From: Boyan Karatotev boyan.karatotev@arm.com
PAuth adds sign/verify controls to enable and disable groups of instructions in hardware for compatibility with libraries that do not implement PAuth. The kernel always enables them if it detects PAuth.
Add a test that checks that each group of instructions is enabled, if the kernel reports PAuth as detected.
Note: For groups, for the purpose of this patch, we intend instructions that use a certain key.
Cc: Shuah Khan shuah@kernel.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will@kernel.org Reviewed-by: Vincenzo Frascino Vincenzo.Frascino@arm.com Reviewed-by: Amit Daniel Kachhap amit.kachhap@arm.com Acked-by: Shuah Khan skhan@linuxfoundation.org Signed-off-by: Boyan Karatotev boyan.karatotev@arm.com --- .../testing/selftests/arm64/pauth/.gitignore | 1 + tools/testing/selftests/arm64/pauth/Makefile | 7 ++- tools/testing/selftests/arm64/pauth/helper.c | 39 ++++++++++++++ tools/testing/selftests/arm64/pauth/helper.h | 9 ++++ tools/testing/selftests/arm64/pauth/pac.c | 51 +++++++++++++++++++ 5 files changed, 105 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/arm64/pauth/helper.c
diff --git a/tools/testing/selftests/arm64/pauth/.gitignore b/tools/testing/selftests/arm64/pauth/.gitignore index b557c916720a..155137d92722 100644 --- a/tools/testing/selftests/arm64/pauth/.gitignore +++ b/tools/testing/selftests/arm64/pauth/.gitignore @@ -1 +1,2 @@ +exec_target pac diff --git a/tools/testing/selftests/arm64/pauth/Makefile b/tools/testing/selftests/arm64/pauth/Makefile index 01d35aaa610a..5c0dd129562f 100644 --- a/tools/testing/selftests/arm64/pauth/Makefile +++ b/tools/testing/selftests/arm64/pauth/Makefile @@ -12,7 +12,7 @@ pauth_cc_support := $(shell if ($(CC) $(CFLAGS) -march=armv8.3-a -E -x c /dev/nu
ifeq ($(pauth_cc_support),1) TEST_GEN_PROGS := pac -TEST_GEN_FILES := pac_corruptor.o +TEST_GEN_FILES := pac_corruptor.o helper.o endif
include ../../lib.mk @@ -23,10 +23,13 @@ ifeq ($(pauth_cc_support),1) $(OUTPUT)/pac_corruptor.o: pac_corruptor.S $(CC) -c $^ -o $@ $(CFLAGS) -march=armv8.3-a
+$(OUTPUT)/helper.o: helper.c + $(CC) -c $^ -o $@ $(CFLAGS) -march=armv8.3-a + # when -mbranch-protection is enabled and the target architecture is ARMv8.3 or # greater, gcc emits pac* instructions which are not in HINT NOP space, # preventing the tests from occurring at all. Compile for ARMv8.2 so tests can # run on earlier targets and print a meaningful error messages -$(OUTPUT)/pac: pac.c $(OUTPUT)/pac_corruptor.o +$(OUTPUT)/pac: pac.c $(OUTPUT)/pac_corruptor.o $(OUTPUT)/helper.o $(CC) $^ -o $@ $(CFLAGS) -march=armv8.2-a endif diff --git a/tools/testing/selftests/arm64/pauth/helper.c b/tools/testing/selftests/arm64/pauth/helper.c new file mode 100644 index 000000000000..2c201e7d0d50 --- /dev/null +++ b/tools/testing/selftests/arm64/pauth/helper.c @@ -0,0 +1,39 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2020 ARM Limited + +#include "helper.h" + +size_t keyia_sign(size_t ptr) +{ + asm volatile("paciza %0" : "+r" (ptr)); + return ptr; +} + +size_t keyib_sign(size_t ptr) +{ + asm volatile("pacizb %0" : "+r" (ptr)); + return ptr; +} + +size_t keyda_sign(size_t ptr) +{ + asm volatile("pacdza %0" : "+r" (ptr)); + return ptr; +} + +size_t keydb_sign(size_t ptr) +{ + asm volatile("pacdzb %0" : "+r" (ptr)); + return ptr; +} + +size_t keyg_sign(size_t ptr) +{ + /* output is encoded in the upper 32 bits */ + size_t dest = 0; + size_t modifier = 0; + + asm volatile("pacga %0, %1, %2" : "=r" (dest) : "r" (ptr), "r" (modifier)); + + return dest; +} diff --git a/tools/testing/selftests/arm64/pauth/helper.h b/tools/testing/selftests/arm64/pauth/helper.h index 3e0a2a404bf4..35c4f3357ae3 100644 --- a/tools/testing/selftests/arm64/pauth/helper.h +++ b/tools/testing/selftests/arm64/pauth/helper.h @@ -4,6 +4,15 @@ #ifndef _HELPER_H_ #define _HELPER_H_
+#include <stdlib.h> + void pac_corruptor(void);
+/* PAuth sign a value with key ia and modifier value 0 */ +size_t keyia_sign(size_t val); +size_t keyib_sign(size_t val); +size_t keyda_sign(size_t val); +size_t keydb_sign(size_t val); +size_t keyg_sign(size_t val); + #endif diff --git a/tools/testing/selftests/arm64/pauth/pac.c b/tools/testing/selftests/arm64/pauth/pac.c index 0293310ba70a..bd3d4c0eca9d 100644 --- a/tools/testing/selftests/arm64/pauth/pac.c +++ b/tools/testing/selftests/arm64/pauth/pac.c @@ -8,12 +8,25 @@ #include "../../kselftest_harness.h" #include "helper.h"
+#define PAC_COLLISION_ATTEMPTS 10 +/* + * The kernel sets TBID by default. So bits 55 and above should remain + * untouched no matter what. + * The VA space size is 48 bits. Bigger is opt-in. + */ +#define PAC_MASK (~0xff80ffffffffffff) #define ASSERT_PAUTH_ENABLED() \ do { \ unsigned long hwcaps = getauxval(AT_HWCAP); \ /* data key instructions are not in NOP space. This prevents a SIGILL */ \ ASSERT_NE(0, hwcaps & HWCAP_PACA) TH_LOG("PAUTH not enabled"); \ } while (0) +#define ASSERT_GENERIC_PAUTH_ENABLED() \ +do { \ + unsigned long hwcaps = getauxval(AT_HWCAP); \ + /* generic key instructions are not in NOP space. This prevents a SIGILL */ \ + ASSERT_NE(0, hwcaps & HWCAP_PACG) TH_LOG("Generic PAUTH not enabled"); \ +} while (0)
sigjmp_buf jmpbuf; void pac_signal_handler(int signum, siginfo_t *si, void *uc) @@ -41,4 +54,42 @@ TEST(corrupt_pac) } }
+/* + * There are no separate pac* and aut* controls so checking only the pac* + * instructions is sufficient + */ +TEST(pac_instructions_not_nop) +{ + size_t keyia = 0; + size_t keyib = 0; + size_t keyda = 0; + size_t keydb = 0; + + ASSERT_PAUTH_ENABLED(); + + for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) { + keyia |= keyia_sign(i) & PAC_MASK; + keyib |= keyib_sign(i) & PAC_MASK; + keyda |= keyda_sign(i) & PAC_MASK; + keydb |= keydb_sign(i) & PAC_MASK; + } + + ASSERT_NE(0, keyia) TH_LOG("keyia instructions did nothing"); + ASSERT_NE(0, keyib) TH_LOG("keyib instructions did nothing"); + ASSERT_NE(0, keyda) TH_LOG("keyda instructions did nothing"); + ASSERT_NE(0, keydb) TH_LOG("keydb instructions did nothing"); +} + +TEST(pac_instructions_not_nop_generic) +{ + size_t keyg = 0; + + ASSERT_GENERIC_PAUTH_ENABLED(); + + for (int i = 0; i < PAC_COLLISION_ATTEMPTS; i++) + keyg |= keyg_sign(i) & PAC_MASK; + + ASSERT_NE(0, keyg) TH_LOG("keyg instructions did nothing"); +} + TEST_HARNESS_MAIN