
> + MAP_SHARED|MAP_ANONYMOUS, -1, 0);
> + if (verbose)
> + tst_res(TINFO, "done");
> +
> + trigger = syncarea;
> + *trigger = 0;
> +
> + child_readback = trigger + 1;
> + *child_readback = 0;
> +
> + fd = SAFE_OPEN(hfile, O_RDWR | O_CREAT, 0600);
> + SAFE_UNLINK(hfile);
> +
> + if (verbose)
> + tst_res(TINFO, "Mapping hugepage area...");
> + p = SAFE_MMAP(NULL, hpage_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
> + if (verbose)
> + tst_res(TINFO, "mapped at %p", p);
> + /* Touch the page for write in parent */
> + if (verbose)
> + tst_res(TINFO, "Parent writes pre-fork...");
> + *p = RANDOM_CONSTANT;
> + if (verbose)
> + tst_res(TINFO, "%x", RANDOM_CONSTANT);
> +
> + SAFE_SIGACTION(SIGCHLD, &sa, NULL);
> +
> + pid = SAFE_FORK();
> +
> + if (pid != 0) {
> + /* Parent */
Useless comment again.
> + if (verbose)
> + tst_res(TINFO, "Parent writes post-fork...");
> + *p = ~RANDOM_CONSTANT;
> + if (verbose)
> + tst_res(TINFO, "~RANDOM_CONSTANT: %x", ~RANDOM_CONSTANT);
> + *trigger = 1;
We do have checkpoint library exactly for synchronization between parent
and child make use of them, see TST_CHECKPOINT_*.
> + while (*trigger != 2)
> + ;
> +
> + if (verbose)
> + tst_res(TINFO, "Parent reads..");
I would be inclined to remove these "Parent does xyz" and "Child does abc"
messages from test once we make use of the CHECKPOINTs the
synchronization is guaranteed to be right.
> + parent_readback = *p;
> + if (verbose)
> + tst_res(TINFO, "Parent readback: %x", parent_readback);
> + *trigger = 3;
> + } else {
> + /* Child */
Here as well.
> + if (verbose)
> + tst_res(TINFO, "Child starts..");
> + while (*trigger != 1)
> + ;
> +
> + if (verbose)
> + tst_res(TINFO, "Child reads...");
> + *child_readback = *p;
> + if (verbose) {
> + tst_res(TINFO, "child readback: %x", *child_readback);
> + tst_res(TINFO, "Child writes...");
> + }
> + *p = OTHER_CONSTANT;
> + if (verbose)
> + tst_res(TINFO, "OTHER_CONSTANT: %x", OTHER_CONSTANT);
> +
> + *trigger = 2;
> +
> + while (*trigger != 3)
> + ;
> + if (verbose)
> + tst_res(TINFO, "Child exits...");
> + exit(0);
> + }
> +
> + if (verbose)
> + tst_res(TINFO, "child_readback = 0x%x, parent_readback = 0x%x\n",
> + *child_readback, parent_readback);
> +
> + if (*child_readback != RANDOM_CONSTANT) {
> + tst_res(TFAIL, "Child read back 0x%x instead of 0x%x",
> + *child_readback, RANDOM_CONSTANT);
> + goto fail;
> + }
> + if (parent_readback != ~RANDOM_CONSTANT) {
> + tst_res(TFAIL, "Parent read back 0x%x instead of 0x%x",
> + parent_readback, RANDOM_CONSTANT);
> + goto fail;
> + }
> +
> + SAFE_WAITPID(pid, &status, 0);
> +
> + tst_res(TPASS, "Successful");
> + SAFE_MUNMAP((void *)p, hpage_size);
> + SAFE_MUNMAP(syncarea, getpagesize());
> + SAFE_CLOSE(fd);
> + return;
> +fail:
> + tst_brk(TBROK, "Once failed, No point in continuing the test");
Here as well.
> +}
> +
> +static void setup(void)
> +{
> + int free_pages = SAFE_READ_MEMINFO("HugePages_Free:");
> +
> + if (tst_hugepages < 2 || free_pages < 2)
> + tst_brk(TCONF, "Not enough hugepages for testing.");
> +
> + if (!Hopt)
> + Hopt = tst_get_tmpdir();
> + SAFE_MOUNT("none", Hopt, "hugetlbfs", 0, NULL);
> +
> + snprintf(hfile, sizeof(hfile), "%s/ltp_hugetlbfile%d", Hopt, getpid());
> + hpage_size = SAFE_READ_MEMINFO("Hugepagesize:")*1024;
> +}
> +
> +static void cleanup(void)
> +{
> + if (fd >= 0)
> + SAFE_CLOSE(fd);
> + umount2(Hopt, MNT_DETACH);
Here as well.
> +}
> +
> +static struct tst_test test = {
> + .needs_root = 1,
> + .needs_tmpdir = 1,
> + .options = (struct tst_option[]) {
> + {"v", &verbose, "Turns on verbose mode"},
> + {"H:", &Hopt, "Location of hugetlbfs, i.e. -H /var/hugetlbfs"},
> + {"s:", &nr_opt, "Set the number of the been allocated hugepages"},
> + {}
> + },
> + .forks_child = 1,
> + .setup = setup,
> + .cleanup = cleanup,
> + .test_all = run_test,
> + .hugepages = {2, TST_REQUEST},
> +};
> --
> 2.31.1
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
--
Cyril Hrubis
chrubis@suse.cz
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