selftests/powerpc: Add uaccess flush test

Also based on the RFI and entry flush tests, it counts the L1D misses
by doing a syscall that does user access: uname, in this case.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
[dja: forward port, rename function]
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210225061949.1213404-1-dja@axtens.net

tools/testing/selftests/powerpc/security/Makefile

 # SPDX-License-Identifier: GPL-2.0+
 
-TEST_GEN_PROGS := rfi_flush entry_flush spectre_v2
+TEST_GEN_PROGS := rfi_flush entry_flush uaccess_flush spectre_v2
 top_srcdir = ../../../../..
 
 CFLAGS += -I../../../../../usr/include
@@ -13,3 +13,4 @@ $(OUTPUT)/spectre_v2: CFLAGS += -m64
 $(OUTPUT)/spectre_v2: ../pmu/event.c branch_loops.S
 $(OUTPUT)/rfi_flush: flush_utils.c
 $(OUTPUT)/entry_flush: flush_utils.c
+$(OUTPUT)/uaccess_flush: flush_utils.c

tools/testing/selftests/powerpc/security/flush_utils.c

@@ -13,6 +13,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <sys/utsname.h>
 #include "utils.h"
 #include "flush_utils.h"
 
@@ -35,6 +36,18 @@ void syscall_loop(char *p, unsigned long iterations,
 	}
 }
 
+void syscall_loop_uaccess(char *p, unsigned long iterations,
+			  unsigned long zero_size)
+{
+	struct utsname utsname;
+
+	for (unsigned long i = 0; i < iterations; i++) {
+		for (unsigned long j = 0; j < zero_size; j += CACHELINE_SIZE)
+			load(p + j);
+		uname(&utsname);
+	}
+}
+
 static void sigill_handler(int signr, siginfo_t *info, void *unused)
 {
 	static int warned;

tools/testing/selftests/powerpc/security/flush_utils.h

@@ -16,6 +16,9 @@
 void syscall_loop(char *p, unsigned long iterations,
 		  unsigned long zero_size);
 
+void syscall_loop_uaccess(char *p, unsigned long iterations,
+			  unsigned long zero_size);
+
 void set_dscr(unsigned long val);
 
 #endif /* _SELFTESTS_POWERPC_SECURITY_FLUSH_UTILS_H */

tools/testing/selftests/powerpc/security/uaccess_flush.c

+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * Copyright 2018 IBM Corporation.
+ * Copyright 2020 Canonical Ltd.
+ */
+
+#define __SANE_USERSPACE_TYPES__
+
+#include <sys/types.h>
+#include <stdint.h>
+#include <malloc.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include "utils.h"
+#include "flush_utils.h"
+
+int uaccess_flush_test(void)
+{
+	char *p;
+	int repetitions = 10;
+	int fd, passes = 0, iter, rc = 0;
+	struct perf_event_read v;
+	__u64 l1d_misses_total = 0;
+	unsigned long iterations = 100000, zero_size = 24 * 1024;
+	unsigned long l1d_misses_expected;
+	int rfi_flush_orig;
+	int entry_flush_orig;
+	int uaccess_flush, uaccess_flush_orig;
+
+	SKIP_IF(geteuid() != 0);
+
+	// The PMU event we use only works on Power7 or later
+	SKIP_IF(!have_hwcap(PPC_FEATURE_ARCH_2_06));
+
+	if (read_debugfs_file("powerpc/rfi_flush", &rfi_flush_orig) < 0) {
+		perror("Unable to read powerpc/rfi_flush debugfs file");
+		SKIP_IF(1);
+	}
+
+	if (read_debugfs_file("powerpc/entry_flush", &entry_flush_orig) < 0) {
+		perror("Unable to read powerpc/entry_flush debugfs file");
+		SKIP_IF(1);
+	}
+
+	if (read_debugfs_file("powerpc/uaccess_flush", &uaccess_flush_orig) < 0) {
+		perror("Unable to read powerpc/entry_flush debugfs file");
+		SKIP_IF(1);
+	}
+
+	if (rfi_flush_orig != 0) {
+		if (write_debugfs_file("powerpc/rfi_flush", 0) < 0) {
+			perror("error writing to powerpc/rfi_flush debugfs file");
+			FAIL_IF(1);
+		}
+	}
+
+	if (entry_flush_orig != 0) {
+		if (write_debugfs_file("powerpc/entry_flush", 0) < 0) {
+			perror("error writing to powerpc/entry_flush debugfs file");
+			FAIL_IF(1);
+		}
+	}
+
+	uaccess_flush = uaccess_flush_orig;
+
+	fd = perf_event_open_counter(PERF_TYPE_HW_CACHE, PERF_L1D_READ_MISS_CONFIG, -1);
+	FAIL_IF(fd < 0);
+
+	p = (char *)memalign(zero_size, CACHELINE_SIZE);
+
+	FAIL_IF(perf_event_enable(fd));
+
+	// disable L1 prefetching
+	set_dscr(1);
+
+	iter = repetitions;
+
+	/*
+	 * We expect to see l1d miss for each cacheline access when entry_flush
+	 * is set. Allow a small variation on this.
+	 */
+	l1d_misses_expected = iterations * (zero_size / CACHELINE_SIZE - 2);
+
+again:
+	FAIL_IF(perf_event_reset(fd));
+
+	syscall_loop_uaccess(p, iterations, zero_size);
+
+	FAIL_IF(read(fd, &v, sizeof(v)) != sizeof(v));
+
+	if (uaccess_flush && v.l1d_misses >= l1d_misses_expected)
+		passes++;
+	else if (!uaccess_flush && v.l1d_misses < (l1d_misses_expected / 2))
+		passes++;
+
+	l1d_misses_total += v.l1d_misses;
+
+	while (--iter)
+		goto again;
+
+	if (passes < repetitions) {
+		printf("FAIL (L1D misses with uaccess_flush=%d: %llu %c %lu) [%d/%d failures]\n",
+		       uaccess_flush, l1d_misses_total, uaccess_flush ? '<' : '>',
+		       uaccess_flush ? repetitions * l1d_misses_expected :
+		       repetitions * l1d_misses_expected / 2,
+		       repetitions - passes, repetitions);
+		rc = 1;
+	} else {
+		printf("PASS (L1D misses with uaccess_flush=%d: %llu %c %lu) [%d/%d pass]\n",
+		       uaccess_flush, l1d_misses_total, uaccess_flush ? '>' : '<',
+		       uaccess_flush ? repetitions * l1d_misses_expected :
+		       repetitions * l1d_misses_expected / 2,
+		       passes, repetitions);
+	}
+
+	if (uaccess_flush == uaccess_flush_orig) {
+		uaccess_flush = !uaccess_flush_orig;
+		if (write_debugfs_file("powerpc/uaccess_flush", uaccess_flush) < 0) {
+			perror("error writing to powerpc/uaccess_flush debugfs file");
+			return 1;
+		}
+		iter = repetitions;
+		l1d_misses_total = 0;
+		passes = 0;
+		goto again;
+	}
+
+	perf_event_disable(fd);
+	close(fd);
+
+	set_dscr(0);
+
+	if (write_debugfs_file("powerpc/rfi_flush", rfi_flush_orig) < 0) {
+		perror("unable to restore original value of powerpc/rfi_flush debugfs file");
+		return 1;
+	}
+
+	if (write_debugfs_file("powerpc/entry_flush", entry_flush_orig) < 0) {
+		perror("unable to restore original value of powerpc/entry_flush debugfs file");
+		return 1;
+	}
+
+	if (write_debugfs_file("powerpc/uaccess_flush", uaccess_flush_orig) < 0) {
+		perror("unable to restore original value of powerpc/uaccess_flush debugfs file");
+		return 1;
+	}
+
+	return rc;
+}
+
+int main(int argc, char *argv[])
+{
+	return test_harness(uaccess_flush_test, "uaccess_flush_test");
+}