selftests/powerpc: Add a signal fuzzer selftest

This is a new selftest that raises SIGUSR1 signals and handles it in a
set of different ways, trying to create different scenario for testing
purpose.

This test works raising a signal and calling sigreturn interleaved
with TM operations, as starting, suspending and terminating a
transaction. The test depends on random numbers, and, based on them,
it sets different TM states.

Other than that, the test fills out the user context struct that is
passed to the sigreturn system call with random data, in order to make
sure that the signal handler syscall can handle different and invalid
states properly.

This selftest has command line parameters to control what kind of
tests the user wants to run, as for example, if a transaction should
be started prior to signal being raised, or, after the signal being
raised and before the sigreturn. If no parameter is given, the default
is enabling all options.

This test does not check if the user context is being read and set
properly by the kernel. Its purpose, at this time, is basically
guaranteeing that the kernel does not crash on invalid scenarios.
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/harness.c

@@ -21,6 +21,7 @@
 
 #define KILL_TIMEOUT	5
 
+/* Setting timeout to -1 disables the alarm */
 static uint64_t timeout = 120;
 
 int run_test(int (test_function)(void), char *name)
@@ -43,8 +44,9 @@ int run_test(int (test_function)(void), char *name)
 
 	setpgid(pid, pid);
 
-	/* Wake us up in timeout seconds */
-	alarm(timeout);
+	if (timeout != -1)
+		/* Wake us up in timeout seconds */
+		alarm(timeout);
 	terminated = false;
 
 wait:

tools/testing/selftests/powerpc/include/reg.h

@@ -79,11 +79,13 @@
 
 /* MSR register bits */
 #define MSR_TS_S_LG     33              /* Trans Mem state: Suspended */
+#define MSR_TS_T_LG	34              /* Trans Mem state: Active */
 
 #define __MASK(X)       (1UL<<(X))
 
 /* macro to check TM MSR bits */
 #define MSR_TS_S        __MASK(MSR_TS_S_LG)   /* Transaction Suspended */
+#define MSR_TS_T	__MASK(MSR_TS_T_LG)   /* Transaction Transactional */
 
 /* Vector Instructions */
 #define VSX_XX1(xs, ra, rb)	(((xs) & 0x1f) << 21 | ((ra) << 16) |  \

tools/testing/selftests/powerpc/signal/.gitignore

 signal
 signal_tm
+sigfuz

tools/testing/selftests/powerpc/signal/Makefile

 # SPDX-License-Identifier: GPL-2.0
-TEST_GEN_PROGS := signal signal_tm
+TEST_GEN_PROGS := signal signal_tm sigfuz
 
 CFLAGS += -maltivec
 $(OUTPUT)/signal_tm: CFLAGS += -mhtm
+$(OUTPUT)/sigfuz: CFLAGS += -pthread -m64
 
 top_srcdir = ../../../../..
 include ../../lib.mk

tools/testing/selftests/powerpc/signal/sigfuz.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018, Breno Leitao, IBM Corp.
+ * Licensed under GPLv2.
+ *
+ * Sigfuz(tm): A PowerPC TM-aware signal fuzzer.
+ *
+ * This is a new selftest that raises SIGUSR1 signals and handles it in a set
+ * of different ways, trying to create different scenario for testing
+ * purpose.
+ *
+ * This test works raising a signal and calling sigreturn interleaved with
+ * TM operations, as starting, suspending and terminating a transaction. The
+ * test depends on random numbers, and, based on them, it sets different TM
+ * states.
+ *
+ * Other than that, the test fills out the user context struct that is passed
+ * to the sigreturn system call with random data, in order to make sure that
+ * the signal handler syscall can handle different and invalid states
+ * properly.
+ *
+ * This selftest has command line parameters to control what kind of tests the
+ * user wants to run, as for example, if a transaction should be started prior
+ * to signal being raised, or, after the signal being raised and before the
+ * sigreturn. If no parameter is given, the default is enabling all options.
+ *
+ * This test does not check if the user context is being read and set
+ * properly by the kernel. Its purpose, at this time, is basically
+ * guaranteeing that the kernel does not crash on invalid scenarios.
+ */
+
+#include <stdio.h>
+#include <limits.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <string.h>
+#include <ucontext.h>
+#include <sys/mman.h>
+#include <pthread.h>
+#include "utils.h"
+
+/* Selftest defaults */
+#define COUNT_MAX	4000		/* Number of interactions */
+#define THREADS		16		/* Number of threads */
+
+/* Arguments options */
+#define ARG_MESS_WITH_TM_AT	0x1
+#define ARG_MESS_WITH_TM_BEFORE	0x2
+#define ARG_MESS_WITH_MSR_AT	0x4
+#define ARG_FOREVER		0x10
+#define ARG_COMPLETE		(ARG_MESS_WITH_TM_AT |		\
+				ARG_MESS_WITH_TM_BEFORE |	\
+				ARG_MESS_WITH_MSR_AT)
+
+static int args;
+static int nthread = THREADS;
+static int count_max = COUNT_MAX;
+
+/* checkpoint context */
+static ucontext_t *tmp_uc;
+
+/* Return true with 1/x probability */
+static int one_in_chance(int x)
+{
+	return rand() % x == 0;
+}
+
+/* Change TM states */
+static void mess_with_tm(void)
+{
+	/* Starts a transaction 33% of the time */
+	if (one_in_chance(3)) {
+		asm ("tbegin.	;"
+		     "beq 8	;");
+
+		/* And suspended half of them */
+		if (one_in_chance(2))
+			asm("tsuspend.	;");
+	}
+
+	/* Call 'tend' in 5% of the runs */
+	if (one_in_chance(20))
+		asm("tend.	;");
+}
+
+/* Signal handler that will be invoked with raise() */
+static void trap_signal_handler(int signo, siginfo_t *si, void *uc)
+{
+	ucontext_t *ucp = uc;
+
+	ucp->uc_link = tmp_uc;
+
+	/*
+	 * Set uc_link in three possible ways:
+	 *  - Setting a single 'int' in the whole chunk
+	 *  - Cloning ucp into uc_link
+	 *  - Allocating a new memory chunk
+	 */
+	if (one_in_chance(3)) {
+		memset(ucp->uc_link, rand(), sizeof(ucontext_t));
+	} else if (one_in_chance(2)) {
+		memcpy(ucp->uc_link, uc, sizeof(ucontext_t));
+	} else if (one_in_chance(2)) {
+		if (tmp_uc) {
+			free(tmp_uc);
+			tmp_uc = NULL;
+		}
+		tmp_uc = malloc(sizeof(ucontext_t));
+		ucp->uc_link = tmp_uc;
+		/* Trying to cause a major page fault at Kernel level */
+		madvise(ucp->uc_link, sizeof(ucontext_t), MADV_DONTNEED);
+	}
+
+	if (args & ARG_MESS_WITH_MSR_AT) {
+		/* Changing the checkpointed registers */
+		if (one_in_chance(4)) {
+			ucp->uc_link->uc_mcontext.gp_regs[PT_MSR] |= MSR_TS_S;
+		} else {
+			if (one_in_chance(2)) {
+				ucp->uc_link->uc_mcontext.gp_regs[PT_MSR] |=
+						 MSR_TS_T;
+			} else if (one_in_chance(2)) {
+				ucp->uc_link->uc_mcontext.gp_regs[PT_MSR] |=
+						MSR_TS_T | MSR_TS_S;
+			}
+		}
+
+		/* Checking the current register context */
+		if (one_in_chance(2)) {
+			ucp->uc_mcontext.gp_regs[PT_MSR] |= MSR_TS_S;
+		} else if (one_in_chance(2)) {
+			if (one_in_chance(2))
+				ucp->uc_mcontext.gp_regs[PT_MSR] |=
+					MSR_TS_T;
+			else if (one_in_chance(2))
+				ucp->uc_mcontext.gp_regs[PT_MSR] |=
+					MSR_TS_T | MSR_TS_S;
+		}
+	}
+
+	if (one_in_chance(20)) {
+		/* Nested transaction start */
+		if (one_in_chance(5))
+			mess_with_tm();
+
+		/* Return without changing any other context info */
+		return;
+	}
+
+	if (one_in_chance(10))
+		ucp->uc_mcontext.gp_regs[PT_MSR] = random();
+	if (one_in_chance(10))
+		ucp->uc_mcontext.gp_regs[PT_NIP] = random();
+	if (one_in_chance(10))
+		ucp->uc_link->uc_mcontext.gp_regs[PT_MSR] = random();
+	if (one_in_chance(10))
+		ucp->uc_link->uc_mcontext.gp_regs[PT_NIP] = random();
+
+	ucp->uc_mcontext.gp_regs[PT_TRAP] = random();
+	ucp->uc_mcontext.gp_regs[PT_DSISR] = random();
+	ucp->uc_mcontext.gp_regs[PT_DAR] = random();
+	ucp->uc_mcontext.gp_regs[PT_ORIG_R3] = random();
+	ucp->uc_mcontext.gp_regs[PT_XER] = random();
+	ucp->uc_mcontext.gp_regs[PT_RESULT] = random();
+	ucp->uc_mcontext.gp_regs[PT_SOFTE] = random();
+	ucp->uc_mcontext.gp_regs[PT_DSCR] = random();
+	ucp->uc_mcontext.gp_regs[PT_CTR] = random();
+	ucp->uc_mcontext.gp_regs[PT_LNK] = random();
+	ucp->uc_mcontext.gp_regs[PT_CCR] = random();
+	ucp->uc_mcontext.gp_regs[PT_REGS_COUNT] = random();
+
+	ucp->uc_link->uc_mcontext.gp_regs[PT_TRAP] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_DSISR] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_DAR] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_ORIG_R3] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_XER] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_RESULT] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_SOFTE] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_DSCR] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_CTR] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_LNK] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_CCR] = random();
+	ucp->uc_link->uc_mcontext.gp_regs[PT_REGS_COUNT] = random();
+
+	if (args & ARG_MESS_WITH_TM_BEFORE) {
+		if (one_in_chance(2))
+			mess_with_tm();
+	}
+}
+
+static void seg_signal_handler(int signo, siginfo_t *si, void *uc)
+{
+	/* Clear exit for process that segfaults */
+	exit(0);
+}
+
+static void *sigfuz_test(void *thrid)
+{
+	struct sigaction trap_sa, seg_sa;
+	int ret, i = 0;
+	pid_t t;
+
+	tmp_uc = malloc(sizeof(ucontext_t));
+
+	/* Main signal handler */
+	trap_sa.sa_flags = SA_SIGINFO;
+	trap_sa.sa_sigaction = trap_signal_handler;
+
+	/* SIGSEGV signal handler */
+	seg_sa.sa_flags = SA_SIGINFO;
+	seg_sa.sa_sigaction = seg_signal_handler;
+
+	/* The signal handler will enable MSR_TS */
+	sigaction(SIGUSR1, &trap_sa, NULL);
+
+	/* If it does not crash, it will segfault, avoid it to retest */
+	sigaction(SIGSEGV, &seg_sa, NULL);
+
+	while (i < count_max) {
+		t = fork();
+
+		if (t == 0) {
+			/* Once seed per process */
+			srand(time(NULL) + getpid());
+			if (args & ARG_MESS_WITH_TM_AT) {
+				if (one_in_chance(2))
+					mess_with_tm();
+			}
+			raise(SIGUSR1);
+			exit(0);
+		} else {
+			waitpid(t, &ret, 0);
+		}
+		if (!(args & ARG_FOREVER))
+			i++;
+	}
+
+	/* If not freed already, free now */
+	if (tmp_uc) {
+		free(tmp_uc);
+		tmp_uc = NULL;
+	}
+
+	return NULL;
+}
+
+static int signal_fuzzer(void)
+{
+	int t, rc;
+	pthread_t *threads;
+
+	threads = malloc(nthread * sizeof(pthread_t));
+
+	for (t = 0; t < nthread; t++) {
+		rc = pthread_create(&threads[t], NULL, sigfuz_test,
+				    (void *)&t);
+		if (rc)
+			perror("Thread creation error\n");
+	}
+
+	for (t = 0; t < nthread; t++) {
+		rc = pthread_join(threads[t], NULL);
+		if (rc)
+			perror("Thread join error\n");
+	}
+
+	free(threads);
+
+	return EXIT_SUCCESS;
+}
+
+static void show_help(char *name)
+{
+	printf("%s: Sigfuzzer for powerpc\n", name);
+	printf("Usage:\n");
+	printf("\t-b\t Mess with TM before raising a SIGUSR1 signal\n");
+	printf("\t-a\t Mess with TM after raising a SIGUSR1 signal\n");
+	printf("\t-m\t Mess with MSR[TS] bits at mcontext\n");
+	printf("\t-x\t Mess with everything above\n");
+	printf("\t-f\t Run forever (Press ^C to Quit)\n");
+	printf("\t-i\t Amount of interactions.	(Default = %d)\n", COUNT_MAX);
+	printf("\t-t\t Amount of threads.	(Default = %d)\n", THREADS);
+	exit(-1);
+}
+
+int main(int argc, char **argv)
+{
+	int opt;
+
+	while ((opt = getopt(argc, argv, "bamxt:fi:h")) != -1) {
+		if (opt == 'b') {
+			printf("Mess with TM before signal\n");
+			args |= ARG_MESS_WITH_TM_BEFORE;
+		} else if (opt == 'a') {
+			printf("Mess with TM at signal handler\n");
+			args |= ARG_MESS_WITH_TM_AT;
+		} else if (opt == 'm') {
+			printf("Mess with MSR[TS] bits in mcontext\n");
+			args |= ARG_MESS_WITH_MSR_AT;
+		} else if (opt == 'x') {
+			printf("Running with all options enabled\n");
+			args |= ARG_COMPLETE;
+		} else if (opt == 't') {
+			nthread = atoi(optarg);
+			printf("Threads = %d\n", nthread);
+		} else if (opt == 'f') {
+			args |= ARG_FOREVER;
+			printf("Press ^C to stop\n");
+			test_harness_set_timeout(-1);
+		} else if (opt == 'i') {
+			count_max = atoi(optarg);
+			printf("Running for %d interactions\n", count_max);
+		} else if (opt == 'h') {
+			show_help(argv[0]);
+		}
+	}
+
+	/* Default test suite */
+	if (!args)
+		args = ARG_COMPLETE;
+
+	test_harness(signal_fuzzer, "signal_fuzzer");
+}