selftests/powerpc: Add test to verify rfi flush across a system call

This adds a test to verify proper functioning of the rfi flush
capability implemented to mitigate meltdown. The test works by
measuring the number of L1d cache misses encountered while loading
data from memory. Across a system call, since the L1d cache is flushed
when rfi_flush is enabled, the number of cache misses is expected to
be relative to the number of cachelines corresponding to the data
being loaded.

The current system setting is reflected via powerpc/rfi_flush under
debugfs (assumed to be /sys/kernel/debug/). This test verifies the
expected result with rfi_flush enabled as well as when it is disabled.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
[mpe: Add SPDX tags, clang format, skip if the debugfs is missing, use
 __u64 and SANE_USERSPACE_TYPES to avoid printf() build errors.]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 152 insertions, 0 deletions

diff --git a/tools/testing/selftests/powerpc/utils.c b/tools/testing/selftests/powerpc/utils.c
index aa8fc1e6365b..43c342845be0 100644
--- a/tools/testing/selftests/powerpc/utils.c
+++ b/tools/testing/selftests/powerpc/utils.c
@@ -10,16 +10,22 @@
 #include <fcntl.h>
 #include <link.h>
 #include <sched.h>
+#include <signal.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
+#include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/utsname.h>
 #include <unistd.h>
+#include <asm/unistd.h>
+#include <linux/limits.h>
 
 #include "utils.h"
 
 static char auxv[4096];
+extern unsigned int dscr_insn[];
 
 int read_auxv(char *buf, ssize_t buf_size)
 {
@@ -121,3 +127,149 @@ bool is_ppc64le(void)
 
 	return strcmp(uts.machine, "ppc64le") == 0;
 }
+
+int read_debugfs_file(char *debugfs_file, int *result)
+{
+	int rc = -1, fd;
+	char path[PATH_MAX];
+	char value[16];
+
+	strcpy(path, "/sys/kernel/debug/");
+	strncat(path, debugfs_file, PATH_MAX - strlen(path) - 1);
+
+	if ((fd = open(path, O_RDONLY)) < 0)
+		return rc;
+
+	if ((rc = read(fd, value, sizeof(value))) < 0)
+		return rc;
+
+	value[15] = 0;
+	*result = atoi(value);
+	close(fd);
+
+	return 0;
+}
+
+int write_debugfs_file(char *debugfs_file, int result)
+{
+	int rc = -1, fd;
+	char path[PATH_MAX];
+	char value[16];
+
+	strcpy(path, "/sys/kernel/debug/");
+	strncat(path, debugfs_file, PATH_MAX - strlen(path) - 1);
+
+	if ((fd = open(path, O_WRONLY)) < 0)
+		return rc;
+
+	snprintf(value, 16, "%d", result);
+
+	if ((rc = write(fd, value, strlen(value))) < 0)
+		return rc;
+
+	close(fd);
+
+	return 0;
+}
+
+static long perf_event_open(struct perf_event_attr *hw_event, pid_t pid,
+		int cpu, int group_fd, unsigned long flags)
+{
+	return syscall(__NR_perf_event_open, hw_event, pid, cpu,
+		      group_fd, flags);
+}
+
+static void perf_event_attr_init(struct perf_event_attr *event_attr,
+					unsigned int type,
+					unsigned long config)
+{
+	memset(event_attr, 0, sizeof(*event_attr));
+
+	event_attr->type = type;
+	event_attr->size = sizeof(struct perf_event_attr);
+	event_attr->config = config;
+	event_attr->read_format = PERF_FORMAT_GROUP;
+	event_attr->disabled = 1;
+	event_attr->exclude_kernel = 1;
+	event_attr->exclude_hv = 1;
+	event_attr->exclude_guest = 1;
+}
+
+int perf_event_open_counter(unsigned int type,
+			    unsigned long config, int group_fd)
+{
+	int fd;
+	struct perf_event_attr event_attr;
+
+	perf_event_attr_init(&event_attr, type, config);
+
+	fd = perf_event_open(&event_attr, 0, -1, group_fd, 0);
+
+	if (fd < 0)
+		perror("perf_event_open() failed");
+
+	return fd;
+}
+
+int perf_event_enable(int fd)
+{
+	if (ioctl(fd, PERF_EVENT_IOC_ENABLE, PERF_IOC_FLAG_GROUP) == -1) {
+		perror("error while enabling perf events");
+		return -1;
+	}
+
+	return 0;
+}
+
+int perf_event_disable(int fd)
+{
+	if (ioctl(fd, PERF_EVENT_IOC_DISABLE, PERF_IOC_FLAG_GROUP) == -1) {
+		perror("error disabling perf events");
+		return -1;
+	}
+
+	return 0;
+}
+
+int perf_event_reset(int fd)
+{
+	if (ioctl(fd, PERF_EVENT_IOC_RESET, PERF_IOC_FLAG_GROUP) == -1) {
+		perror("error resetting perf events");
+		return -1;
+	}
+
+	return 0;
+}
+
+static void sigill_handler(int signr, siginfo_t *info, void *unused)
+{
+	static int warned = 0;
+	ucontext_t *ctx = (ucontext_t *)unused;
+	unsigned long *pc = &UCONTEXT_NIA(ctx);
+
+	if (*pc == (unsigned long)&dscr_insn) {
+		if (!warned++)
+			printf("WARNING: Skipping over dscr setup. Consider running 'ppc64_cpu --dscr=1' manually.\n");
+		*pc += 4;
+	} else {
+		printf("SIGILL at %p\n", pc);
+		abort();
+	}
+}
+
+void set_dscr(unsigned long val)
+{
+	static int init = 0;
+	struct sigaction sa;
+
+	if (!init) {
+		memset(&sa, 0, sizeof(sa));
+		sa.sa_sigaction = sigill_handler;
+		sa.sa_flags = SA_SIGINFO;
+		if (sigaction(SIGILL, &sa, NULL))
+			perror("sigill_handler");
+		init = 1;
+	}
+
+	asm volatile("dscr_insn: mtspr %1,%0" : : "r" (val), "i" (SPRN_DSCR));
+}