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Message-ID: <356f1e7b2c3c1dfee74f030bca603ffc9549ffb4.1740403209.git.dvyukov@google.com>
Date: Mon, 24 Feb 2025 14:20:48 +0100
From: Dmitry Vyukov <dvyukov@...gle.com>
To: mathieu.desnoyers@...icios.com, peterz@...radead.org, boqun.feng@...il.com,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, hpa@...or.com, aruna.ramakrishna@...cle.com,
elver@...gle.com
Cc: Dmitry Vyukov <dvyukov@...gle.com>, "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 4/4] selftests/rseq: Add test for rseq+pkeys
Add a test that ensures that PKEY-protected struct rseq_cs
works and does not lead to process kills.
Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Aruna Ramakrishna <aruna.ramakrishna@...cle.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Fixes: d7822b1e24f2 ("rseq: Introduce restartable sequences system call")
---
Changes in v4:
- Added Fixes tag
Changes in v3:
- added Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
- rework the test to work when only pkey 0 is supported for rseq
Changes in v2:
- change test to install protected rseq_cs instead of rseq
---
tools/testing/selftests/rseq/Makefile | 2 +-
tools/testing/selftests/rseq/pkey_test.c | 99 ++++++++++++++++++++++++
tools/testing/selftests/rseq/rseq.h | 1 +
3 files changed, 101 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/rseq/Makefile b/tools/testing/selftests/rseq/Makefile
index 5a3432fceb586..9111d25fea3af 100644
--- a/tools/testing/selftests/rseq/Makefile
+++ b/tools/testing/selftests/rseq/Makefile
@@ -16,7 +16,7 @@ OVERRIDE_TARGETS = 1
TEST_GEN_PROGS = basic_test basic_percpu_ops_test basic_percpu_ops_mm_cid_test param_test \
param_test_benchmark param_test_compare_twice param_test_mm_cid \
- param_test_mm_cid_benchmark param_test_mm_cid_compare_twice
+ param_test_mm_cid_benchmark param_test_mm_cid_compare_twice pkey_test
TEST_GEN_PROGS_EXTENDED = librseq.so
diff --git a/tools/testing/selftests/rseq/pkey_test.c b/tools/testing/selftests/rseq/pkey_test.c
new file mode 100644
index 0000000000000..8752ecea21ba8
--- /dev/null
+++ b/tools/testing/selftests/rseq/pkey_test.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: LGPL-2.1
+/*
+ * Ensure that rseq works when rseq data is inaccessible due to PKEYs.
+ */
+
+#define _GNU_SOURCE
+#include <err.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <ucontext.h>
+#include <unistd.h>
+
+#include "rseq.h"
+#include "rseq-abi.h"
+
+int pkey;
+ucontext_t ucp0, ucp1;
+
+void coroutine(void)
+{
+ int i, orig_pk0, old_pk0, old_pk1, pk0, pk1;
+ /*
+ * When we disable access to pkey 0, globals and TLS become
+ * inaccessible too, so we need to tread carefully.
+ * Pkey is global so we need to copy it to onto stack.
+ * If ts is not volatile, then compiler may try to init it
+ * by loading a global 16-byte value.
+ */
+ volatile int pk = pkey;
+ volatile struct timespec ts;
+
+ orig_pk0 = pkey_get(0);
+ if (pkey_set(0, PKEY_DISABLE_ACCESS))
+ err(1, "pkey_set failed");
+ old_pk0 = pkey_get(0);
+ old_pk1 = pkey_get(pk);
+
+ /*
+ * If the kernel misbehaves, context switches in the following loop
+ * will terminate the process with SIGSEGV.
+ */
+ ts.tv_sec = 0;
+ ts.tv_nsec = 10 * 1000;
+ /*
+ * Trigger preemption w/o accessing TLS.
+ * Note that glibc's usleep touches errno always.
+ */
+ for (i = 0; i < 10; i++)
+ syscall(SYS_clock_nanosleep, CLOCK_MONOTONIC, 0, &ts, NULL);
+
+ pk0 = pkey_get(0);
+ pk1 = pkey_get(pk);
+ if (pkey_set(0, orig_pk0))
+ err(1, "pkey_set failed");
+
+ /*
+ * Ensure that the kernel has restored the previous value of pkeys
+ * register after changing them.
+ */
+ if (old_pk0 != pk0)
+ errx(1, "pkey 0 changed %d->%d", old_pk0, pk0);
+ if (old_pk1 != pk1)
+ errx(1, "pkey 1 changed %d->%d", old_pk1, pk1);
+
+ swapcontext(&ucp1, &ucp0);
+ abort();
+}
+
+int main(int argc, char **argv)
+{
+ pkey = pkey_alloc(0, 0);
+ if (pkey == -1) {
+ printf("[SKIP]\tKernel does not support PKEYs: %s\n",
+ strerror(errno));
+ return 0;
+ }
+
+ if (rseq_register_current_thread())
+ err(1, "rseq_register_current_thread failed");
+
+ if (getcontext(&ucp1))
+ err(1, "getcontext failed");
+ ucp1.uc_stack.ss_size = getpagesize() * 4;
+ ucp1.uc_stack.ss_sp = mmap(NULL, ucp1.uc_stack.ss_size,
+ PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
+ if (ucp1.uc_stack.ss_sp == MAP_FAILED)
+ err(1, "mmap failed");
+ if (pkey_mprotect(ucp1.uc_stack.ss_sp, ucp1.uc_stack.ss_size,
+ PROT_READ | PROT_WRITE, pkey))
+ err(1, "pkey_mprotect failed");
+ makecontext(&ucp1, coroutine, 0);
+ if (swapcontext(&ucp0, &ucp1))
+ err(1, "swapcontext failed");
+ return 0;
+}
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index ba424ce80a719..65da4a727c550 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -8,6 +8,7 @@
#ifndef RSEQ_H
#define RSEQ_H
+#include <assert.h>
#include <stdint.h>
#include <stdbool.h>
#include <pthread.h>
--
2.48.1.601.g30ceb7b040-goog
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