The arm64 Guarded Control Stack (GCS) feature provides support for
hardware protected stacks of return addresses, intended to provide
hardening against return oriented programming (ROP) attacks and to make
it easier to gather call stacks for applications such as profiling.
When GCS is active a secondary stack called the Guarded Control Stack is
maintained, protected with a memory attribute which means that it can
only be written with specific GCS operations. The current GCS pointer
can not be directly written to by userspace. When a BL is executed the
value stored in LR is also pushed onto the GCS, and when a RET is
executed the top of the GCS is popped and compared to LR with a fault
being raised if the values do not match. GCS operations may only be
performed on GCS pages, a data abort is generated if they are not.
The combination of hardware enforcement and lack of extra instructions
in the function entry and exit paths should result in something which
has less overhead and is more difficult to attack than a purely software
implementation like clang's shadow stacks.
This series implements support for use of GCS by userspace, along with
support for use of GCS within KVM guests. It does not enable use of GCS
by either EL1 or EL2, this will be implemented separately. Executables
are started without GCS and must use a prctl() to enable it, it is
expected that this will be done very early in application execution by
the dynamic linker or other startup code. For dynamic linking this will
be done by checking that everything in the executable is marked as GCS
compatible.
x86 has an equivalent feature called shadow stacks, this series depends
on the x86 patches for generic memory management support for the new
guarded/shadow stack page type and shares APIs as much as possible. As
there has been extensive discussion with the wider community around the
ABI for shadow stacks I have as far as practical kept implementation
decisions close to those for x86, anticipating that review would lead to
similar conclusions in the absence of strong reasoning for divergence.
The main divergence I am concious of is that x86 allows shadow stack to
be enabled and disabled repeatedly, freeing the shadow stack for the
thread whenever disabled, while this implementation keeps the GCS
allocated after disable but refuses to reenable it. This is to avoid
races with things actively walking the GCS during a disable, we do
anticipate that some systems will wish to disable GCS at runtime but are
not aware of any demand for subsequently reenabling it.
x86 uses an arch_prctl() to manage enable and disable, since only x86
and S/390 use arch_prctl() a generic prctl() was proposed[1] as part of a
patch set for the equivalent RISC-V zisslpcfi feature which I initially
adopted fairly directly but following review feedback has been revised
quite a bit.
There is an open issue with support for CRIU, on x86 this required the
ability to set the GCS mode via ptrace. This series supports
configuring mode bits other than enable/disable via ptrace but it needs
to be confirmed if this is sufficient.
There's a few bits where I'm not convinced with where I've placed
things, in particular the GCS write operation is in the GCS header not
in uaccess.h, I wasn't sure what was clearest there and am probably too
close to the code to have a clear opinion. The reporting of GCS in
/proc/PID/smaps is also a bit awkward.
The series depends on the x86 shadow stack support:
https://lore.kernel.org/lkml/20230227222957.24501-1-rick.p.edgecombe@intel.…
I've rebased this onto v6.5-rc4 but not included it in the series in
order to avoid confusion with Rick's work and cut down the size of the
series, you can see the branch at:
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/misc.git arm64-gcs
[1] https://lore.kernel.org/lkml/20230213045351.3945824-1-debug@rivosinc.com/
Pending feedback from Catalin:
- Use clone3() paramaters to size/place the GCS.
- Switch copy_to_user_gcs() to be put_user_gcs().
Signed-off-by: Mark Brown <broonie(a)kernel.org>
---
Changes in v6:
- Rebase onto v6.6-rc3.
- Add some more gcsb_dsync() barriers following spec clarifications.
- Due to ongoing discussion around clone()/clone3() I've not updated
anything there, the behaviour is the same as on previous versions.
- Link to v5: https://lore.kernel.org/r/20230822-arm64-gcs-v5-0-9ef181dd6324@kernel.org
Changes in v5:
- Don't map any permissions for user GCSs, we always use EL0 accessors
or use a separate mapping of the page.
- Reduce the standard size of the GCS to RLIMIT_STACK/2.
- Enforce a PAGE_SIZE alignment requirement on map_shadow_stack().
- Clarifications and fixes to documentation.
- More tests.
- Link to v4: https://lore.kernel.org/r/20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org
Changes in v4:
- Implement flags for map_shadow_stack() allowing the cap and end of
stack marker to be enabled independently or not at all.
- Relax size and alignment requirements for map_shadow_stack().
- Add more blurb explaining the advantages of hardware enforcement.
- Link to v3: https://lore.kernel.org/r/20230731-arm64-gcs-v3-0-cddf9f980d98@kernel.org
Changes in v3:
- Rebase onto v6.5-rc4.
- Add a GCS barrier on context switch.
- Add a GCS stress test.
- Link to v2: https://lore.kernel.org/r/20230724-arm64-gcs-v2-0-dc2c1d44c2eb@kernel.org
Changes in v2:
- Rebase onto v6.5-rc3.
- Rework prctl() interface to allow each bit to be locked independently.
- map_shadow_stack() now places the cap token based on the size
requested by the caller not the actual space allocated.
- Mode changes other than enable via ptrace are now supported.
- Expand test coverage.
- Various smaller fixes and adjustments.
- Link to v1: https://lore.kernel.org/r/20230716-arm64-gcs-v1-0-bf567f93bba6@kernel.org
---
Mark Brown (38):
arm64/mm: Restructure arch_validate_flags() for extensibility
prctl: arch-agnostic prctl for shadow stack
mman: Add map_shadow_stack() flags
arm64: Document boot requirements for Guarded Control Stacks
arm64/gcs: Document the ABI for Guarded Control Stacks
arm64/sysreg: Add new system registers for GCS
arm64/sysreg: Add definitions for architected GCS caps
arm64/gcs: Add manual encodings of GCS instructions
arm64/gcs: Provide copy_to_user_gcs()
arm64/cpufeature: Runtime detection of Guarded Control Stack (GCS)
arm64/mm: Allocate PIE slots for EL0 guarded control stack
mm: Define VM_SHADOW_STACK for arm64 when we support GCS
arm64/mm: Map pages for guarded control stack
KVM: arm64: Manage GCS registers for guests
arm64/gcs: Allow GCS usage at EL0 and EL1
arm64/idreg: Add overrride for GCS
arm64/hwcap: Add hwcap for GCS
arm64/traps: Handle GCS exceptions
arm64/mm: Handle GCS data aborts
arm64/gcs: Context switch GCS state for EL0
arm64/gcs: Allocate a new GCS for threads with GCS enabled
arm64/gcs: Implement shadow stack prctl() interface
arm64/mm: Implement map_shadow_stack()
arm64/signal: Set up and restore the GCS context for signal handlers
arm64/signal: Expose GCS state in signal frames
arm64/ptrace: Expose GCS via ptrace and core files
arm64: Add Kconfig for Guarded Control Stack (GCS)
kselftest/arm64: Verify the GCS hwcap
kselftest/arm64: Add GCS as a detected feature in the signal tests
kselftest/arm64: Add framework support for GCS to signal handling tests
kselftest/arm64: Allow signals tests to specify an expected si_code
kselftest/arm64: Always run signals tests with GCS enabled
kselftest/arm64: Add very basic GCS test program
kselftest/arm64: Add a GCS test program built with the system libc
kselftest/arm64: Add test coverage for GCS mode locking
selftests/arm64: Add GCS signal tests
kselftest/arm64: Add a GCS stress test
kselftest/arm64: Enable GCS for the FP stress tests
Documentation/admin-guide/kernel-parameters.txt | 6 +
Documentation/arch/arm64/booting.rst | 22 +
Documentation/arch/arm64/elf_hwcaps.rst | 3 +
Documentation/arch/arm64/gcs.rst | 233 +++++++
Documentation/arch/arm64/index.rst | 1 +
Documentation/filesystems/proc.rst | 2 +-
arch/arm64/Kconfig | 19 +
arch/arm64/include/asm/cpufeature.h | 6 +
arch/arm64/include/asm/el2_setup.h | 17 +
arch/arm64/include/asm/esr.h | 28 +-
arch/arm64/include/asm/exception.h | 2 +
arch/arm64/include/asm/gcs.h | 106 +++
arch/arm64/include/asm/hwcap.h | 1 +
arch/arm64/include/asm/kvm_arm.h | 4 +-
arch/arm64/include/asm/kvm_host.h | 12 +
arch/arm64/include/asm/mman.h | 23 +-
arch/arm64/include/asm/pgtable-prot.h | 14 +-
arch/arm64/include/asm/processor.h | 7 +
arch/arm64/include/asm/sysreg.h | 20 +
arch/arm64/include/asm/uaccess.h | 42 ++
arch/arm64/include/uapi/asm/hwcap.h | 1 +
arch/arm64/include/uapi/asm/ptrace.h | 8 +
arch/arm64/include/uapi/asm/sigcontext.h | 9 +
arch/arm64/kernel/cpufeature.c | 19 +
arch/arm64/kernel/cpuinfo.c | 1 +
arch/arm64/kernel/entry-common.c | 23 +
arch/arm64/kernel/idreg-override.c | 2 +
arch/arm64/kernel/process.c | 92 +++
arch/arm64/kernel/ptrace.c | 59 ++
arch/arm64/kernel/signal.c | 237 ++++++-
arch/arm64/kernel/traps.c | 11 +
arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 17 +
arch/arm64/kvm/sys_regs.c | 22 +
arch/arm64/mm/Makefile | 1 +
arch/arm64/mm/fault.c | 79 ++-
arch/arm64/mm/gcs.c | 228 +++++++
arch/arm64/mm/mmap.c | 13 +-
arch/arm64/tools/cpucaps | 1 +
arch/arm64/tools/sysreg | 55 ++
arch/x86/include/uapi/asm/mman.h | 3 -
fs/proc/task_mmu.c | 3 +
include/linux/mm.h | 16 +-
include/uapi/asm-generic/mman.h | 4 +
include/uapi/asm-generic/unistd.h | 5 +-
include/uapi/linux/elf.h | 1 +
include/uapi/linux/prctl.h | 22 +
kernel/sys.c | 30 +
tools/testing/selftests/arm64/Makefile | 2 +-
tools/testing/selftests/arm64/abi/hwcap.c | 19 +
tools/testing/selftests/arm64/fp/assembler.h | 15 +
tools/testing/selftests/arm64/fp/fpsimd-test.S | 2 +
tools/testing/selftests/arm64/fp/sve-test.S | 2 +
tools/testing/selftests/arm64/fp/za-test.S | 2 +
tools/testing/selftests/arm64/fp/zt-test.S | 2 +
tools/testing/selftests/arm64/gcs/.gitignore | 5 +
tools/testing/selftests/arm64/gcs/Makefile | 24 +
tools/testing/selftests/arm64/gcs/asm-offsets.h | 0
tools/testing/selftests/arm64/gcs/basic-gcs.c | 356 ++++++++++
tools/testing/selftests/arm64/gcs/gcs-locking.c | 200 ++++++
.../selftests/arm64/gcs/gcs-stress-thread.S | 311 +++++++++
tools/testing/selftests/arm64/gcs/gcs-stress.c | 532 +++++++++++++++
tools/testing/selftests/arm64/gcs/gcs-util.h | 100 +++
tools/testing/selftests/arm64/gcs/libc-gcs.c | 742 +++++++++++++++++++++
tools/testing/selftests/arm64/signal/.gitignore | 1 +
.../testing/selftests/arm64/signal/test_signals.c | 17 +-
.../testing/selftests/arm64/signal/test_signals.h | 6 +
.../selftests/arm64/signal/test_signals_utils.c | 32 +-
.../selftests/arm64/signal/test_signals_utils.h | 39 ++
.../arm64/signal/testcases/gcs_exception_fault.c | 59 ++
.../selftests/arm64/signal/testcases/gcs_frame.c | 78 +++
.../arm64/signal/testcases/gcs_write_fault.c | 67 ++
.../selftests/arm64/signal/testcases/testcases.c | 7 +
.../selftests/arm64/signal/testcases/testcases.h | 1 +
73 files changed, 4110 insertions(+), 41 deletions(-)
---
base-commit: 6465e260f48790807eef06b583b38ca9789b6072
change-id: 20230303-arm64-gcs-e311ab0d8729
Best regards,
--
Mark Brown <broonie(a)kernel.org>
On Sun, Oct 8, 2023 at 7:22 AM Akihiko Odaki <akihiko.odaki(a)daynix.com> wrote:
>
> tun_vnet_hash can use this flag to indicate it stored virtio-net hash
> cache to cb.
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki(a)daynix.com>
> ---
> include/linux/skbuff.h | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 4174c4b82d13..e638f157c13c 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -837,6 +837,7 @@ typedef unsigned char *sk_buff_data_t;
> * @truesize: Buffer size
> * @users: User count - see {datagram,tcp}.c
> * @extensions: allocated extensions, valid if active_extensions is nonzero
> + * @tun_vnet_hash: tun stored virtio-net hash cache to cb
> */
>
> struct sk_buff {
> @@ -989,6 +990,7 @@ struct sk_buff {
> #if IS_ENABLED(CONFIG_IP_SCTP)
> __u8 csum_not_inet:1;
> #endif
> + __u8 tun_vnet_hash:1;
sk_buff space is very limited.
No need to extend it, especially for code that stays within a single
subsystem (tun).
To a lesser extent the same point applies to the qdisc_skb_cb.
On Sun, Oct 8, 2023 at 7:21 AM Akihiko Odaki <akihiko.odaki(a)daynix.com> wrote:
>
> virtio-net have two usage of hashes: one is RSS and another is hash
> reporting. Conventionally the hash calculation was done by the VMM.
> However, computing the hash after the queue was chosen defeats the
> purpose of RSS.
>
> Another approach is to use eBPF steering program. This approach has
> another downside: it cannot report the calculated hash due to the
> restrictive nature of eBPF.
>
> Introduce the code to compute hashes to the kernel in order to overcome
> thse challenges.
>
> An alternative solution is to extend the eBPF steering program so that it
> will be able to report to the userspace, but it makes little sense to
> allow to implement different hashing algorithms with eBPF since the hash
> value reported by virtio-net is strictly defined by the specification.
But using the existing BPF steering may have the benefit of requiring
a lot less new code.
There is ample precedence for BPF programs that work this way. The
flow dissector comes to mind.
The test will not work for systems with pagesize != 4096 like aarch64
and some others.
Other testcases are already testing the same functionality:
* auxv_AT_UID tests getauxval() in general.
* test_getpagesize() tests pagesize() which directly calls
getauxval(AT_PAGESZ).
Fixes: 48967b73f8fe ("selftests/nolibc: add testcases for startup code")
Cc: stable(a)vger.kernel.org
Signed-off-by: Thomas Weißschuh <linux(a)weissschuh.net>
---
Note:
This should probably also make it into 6.6.
---
tools/testing/selftests/nolibc/nolibc-test.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index a3ee4496bf0a..7e3936c182dc 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -630,7 +630,6 @@ int run_startup(int min, int max)
CASE_TEST(environ_HOME); EXPECT_PTRNZ(1, getenv("HOME")); break;
CASE_TEST(auxv_addr); EXPECT_PTRGT(test_auxv != (void *)-1, test_auxv, brk); break;
CASE_TEST(auxv_AT_UID); EXPECT_EQ(1, getauxval(AT_UID), getuid()); break;
- CASE_TEST(auxv_AT_PAGESZ); EXPECT_GE(1, getauxval(AT_PAGESZ), 4096); break;
case __LINE__:
return ret; /* must be last */
/* note: do not set any defaults so as to permit holes above */
---
base-commit: ab663cc32912914258bc8a2fbd0e753f552ee9d8
change-id: 20231007-nolibc-auxval-pagesz-05f5ff79c4c4
Best regards,
--
Thomas Weißschuh <linux(a)weissschuh.net>
The indentation of parameterized tests messages is currently broken in kunit.
Try to fix that by introducing a test level attribute, that will be increased
during nested parameterized tests execution, and use it to generate correct
indent at the runtime when printing message or writing them to the log.
Also improve kunit by providing test plan for the parameterized tests.
Cc: David Gow <davidgow(a)google.com>
Cc: Rae Moar <rmoar(a)google.com>
Michal Wajdeczko (4):
kunit: Drop redundant text from suite init failure message
kunit: Fix indentation level of suite messages
kunit: Fix indentation of parameterized tests messages
kunit: Prepare test plan for parameterized subtests
include/kunit/test.h | 25 ++++++++++++--
lib/kunit/test.c | 79 +++++++++++++++++++++++---------------------
2 files changed, 65 insertions(+), 39 deletions(-)
--
2.25.1
Today we reset the suite counter as part of the suite cleanup,
called from the module exit callback, but it might not work that
well as one can try to collect results without unloading a previous
test (either unintentionally or due to dependencies).
For easy reproduction try to load the kunit-test.ko and then
collect and parse results from the kunit-example-test.ko load.
Parser will complain about mismatch of expected test number:
[ ] KTAP version 1
[ ] 1..1
[ ] # example: initializing suite
[ ] KTAP version 1
[ ] # Subtest: example
..
[ ] # example: pass:5 fail:0 skip:4 total:9
[ ] # Totals: pass:6 fail:0 skip:6 total:12
[ ] ok 7 example
[ ] [ERROR] Test: example: Expected test number 1 but found 7
[ ] ===================== [PASSED] example =====================
[ ] ============================================================
[ ] Testing complete. Ran 12 tests: passed: 6, skipped: 6, errors: 1
Since we are now printing suite test plan on every module load,
right before running suite tests, we should make sure that suite
counter will also start from 1. Easiest solution seems to be move
counter reset to the __kunit_test_suites_init() function.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko(a)intel.com>
Cc: David Gow <davidgow(a)google.com>
Cc: Rae Moar <rmoar(a)google.com>
---
lib/kunit/test.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index f2eb71f1a66c..9325d309ed82 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -670,6 +670,8 @@ int __kunit_test_suites_init(struct kunit_suite * const * const suites, int num_
return 0;
}
+ kunit_suite_counter = 1;
+
static_branch_inc(&kunit_running);
for (i = 0; i < num_suites; i++) {
@@ -696,8 +698,6 @@ void __kunit_test_suites_exit(struct kunit_suite **suites, int num_suites)
for (i = 0; i < num_suites; i++)
kunit_exit_suite(suites[i]);
-
- kunit_suite_counter = 1;
}
EXPORT_SYMBOL_GPL(__kunit_test_suites_exit);
--
2.25.1
With the startup code moved to C, implementing support for
constructors and deconstructors is fairly easy to implement.
Examples for code size impact:
text data bss dec hex filename
21837 104 88 22029 560d nolibc-test.before
22135 120 88 22343 5747 nolibc-test.after
21970 104 88 22162 5692 nolibc-test.after-only-crt.h-changes
The sections are defined by [0].
[0] https://refspecs.linuxfoundation.org/elf/gabi4+/ch5.dynamic.html
Signed-off-by: Thomas Weißschuh <linux(a)weissschuh.net>
---
Note:
This is only an RFC as I'm not 100% sure it belong into nolibc.
But at least the code is visible as an example.
Also it is one prerequisite for full ksefltest_harness.h support in
nolibc, should we want that.
---
tools/include/nolibc/crt.h | 23 ++++++++++++++++++++++-
tools/testing/selftests/nolibc/nolibc-test.c | 16 ++++++++++++++++
2 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h
index a5f33fef1672..c1176611d9a9 100644
--- a/tools/include/nolibc/crt.h
+++ b/tools/include/nolibc/crt.h
@@ -13,11 +13,22 @@ const unsigned long *_auxv __attribute__((weak));
static void __stack_chk_init(void);
static void exit(int);
+extern void (*const __preinit_array_start[])(void) __attribute__((weak));
+extern void (*const __preinit_array_end[])(void) __attribute__((weak));
+
+extern void (*const __init_array_start[])(void) __attribute__((weak));
+extern void (*const __init_array_end[])(void) __attribute__((weak));
+
+extern void (*const __fini_array_start[])(void) __attribute__((weak));
+extern void (*const __fini_array_end[])(void) __attribute__((weak));
+
void _start_c(long *sp)
{
long argc;
char **argv;
char **envp;
+ int exitcode;
+ void (* const *func)(void);
const unsigned long *auxv;
/* silence potential warning: conflicting types for 'main' */
int _nolibc_main(int, char **, char **) __asm__ ("main");
@@ -54,8 +65,18 @@ void _start_c(long *sp)
;
_auxv = auxv;
+ for (func = __preinit_array_start; func < __preinit_array_end; func++)
+ (*func)();
+ for (func = __init_array_start; func < __init_array_end; func++)
+ (*func)();
+
/* go to application */
- exit(_nolibc_main(argc, argv, envp));
+ exitcode = _nolibc_main(argc, argv, envp);
+
+ for (func = __fini_array_end - 1; func >= __fini_array_start; func--)
+ (*func)();
+
+ exit(exitcode);
}
#endif /* _NOLIBC_CRT_H */
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index a3ee4496bf0a..f166b425613a 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -57,6 +57,9 @@ static int test_argc;
/* will be used by some test cases as readable file, please don't write it */
static const char *argv0;
+/* will be used by constructor tests */
+static int constructor_test_value;
+
/* definition of a series of tests */
struct test {
const char *name; /* test name */
@@ -594,6 +597,18 @@ int expect_strne(const char *expr, int llen, const char *cmp)
#define CASE_TEST(name) \
case __LINE__: llen += printf("%d %s", test, #name);
+__attribute__((constructor))
+static void constructor1(void)
+{
+ constructor_test_value = 1;
+}
+
+__attribute__((constructor))
+static void constructor2(void)
+{
+ constructor_test_value *= 2;
+}
+
int run_startup(int min, int max)
{
int test;
@@ -631,6 +646,7 @@ int run_startup(int min, int max)
CASE_TEST(auxv_addr); EXPECT_PTRGT(test_auxv != (void *)-1, test_auxv, brk); break;
CASE_TEST(auxv_AT_UID); EXPECT_EQ(1, getauxval(AT_UID), getuid()); break;
CASE_TEST(auxv_AT_PAGESZ); EXPECT_GE(1, getauxval(AT_PAGESZ), 4096); break;
+ CASE_TEST(constructor); EXPECT_EQ(1, constructor_test_value, 2); break;
case __LINE__:
return ret; /* must be last */
/* note: do not set any defaults so as to permit holes above */
---
base-commit: ab663cc32912914258bc8a2fbd0e753f552ee9d8
change-id: 20231005-nolibc-constructors-b2aebffe9b65
Best regards,
--
Thomas Weißschuh <linux(a)weissschuh.net>
The original order of cases in kunit_module_notify() is confusing and
misleading.
And the best practice is return the err code from
MODULE_STATE_COMING func.
And the test suits should be executed when notify MODULE_STATE_LIVE.
Jinjie Ruan (3):
kunit: Make the cases sequence more reasonable for
kunit_module_notify()
kunit: Return error from kunit_module_init()
kunit: Init and run test suites in the right state
lib/kunit/test.c | 37 +++++++++++++++++++++++--------------
1 file changed, 23 insertions(+), 14 deletions(-)
--
2.34.1