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    SubjectRe: [PATCH 3/4] kselftests/arm64: add PAuth test for whether exec() changes keys
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    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@kernel.org>
    >> Cc: Catalin Marinas <catalin.marinas@arm.com>
    >> Cc: Will Deacon <will@kernel.org>
    >> Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.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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