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tests: Add more shared shadow regression tests

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The new tests exercise simulated COW that occurs when the protections on
a wired, copy-on-write mapping are changed from read-only to read-write.

MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D35636
This commit is contained in:
Mark Johnston 2022-08-09 16:17:56 -04:00
parent 2bed73739a
commit 1dfa8b73f6
1 changed files with 128 additions and 54 deletions
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182
tests/sys/vm/shared_shadow_inval_test.c
View File

@ -1,5 +1,9 @@
/*
* Copyright (c) 2021 Dell Inc. or its subsidiaries. All Rights Reserved.
* Copyright (c) 2022 The FreeBSD Foundation
*
* Portions of this software were developed by Mark Johnston under sponsorship
* from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@ -25,7 +29,13 @@
/*
* Test behavior when a mapping of a shared shadow vm object is
* invalidated by COW from another mapping.
* invalidated by COW from another mapping. In particular, when
* minherit(INHERT_SHARE) is applied to a COW mapping, a subsequently
* forked child process will share the parent's shadow object. Thus,
* pages already mapped into one sharing process may be written from
* another, triggering a copy into the shadow object. The VM system
* expects that a fully shadowed page is unmapped, but at one point the
* use of a shared shadow object could break this invariant.
*
* This is a regression test for an issue isolated by rlibby@FreeBSD.org
* from an issue detected by stress2's collapse.sh by jeff@FreeBSD.org.
@ -35,10 +45,13 @@
* standalone program with -DSTANDALONE (and optionally -DDEBUG).
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <sys/procctl.h>
#include <sys/resource.h>
#include <sys/sysctl.h>
#include <sys/wait.h>
#include <machine/atomic.h>
#include <err.h>
@ -49,7 +62,7 @@
#include <stdlib.h>
#include <unistd.h>
#ifdef STANDALONE
#ifdef STANDALONE
#define ATF_REQUIRE(x) do { \
if (!(x)) \
errx(1, "%s", #x); \
@ -58,7 +71,7 @@
#include <atf-c.h>
#endif
#ifdef DEBUG
#ifdef DEBUG
#define dprintf(...) printf(__VA_ARGS__)
#else
#define dprintf(...)
@ -66,20 +79,25 @@
#define DEPTH 5
#define FLAG_COLLAPSE 0x1
#define FLAG_BLOCK_XFER 0x2
#define FLAG_FULLMOD 0x4
#define FLAG_MASK (FLAG_COLLAPSE | FLAG_BLOCK_XFER | FLAG_FULLMOD)
struct shared_state {
void *p;
size_t len;
size_t modlen;
size_t pagesize;
bool collapse;
bool block_xfer;
bool lazy_cow;
bool okay;
volatile bool exiting[DEPTH];
volatile bool exit;
volatile bool p3_did_write;
};
static long g_pagesize;
/*
* Program flow. There are three or four processes that are descendants
* of the process running the test (P0), where arrows go from parents to
@ -123,7 +141,7 @@ child_fault(struct shared_state *ss)
{
size_t i;
for (i = 0; i < ss->len; i += g_pagesize)
for (i = 0; i < ss->len; i += ss->pagesize)
(void)((volatile char *)ss->p)[i];
}
@ -132,7 +150,7 @@ child_write(struct shared_state *ss, int val, size_t len)
{
size_t i;
for (i = 0; i < len; i += g_pagesize)
for (i = 0; i < len; i += ss->pagesize)
((int *)ss->p)[i / sizeof(int)] = val;
atomic_thread_fence_rel();
}
@ -154,7 +172,7 @@ child_verify(struct shared_state *ss, int depth, int newval, int oldval)
size_t i;
int expectval, foundval;
for (i = 0; i < ss->len; i += g_pagesize) {
for (i = 0; i < ss->len; i += ss->pagesize) {
expectval = i < ss->modlen ? newval : oldval;
foundval = ((int *)ss->p)[i / sizeof(int)];
if (foundval == expectval)
@ -180,8 +198,15 @@ child(struct shared_state *ss, int depth)
MAP_SHARED | MAP_ANON, -1, 0);
if (ss->p == MAP_FAILED)
child_err("mmap");
/* P1 stamps the shared memory. */
child_write(ss, mypid, ss->len);
if (!ss->lazy_cow) {
if (mlock(ss->p, ss->len) == -1)
child_err("mprotect");
if (mprotect(ss->p, ss->len, PROT_READ) == -1)
child_err("mprotect");
}
if (ss->block_xfer) {
/*
* P4 is forked so that its existence blocks a page COW
@ -216,12 +241,16 @@ child(struct shared_state *ss, int depth)
*/
if (minherit(ss->p, ss->len, INHERIT_SHARE) != 0)
child_err("minherit");
/*
* P2 faults a page in P1's object before P1 exits and the
* shadow chain is collapsed.
* shadow chain is collapsed. This may be redundant if the
* (read-only) mappings were copied by fork(), but it doesn't
* hurt.
*/
child_fault(ss);
oldval = atomic_load_acq_int(ss->p);
/* Fork P3. */
pid = child_fork(ss, depth + 1);
if (ss->collapse) {
@ -242,6 +271,19 @@ child(struct shared_state *ss, int depth)
ss->exit = true;
break;
case 3:
/*
* Use mlock()+mprotect() to trigger the COW. This
* exercises a different COW handler than the one used
* for lazy faults.
*/
if (!ss->lazy_cow) {
if (mlock(ss->p, ss->len) == -1)
child_err("mlock");
if (mprotect(ss->p, ss->len, PROT_READ | PROT_WRITE) ==
-1)
child_err("mprotect");
}
/*
* P3 writes the memory. A page is faulted into the shared
* P2/P3 shadow object. P2's mapping of the page in P1's
@ -268,19 +310,18 @@ child(struct shared_state *ss, int depth)
}
static void
do_shared_shadow_inval(bool collapse, bool block_xfer, bool full_mod)
do_one_shared_shadow_inval(bool lazy_cow, size_t pagesize, size_t len,
unsigned int flags)
{
struct shared_state *ss;
pid_t pid;
int status;
pid = getpid();
dprintf("P0 (pid %d) %s(collapse=%d, block_xfer=%d, full_mod=%d)\n",
pid, __func__, (int)collapse, (int)block_xfer, (int)full_mod);
g_pagesize = sysconf(_SC_PAGESIZE);
ATF_REQUIRE(g_pagesize > 0);
ATF_REQUIRE(procctl(P_PID, pid, PROC_REAP_ACQUIRE, NULL) == 0);
/* Shared memory for coordination. */
@ -288,10 +329,12 @@ do_shared_shadow_inval(bool collapse, bool block_xfer, bool full_mod)
MAP_SHARED | MAP_ANON, -1, 0);
ATF_REQUIRE(ss != MAP_FAILED);
ss->len = 2 * 1024 * 1024 + g_pagesize; /* 2 MB + page size */
ss->modlen = full_mod ? ss->len : ss->len / 2;
ss->collapse = collapse;
ss->block_xfer = block_xfer;
ss->len = len;
ss->modlen = (flags & FLAG_FULLMOD) ? ss->len : ss->len / 2;
ss->pagesize = pagesize;
ss->collapse = (flags & FLAG_COLLAPSE) != 0;
ss->block_xfer = (flags & FLAG_BLOCK_XFER) != 0;
ss->lazy_cow = lazy_cow;
pid = fork();
ATF_REQUIRE(pid != -1);
@ -300,7 +343,8 @@ do_shared_shadow_inval(bool collapse, bool block_xfer, bool full_mod)
/* Wait for all descendants to exit. */
do {
pid = wait(NULL);
pid = wait(&status);
ATF_REQUIRE(WIFEXITED(status));
} while (pid != -1 || errno != ECHILD);
atomic_thread_fence_acq();
@ -310,51 +354,81 @@ do_shared_shadow_inval(bool collapse, bool block_xfer, bool full_mod)
ATF_REQUIRE(procctl(P_PID, getpid(), PROC_REAP_RELEASE, NULL) == 0);
}
static void
do_shared_shadow_inval(bool lazy_cow)
{
size_t largepagesize, pagesize, pagesizes[MAXPAGESIZES], sysctllen;
sysctllen = sizeof(pagesizes);
ATF_REQUIRE(sysctlbyname("hw.pagesizes", pagesizes, &sysctllen, NULL,
0) == 0);
ATF_REQUIRE(sysctllen >= sizeof(size_t));
pagesize = pagesizes[0];
largepagesize = sysctllen >= 2 * sizeof(size_t) ?
pagesizes[1] : 2 * 1024 * 1024;
for (unsigned int i = 0; i <= FLAG_MASK; i++) {
do_one_shared_shadow_inval(lazy_cow, pagesize,
pagesize, i);
do_one_shared_shadow_inval(lazy_cow, pagesize,
2 * pagesize, i);
do_one_shared_shadow_inval(lazy_cow, pagesize,
largepagesize - pagesize, i);
do_one_shared_shadow_inval(lazy_cow, pagesize,
largepagesize, i);
do_one_shared_shadow_inval(lazy_cow, pagesize,
largepagesize + pagesize, i);
}
}
static void
do_shared_shadow_inval_eager(void)
{
struct rlimit rl;
rl.rlim_cur = rl.rlim_max = RLIM_INFINITY;
ATF_REQUIRE(setrlimit(RLIMIT_MEMLOCK, &rl) == 0);
do_shared_shadow_inval(false);
}
static void
do_shared_shadow_inval_lazy(void)
{
do_shared_shadow_inval(true);
}
#ifdef STANDALONE
int
main(void)
{
do_shared_shadow_inval(false, false, false);
do_shared_shadow_inval(false, false, true);
do_shared_shadow_inval(false, true, false);
do_shared_shadow_inval(false, true, true);
do_shared_shadow_inval(true, false, false);
do_shared_shadow_inval(true, false, true);
do_shared_shadow_inval(true, true, false);
do_shared_shadow_inval(true, true, true);
do_shared_shadow_inval_lazy();
do_shared_shadow_inval_eager();
printf("pass\n");
}
#else
#define SHARED_SHADOW_INVAL_TC(suffix, collapse, block_xfer, full_mod) \
ATF_TC_WITHOUT_HEAD(shared_shadow_inval__##suffix); \
ATF_TC_BODY(shared_shadow_inval__##suffix, tc) \
{ \
do_shared_shadow_inval(collapse, block_xfer, full_mod); \
ATF_TC_WITHOUT_HEAD(shared_shadow_inval__lazy_cow);
ATF_TC_BODY(shared_shadow_inval__lazy_cow, tc)
{
do_shared_shadow_inval_lazy();
}
SHARED_SHADOW_INVAL_TC(nocollapse_noblockxfer_nofullmod, false, false, false);
SHARED_SHADOW_INVAL_TC(nocollapse_noblockxfer_fullmod, false, false, true);
SHARED_SHADOW_INVAL_TC(nocollapse_blockxfer_nofullmod, false, true, false);
SHARED_SHADOW_INVAL_TC(nocollapse_blockxfer_fullmod, false, true, true);
SHARED_SHADOW_INVAL_TC(collapse_noblockxfer_nofullmod, true, false, false);
SHARED_SHADOW_INVAL_TC(collapse_noblockxfer_fullmod, true, false, true);
SHARED_SHADOW_INVAL_TC(collapse_blockxfer_nofullmod, true, true, false);
SHARED_SHADOW_INVAL_TC(collapse_blockxfer_fullmod, true, true, true);
ATF_TC(shared_shadow_inval__eager_cow);
ATF_TC_HEAD(shared_shadow_inval__eager_cow, tc)
{
/* Needed to raise the mlock() limit. */
atf_tc_set_md_var(tc, "require.user", "root");
}
ATF_TC_BODY(shared_shadow_inval__eager_cow, tc)
{
do_shared_shadow_inval_eager();
}
ATF_TP_ADD_TCS(tp)
{
ATF_TP_ADD_TC(tp,
shared_shadow_inval__nocollapse_noblockxfer_nofullmod);
ATF_TP_ADD_TC(tp, shared_shadow_inval__nocollapse_noblockxfer_fullmod);
ATF_TP_ADD_TC(tp, shared_shadow_inval__nocollapse_blockxfer_nofullmod);
ATF_TP_ADD_TC(tp, shared_shadow_inval__nocollapse_blockxfer_fullmod);
ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_noblockxfer_nofullmod);
ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_noblockxfer_fullmod);
ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_blockxfer_nofullmod);
ATF_TP_ADD_TC(tp, shared_shadow_inval__collapse_blockxfer_fullmod);
return atf_no_error();
ATF_TP_ADD_TC(tp, shared_shadow_inval__lazy_cow);
ATF_TP_ADD_TC(tp, shared_shadow_inval__eager_cow);
return (atf_no_error());
}
#endif
#endif /* !STANDALONE */