[PATCH v3 2/2] selftests/powerpc: New TM signal self test
Breno Leitao
leitao at debian.org
Fri Jan 4 03:11:02 AEDT 2019
A new self test that forces MSR[TS] to be set without calling any TM
instruction. This test also tries to cause a page fault at a signal
handler, exactly between MSR[TS] set and tm_recheckpoint(), forcing
thread->texasr to be rewritten with TEXASR[FS] = 0, which will cause a BUG
when tm_recheckpoint() is called.
This test is not deterministic, since it is hard to guarantee that the page
access will cause a page fault. In order to force more page faults at
signal context, the signal handler and the ucontext are being mapped into a
MADV_DONTNEED memory chunks.
Tests have shown that the bug could be exposed with few interactions in a
buggy kernel. This test is configured to loop 5000x, having a good chance
to hit the kernel issue in just one run. This self test takes less than
two seconds to run.
This test uses set/getcontext because the kernel will recheckpoint
zeroed structures, causing the test to segfault, which is undesired because
the test needs to rerun, so, there is a signal handler for SIGSEGV which
will restart the test.
v2: Uses the MADV_DONTNEED memory advice
v3: Fix memcpy and 32-bits compilation
Signed-off-by: Breno Leitao <leitao at debian.org>
---
.../testing/selftests/powerpc/include/utils.h | 2 +
tools/testing/selftests/powerpc/tm/.gitignore | 1 +
tools/testing/selftests/powerpc/tm/Makefile | 4 +-
.../powerpc/tm/tm-signal-context-force-tm.c | 184 ++++++++++++++++++
4 files changed, 190 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/powerpc/tm/tm-signal-context-force-tm.c
diff --git a/tools/testing/selftests/powerpc/include/utils.h b/tools/testing/selftests/powerpc/include/utils.h
index ae43a614835d..7636bf45d5d5 100644
--- a/tools/testing/selftests/powerpc/include/utils.h
+++ b/tools/testing/selftests/powerpc/include/utils.h
@@ -102,8 +102,10 @@ do { \
#if defined(__powerpc64__)
#define UCONTEXT_NIA(UC) (UC)->uc_mcontext.gp_regs[PT_NIP]
+#define UCONTEXT_MSR(UC) (UC)->uc_mcontext.gp_regs[PT_MSR]
#elif defined(__powerpc__)
#define UCONTEXT_NIA(UC) (UC)->uc_mcontext.uc_regs->gregs[PT_NIP]
+#define UCONTEXT_MSR(UC) (UC)->uc_mcontext.uc_regs->gregs[PT_MSR]
#else
#error implement UCONTEXT_NIA
#endif
diff --git a/tools/testing/selftests/powerpc/tm/.gitignore b/tools/testing/selftests/powerpc/tm/.gitignore
index 208452a93e2c..951fe855f7cd 100644
--- a/tools/testing/selftests/powerpc/tm/.gitignore
+++ b/tools/testing/selftests/powerpc/tm/.gitignore
@@ -11,6 +11,7 @@ tm-signal-context-chk-fpu
tm-signal-context-chk-gpr
tm-signal-context-chk-vmx
tm-signal-context-chk-vsx
+tm-signal-context-force-tm
tm-signal-sigreturn-nt
tm-vmx-unavail
tm-unavailable
diff --git a/tools/testing/selftests/powerpc/tm/Makefile b/tools/testing/selftests/powerpc/tm/Makefile
index 75a685359129..c0734ed0ef56 100644
--- a/tools/testing/selftests/powerpc/tm/Makefile
+++ b/tools/testing/selftests/powerpc/tm/Makefile
@@ -4,7 +4,8 @@ SIGNAL_CONTEXT_CHK_TESTS := tm-signal-context-chk-gpr tm-signal-context-chk-fpu
TEST_GEN_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack \
tm-vmxcopy tm-fork tm-tar tm-tmspr tm-vmx-unavail tm-unavailable tm-trap \
- $(SIGNAL_CONTEXT_CHK_TESTS) tm-sigreturn tm-signal-sigreturn-nt
+ $(SIGNAL_CONTEXT_CHK_TESTS) tm-sigreturn tm-signal-sigreturn-nt \
+ tm-signal-context-force-tm
top_srcdir = ../../../../..
include ../../lib.mk
@@ -20,6 +21,7 @@ $(OUTPUT)/tm-vmx-unavail: CFLAGS += -pthread -m64
$(OUTPUT)/tm-resched-dscr: ../pmu/lib.c
$(OUTPUT)/tm-unavailable: CFLAGS += -O0 -pthread -m64 -Wno-error=uninitialized -mvsx
$(OUTPUT)/tm-trap: CFLAGS += -O0 -pthread -m64
+$(OUTPUT)/tm-signal-context-force-tm: CFLAGS += -pthread -m64
SIGNAL_CONTEXT_CHK_TESTS := $(patsubst %,$(OUTPUT)/%,$(SIGNAL_CONTEXT_CHK_TESTS))
$(SIGNAL_CONTEXT_CHK_TESTS): tm-signal.S
diff --git a/tools/testing/selftests/powerpc/tm/tm-signal-context-force-tm.c b/tools/testing/selftests/powerpc/tm/tm-signal-context-force-tm.c
new file mode 100644
index 000000000000..31717625f318
--- /dev/null
+++ b/tools/testing/selftests/powerpc/tm/tm-signal-context-force-tm.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018, Breno Leitao, Gustavo Romero, IBM Corp.
+ *
+ * This test raises a SIGUSR1 signal, and toggle the MSR[TS]
+ * fields at the signal handler. With MSR[TS] being set, the kernel will
+ * force a recheckpoint, which may cause a segfault when returning to
+ * user space. Since the test needs to re-run, the segfault needs to be
+ * caught and handled.
+ *
+ * In order to continue the test even after a segfault, the context is
+ * saved prior to the signal being raised, and it is restored when there is
+ * a segmentation fault. This happens for COUNT_MAX times.
+ *
+ * This test never fails (as returning EXIT_FAILURE). It either succeeds,
+ * or crash the kernel (on a buggy kernel).
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <string.h>
+#include <ucontext.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#include "tm.h"
+#include "utils.h"
+#include "reg.h"
+
+#define COUNT_MAX 5000 /* Number of interactions */
+
+/*
+ * This test only runs on 64 bits system. Unsetting MSR_TS_S to avoid
+ * compilation issue on 32 bits system. There is no side effect, since the
+ * whole test will be skipped if it is not running on 64 bits system.
+ */
+#ifndef __powerpc64__
+#undef MSR_TS_S
+#define MSR_TS_S 0
+#endif
+
+/* Setting contexts because the test will crash and we want to recover */
+ucontext_t init_context, main_context;
+
+static int count, first_time;
+
+void usr_signal_handler(int signo, siginfo_t *si, void *uc)
+{
+ ucontext_t *ucp = uc;
+ int ret;
+
+ /*
+ * Allocating memory in a signal handler, and never freeing it on
+ * purpose, forcing the heap increase, so, the memory leak is what
+ * we want here.
+ */
+ ucp->uc_link = mmap(NULL, sizeof(ucontext_t),
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+ if (ucp->uc_link == (void *)-1) {
+ perror("Mmap failed");
+ exit(-1);
+ }
+
+ /* Forcing the page to be allocated in a page fault */
+ ret = madvise(ucp->uc_link, sizeof(ucontext_t), MADV_DONTNEED);
+ if (ret) {
+ perror("madvise failed");
+ exit(-1);
+ }
+
+ memcpy(&ucp->uc_link->uc_mcontext, &ucp->uc_mcontext,
+ sizeof(ucp->uc_mcontext));
+
+ /* Forcing to enable MSR[TM] */
+ UCONTEXT_MSR(ucp) |= MSR_TS_S;
+
+ /*
+ * A fork inside a signal handler seems to be more efficient than a
+ * fork() prior to the signal being raised.
+ */
+ if (fork() == 0) {
+ /*
+ * Both child and parent will return, but, child returns
+ * with count set so it will exit in the next segfault.
+ * Parent will continue to loop.
+ */
+ count = COUNT_MAX;
+ }
+
+ /*
+ * If the change above does not hit the bug, it will cause a
+ * segmentation fault, since the ck structures are NULL.
+ */
+}
+
+void seg_signal_handler(int signo, siginfo_t *si, void *uc)
+{
+ if (count == COUNT_MAX) {
+ /* Return to tm_signal_force_msr() and exit */
+ setcontext(&main_context);
+ }
+
+ count++;
+
+ /* Reexecute the test */
+ setcontext(&init_context);
+}
+
+void tm_trap_test(void)
+{
+ struct sigaction usr_sa, seg_sa;
+ stack_t ss;
+
+ usr_sa.sa_flags = SA_SIGINFO | SA_ONSTACK;
+ usr_sa.sa_sigaction = usr_signal_handler;
+
+ seg_sa.sa_flags = SA_SIGINFO;
+ seg_sa.sa_sigaction = seg_signal_handler;
+
+ /*
+ * Set initial context. Will get back here from
+ * seg_signal_handler()
+ */
+ getcontext(&init_context);
+
+ /* Allocated an alternative signal stack area */
+ ss.ss_sp = mmap(NULL, SIGSTKSZ, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+ ss.ss_size = SIGSTKSZ;
+ ss.ss_flags = 0;
+
+ if (ss.ss_sp == (void *)-1) {
+ perror("mmap error\n");
+ exit(-1);
+ }
+
+ /* Force the allocation through a page fault */
+ if (madvise(ss.ss_sp, SIGSTKSZ, MADV_DONTNEED)) {
+ perror("madvise\n");
+ exit(-1);
+ }
+
+ /* Setting an alternative stack to generate a page fault when
+ * the signal is raised.
+ */
+ if (sigaltstack(&ss, NULL)) {
+ perror("sigaltstack\n");
+ exit(-1);
+ }
+
+ /* The signal handler will enable MSR_TS */
+ sigaction(SIGUSR1, &usr_sa, NULL);
+ /* If it does not crash, it will segfault, avoid it to retest */
+ sigaction(SIGSEGV, &seg_sa, NULL);
+
+ raise(SIGUSR1);
+}
+
+int tm_signal_context_force_tm(void)
+{
+ SKIP_IF(!have_htm());
+ /*
+ * Skipping if not running on 64 bits system, since I think it is
+ * not possible to set mcontext's [MSR] with TS, due to it being 32
+ * bits.
+ */
+ SKIP_IF(!is_ppc64le());
+
+ /* Will get back here after COUNT_MAX interactions */
+ getcontext(&main_context);
+
+ if (!first_time++)
+ tm_trap_test();
+
+ return EXIT_SUCCESS;
+}
+
+int main(int argc, char **argv)
+{
+ test_harness(tm_signal_context_force_tm, "tm_signal_context_force_tm");
+}
--
2.19.0
More information about the Linuxppc-dev
mailing list