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Subject[PATCH 5.4 05/17] selftests/powerpc: entry flush test
Date
From: Daniel Axtens <dja@axtens.net>

commit 89a83a0c69c81a25ce91002b90ca27ed86132a0a upstream.

Add a test modelled on the RFI flush test which counts the number
of L1D misses doing a simple syscall with the entry flush on and off.

For simplicity of backporting, this test duplicates a lot of code from
the upstream rfi_flush. This is cleaned up upstream, but we don't clean
it up here because it would involve bringing in even more commits.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/powerpc/kernel/setup_64.c | 2
arch/powerpc/platforms/powernv/setup.c | 6
tools/testing/selftests/powerpc/security/.gitignore | 1
tools/testing/selftests/powerpc/security/Makefile | 2
tools/testing/selftests/powerpc/security/entry_flush.c | 163 +++++++++++++++++
5 files changed, 170 insertions(+), 4 deletions(-)
create mode 100644 tools/testing/selftests/powerpc/security/entry_flush.c

--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -1025,7 +1025,7 @@ void setup_uaccess_flush(bool enable)
return;

if (!no_uaccess_flush)
- uaccess_flush_enable(true);
+ uaccess_flush_enable(enable);
}

#ifdef CONFIG_DEBUG_FS
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -124,10 +124,12 @@ static void pnv_setup_rfi_flush(void)

/*
* If we are non-Power9 bare metal, we don't need to flush on kernel
- * entry: it fixes a P9 specific vulnerability.
+ * entry or after user access: they fix a P9 specific vulnerability.
*/
- if (!pvr_version_is(PVR_POWER9))
+ if (!pvr_version_is(PVR_POWER9)) {
security_ftr_clear(SEC_FTR_L1D_FLUSH_ENTRY);
+ security_ftr_clear(SEC_FTR_L1D_FLUSH_UACCESS);
+ }

enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && \
(security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) || \
--- a/tools/testing/selftests/powerpc/security/.gitignore
+++ b/tools/testing/selftests/powerpc/security/.gitignore
@@ -1 +1,2 @@
rfi_flush
+entry_flush
--- a/tools/testing/selftests/powerpc/security/Makefile
+++ b/tools/testing/selftests/powerpc/security/Makefile
@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0+

-TEST_GEN_PROGS := rfi_flush
+TEST_GEN_PROGS := rfi_flush entry_flush
top_srcdir = ../../../../..

CFLAGS += -I../../../../../usr/include
--- /dev/null
+++ b/tools/testing/selftests/powerpc/security/entry_flush.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ * Copyright 2018 IBM Corporation.
+ */
+
+#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"
+
+#define CACHELINE_SIZE 128
+
+struct perf_event_read {
+ __u64 nr;
+ __u64 l1d_misses;
+};
+
+static inline __u64 load(void *addr)
+{
+ __u64 tmp;
+
+ asm volatile("ld %0,0(%1)" : "=r"(tmp) : "b"(addr));
+
+ return tmp;
+}
+
+static void syscall_loop(char *p, unsigned long iterations,
+ unsigned long zero_size)
+{
+ for (unsigned long i = 0; i < iterations; i++) {
+ for (unsigned long j = 0; j < zero_size; j += CACHELINE_SIZE)
+ load(p + j);
+ getppid();
+ }
+}
+
+int entry_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, entry_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 (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);
+ }
+ }
+
+ entry_flush = entry_flush_orig;
+
+ fd = perf_event_open_counter(PERF_TYPE_RAW, /* L1d miss */ 0x400f0, -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(p, iterations, zero_size);
+
+ FAIL_IF(read(fd, &v, sizeof(v)) != sizeof(v));
+
+ if (entry_flush && v.l1d_misses >= l1d_misses_expected)
+ passes++;
+ else if (!entry_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 entry_flush=%d: %llu %c %lu) [%d/%d failures]\n",
+ entry_flush, l1d_misses_total, entry_flush ? '<' : '>',
+ entry_flush ? repetitions * l1d_misses_expected :
+ repetitions * l1d_misses_expected / 2,
+ repetitions - passes, repetitions);
+ rc = 1;
+ } else
+ printf("PASS (L1D misses with entry_flush=%d: %llu %c %lu) [%d/%d pass]\n",
+ entry_flush, l1d_misses_total, entry_flush ? '>' : '<',
+ entry_flush ? repetitions * l1d_misses_expected :
+ repetitions * l1d_misses_expected / 2,
+ passes, repetitions);
+
+ if (entry_flush == entry_flush_orig) {
+ entry_flush = !entry_flush_orig;
+ if (write_debugfs_file("powerpc/entry_flush", entry_flush) < 0) {
+ perror("error writing to powerpc/entry_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;
+ }
+
+ return rc;
+}
+
+int main(int argc, char *argv[])
+{
+ return test_harness(entry_flush_test, "entry_flush_test");
+}

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