On 02/09/2020 18:00, Dave Martin wrote:

On Fri, Aug 28, 2020 at 02:16:05PM +0100, Boyan Karatotev wrote:

quoted

Kernel documentation states that it will change PAuth keys on exec() calls.

Verify that all keys are correctly switched to new ones.

Cc: Shuah Khan <shuah@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Boyan Karatotev <redacted>
---
 tools/testing/selftests/arm64/pauth/Makefile  |   4 +
 .../selftests/arm64/pauth/exec_target.c       |  35 +++++
 tools/testing/selftests/arm64/pauth/helper.h  |  10 ++
 tools/testing/selftests/arm64/pauth/pac.c     | 148 ++++++++++++++++++
 4 files changed, 197 insertions(+)
 create mode 100644 tools/testing/selftests/arm64/pauth/exec_target.c

diff --git a/tools/testing/selftests/arm64/pauth/Makefile b/tools/testing/selftests/arm64/pauth/Makefile
index a017d1c8dd58..2e237b21ccf6 100644
--- a/tools/testing/selftests/arm64/pauth/Makefile
+++ b/tools/testing/selftests/arm64/pauth/Makefile

@@ -5,6 +5,7 @@ CFLAGS += -mbranch-protection=pac-ret
 
 TEST_GEN_PROGS := pac
 TEST_GEN_FILES := pac_corruptor.o helper.o
+TEST_GEN_PROGS_EXTENDED := exec_target
 
 include ../../lib.mk
 

@@ -20,6 +21,9 @@ $(OUTPUT)/helper.o: helper.c
 # greater, gcc emits pac* instructions which are not in HINT NOP space,
 # preventing the tests from occurring at all. Compile for ARMv8.2 so tests can
 # run on earlier targets and print a meaningful error messages
+$(OUTPUT)/exec_target: exec_target.c $(OUTPUT)/helper.o
+	$(CC) $^ -o $@ $(CFLAGS) -march=armv8.2-a
+
 $(OUTPUT)/pac: pac.c $(OUTPUT)/pac_corruptor.o $(OUTPUT)/helper.o
 	$(CC) $^ -o $@ $(CFLAGS) -march=armv8.2-a
 

diff --git a/tools/testing/selftests/arm64/pauth/exec_target.c b/tools/testing/selftests/arm64/pauth/exec_target.c
new file mode 100644
index 000000000000..07addef5a1d7
--- /dev/null
+++ b/tools/testing/selftests/arm64/pauth/exec_target.c

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2020 ARM Limited
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/auxv.h>
+
+#include "helper.h"
+
+
+int main(void)
+{
+	struct signatures signed_vals;
+	unsigned long hwcaps;
+	size_t val;
+
+	fread(&val, sizeof(size_t), 1, stdin);
+
+	/* don't try to execute illegal (unimplemented) instructions) caller
+	 * should have checked this and keep worker simple
+	 */
+	hwcaps = getauxval(AT_HWCAP);
+
+	if (hwcaps & HWCAP_PACA) {
+		signed_vals.keyia = keyia_sign(val);
+		signed_vals.keyib = keyib_sign(val);
+		signed_vals.keyda = keyda_sign(val);
+		signed_vals.keydb = keydb_sign(val);
+	}
+	signed_vals.keyg = (hwcaps & HWCAP_PACG) ?  keyg_sign(val) : 0;
+
+	fwrite(&signed_vals, sizeof(struct signatures), 1, stdout);
+
+	return 0;
+}

diff --git a/tools/testing/selftests/arm64/pauth/helper.h b/tools/testing/selftests/arm64/pauth/helper.h
index b3cf709e249d..fceaa1e4824a 100644
--- a/tools/testing/selftests/arm64/pauth/helper.h
+++ b/tools/testing/selftests/arm64/pauth/helper.h

@@ -6,6 +6,16 @@
 
 #include <stdlib.h>
 
+#define NKEYS 5
+
+
+struct signatures {
+	size_t keyia;
+	size_t keyib;
+	size_t keyda;
+	size_t keydb;
+	size_t keyg;
+};
 
 void pac_corruptor(void);
 

diff --git a/tools/testing/selftests/arm64/pauth/pac.c b/tools/testing/selftests/arm64/pauth/pac.c
index cdbffa8bf61e..16dea47b11c7 100644
--- a/tools/testing/selftests/arm64/pauth/pac.c
+++ b/tools/testing/selftests/arm64/pauth/pac.c

@@ -2,6 +2,8 @@
 // Copyright (C) 2020 ARM Limited
 
 #include <sys/auxv.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 #include <signal.h>
 
 #include "../../kselftest_harness.h"

@@ -33,6 +35,117 @@ do { \
 } while (0)
 
 
+void sign_specific(struct signatures *sign, size_t val)
+{
+	sign->keyia = keyia_sign(val);
+	sign->keyib = keyib_sign(val);
+	sign->keyda = keyda_sign(val);
+	sign->keydb = keydb_sign(val);
+}
+
+void sign_all(struct signatures *sign, size_t val)
+{
+	sign->keyia = keyia_sign(val);
+	sign->keyib = keyib_sign(val);
+	sign->keyda = keyda_sign(val);
+	sign->keydb = keydb_sign(val);
+	sign->keyg  = keyg_sign(val);
+}
+
+int are_same(struct signatures *old, struct signatures *new, int nkeys)
+{
+	int res = 0;
+
+	res |= old->keyia == new->keyia;
+	res |= old->keyib == new->keyib;
+	res |= old->keyda == new->keyda;
+	res |= old->keydb == new->keydb;
+	if (nkeys == NKEYS)
+		res |= old->keyg  == new->keyg;
+
+	return res;
+}
+
+int exec_sign_all(struct signatures *signed_vals, size_t val)
+{

Could popen(3) be used here?

Fork-and-exec is notoriously fiddly, so it's preferable to use a library
function to do it where applicable.I would love to, but the worker needs a bidirectional channel and popen

only gives a unidirectional stream.

[...]

Cheers
---Dave

-- 
Regards,
Boyan

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