kselftest/arm64: check GCR_EL1 after context switch

This test is specific to MTE and verifies that the GCR_EL1 register is
context switched correctly.

It spawns 1024 processes and each process spawns 5 threads. Each thread
writes a random setting of GCR_EL1 through the prctl() system call and
reads it back verifying that it is the same. If the values are not the
same it reports a failure.

Note: The test has been extended to verify that even SYNC and ASYNC mode
setting is preserved correctly over context switching.

Link: https://lkml.kernel.org/r/b5[e-mail]
Signed-off-by: Vincenzo Frascino <[e-mail]>
Signed-off-by: Andrey Konovalov <[e-mail]>
Acked-by: Catalin Marinas <[e-mail]>
Tested-by: Vincenzo Frascino <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Branislav Rankov <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Evgenii Stepanov <[e-mail]>
Cc: Kevin Brodsky <[e-mail]>
Cc: Marco Elver <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Cc: Will Deacon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

tools/testing/selftests/arm64/mte/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
 # Copyright (C) 2020 ARM Limited
 
-CFLAGS += -std=gnu99 -I.
+CFLAGS += -std=gnu99 -I. -lpthread
 SRCS := $(filter-out mte_common_util.c,$(wildcard *.c))
 PROGS := $(patsubst %.c,%,$(SRCS))
 

tools/testing/selftests/arm64/mte/check_gcr_el1_cswitch.c

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2020 ARM Limited
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+#include <sys/auxv.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "kselftest.h"
+#include "mte_common_util.h"
+
+#define PR_SET_TAGGED_ADDR_CTRL 55
+#define PR_GET_TAGGED_ADDR_CTRL 56
+# define PR_TAGGED_ADDR_ENABLE  (1UL << 0)
+# define PR_MTE_TCF_SHIFT	1
+# define PR_MTE_TCF_NONE	(0UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TCF_SYNC	(1UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TCF_ASYNC	(2UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TCF_MASK	(3UL << PR_MTE_TCF_SHIFT)
+# define PR_MTE_TAG_SHIFT	3
+# define PR_MTE_TAG_MASK	(0xffffUL << PR_MTE_TAG_SHIFT)
+
+#include "mte_def.h"
+
+#define NUM_ITERATIONS		1024
+#define MAX_THREADS		5
+#define THREAD_ITERATIONS	1000
+
+void *execute_thread(void *x)
+{
+	pid_t pid = *((pid_t *)x);
+	pid_t tid = gettid();
+	uint64_t prctl_tag_mask;
+	uint64_t prctl_set;
+	uint64_t prctl_get;
+	uint64_t prctl_tcf;
+
+	srand(time(NULL) ^ (pid << 16) ^ (tid << 16));
+
+	prctl_tag_mask = rand() & 0xffff;
+
+	if (prctl_tag_mask % 2)
+		prctl_tcf = PR_MTE_TCF_SYNC;
+	else
+		prctl_tcf = PR_MTE_TCF_ASYNC;
+
+	prctl_set = PR_TAGGED_ADDR_ENABLE | prctl_tcf | (prctl_tag_mask << PR_MTE_TAG_SHIFT);
+
+	for (int j = 0; j < THREAD_ITERATIONS; j++) {
+		if (prctl(PR_SET_TAGGED_ADDR_CTRL, prctl_set, 0, 0, 0)) {
+			perror("prctl() failed");
+			goto fail;
+		}
+
+		prctl_get = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+
+		if (prctl_set != prctl_get) {
+			ksft_print_msg("Error: prctl_set: 0x%lx != prctl_get: 0x%lx\n",
+						prctl_set, prctl_get);
+			goto fail;
+		}
+	}
+
+	return (void *)KSFT_PASS;
+
+fail:
+	return (void *)KSFT_FAIL;
+}
+
+int execute_test(pid_t pid)
+{
+	pthread_t thread_id[MAX_THREADS];
+	int thread_data[MAX_THREADS];
+
+	for (int i = 0; i < MAX_THREADS; i++)
+		pthread_create(&thread_id[i], NULL,
+			       execute_thread, (void *)&pid);
+
+	for (int i = 0; i < MAX_THREADS; i++)
+		pthread_join(thread_id[i], (void *)&thread_data[i]);
+
+	for (int i = 0; i < MAX_THREADS; i++)
+		if (thread_data[i] == KSFT_FAIL)
+			return KSFT_FAIL;
+
+	return KSFT_PASS;
+}
+
+int mte_gcr_fork_test(void)
+{
+	pid_t pid;
+	int results[NUM_ITERATIONS];
+	pid_t cpid;
+	int res;
+
+	for (int i = 0; i < NUM_ITERATIONS; i++) {
+		pid = fork();
+
+		if (pid < 0)
+			return KSFT_FAIL;
+
+		if (pid == 0) {
+			cpid = getpid();
+
+			res = execute_test(cpid);
+
+			exit(res);
+		}
+	}
+
+	for (int i = 0; i < NUM_ITERATIONS; i++) {
+		wait(&res);
+
+		if (WIFEXITED(res))
+			results[i] = WEXITSTATUS(res);
+		else
+			--i;
+	}
+
+	for (int i = 0; i < NUM_ITERATIONS; i++)
+		if (results[i] == KSFT_FAIL)
+			return KSFT_FAIL;
+
+	return KSFT_PASS;
+}
+
+int main(int argc, char *argv[])
+{
+	int err;
+
+	err = mte_default_setup();
+	if (err)
+		return err;
+
+	ksft_set_plan(1);
+
+	evaluate_test(mte_gcr_fork_test(),
+		"Verify that GCR_EL1 is set correctly on context switch\n");
+
+	mte_restore_setup();
+	ksft_print_cnts();
+
+	return ksft_get_fail_cnt() == 0 ? KSFT_PASS : KSFT_FAIL;
+}