diff mbox series

[v7,36/39] selftests/arm64: Add GCS signal tests

Message ID 20231122-arm64-gcs-v7-36-201c483bd775@kernel.org (mailing list archive)
State Handled Elsewhere
Headers show
Series arm64/gcs: Provide support for GCS in userspace | expand

Checks

Context Check Description
conchuod/vmtest-fixes-PR fail merge-conflict

Commit Message

Mark Brown Nov. 22, 2023, 9:42 a.m. UTC
Do some testing of the signal handling for GCS, checking that a GCS
frame has the expected information in it and that the expected signals
are delivered with invalid operations.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/arm64/signal/.gitignore    |  1 +
 .../selftests/arm64/signal/test_signals_utils.h    | 10 +++
 .../arm64/signal/testcases/gcs_exception_fault.c   | 59 ++++++++++++++++
 .../selftests/arm64/signal/testcases/gcs_frame.c   | 78 ++++++++++++++++++++++
 .../arm64/signal/testcases/gcs_write_fault.c       | 67 +++++++++++++++++++
 5 files changed, 215 insertions(+)

Comments

Thiago Jung Bauermann Dec. 17, 2023, 2:12 a.m. UTC | #1
Mark Brown <broonie@kernel.org> writes:

> diff --git a/tools/testing/selftests/arm64/signal/testcases/gcs_exception_fault.c b/tools/testing/selftests/arm64/signal/testcases/gcs_exception_fault.c
> new file mode 100644
> index 000000000000..532d533592a1
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/signal/testcases/gcs_exception_fault.c
> @@ -0,0 +1,59 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023 ARM Limited
> + */
> +
> +#include <errno.h>
> +#include <signal.h>
> +#include <unistd.h>
> +
> +#include <sys/mman.h>
> +#include <sys/prctl.h>
> +
> +#include "test_signals_utils.h"
> +#include "testcases.h"
> +
> +/* This should be includable from some standard header, but which? */
> +#ifndef SEGV_CPERR
> +#define SEGV_CPERR 10
> +#endif

One suggestion is include/uapi/asm-generic/siginfo.h. It already has
SEGV_MTEAERR and SEGV_MTESERR, as well as si_codes specific to other
arches.

From there, it should find its way to glibc's
sysdeps/unix/sysv/linux/bits/siginfo-consts.h.

> +static int gcs_regs(struct tdescr *td, siginfo_t *si, ucontext_t *uc)
> +{
> +	size_t offset;
> +	struct _aarch64_ctx *head = GET_BUF_RESV_HEAD(context);
> +	struct gcs_context *gcs;
> +	unsigned long expected, gcspr;
> +	int ret;
> +
> +	ret = prctl(PR_GET_SHADOW_STACK_STATUS, &expected, 0, 0, 0);
> +	if (ret != 0) {
> +		fprintf(stderr, "Unable to query GCS status\n");
> +		return 1;
> +	}
> +
> +	/* We expect a cap to be added to the GCS in the signal frame */
> +	gcspr = get_gcspr_el0();
> +	gcspr -= 8;
> +	fprintf(stderr, "Expecting GCSPR_EL0 %lx\n", gcspr);
> +
> +	if (!get_current_context(td, &context.uc, sizeof(context))) {
> +		fprintf(stderr, "Failed getting context\n");
> +		return 1;
> +	}

At this point, before any function call is made, can the test check that
*(gcspr + 8) == 0? This would detect the issue I mentioned in
patch 24 of gcs_restore_signal() not zeroing the location of the cap.

> +	fprintf(stderr, "Got context\n");
> +
> +	head = get_header(head, GCS_MAGIC, GET_BUF_RESV_SIZE(context),
> +			  &offset);
> +	if (!head) {
> +		fprintf(stderr, "No GCS context\n");
> +		return 1;
> +	}
> +
> +	gcs = (struct gcs_context *)head;
> +
> +	/* Basic size validation is done in get_current_context() */
> +
> +	if (gcs->features_enabled != expected) {
> +		fprintf(stderr, "Features enabled %llx but expected %lx\n",
> +			gcs->features_enabled, expected);
> +		return 1;
> +	}
> +
> +	if (gcs->gcspr != gcspr) {
> +		fprintf(stderr, "Got GCSPR %llx but expected %lx\n",
> +			gcs->gcspr, gcspr);
> +		return 1;
> +	}

I suggest adding a new check here to ensure that gcs->reserved == 0.

> +	fprintf(stderr, "GCS context validated\n");
> +	td->pass = 1;
> +
> +	return 0;
> +}
> +
> +struct tdescr tde = {
> +	.name = "GCS basics",
> +	.descr = "Validate a GCS signal context",
> +	.feats_required = FEAT_GCS,
> +	.timeout = 3,
> +	.run = gcs_regs,
> +};
> diff --git a/tools/testing/selftests/arm64/signal/testcases/gcs_write_fault.c b/tools/testing/selftests/arm64/signal/testcases/gcs_write_fault.c
> new file mode 100644
> index 000000000000..126b1a294a29
> --- /dev/null
> +++ b/tools/testing/selftests/arm64/signal/testcases/gcs_write_fault.c
> @@ -0,0 +1,67 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2023 ARM Limited
> + */
> +
> +#include <errno.h>
> +#include <signal.h>
> +#include <unistd.h>
> +
> +#include <sys/mman.h>
> +#include <sys/prctl.h>
> +
> +#include "test_signals_utils.h"
> +#include "testcases.h"
> +
> +static uint64_t *gcs_page;
> +
> +#ifndef __NR_map_shadow_stack
> +#define __NR_map_shadow_stack 452
> +#endif
> +
> +static bool alloc_gcs(struct tdescr *td)
> +{
> +	long page_size = sysconf(_SC_PAGE_SIZE);
> +
> +	gcs_page = (void *)syscall(__NR_map_shadow_stack, 0,
> +				   page_size, 0);
> +	if (gcs_page == MAP_FAILED) {
> +		fprintf(stderr, "Failed to map %ld byte GCS: %d\n",
> +			page_size, errno);

This call is failing with EINVAL for me:

# timeout set to 45
# selftests: arm64/signal: gcs_write_fault
# # GCS write fault :: Normal writes to a GCS segfault
# Registered handlers for all signals.
# Detected MINSTKSIGSZ:4720
# Required Features: [ GCS ] supported
# Incompatible Features: [] absent
# Failed to map 4096 byte GCS: 22
# FAILED Testcase initialization.
# ==>> completed. FAIL(0)
not ok 11 selftests: arm64/signal: gcs_write_fault # exit=1

> +		return false;
> +	}
> +
> +	return true;
> +}
Mark Brown Jan. 18, 2024, 9:10 p.m. UTC | #2
On Sat, Dec 16, 2023 at 11:12:37PM -0300, Thiago Jung Bauermann wrote:
> Mark Brown <broonie@kernel.org> writes:

> > +/* This should be includable from some standard header, but which? */
> > +#ifndef SEGV_CPERR
> > +#define SEGV_CPERR 10
> > +#endif

> One suggestion is include/uapi/asm-generic/siginfo.h. It already has
> SEGV_MTEAERR and SEGV_MTESERR, as well as si_codes specific to other
> arches.

Sadly the testsuite is being very clever with redefining siginfo_t which
means it conflicts with that header.  I'll update the comment.

> > +	if (!get_current_context(td, &context.uc, sizeof(context))) {
> > +		fprintf(stderr, "Failed getting context\n");
> > +		return 1;
> > +	}

> At this point, before any function call is made, can the test check that
> *(gcspr + 8) == 0? This would detect the issue I mentioned in
> patch 24 of gcs_restore_signal() not zeroing the location of the cap.

Sure.

> > +	if (gcs->gcspr != gcspr) {
> > +		fprintf(stderr, "Got GCSPR %llx but expected %lx\n",
> > +			gcs->gcspr, gcspr);
> > +		return 1;
> > +	}

> I suggest adding a new check here to ensure that gcs->reserved == 0.

This would mean that you couldn't use an old kselftest build to verify
a new kernel that starts using the reserved bits.  It's niche but it
does seem like something that should work.
diff mbox series

Patch

diff --git a/tools/testing/selftests/arm64/signal/.gitignore b/tools/testing/selftests/arm64/signal/.gitignore
index 839e3a252629..26de12918890 100644
--- a/tools/testing/selftests/arm64/signal/.gitignore
+++ b/tools/testing/selftests/arm64/signal/.gitignore
@@ -1,6 +1,7 @@ 
 # SPDX-License-Identifier: GPL-2.0-only
 mangle_*
 fake_sigreturn_*
+gcs_*
 sme_*
 ssve_*
 sve_*
diff --git a/tools/testing/selftests/arm64/signal/test_signals_utils.h b/tools/testing/selftests/arm64/signal/test_signals_utils.h
index 1e80808ee105..36fc12b3cd60 100644
--- a/tools/testing/selftests/arm64/signal/test_signals_utils.h
+++ b/tools/testing/selftests/arm64/signal/test_signals_utils.h
@@ -6,6 +6,7 @@ 
 
 #include <assert.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <string.h>
 
 #include <linux/compiler.h>
@@ -47,6 +48,15 @@  void test_result(struct tdescr *td);
 		_arg1;							\
 	})
 
+static inline __attribute__((always_inline)) uint64_t get_gcspr_el0(void)
+{
+	uint64_t val;
+
+	asm volatile("mrs %0, S3_3_C2_C5_1" : "=r" (val));
+
+	return val;
+}
+
 static inline bool feats_ok(struct tdescr *td)
 {
 	if (td->feats_incompatible & td->feats_supported)
diff --git a/tools/testing/selftests/arm64/signal/testcases/gcs_exception_fault.c b/tools/testing/selftests/arm64/signal/testcases/gcs_exception_fault.c
new file mode 100644
index 000000000000..532d533592a1
--- /dev/null
+++ b/tools/testing/selftests/arm64/signal/testcases/gcs_exception_fault.c
@@ -0,0 +1,59 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 ARM Limited
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include <sys/mman.h>
+#include <sys/prctl.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+/* This should be includable from some standard header, but which? */
+#ifndef SEGV_CPERR
+#define SEGV_CPERR 10
+#endif
+
+static inline void gcsss1(uint64_t Xt)
+{
+	asm volatile (
+		"sys #3, C7, C7, #2, %0\n"
+		:
+		: "rZ" (Xt)
+		: "memory");
+}
+
+static int gcs_op_fault_trigger(struct tdescr *td)
+{
+	/*
+	 * The slot below our current GCS should be in a valid GCS but
+	 * must not have a valid cap in it.
+	 */
+	gcsss1(get_gcspr_el0() - 8);
+
+	return 0;
+}
+
+static int gcs_op_fault_signal(struct tdescr *td, siginfo_t *si,
+				  ucontext_t *uc)
+{
+	ASSERT_GOOD_CONTEXT(uc);
+
+	return 1;
+}
+
+struct tdescr tde = {
+	.name = "Invalid GCS operation",
+	.descr = "An invalid GCS operation generates the expected signal",
+	.feats_required = FEAT_GCS,
+	.timeout = 3,
+	.sig_ok = SIGSEGV,
+	.sig_ok_code = SEGV_CPERR,
+	.sanity_disabled = true,
+	.trigger = gcs_op_fault_trigger,
+	.run = gcs_op_fault_signal,
+};
diff --git a/tools/testing/selftests/arm64/signal/testcases/gcs_frame.c b/tools/testing/selftests/arm64/signal/testcases/gcs_frame.c
new file mode 100644
index 000000000000..d67cb26195a6
--- /dev/null
+++ b/tools/testing/selftests/arm64/signal/testcases/gcs_frame.c
@@ -0,0 +1,78 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 ARM Limited
+ */
+
+#include <signal.h>
+#include <ucontext.h>
+#include <sys/prctl.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+static union {
+	ucontext_t uc;
+	char buf[1024 * 64];
+} context;
+
+static int gcs_regs(struct tdescr *td, siginfo_t *si, ucontext_t *uc)
+{
+	size_t offset;
+	struct _aarch64_ctx *head = GET_BUF_RESV_HEAD(context);
+	struct gcs_context *gcs;
+	unsigned long expected, gcspr;
+	int ret;
+
+	ret = prctl(PR_GET_SHADOW_STACK_STATUS, &expected, 0, 0, 0);
+	if (ret != 0) {
+		fprintf(stderr, "Unable to query GCS status\n");
+		return 1;
+	}
+
+	/* We expect a cap to be added to the GCS in the signal frame */
+	gcspr = get_gcspr_el0();
+	gcspr -= 8;
+	fprintf(stderr, "Expecting GCSPR_EL0 %lx\n", gcspr);
+
+	if (!get_current_context(td, &context.uc, sizeof(context))) {
+		fprintf(stderr, "Failed getting context\n");
+		return 1;
+	}
+	fprintf(stderr, "Got context\n");
+
+	head = get_header(head, GCS_MAGIC, GET_BUF_RESV_SIZE(context),
+			  &offset);
+	if (!head) {
+		fprintf(stderr, "No GCS context\n");
+		return 1;
+	}
+
+	gcs = (struct gcs_context *)head;
+
+	/* Basic size validation is done in get_current_context() */
+
+	if (gcs->features_enabled != expected) {
+		fprintf(stderr, "Features enabled %llx but expected %lx\n",
+			gcs->features_enabled, expected);
+		return 1;
+	}
+
+	if (gcs->gcspr != gcspr) {
+		fprintf(stderr, "Got GCSPR %llx but expected %lx\n",
+			gcs->gcspr, gcspr);
+		return 1;
+	}
+
+	fprintf(stderr, "GCS context validated\n");
+	td->pass = 1;
+
+	return 0;
+}
+
+struct tdescr tde = {
+	.name = "GCS basics",
+	.descr = "Validate a GCS signal context",
+	.feats_required = FEAT_GCS,
+	.timeout = 3,
+	.run = gcs_regs,
+};
diff --git a/tools/testing/selftests/arm64/signal/testcases/gcs_write_fault.c b/tools/testing/selftests/arm64/signal/testcases/gcs_write_fault.c
new file mode 100644
index 000000000000..126b1a294a29
--- /dev/null
+++ b/tools/testing/selftests/arm64/signal/testcases/gcs_write_fault.c
@@ -0,0 +1,67 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 ARM Limited
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include <sys/mman.h>
+#include <sys/prctl.h>
+
+#include "test_signals_utils.h"
+#include "testcases.h"
+
+static uint64_t *gcs_page;
+
+#ifndef __NR_map_shadow_stack
+#define __NR_map_shadow_stack 452
+#endif
+
+static bool alloc_gcs(struct tdescr *td)
+{
+	long page_size = sysconf(_SC_PAGE_SIZE);
+
+	gcs_page = (void *)syscall(__NR_map_shadow_stack, 0,
+				   page_size, 0);
+	if (gcs_page == MAP_FAILED) {
+		fprintf(stderr, "Failed to map %ld byte GCS: %d\n",
+			page_size, errno);
+		return false;
+	}
+
+	return true;
+}
+
+static int gcs_write_fault_trigger(struct tdescr *td)
+{
+	/* Verify that the page is readable (ie, not completely unmapped) */
+	fprintf(stderr, "Read value 0x%lx\n", gcs_page[0]);
+
+	/* A regular write should trigger a fault */
+	gcs_page[0] = EINVAL;
+
+	return 0;
+}
+
+static int gcs_write_fault_signal(struct tdescr *td, siginfo_t *si,
+				  ucontext_t *uc)
+{
+	ASSERT_GOOD_CONTEXT(uc);
+
+	return 1;
+}
+
+
+struct tdescr tde = {
+	.name = "GCS write fault",
+	.descr = "Normal writes to a GCS segfault",
+	.feats_required = FEAT_GCS,
+	.timeout = 3,
+	.sig_ok = SIGSEGV,
+	.sanity_disabled = true,
+	.init = alloc_gcs,
+	.trigger = gcs_write_fault_trigger,
+	.run = gcs_write_fault_signal,
+};