kernel/lib/Kconfig.debug, branch linux-4.15.y

kasan: rework Kconfig settings

2018-02-16T19:06:53Z

commit e7c52b84fb18f08ce49b6067ae6285aca79084a8 upstream. We get a lot of very large stack frames using gcc-7.0.1 with the default -fsanitize-address-use-after-scope --param asan-stack=1 options, which can easily cause an overflow of the kernel stack, e.g. drivers/gpu/drm/i915/gvt/handlers.c:2434:1: warning: the frame size of 46176 bytes is larger than 3072 bytes drivers/net/wireless/ralink/rt2x00/rt2800lib.c:5650:1: warning: the frame size of 23632 bytes is larger than 3072 bytes lib/atomic64_test.c:250:1: warning: the frame size of 11200 bytes is larger than 3072 bytes drivers/gpu/drm/i915/gvt/handlers.c:2621:1: warning: the frame size of 9208 bytes is larger than 3072 bytes drivers/media/dvb-frontends/stv090x.c:3431:1: warning: the frame size of 6816 bytes is larger than 3072 bytes fs/fscache/stats.c:287:1: warning: the frame size of 6536 bytes is larger than 3072 bytes To reduce this risk, -fsanitize-address-use-after-scope is now split out into a separate CONFIG_KASAN_EXTRA Kconfig option, leading to stack frames that are smaller than 2 kilobytes most of the time on x86_64. An earlier version of this patch also prevented combining KASAN_EXTRA with KASAN_INLINE, but that is no longer necessary with gcc-7.0.1. All patches to get the frame size below 2048 bytes with CONFIG_KASAN=y and CONFIG_KASAN_EXTRA=n have been merged by maintainers now, so we can bring back that default now. KASAN_EXTRA=y still causes lots of warnings but now defaults to !COMPILE_TEST to disable it in allmodconfig, and it remains disabled in all other defconfigs since it is a new option. I arbitrarily raise the warning limit for KASAN_EXTRA to 3072 to reduce the noise, but an allmodconfig kernel still has around 50 warnings on gcc-7. I experimented a bit more with smaller stack frames and have another follow-up series that reduces the warning limit for 64-bit architectures to 1280 bytes (without CONFIG_KASAN). With earlier versions of this patch series, I also had patches to address the warnings we get with KASAN and/or KASAN_EXTRA, using a "noinline_if_stackbloat" annotation. That annotation now got replaced with a gcc-8 bugfix (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715) and a workaround for older compilers, which means that KASAN_EXTRA is now just as bad as before and will lead to an instant stack overflow in a few extreme cases. This reverts parts of commit 3f181b4d8652 ("lib/Kconfig.debug: disable -Wframe-larger-than warnings with KASAN=y"). Two patches in linux-next should be merged first to avoid introducing warnings in an allmodconfig build: 3cd890dbe2a4 ("media: dvb-frontends: fix i2c access helpers for KASAN") 16c3ada89cff ("media: r820t: fix r820t_write_reg for KASAN") Do we really need to backport this? I think we do: without this patch, enabling KASAN will lead to unavoidable kernel stack overflow in certain device drivers when built with gcc-7 or higher on linux-4.10+ or any version that contains a backport of commit c5caf21ab0cf8. Most people are probably still on older compilers, but it will get worse over time as they upgrade their distros. The warnings we get on kernels older than this should all be for code that uses dangerously large stack frames, though most of them do not cause an actual stack overflow by themselves.The asan-stack option was added in linux-4.0, and commit 3f181b4d8652 ("lib/Kconfig.debug: disable -Wframe-larger-than warnings with KASAN=y") effectively turned off the warning for allmodconfig kernels, so I would like to see this fix backported to any kernels later than 4.0. I have done dozens of fixes for individual functions with stack frames larger than 2048 bytes with asan-stack, and I plan to make sure that all those fixes make it into the stable kernels as well (most are already there). Part of the complication here is that asan-stack (from 4.0) was originally assumed to always require much larger stacks, but that turned out to be a combination of multiple gcc bugs that we have now worked around and fixed, but sanitize-address-use-after-scope (from v4.10) has a much higher inherent stack usage and also suffers from at least three other problems that we have analyzed but not yet fixed upstream, each of them makes the stack usage more severe than it should be. Link: http://lkml.kernel.org/r/20171221134744.2295529-1-arnd@arndb.de Signed-off-by: Arnd Bergmann Acked-by: Andrey Ryabinin Cc: Mauro Carvalho Chehab Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Andrey Konovalov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

locking/lockdep: Remove the cross-release locking checks

2017-12-12T11:38:51Z

This code (CONFIG_LOCKDEP_CROSSRELEASE=y and CONFIG_LOCKDEP_COMPLETIONS=y), while it found a number of old bugs initially, was also causing too many false positives that caused people to disable lockdep - which is arguably a worse overall outcome. If we disable cross-release by default but keep the code upstream then in practice the most likely outcome is that we'll allow the situation to degrade gradually, by allowing entropy to introduce more and more false positives, until it overwhelms maintenance capacity. Another bad side effect was that people were trying to work around the false positives by uglifying/complicating unrelated code. There's a marked difference between annotating locking operations and uglifying good code just due to bad lock debugging code ... This gradual decrease in quality happened to a number of debugging facilities in the kernel, and lockdep is pretty complex already, so we cannot risk this outcome. Either cross-release checking can be done right with no false positives, or it should not be included in the upstream kernel. ( Note that it might make sense to maintain it out of tree and go through the false positives every now and then and see whether new bugs were introduced. ) Cc: Byungchul Park Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar

Makefile: support flag -fsanitizer-coverage=trace-cmp

2017-11-18T00:10:04Z

The flag enables Clang instrumentation of comparison operations (currently not supported by GCC). This instrumentation is needed by the new KCOV device to collect comparison operands. Link: http://lkml.kernel.org/r/20171011095459.70721-2-glider@google.com Signed-off-by: Victor Chibotaru Signed-off-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: Andrey Konovalov Cc: Mark Rutland Cc: Alexander Popov Cc: Andrey Ryabinin Cc: Kees Cook Cc: Vegard Nossum Cc: Quentin Casasnovas Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib: test module for find_*_bit() functions

2017-11-18T00:10:02Z

find_bit functions are widely used in the kernel, including hot paths. This module tests performance of those functions in 2 typical scenarios: randomly filled bitmap with relatively equal distribution of set and cleared bits, and sparse bitmap which has 1 set bit for 500 cleared bits. On ThunderX machine: Start testing find_bit() with random-filled bitmap find_next_bit: 240043 cycles, 164062 iterations find_next_zero_bit: 312848 cycles, 163619 iterations find_last_bit: 193748 cycles, 164062 iterations find_first_bit: 177720874 cycles, 164062 iterations Start testing find_bit() with sparse bitmap find_next_bit: 3633 cycles, 656 iterations find_next_zero_bit: 620399 cycles, 327025 iterations find_last_bit: 3038 cycles, 656 iterations find_first_bit: 691407 cycles, 656 iterations [arnd@arndb.de: use correct format string for find-bit tests] Link: http://lkml.kernel.org/r/20171113135605.3166307-1-arnd@arndb.de Link: http://lkml.kernel.org/r/20171109140714.13168-1-ynorov@caviumnetworks.com Signed-off-by: Yury Norov Signed-off-by: Arnd Bergmann Reviewed-by: Clement Courbet Cc: Alexey Dobriyan Cc: Matthew Wilcox Cc: Rasmus Villemoes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'driver-core-4.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

2017-11-16T16:55:30Z

Pull driver core updates from Greg KH: "Here is the set of driver core / debugfs patches for 4.15-rc1. Not many here, mostly all are debugfs fixes to resolve some long-reported problems with files going away with references to them in userspace. There's also some SPDX cleanups for the debugfs code, as well as a few other minor driver core changes for issues reported by people. All of these have been in linux-next for a week or more with no reported issues" * tag 'driver-core-4.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: driver core: Fix device link deferred probe debugfs: Remove redundant license text debugfs: add SPDX identifiers to all debugfs files debugfs: defer debugfs_fsdata allocation to first usage debugfs: call debugfs_real_fops() only after debugfs_file_get() debugfs: purge obsolete SRCU based removal protection IB/hfi1: convert to debugfs_file_get() and -put() debugfs: convert to debugfs_file_get() and -put() debugfs: debugfs_real_fops(): drop __must_hold sparse annotation debugfs: implement per-file removal protection debugfs: add support for more elaborate ->d_fsdata driver core: Move device_links_purge() after bus_remove_device() arch_topology: Fix section miss match warning due to free_raw_capacity() driver-core: pr_err() strings should end with newlines

kmemcheck: rip it out

2017-11-16T02:21:05Z

Fix up makefiles, remove references, and git rm kmemcheck. Link: http://lkml.kernel.org/r/20171007030159.22241-4-alexander.levin@verizon.com Signed-off-by: Sasha Levin Cc: Steven Rostedt Cc: Vegard Nossum Cc: Pekka Enberg Cc: Michal Hocko Cc: Eric W. Biederman Cc: Alexander Potapenko Cc: Tim Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-11-13T22:13:48Z

Pull x86 core updates from Ingo Molnar: "Note that in this cycle most of the x86 topics interacted at a level that caused them to be merged into tip:x86/asm - but this should be a temporary phenomenon, hopefully we'll back to the usual patterns in the next merge window. The main changes in this cycle were: Hardware enablement: - Add support for the Intel UMIP (User Mode Instruction Prevention) CPU feature. This is a security feature that disables certain instructions such as SGDT, SLDT, SIDT, SMSW and STR. (Ricardo Neri) [ Note that this is disabled by default for now, there are some smaller enhancements in the pipeline that I'll follow up with in the next 1-2 days, which allows this to be enabled by default.] - Add support for the AMD SEV (Secure Encrypted Virtualization) CPU feature, on top of SME (Secure Memory Encryption) support that was added in v4.14. (Tom Lendacky, Brijesh Singh) - Enable new SSE/AVX/AVX512 CPU features: AVX512_VBMI2, GFNI, VAES, VPCLMULQDQ, AVX512_VNNI, AVX512_BITALG. (Gayatri Kammela) Other changes: - A big series of entry code simplifications and enhancements (Andy Lutomirski) - Make the ORC unwinder default on x86 and various objtool enhancements. (Josh Poimboeuf) - 5-level paging enhancements (Kirill A. Shutemov) - Micro-optimize the entry code a bit (Borislav Petkov) - Improve the handling of interdependent CPU features in the early FPU init code (Andi Kleen) - Build system enhancements (Changbin Du, Masahiro Yamada) - ... plus misc enhancements, fixes and cleanups" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (118 commits) x86/build: Make the boot image generation less verbose selftests/x86: Add tests for the STR and SLDT instructions selftests/x86: Add tests for User-Mode Instruction Prevention x86/traps: Fix up general protection faults caused by UMIP x86/umip: Enable User-Mode Instruction Prevention at runtime x86/umip: Force a page fault when unable to copy emulated result to user x86/umip: Add emulation code for UMIP instructions x86/cpufeature: Add User-Mode Instruction Prevention definitions x86/insn-eval: Add support to resolve 16-bit address encodings x86/insn-eval: Handle 32-bit address encodings in virtual-8086 mode x86/insn-eval: Add wrapper function for 32 and 64-bit addresses x86/insn-eval: Add support to resolve 32-bit address encodings x86/insn-eval: Compute linear address in several utility functions resource: Fix resource_size.cocci warnings X86/KVM: Clear encryption attribute when SEV is active X86/KVM: Decrypt shared per-cpu variables when SEV is active percpu: Introduce DEFINE_PER_CPU_DECRYPTED x86: Add support for changing memory encryption attribute in early boot x86/io: Unroll string I/O when SEV is active x86/boot: Add early boot support when running with SEV active ...

debugfs: purge obsolete SRCU based removal protection

2017-11-07T19:25:02Z

Purge the SRCU based file removal race protection in favour of the new, refcount based debugfs_file_get()/debugfs_file_put() API. Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data") Signed-off-by: Nicolai Stange Signed-off-by: Greg Kroah-Hartman

locking/lockdep: Introduce CONFIG_BOOTPARAM_LOCKDEP_CROSSRELEASE_FULLSTACK=y

2017-10-25T10:19:02Z

Add a Kconfig knob that enables the lockdep "crossrelease_fullstack" boot parameter. Suggested-by: Ingo Molnar Signed-off-by: Byungchul Park Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: amir73il@gmail.com Cc: axboe@kernel.dk Cc: darrick.wong@oracle.com Cc: david@fromorbit.com Cc: hch@infradead.org Cc: idryomov@gmail.com Cc: johan@kernel.org Cc: johannes.berg@intel.com Cc: kernel-team@lge.com Cc: linux-block@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-xfs@vger.kernel.org Cc: oleg@redhat.com Cc: tj@kernel.org Link: http://lkml.kernel.org/r/1508921765-15396-7-git-send-email-byungchul.park@lge.com Signed-off-by: Ingo Molnar

locking/lockdep: Remove the BROKEN flag from CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS

2017-10-25T10:19:01Z

Now that the performance regression is fixed, re-enable CONFIG_LOCKDEP_CROSSRELEASE=y and CONFIG_LOCKDEP_COMPLETIONS=y. Signed-off-by: Byungchul Park Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: amir73il@gmail.com Cc: axboe@kernel.dk Cc: darrick.wong@oracle.com Cc: david@fromorbit.com Cc: hch@infradead.org Cc: idryomov@gmail.com Cc: johan@kernel.org Cc: johannes.berg@intel.com Cc: kernel-team@lge.com Cc: linux-block@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-xfs@vger.kernel.org Cc: oleg@redhat.com Cc: tj@kernel.org Link: http://lkml.kernel.org/r/1508921765-15396-6-git-send-email-byungchul.park@lge.com Signed-off-by: Ingo Molnar