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Message-ID: <70e207ea-f7c2-2c9d-e868-3ba3b6451c6f@arm.com>
Date: Thu, 3 Sep 2020 11:20:25 +0100
From: Boyan Karatotev <boyan.karatotev@....com>
To: Dave Martin <Dave.Martin@....com>
Cc: linux-arm-kernel@...ts.infradead.org,
linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
Will Deacon <will@...nel.org>, boian4o1@...il.com,
Catalin Marinas <catalin.marinas@....com>,
amit.kachhap@....com, vincenzo.frascino@....com,
Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH 3/4] kselftests/arm64: add PAuth test for whether exec()
changes keys
On 02/09/2020 18:00, Dave Martin wrote:
> On Fri, Aug 28, 2020 at 02:16:05PM +0100, Boyan Karatotev wrote:
>> 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@...nel.org>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Signed-off-by: Boyan Karatotev <boyan.karatotev@....com>
>> ---
>> 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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