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[PATCH v5 00/37] arm64/gcs: Provide support for GCS in userspace

by Mark Brown

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: - Switch copy_to_user_gcs() to be put_user_gcs(). Signed-off-by: Mark Brown <broonie(a)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 (37): arm64/mm: Restructure arch_validate_flags() for extensibility prctl: arch-agnostic prctl for shadow stack 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 | 3 + 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 | 20 +- 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 | 89 +++ 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 | 225 +++++++ arch/arm64/mm/mmap.c | 13 +- arch/arm64/tools/cpucaps | 1 + arch/arm64/tools/sysreg | 55 ++ fs/proc/task_mmu.c | 3 + include/linux/mm.h | 16 +- include/linux/syscalls.h | 1 + include/uapi/asm-generic/unistd.h | 5 +- include/uapi/linux/elf.h | 1 + include/uapi/linux/prctl.h | 22 + kernel/sys.c | 30 + kernel/sys_ni.c | 1 + 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, 4096 insertions(+), 38 deletions(-) --- base-commit: e514f673179ed8af6c64d79f8d43e2569ad6cb9f change-id: 20230303-arm64-gcs-e311ab0d8729 Best regards, -- Mark Brown <broonie(a)kernel.org>

2 years

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[PATCH v2 0/2] selftests: cachestat: fix run on older kernels

by Andre Przywara

I ran all kernel selftests on some test machine, and stumbled upon cachestat failing (among others). These patches fix the run on older kernels and when the current directory is on a tmpfs instance. I dropped the first two fix patches from v1, since Shuah applied those already. [PATCH v2 1/2] is almost the same as [PATCH 3/3] from v1, but using the proper skip function from kselftest.h. I am not sure if Shuah applied that already, if yes, it's not a big problem, the output is the same. Patch 2/2 implements the tmpfs detection that Nhat suggested the last time (many thanks for pointing me to statfs and the magics!). Cheers, Andre Andre Przywara (2): selftests: cachestat: test for cachestat availability selftests: cachestat: catch failing fsync test on tmpfs .../selftests/cachestat/test_cachestat.c | 80 +++++++++++++++---- 1 file changed, 65 insertions(+), 15 deletions(-) -- 2.25.1

2 years

2
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[PATCH] selftests: Keep symlinks, when possible

by Björn Töpel

From: Björn Töpel <bjorn(a)rivosinc.com> When kselftest is built/installed with the 'gen_tar' target, rsync is used for the installation step to copy files. Extra care is needed for tests that have symlinks. Commit ae108c48b5d2 ("selftests: net: Fix cross-tree inclusion of scripts") added '-L' (transform symlink into referent file/dir) to rsync, to fix dangling links. However, that broke some tests where the symlink (being a symlink) is part of the test (e.g. exec:execveat). Use rsync's '--copy-unsafe-links' that does right thing. Fixes: ae108c48b5d2 ("selftests: net: Fix cross-tree inclusion of scripts") Signed-off-by: Björn Töpel <bjorn(a)rivosinc.com> --- tools/testing/selftests/lib.mk | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/lib.mk b/tools/testing/selftests/lib.mk index d17854285f2b..118e0964bda9 100644 --- a/tools/testing/selftests/lib.mk +++ b/tools/testing/selftests/lib.mk @@ -106,7 +106,7 @@ endef run_tests: all ifdef building_out_of_srctree @if [ "X$(TEST_PROGS)$(TEST_PROGS_EXTENDED)$(TEST_FILES)" != "X" ]; then \ - rsync -aLq $(TEST_PROGS) $(TEST_PROGS_EXTENDED) $(TEST_FILES) $(OUTPUT); \ + rsync -aq --copy-unsafe-links $(TEST_PROGS) $(TEST_PROGS_EXTENDED) $(TEST_FILES) $(OUTPUT); \ fi @if [ "X$(TEST_PROGS)" != "X" ]; then \ $(call RUN_TESTS, $(TEST_GEN_PROGS) $(TEST_CUSTOM_PROGS) \ @@ -120,7 +120,7 @@ endif define INSTALL_SINGLE_RULE $(if $(INSTALL_LIST),@mkdir -p $(INSTALL_PATH)) - $(if $(INSTALL_LIST),rsync -aL $(INSTALL_LIST) $(INSTALL_PATH)/) + $(if $(INSTALL_LIST),rsync -a --copy-unsafe-links $(INSTALL_LIST) $(INSTALL_PATH)/) endef define INSTALL_RULE base-commit: f7757129e3dea336c407551c98f50057c22bb266 -- 2.39.2

2 years

2
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[PATCH v4 00/10] kunit: Add dynamically-extending log

by Richard Fitzgerald

This patch chain changes the logging implementation to use string_stream so that the log will grow dynamically. The first 8 patches add test code for string_stream, and make some changes to string_stream needed to be able to use it for the log. The final patch adds a performance report of string_stream. CHANGES SINCE V3: Completely rewritten to use string_stream instead of implementing a separate extending-buffer implementation for logging. I have used the performance test from the final patch on my original fixed-size-fragment implementation from V3 to get a comparison of the two implementations (run on i3-8145UE CPU @ 2.20GHz): string_stream V3 fixed-size-buffer Time elapsed: 7748 us 3251 us Total string length: 573890 573890 Bytes requested: 823994 728336 Actual bytes allocated: 1061440 728352 I don't think the difference is enough to be worth complicating the string_stream implementation with my fixed-fragment implementation from V3 of this patch chain. Richard Fitzgerald (10): kunit: string-stream: Improve testing of string_stream kunit: string-stream: Don't create a fragment for empty strings kunit: string-stream: Add cases for adding empty strings to a string_stream kunit: string-stream: Add option to make all lines end with newline kunit: string-stream: Add cases for string_stream newline appending kunit: string-stream: Pass struct kunit to string_stream_get_string() kunit: string-stream: Decouple string_stream from kunit kunit: string-stream: Add test for freeing resource-managed string_stream kunit: Use string_stream for test log kunit: string-stream: Test performance of string_stream include/kunit/test.h | 14 +- lib/kunit/Makefile | 5 +- lib/kunit/debugfs.c | 36 ++- lib/kunit/kunit-test.c | 52 +--- lib/kunit/log-test.c | 72 ++++++ lib/kunit/string-stream-test.c | 447 +++++++++++++++++++++++++++++++-- lib/kunit/string-stream.c | 129 +++++++--- lib/kunit/string-stream.h | 22 +- lib/kunit/test.c | 48 +--- 9 files changed, 656 insertions(+), 169 deletions(-) create mode 100644 lib/kunit/log-test.c -- 2.30.2

2 years

4
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clang-17: selftests: sgx: clang: error: -z noexecstack: 'linker' input unused [-Werror,-Wunused-command-line-argument]

by Naresh Kamboju

Recently we have updated the toolchain clang-17 version. While building selftests sgx following warnings / errors noticed on the Linux next with clang-17. Reported-by: Linux Kernel Functional Testing <lkft(a)linaro.org> sgx/main.o clang: error: -z noexecstack: 'linker' input unused [-Werror,-Wunused-command-line-argument] Links: - https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… Steps to reproduce: - https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… tuxmake --runtime podman --target-arch x86_64 --toolchain clang-17 --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… LLVM=1 LLVM_IAS=1 debugkernel cpupower headers kernel kselftest modules -- Linaro LKFT https://lkft.linaro.org

2 years

2
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landlock: fs_test: fs_test.c:4524:9: error: initializer element is not a compile-time constant

by Naresh Kamboju

While building selftests landlock following warnings / errors noticed on the Linux next with clang-17. Reported-by: Linux Kernel Functional Testing <lkft(a)linaro.org> Build errors: ------------ landlock/fs_test fs_test.c:4524:9: error: initializer element is not a compile-time constant 4524 | .mnt = mnt_tmp, | ^~~~~~~ 1 error generated. Links: - https://storage.tuxsuite.com/public/linaro/lkft/builds/2U69ue7AaypfY7eRU4UU… Steps to reproduce: tuxmake --runtime podman --target-arch arm64 --toolchain clang-17 --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2U69ue7AaypfY7eRU4UU… LLVM=1 LLVM_IAS=1 dtbs dtbs-legacy headers kernel kselftest modules -- Linaro LKFT https://lkft.linaro.org

2 years

2
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[PATCH v4 4.19 1/1] test_firmware: prevent race conditions by a correct implementation of locking

by Mirsad Goran Todorovac

[ Upstream commit 4acfe3dfde685a5a9eaec5555351918e2d7266a1 ] Dan Carpenter spotted a race condition in a couple of situations like these in the test_firmware driver: static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg) { u8 val; int ret; ret = kstrtou8(buf, 10, &val); if (ret) return ret; mutex_lock(&test_fw_mutex); *(u8 *)cfg = val; mutex_unlock(&test_fw_mutex); /* Always return full write size even if we didn't consume all */ return size; } static ssize_t config_num_requests_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { int rc; mutex_lock(&test_fw_mutex); if (test_fw_config->reqs) { pr_err("Must call release_all_firmware prior to changing config\n"); rc = -EINVAL; mutex_unlock(&test_fw_mutex); goto out; } mutex_unlock(&test_fw_mutex); // NOTE: HERE is the race!!! Function can be preempted! // test_fw_config->reqs can change between the release of // the lock about and acquire of the lock in the // test_dev_config_update_u8() rc = test_dev_config_update_u8(buf, count, &test_fw_config->num_requests); out: return rc; } static ssize_t config_read_fw_idx_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { return test_dev_config_update_u8(buf, count, &test_fw_config->read_fw_idx); } The function test_dev_config_update_u8() is called from both the locked and the unlocked context, function config_num_requests_store() and config_read_fw_idx_store() which can both be called asynchronously as they are driver's methods, while test_dev_config_update_u8() and siblings change their argument pointed to by u8 *cfg or similar pointer. To avoid deadlock on test_fw_mutex, the lock is dropped before calling test_dev_config_update_u8() and re-acquired within test_dev_config_update_u8() itself, but alas this creates a race condition. Having two locks wouldn't assure a race-proof mutual exclusion. This situation is best avoided by the introduction of a new, unlocked function __test_dev_config_update_u8() which can be called from the locked context and reducing test_dev_config_update_u8() to: static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg) { int ret; mutex_lock(&test_fw_mutex); ret = __test_dev_config_update_u8(buf, size, cfg); mutex_unlock(&test_fw_mutex); return ret; } doing the locking and calling the unlocked primitive, which enables both locked and unlocked versions without duplication of code. Fixes: c92316bf8e948 ("test_firmware: add batched firmware tests") Cc: Luis R. Rodriguez <mcgrof(a)kernel.org> Cc: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> Cc: Russ Weight <russell.h.weight(a)intel.com> Cc: Takashi Iwai <tiwai(a)suse.de> Cc: Tianfei Zhang <tianfei.zhang(a)intel.com> Cc: Shuah Khan <shuah(a)kernel.org> Cc: Colin Ian King <colin.i.king(a)gmail.com> Cc: Randy Dunlap <rdunlap(a)infradead.org> Cc: linux-kselftest(a)vger.kernel.org Cc: stable(a)vger.kernel.org # v5.4, 4.19, 4.14 Suggested-by: Dan Carpenter <error27(a)gmail.com> Link: https://lore.kernel.org/r/20230509084746.48259-1-mirsad.todorovac@alu.unizg… Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac(a)alu.unizg.hr> [ This is the patch to fix the racing condition in locking for the 5.4, ] [ 4.19 and 4.14 stable branches. Not all the fixes from the upstream ] [ commit apply, but those which do are verbatim equal to those in the ] [ upstream commit. ] --- v4: verbatim the same patch as for the 5.4 stable tree which patchwork failed to apply. lib/test_firmware.c | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) diff --git a/lib/test_firmware.c b/lib/test_firmware.c index b5e779bcfb34..be3baea88b61 100644 --- a/lib/test_firmware.c +++ b/lib/test_firmware.c @@ -284,16 +284,26 @@ static ssize_t config_test_show_str(char *dst, return len; } -static int test_dev_config_update_bool(const char *buf, size_t size, - bool *cfg) +static inline int __test_dev_config_update_bool(const char *buf, size_t size, + bool *cfg) { int ret; - mutex_lock(&test_fw_mutex); if (strtobool(buf, cfg) < 0) ret = -EINVAL; else ret = size; + + return ret; +} + +static int test_dev_config_update_bool(const char *buf, size_t size, + bool *cfg) +{ + int ret; + + mutex_lock(&test_fw_mutex); + ret = __test_dev_config_update_bool(buf, size, cfg); mutex_unlock(&test_fw_mutex); return ret; @@ -323,7 +333,7 @@ static ssize_t test_dev_config_show_int(char *buf, int cfg) return snprintf(buf, PAGE_SIZE, "%d\n", val); } -static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg) +static inline int __test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg) { int ret; long new; @@ -335,14 +345,23 @@ static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg) if (new > U8_MAX) return -EINVAL; - mutex_lock(&test_fw_mutex); *(u8 *)cfg = new; - mutex_unlock(&test_fw_mutex); /* Always return full write size even if we didn't consume all */ return size; } +static int test_dev_config_update_u8(const char *buf, size_t size, u8 *cfg) +{ + int ret; + + mutex_lock(&test_fw_mutex); + ret = __test_dev_config_update_u8(buf, size, cfg); + mutex_unlock(&test_fw_mutex); + + return ret; +} + static ssize_t test_dev_config_show_u8(char *buf, u8 cfg) { u8 val; @@ -375,10 +394,10 @@ static ssize_t config_num_requests_store(struct device *dev, mutex_unlock(&test_fw_mutex); goto out; } - mutex_unlock(&test_fw_mutex); - rc = test_dev_config_update_u8(buf, count, - &test_fw_config->num_requests); + rc = __test_dev_config_update_u8(buf, count, + &test_fw_config->num_requests); + mutex_unlock(&test_fw_mutex); out: return rc; -- 2.34.1

2 years

3
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[PATCH v32 0/6] Implement IOCTL to get and optionally clear info about PTEs

by Muhammad Usama Anjum

*Changes in v31 and v32*: - Minor updates *Changes in v30*: - Rebase on top of next-20230815 - Minor nitpicks *Changes in v29:* - Polish IOCTL and improve documentation *Changes in v28:* - Fix walk_end and add 17 test cases in selftests patch *Changes in v27:* - Handle review comments and minor improvements - Add performance improvement patch on top with test for easy review *Changes in v26:* - Code re-structurring and API changes in PAGEMAP_IOCTL *Changes in v25*: - Do proper filtering on hole as well (hole got missed earlier) *Changes in v24*: - Rebase on top of next-20230710 - Place WP markers in case of hole as well *Changes in v23*: - Set vec_buf_index in loop only when vec_buf_index is set - Return -EFAULT instead of -EINVAL if vec is NULL - Correctly return the walk ending address to the page granularity *Changes in v22*: - Interface change: - Replace [start start + len) with [start, end) - Return the ending address of the address walk in start *Changes in v21*: - Abort walk instead of returning error if WP is to be performed on partial hugetlb *Changes in v20* - Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO *Changes in v19* - Minor changes and interface updates *Changes in v18* - Rebase on top of next-20230613 - Minor updates *Changes in v17* - Rebase on top of next-20230606 - Minor improvements in PAGEMAP_SCAN IOCTL patch *Changes in v16* - Fix a corner case - Add exclusive PM_SCAN_OP_WP back *Changes in v15* - Build fix (Add missed build fix in RESEND) *Changes in v14* - Fix build error caused by #ifdef added at last minute in some configs *Changes in v13* - Rebase on top of next-20230414 - Give-up on using uffd_wp_range() and write new helpers, flush tlb only once *Changes in v12* - Update and other memory types to UFFD_FEATURE_WP_ASYNC - Rebaase on top of next-20230406 - Review updates *Changes in v11* - Rebase on top of next-20230307 - Base patches on UFFD_FEATURE_WP_UNPOPULATED - Do a lot of cosmetic changes and review updates - Remove ENGAGE_WP + !GET operation as it can be performed with UFFDIO_WRITEPROTECT *Changes in v10* - Add specific condition to return error if hugetlb is used with wp async - Move changes in tools/include/uapi/linux/fs.h to separate patch - Add documentation *Changes in v9:* - Correct fault resolution for userfaultfd wp async - Fix build warnings and errors which were happening on some configs - Simplify pagemap ioctl's code *Changes in v8:* - Update uffd async wp implementation - Improve PAGEMAP_IOCTL implementation *Changes in v7:* - Add uffd wp async - Update the IOCTL to use uffd under the hood instead of soft-dirty flags *Motivation* The real motivation for adding PAGEMAP_SCAN IOCTL is to emulate Windows GetWriteWatch() and ResetWriteWatch() syscalls [1]. The GetWriteWatch() retrieves the addresses of the pages that are written to in a region of virtual memory. This syscall is used in Windows applications and games etc. This syscall is being emulated in pretty slow manner in userspace. Our purpose is to enhance the kernel such that we translate it efficiently in a better way. Currently some out of tree hack patches are being used to efficiently emulate it in some kernels. We intend to replace those with these patches. So the whole gaming on Linux can effectively get benefit from this. It means there would be tons of users of this code. CRIU use case [2] was mentioned by Andrei and Danylo: > Use cases for migrating sparse VMAs are binaries sanitized with ASAN, > MSAN or TSAN [3]. All of these sanitizers produce sparse mappings of > shadow memory [4]. Being able to migrate such binaries allows to highly > reduce the amount of work needed to identify and fix post-migration > crashes, which happen constantly. Andrei's defines the following uses of this code: * it is more granular and allows us to track changed pages more effectively. The current interface can clear dirty bits for the entire process only. In addition, reading info about pages is a separate operation. It means we must freeze the process to read information about all its pages, reset dirty bits, only then we can start dumping pages. The information about pages becomes more and more outdated, while we are processing pages. The new interface solves both these downsides. First, it allows us to read pte bits and clear the soft-dirty bit atomically. It means that CRIU will not need to freeze processes to pre-dump their memory. Second, it clears soft-dirty bits for a specified region of memory. It means CRIU will have actual info about pages to the moment of dumping them. * The new interface has to be much faster because basic page filtering is happening in the kernel. With the old interface, we have to read pagemap for each page. *Implementation Evolution (Short Summary)* From the definition of GetWriteWatch(), we feel like kernel's soft-dirty feature can be used under the hood with some additions like: * reset soft-dirty flag for only a specific region of memory instead of clearing the flag for the entire process * get and clear soft-dirty flag for a specific region atomically So we decided to use ioctl on pagemap file to read or/and reset soft-dirty flag. But using soft-dirty flag, sometimes we get extra pages which weren't even written. They had become soft-dirty because of VMA merging and VM_SOFTDIRTY flag. This breaks the definition of GetWriteWatch(). We were able to by-pass this short coming by ignoring VM_SOFTDIRTY until David reported that mprotect etc messes up the soft-dirty flag while ignoring VM_SOFTDIRTY [5]. This wasn't happening until [6] got introduced. We discussed if we can revert these patches. But we could not reach to any conclusion. So at this point, I made couple of tries to solve this whole VM_SOFTDIRTY issue by correcting the soft-dirty implementation: * [7] Correct the bug fixed wrongly back in 2014. It had potential to cause regression. We left it behind. * [8] Keep a list of soft-dirty part of a VMA across splits and merges. I got the reply don't increase the size of the VMA by 8 bytes. At this point, we left soft-dirty considering it is too much delicate and userfaultfd [9] seemed like the only way forward. From there onward, we have been basing soft-dirty emulation on userfaultfd wp feature where kernel resolves the faults itself when WP_ASYNC feature is used. It was straight forward to add WP_ASYNC feature in userfautlfd. Now we get only those pages dirty or written-to which are really written in reality. (PS There is another WP_UNPOPULATED userfautfd feature is required which is needed to avoid pre-faulting memory before write-protecting [9].) All the different masks were added on the request of CRIU devs to create interface more generic and better. [1] https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-… [2] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com [3] https://github.com/google/sanitizers [4] https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#64-bit [5] https://lore.kernel.org/all/bfcae708-db21-04b4-0bbe-712badd03071@redhat.com [6] https://lore.kernel.org/all/20220725142048.30450-1-peterx@redhat.com/ [7] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.… [8] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.… [9] https://lore.kernel.org/all/20230306213925.617814-1-peterx@redhat.com [10] https://lore.kernel.org/all/20230125144529.1630917-1-mdanylo@google.com * Original Cover letter from v8* Hello, Note: Soft-dirty pages and pages which have been written-to are synonyms. As kernel already has soft-dirty feature inside which we have given up to use, we are using written-to terminology while using UFFD async WP under the hood. It is possible to find and clear soft-dirty pages entirely in userspace. But it isn't efficient: - The mprotect and SIGSEGV handler for bookkeeping - The userfaultfd wp (synchronous) with the handler for bookkeeping Some benchmarks can be seen here[1]. This series adds features that weren't present earlier: - There is no atomic get soft-dirty/Written-to status and clear present in the kernel. - The pages which have been written-to can not be found in accurate way. (Kernel's soft-dirty PTE bit + sof_dirty VMA bit shows more soft-dirty pages than there actually are.) Historically, soft-dirty PTE bit tracking has been used in the CRIU project. The procfs interface is enough for finding the soft-dirty bit status and clearing the soft-dirty bit of all the pages of a process. We have the use case where we need to track the soft-dirty PTE bit for only specific pages on-demand. We need this tracking and clear mechanism of a region of memory while the process is running to emulate the getWriteWatch() syscall of Windows. *(Moved to using UFFD instead of soft-dirty feature to find pages which have been written-to from v7 patch series)*: Stop using the soft-dirty flags for finding which pages have been written to. It is too delicate and wrong as it shows more soft-dirty pages than the actual soft-dirty pages. There is no interest in correcting it [2][3] as this is how the feature was written years ago. It shouldn't be updated to changed behaviour. Peter Xu has suggested using the async version of the UFFD WP [4] as it is based inherently on the PTEs. So in this patch series, I've added a new mode to the UFFD which is asynchronous version of the write protect. When this variant of the UFFD WP is used, the page faults are resolved automatically by the kernel. The pages which have been written-to can be found by reading pagemap file (!PM_UFFD_WP). This feature can be used successfully to find which pages have been written to from the time the pages were write protected. This works just like the soft-dirty flag without showing any extra pages which aren't soft-dirty in reality. The information related to pages if the page is file mapped, present and swapped is required for the CRIU project [5][6]. The addition of the required mask, any mask, excluded mask and return masks are also required for the CRIU project [5]. The IOCTL returns the addresses of the pages which match the specific masks. The page addresses are returned in struct page_region in a compact form. The max_pages is needed to support a use case where user only wants to get a specific number of pages. So there is no need to find all the pages of interest in the range when max_pages is specified. The IOCTL returns when the maximum number of the pages are found. The max_pages is optional. If max_pages is specified, it must be equal or greater than the vec_size. This restriction is needed to handle worse case when one page_region only contains info of one page and it cannot be compacted. This is needed to emulate the Windows getWriteWatch() syscall. The patch series include the detailed selftest which can be used as an example for the uffd async wp test and PAGEMAP_IOCTL. It shows the interface usages as well. [1] https://lore.kernel.org/lkml/54d4c322-cd6e-eefd-b161-2af2b56aae24@collabora… [2] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.… [3] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.… [4] https://lore.kernel.org/all/Y6Hc2d+7eTKs7AiH@x1n [5] https://lore.kernel.org/all/YyiDg79flhWoMDZB@gmail.com/ [6] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com/ Regards, Muhammad Usama Anjum Muhammad Usama Anjum (5): fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs fs/proc/task_mmu: Add fast paths to get/clear PAGE_IS_WRITTEN flag tools headers UAPI: Update linux/fs.h with the kernel sources mm/pagemap: add documentation of PAGEMAP_SCAN IOCTL selftests: mm: add pagemap ioctl tests Peter Xu (1): userfaultfd: UFFD_FEATURE_WP_ASYNC Documentation/admin-guide/mm/pagemap.rst | 89 + Documentation/admin-guide/mm/userfaultfd.rst | 35 + fs/proc/task_mmu.c | 705 ++++++++ fs/userfaultfd.c | 26 +- include/linux/hugetlb.h | 1 + include/linux/userfaultfd_k.h | 28 +- include/uapi/linux/fs.h | 59 + include/uapi/linux/userfaultfd.h | 9 +- mm/hugetlb.c | 34 +- mm/memory.c | 28 +- tools/include/uapi/linux/fs.h | 59 + tools/testing/selftests/mm/.gitignore | 2 + tools/testing/selftests/mm/Makefile | 3 +- tools/testing/selftests/mm/config | 1 + tools/testing/selftests/mm/pagemap_ioctl.c | 1660 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 16 files changed, 2719 insertions(+), 24 deletions(-) create mode 100644 tools/testing/selftests/mm/pagemap_ioctl.c -- 2.40.1

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clang-17: selftests: exec/load_address_4096 clang: error: argument unused during compilation: '-pie' [-Werror,-Wunused-command-line-argument]

by Naresh Kamboju

Recently we have updated the toolchain clang-17 version. While building selftests exec following warnings / errors noticed on the Linux next with clang-17. But pass with gcc-13. Reported-by: Linux Kernel Functional Testing <lkft(a)linaro.org> exec/load_address_4096 clang: error: argument unused during compilation: '-pie' [-Werror,-Wunused-command-line-argument] Links: - https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20230821/te… Steps to reproduce: - https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… tuxmake --runtime podman --target-arch x86_64 --toolchain clang-17 --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… LLVM=1 LLVM_IAS=1 debugkernel cpupower headers kernel kselftest modules -- Linaro LKFT https://lkft.linaro.org

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clang: error: cannot specify -o when generating multiple output files

by Naresh Kamboju

Recently we have updated the toolchain clang-17 version. While building selftests filesystems/binderfs, openat2, resctrl and x86 following warnings / errors noticed on the Linux next with clang-17. But pass with gcc-13. Reported-by: Linux Kernel Functional Testing <lkft(a)linaro.org> Build logs: ======== binderfs_test clang: error: cannot specify -o when generating multiple output files ... openat2/openat2_test clang: error: cannot specify -o when generating multiple output files ... resctrl/resctrl_tests clang: error: cannot specify -o when generating multiple output files ... make[4]: Entering directory 'tools/testing/selftests/x86' clang --target=x86_64-linux-gnu -fintegrated-as -Werror=unknown-warning-option -Werror=ignored-optimization-argument -Werror=option-ignored -Werror=unused-command-line-argument --target=x86_64-linux-gnu -fintegrated-as -m64 -o /home/tuxbuild/.cache/tuxmake/builds/1/build/kselftest/x86/single_step_syscall_64 -O2 -g -std=gnu99 -pthread -Wall -isystem /home/tuxbuild/.cache/tuxmake/builds/1/build/usr/include -no-pie -DCAN_BUILD_64 single_step_syscall.c helpers.h -lrt -ldl clang: error: cannot specify -o when generating multiple output files make[4]: *** [Makefile:78: /home/tuxbuild/.cache/tuxmake/builds/1/build/kselftest/x86/single_step_syscall_64] Error 1 Links: - https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20230821/te… - https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20230821/te… - Steps to reproduce: - https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… tuxmake --runtime podman --target-arch x86_64 --toolchain clang-17 --kconfig https://storage.tuxsuite.com/public/linaro/lkft/builds/2UHhSg0TPLhjp9Uq9EFc… LLVM=1 LLVM_IAS=1 debugkernel cpupower headers kernel kselftest modules -- Linaro LKFT https://lkft.linaro.org

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