shared shadow vm object invalidation regression test
Add a regression test for a scenario where a shadow vm object is shared
by multiple mappings. If a page COW occurs through one of the mappings,
then the virtual-to-physical mapping may become invalidated.
This tests the scenario from CVE-2021-29626 which was fixed by
982693bb72.
Reviewed by: markj
Sponsored by: Dell EMC Isilon
This commit is contained in:
Ryan Libby
parent
2b1d0c0087
commit
13d4f96130
@ -6,6 +6,7 @@ TESTSDIR= ${TESTSBASE}/sys/vm
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ATF_TESTS_C+= mlock_test \
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mmap_test \
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page_fault_signal
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page_fault_signal \
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shared_shadow_inval_test
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.include <bsd.test.mk>
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360
tests/sys/vm/shared_shadow_inval_test.c
Normal file
360
tests/sys/vm/shared_shadow_inval_test.c
Normal file
@ -0,0 +1,360 @@
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/*
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* Copyright (c) 2021 Dell Inc. or its subsidiaries. All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Test behavior when a mapping of a shared shadow vm object is
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* invalidated by COW from another mapping.
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*
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* This is a regression test for an issue isolated by rlibby@FreeBSD.org
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* from an issue detected by stress2's collapse.sh by jeff@FreeBSD.org.
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* The issue became CVE-2021-29626.
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*
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* This file is written as an ATF test suite but may be compiled as a
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* standalone program with -DSTANDALONE (and optionally -DDEBUG).
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*/
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <sys/procctl.h>
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#include <sys/wait.h>
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#include <machine/atomic.h>
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#include <err.h>
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#include <errno.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#ifdef STANDALONE
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#define ATF_REQUIRE(x) do { \
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if (!(x)) \
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errx(1, "%s", #x); \
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} while (0)
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#else
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#include <atf-c.h>
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#endif
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#ifdef DEBUG
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#define dprintf(...) printf(__VA_ARGS__)
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#else
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#define dprintf(...)
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#endif
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#define DEPTH 5
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struct shared_state {
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void *p;
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size_t len;
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size_t modlen;
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bool collapse;
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bool block_xfer;
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bool okay;
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volatile bool exiting[DEPTH];
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volatile bool exit;
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volatile bool p3_did_write;
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};
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static long g_pagesize;
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/*
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* Program flow. There are three or four processes that are descendants
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* of the process running the test (P0), where arrows go from parents to
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* children, and thicker arrows indicate sharing a certain memory region
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* without COW semantics:
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* P0 -> P1 -> P2 => P3
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* \=> P4
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* The main idea is that P1 maps a memory region, and that region is
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* shared with P2/P3, but with COW semantics. When P3 modifies the
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* memory, P2 ought to see that modification. P4 optionally exists to
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* defeat a COW optimization.
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*/
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#define child_err(...) do { \
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ss->exit = true; \
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err(1, __VA_ARGS__); \
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} while (0)
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#define child_errx(...) do { \
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ss->exit = true; \
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errx(1, __VA_ARGS__); \
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} while (0)
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#define SLEEP_TIME_US 1000
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static void child(struct shared_state *ss, int depth);
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static pid_t
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child_fork(struct shared_state *ss, int depth)
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{
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pid_t pid = fork();
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if (pid == -1)
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child_err("fork");
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else if (pid == 0)
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child(ss, depth);
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return pid;
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}
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static void
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child_fault(struct shared_state *ss)
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{
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size_t i;
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for (i = 0; i < ss->len; i += g_pagesize)
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(void)((volatile char *)ss->p)[i];
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}
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static void
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child_write(struct shared_state *ss, int val, size_t len)
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{
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size_t i;
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for (i = 0; i < len; i += g_pagesize)
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((int *)ss->p)[i / sizeof(int)] = val;
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atomic_thread_fence_rel();
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}
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static void
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child_wait_p3_write(struct shared_state *ss)
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{
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while (!ss->p3_did_write) {
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if (ss->exit)
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exit(1);
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usleep(SLEEP_TIME_US);
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}
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atomic_thread_fence_acq();
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}
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static void
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child_verify(struct shared_state *ss, int depth, int newval, int oldval)
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{
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size_t i;
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int expectval, foundval;
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for (i = 0; i < ss->len; i += g_pagesize) {
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expectval = i < ss->modlen ? newval : oldval;
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foundval = ((int *)ss->p)[i / sizeof(int)];
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if (foundval == expectval)
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continue;
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child_errx("P%d saw %d but expected %d, %d was the old value",
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depth, foundval, expectval, oldval);
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}
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}
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static void
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child(struct shared_state *ss, int depth)
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{
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pid_t mypid, oldval, pid;
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if (depth < 1 || depth >= DEPTH)
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child_errx("Bad depth %d", depth);
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mypid = getpid();
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dprintf("P%d (pid %d) started\n", depth, mypid);
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switch (depth) {
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case 1:
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/* Shared memory undergoing test. */
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ss->p = mmap(NULL, ss->len, PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_ANON, -1, 0);
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if (ss->p == MAP_FAILED)
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child_err("mmap");
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/* P1 stamps the shared memory. */
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child_write(ss, mypid, ss->len);
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if (ss->block_xfer) {
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/*
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* P4 is forked so that its existence blocks a page COW
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* path where the page is simply transferred between
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* objects, rather than being copied.
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*/
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child_fork(ss, 4);
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}
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/*
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* P1 specifies that modifications from its child processes not
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* be shared with P1. Child process reads can be serviced from
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* pages in P1's object, but writes must be COW'd.
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*/
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if (minherit(ss->p, ss->len, INHERIT_COPY) != 0)
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child_err("minherit");
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/* Fork P2. */
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child_fork(ss, depth + 1);
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/* P1 and P4 wait for P3's writes before exiting. */
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child_wait_p3_write(ss);
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child_verify(ss, depth, mypid, mypid);
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if (!ss->collapse) {
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/* Hang around to prevent collapse. */
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while (!ss->exit)
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usleep(SLEEP_TIME_US);
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}
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/* Exit so the P2 -> P1/P4 shadow chain can collapse. */
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break;
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case 2:
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/*
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* P2 now specifies that modifications from its child processes
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* be shared. P2 and P3 will share a shadow object.
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*/
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if (minherit(ss->p, ss->len, INHERIT_SHARE) != 0)
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child_err("minherit");
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/*
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* P2 faults a page in P1's object before P1 exits and the
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* shadow chain is collapsed.
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*/
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child_fault(ss);
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oldval = atomic_load_acq_int(ss->p);
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/* Fork P3. */
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pid = child_fork(ss, depth + 1);
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if (ss->collapse) {
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/* Wait for P1 and P4 to exit, triggering collapse. */
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while (!ss->exiting[1] ||
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(ss->block_xfer && !ss->exiting[4]))
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usleep(SLEEP_TIME_US);
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/*
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* This is racy, just guess at how long it may take
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* them to finish exiting.
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*/
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usleep(100 * 1000);
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}
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/* P2 waits for P3's modification. */
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child_wait_p3_write(ss);
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child_verify(ss, depth, pid, oldval);
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ss->okay = true;
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ss->exit = true;
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break;
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case 3:
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/*
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* P3 writes the memory. A page is faulted into the shared
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* P2/P3 shadow object. P2's mapping of the page in P1's
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* object must now be shot down, or else P2 will wrongly
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* continue to have that page mapped.
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*/
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child_write(ss, mypid, ss->modlen);
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ss->p3_did_write = true;
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dprintf("P3 (pid %d) wrote its pid\n", mypid);
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break;
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case 4:
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/* Just hang around until P3 is done writing. */
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oldval = atomic_load_acq_int(ss->p);
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child_wait_p3_write(ss);
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child_verify(ss, depth, oldval, oldval);
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break;
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default:
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child_errx("Bad depth %d", depth);
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}
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dprintf("P%d (pid %d) exiting\n", depth, mypid);
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ss->exiting[depth] = true;
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exit(0);
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}
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static void
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do_shared_shadow_inval(bool collapse, bool block_xfer, bool full_mod)
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{
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struct shared_state *ss;
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pid_t pid;
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pid = getpid();
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dprintf("P0 (pid %d) %s(collapse=%d, block_xfer=%d, full_mod=%d)\n",
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pid, __func__, (int)collapse, (int)block_xfer, (int)full_mod);
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g_pagesize = sysconf(_SC_PAGESIZE);
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ATF_REQUIRE(g_pagesize > 0);
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ATF_REQUIRE(procctl(P_PID, pid, PROC_REAP_ACQUIRE, NULL) == 0);
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/* Shared memory for coordination. */
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ss = mmap(NULL, sizeof(*ss), PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_ANON, -1, 0);
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ATF_REQUIRE(ss != MAP_FAILED);
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ss->len = 2 * 1024 * 1024 + g_pagesize; /* 2 MB + page size */
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ss->modlen = full_mod ? ss->len : ss->len / 2;
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ss->collapse = collapse;
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ss->block_xfer = block_xfer;
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pid = fork();
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ATF_REQUIRE(pid != -1);
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if (pid == 0)
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child(ss, 1);
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/* Wait for all descendants to exit. */
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do {
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pid = wait(NULL);
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} while (pid != -1 || errno != ECHILD);
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atomic_thread_fence_acq();
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ATF_REQUIRE(ss->okay);
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ATF_REQUIRE(munmap(ss, sizeof(*ss)) == 0);
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ATF_REQUIRE(procctl(P_PID, getpid(), PROC_REAP_RELEASE, NULL) == 0);
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}
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#ifdef STANDALONE
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int
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main(void)
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{
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do_shared_shadow_inval(false, false, false);
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do_shared_shadow_inval(false, false, true);
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do_shared_shadow_inval(false, true, false);
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do_shared_shadow_inval(false, true, true);
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do_shared_shadow_inval(true, false, false);
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do_shared_shadow_inval(true, false, true);
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do_shared_shadow_inval(true, true, false);
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do_shared_shadow_inval(true, true, true);
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printf("pass\n");
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}
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#else
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#define SHARED_SHADOW_INVAL_TC(suffix, collapse, block_xfer, full_mod) \
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ATF_TC_WITHOUT_HEAD(shared_shadow_inval__##suffix); \
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ATF_TC_BODY(shared_shadow_inval__##suffix, tc) \
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{ \
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do_shared_shadow_inval(collapse, block_xfer, full_mod); \
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}
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SHARED_SHADOW_INVAL_TC(nocollapse_noblockxfer_nofullmod, false, false, false);
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SHARED_SHADOW_INVAL_TC(nocollapse_noblockxfer_fullmod, false, false, true);
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SHARED_SHADOW_INVAL_TC(nocollapse_blockxfer_nofullmod, false, true, false);
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SHARED_SHADOW_INVAL_TC(nocollapse_blockxfer_fullmod, false, true, true);
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SHARED_SHADOW_INVAL_TC(collapse_noblockxfer_nofullmod, true, false, false);
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SHARED_SHADOW_INVAL_TC(collapse_noblockxfer_fullmod, true, false, true);
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SHARED_SHADOW_INVAL_TC(collapse_blockxfer_nofullmod, true, true, false);
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SHARED_SHADOW_INVAL_TC(collapse_blockxfer_fullmod, true, true, true);
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ATF_TP_ADD_TCS(tp)
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{
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ATF_TP_ADD_TC(tp,
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shared_shadow_inval__nocollapse_noblockxfer_nofullmod);
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ATF_TP_ADD_TC(tp, shared_shadow_inval__nocollapse_noblockxfer_fullmod);
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ATF_TP_ADD_TC(tp, shared_shadow_inval__nocollapse_blockxfer_nofullmod);
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ATF_TP_ADD_TC(tp, shared_shadow_inval__nocollapse_blockxfer_fullmod);
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ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_noblockxfer_nofullmod);
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ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_noblockxfer_fullmod);
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ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_blockxfer_nofullmod);
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ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_blockxfer_fullmod);
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return atf_no_error();
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}
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#endif
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