December 2024 - Linux-kselftest-mirror

[PATCH bpf-next/net v2 0/7] bpf: Add mptcp_subflow bpf_iter support

by Matthieu Baerts (NGI0)

Here is a series from Geliang, adding mptcp_subflow bpf_iter support. We are working on extending MPTCP with BPF, e.g. to control the path manager -- in charge of the creation, deletion, and announcements of subflows (paths) -- and the packet scheduler -- in charge of selecting which available path the next data will be sent to. These extensions need to iterate over the list of subflows attached to an MPTCP connection, and do some specific actions via some new kfunc that will be added later on. This preparation work is split in different patches: - Patch 1: extend bpf_skc_to_mptcp_sock() to be called with msk. - Patch 2: allow using skc_to_mptcp_sock() in CGroup sockopt hooks. - Patch 3: register some "basic" MPTCP kfunc. - Patch 4: add mptcp_subflow bpf_iter support. Note that previous versions of this single patch have already been shared to the BPF mailing list. The changelog has been kept with a comment, but the version number has been reset to avoid confusions. - Patch 5: add kfunc to make sure the msk is valid - Patch 6: add more MPTCP endpoints in the selftests, in order to create more than 2 subflows. - Patch 7: add a very simple test validating mptcp_subflow bpf_iter support. This test could be written without the new bpf_iter, but it is there only to make sure this specific feature works as expected. Signed-off-by: Matthieu Baerts (NGI0) <matttbe(a)kernel.org> --- Changes in v2: - Patches 1-2: new ones. - Patch 3: remove two kfunc, more restrictions. (Martin) - Patch 4: add BUILD_BUG_ON(), more restrictions. (Martin) - Patch 7: adaptations due to modifications in patches 1-4. - Link to v1: https://lore.kernel.org/r/20241108-bpf-next-net-mptcp-bpf_iter-subflows-v1-… --- Geliang Tang (7): bpf: Extend bpf_skc_to_mptcp_sock to MPTCP sock bpf: Allow use of skc_to_mptcp_sock in cg_sockopt bpf: Register mptcp common kfunc set bpf: Add mptcp_subflow bpf_iter bpf: Acquire and release mptcp socket selftests/bpf: More endpoints for endpoint_init selftests/bpf: Add mptcp_subflow bpf_iter subtest include/net/mptcp.h | 4 +- kernel/bpf/cgroup.c | 2 + net/core/filter.c | 2 +- net/mptcp/bpf.c | 113 +++++++++++++++++- tools/testing/selftests/bpf/bpf_experimental.h | 8 ++ tools/testing/selftests/bpf/prog_tests/mptcp.c | 129 ++++++++++++++++++++- tools/testing/selftests/bpf/progs/mptcp_bpf.h | 9 ++ .../testing/selftests/bpf/progs/mptcp_bpf_iters.c | 63 ++++++++++ 8 files changed, 318 insertions(+), 12 deletions(-) --- base-commit: dad704ebe38642cd405e15b9c51263356391355c change-id: 20241108-bpf-next-net-mptcp-bpf_iter-subflows-027f6d87770e Best regards, -- Matthieu Baerts (NGI0) <matttbe(a)kernel.org>

7 months, 3 weeks

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[PATCH v4 0/9] mm: workingset reporting

by Yuanchu Xie

This patch series provides workingset reporting of user pages in lruvecs, of which coldness can be tracked by accessed bits and fd references. However, the concept of workingset applies generically to all types of memory, which could be kernel slab caches, discardable userspace caches (databases), or CXL.mem. Therefore, data sources might come from slab shrinkers, device drivers, or the userspace. Another interesting idea might be hugepage workingset, so that we can measure the proportion of hugepages backing cold memory. However, with architectures like arm, there may be too many hugepage sizes leading to a combinatorial explosion when exporting stats to the userspace. Nonetheless, the kernel should provide a set of workingset interfaces that is generic enough to accommodate the various use cases, and extensible to potential future use cases. Use cases ========== Job scheduling On overcommitted hosts, workingset information improves efficiency and reliability by allowing the job scheduler to have better stats on the exact memory requirements of each job. This can manifest in efficiency by landing more jobs on the same host or NUMA node. On the other hand, the job scheduler can also ensure each node has a sufficient amount of memory and does not enter direct reclaim or the kernel OOM path. With workingset information and job priority, the userspace OOM killing or proactive reclaim policy can kick in before the system is under memory pressure. If the job shape is very different from the machine shape, knowing the workingset per-node can also help inform page allocation policies. Proactive reclaim Workingset information allows the a container manager to proactively reclaim memory while not impacting a job's performance. While PSI may provide a reactive measure of when a proactive reclaim has reclaimed too much, workingset reporting allows the policy to be more accurate and flexible. Ballooning (similar to proactive reclaim) The last patch of the series extends the virtio-balloon device to report the guest workingset. Balloon policies benefit from workingset to more precisely determine the size of the memory balloon. On end-user devices where memory is scarce and overcommitted, the balloon sizing in multiple VMs running on the same device can be orchestrated with workingset reports from each one. On the server side, workingset reporting allows the balloon controller to inflate the balloon without causing too much file cache to be reclaimed in the guest. Promotion/Demotion If different mechanisms are used for promition and demotion, workingset information can help connect the two and avoid pages being migrated back and forth. For example, given a promotion hot page threshold defined in reaccess distance of N seconds (promote pages accessed more often than every N seconds). The threshold N should be set so that ~80% (e.g.) of pages on the fast memory node passes the threshold. This calculation can be done with workingset reports. To be directly useful for promotion policies, the workingset report interfaces need to be extended to report hotness and gather hotness information from the devices[1]. [1] https://www.opencompute.org/documents/ocp-cms-hotness-tracking-requirements… Sysfs and Cgroup Interfaces ========== The interfaces are detailed in the patches that introduce them. The main idea here is we break down the workingset per-node per-memcg into time intervals (ms), e.g. 1000 anon=137368 file=24530 20000 anon=34342 file=0 30000 anon=353232 file=333608 40000 anon=407198 file=206052 9223372036854775807 anon=4925624 file=892892 Implementation ========== The reporting of user pages is based off of MGLRU, and therefore requires CONFIG_LRU_GEN=y. We would benefit from more MGLRU generations for a more fine-grained workingset report, but we can already gather a lot of data with just four generations. The workingset reporting mechanism is gated behind CONFIG_WORKINGSET_REPORT, and the aging thread is behind CONFIG_WORKINGSET_REPORT_AGING. Benchmarks ========== Ghait Ouled Amar Ben Cheikh has implemented a simple policy and ran Linux compile and redis benchmarks from openbenchmarking.org. The policy and runner is referred to as WMO (Workload Memory Optimization). The results were based on v3 of the series, but v4 doesn't change the core of the working set reporting and just adds the ballooning counterpart. The timed Linux kernel compilation benchmark shows improvements in peak memory usage with a policy of "swap out all bytes colder than 10 seconds every 40 seconds". A swapfile is configured on SSD. -------------------------------------------- peak memory usage (with WMO): 4982.61328 MiB peak memory usage (control): 9569.1367 MiB peak memory reduction: 47.9% -------------------------------------------- Benchmark | Experimental |Control | Experimental_Std_Dev | Control_Std_Dev Timed Linux Kernel Compilation - allmodconfig (sec) | 708.486 (95.91%) | 679.499 (100%) | 0.6% | 0.1% -------------------------------------------- Seconds, fewer is better The redis benchmark shows employs the same policy: -------------------------------------------- peak memory usage (with WMO): 375.9023 MiB peak memory usage (control): 509.765 MiB peak memory reduction: 26% -------------------------------------------- Benchmark | Experimental | Control | Experimental_Std_Dev | Control_Std_Dev Redis - LPOP (Reqs/sec) | 2023130 (98.22%) | 2059849 (100%) | 1.2% | 2% Redis - SADD (Reqs/sec) | 2539662 (98.63%) | 2574811 (100%) | 2.3% | 1.4% Redis - LPUSH (Reqs/sec)| 2024880 (100%) | 2000884 (98.81%) | 1.1% | 0.8% Redis - GET (Reqs/sec) | 2835764 (100%) | 2763722 (97.46%) | 2.7% | 1.6% Redis - SET (Reqs/sec) | 2340723 (100%) | 2327372 (99.43%) | 2.4% | 1.8% -------------------------------------------- Reqs/sec, more is better The detailed report and benchmarking results are in Ghait's repo: https://github.com/miloudi98/WMO Changelog ========== Changes from PATCH v3 -> v4: - Added documentation for cgroup-v2 (Waiman Long) - Fixed types in documentation (Randy Dunlap) - Added implementation for the ballooning use case - Added detailed description of benchmark results (Andrew Morton) Changes from PATCH v2 -> v3: - Fixed typos in commit messages and documentation (Lance Yang, Randy Dunlap) - Split out the force_scan patch to be reviewed separately - Added benchmarks from Ghait Ouled Amar Ben Cheikh - Fixed reported compile error without CONFIG_MEMCG Changes from PATCH v1 -> v2: - Updated selftest to use ksft_test_result_code instead of switch-case (Muhammad Usama Anjum) - Included more use cases in the cover letter (Huang, Ying) - Added documentation for sysfs and memcg interfaces - Added an aging-specific struct lru_gen_mm_walk in struct pglist_data to avoid allocating for each lruvec. [v1] https://lore.kernel.org/linux-mm/20240504073011.4000534-1-yuanchu@google.co… [v2] https://lore.kernel.org/linux-mm/20240604020549.1017540-1-yuanchu@google.co… [v3] https://lore.kernel.org/linux-mm/20240813165619.748102-1-yuanchu@google.com/ Yuanchu Xie (9): mm: aggregate workingset information into histograms mm: use refresh interval to rate-limit workingset report aggregation mm: report workingset during memory pressure driven scanning mm: extend workingset reporting to memcgs mm: add kernel aging thread for workingset reporting selftest: test system-wide workingset reporting Docs/admin-guide/mm/workingset_report: document sysfs and memcg interfaces Docs/admin-guide/cgroup-v2: document workingset reporting virtio-balloon: add workingset reporting Documentation/admin-guide/cgroup-v2.rst | 35 + Documentation/admin-guide/mm/index.rst | 1 + .../admin-guide/mm/workingset_report.rst | 105 +++ drivers/base/node.c | 6 + drivers/virtio/virtio_balloon.c | 390 ++++++++++- include/linux/balloon_compaction.h | 1 + include/linux/memcontrol.h | 21 + include/linux/mmzone.h | 13 + include/linux/workingset_report.h | 167 +++++ include/uapi/linux/virtio_balloon.h | 30 + mm/Kconfig | 15 + mm/Makefile | 2 + mm/internal.h | 19 + mm/memcontrol.c | 162 ++++- mm/mm_init.c | 2 + mm/mmzone.c | 2 + mm/vmscan.c | 56 +- mm/workingset_report.c | 653 ++++++++++++++++++ mm/workingset_report_aging.c | 127 ++++ tools/testing/selftests/mm/.gitignore | 1 + tools/testing/selftests/mm/Makefile | 3 + tools/testing/selftests/mm/run_vmtests.sh | 5 + .../testing/selftests/mm/workingset_report.c | 306 ++++++++ .../testing/selftests/mm/workingset_report.h | 39 ++ .../selftests/mm/workingset_report_test.c | 330 +++++++++ 25 files changed, 2482 insertions(+), 9 deletions(-) create mode 100644 Documentation/admin-guide/mm/workingset_report.rst create mode 100644 include/linux/workingset_report.h create mode 100644 mm/workingset_report.c create mode 100644 mm/workingset_report_aging.c create mode 100644 tools/testing/selftests/mm/workingset_report.c create mode 100644 tools/testing/selftests/mm/workingset_report.h create mode 100644 tools/testing/selftests/mm/workingset_report_test.c -- 2.47.0.338.g60cca15819-goog

7 months, 3 weeks

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[PATCH v5 0/3] selftests/lam: get_user additions and LAM enabled check

by Maciej Wieczor-Retman

Recent change in how get_user() handles pointers [1] has a specific case for LAM. It assigns a different bitmask that's later used to check whether a pointer comes from userland in get_user(). While currently commented out (until LASS [2] is merged into the kernel) it's worth making changes to the LAM selftest ahead of time. Modify cpu_has_la57() so it provides current paging level information instead of the cpuid one. Add test case to LAM that utilizes a ioctl (FIOASYNC) syscall which uses get_user() in its implementation. Execute the syscall with differently tagged pointers to verify that valid user pointers are passing through and invalid kernel/non-canonical pointers are not. Also to avoid unhelpful test failures add a check in main() to skip running tests if LAM was not compiled into the kernel. Code was tested on a Sierra Forest Xeon machine that's LAM capable. The test was ran without issues with both the LAM lines from [1] untouched and commented out. The test was also ran without issues with LAM_SUP both enabled and disabled. 4/5 level pagetables code paths were also successfully tested in Simics on a 5-level capable machine. [1] https://lore.kernel.org/all/20241024013214.129639-1-torvalds@linux-foundati… [2] https://lore.kernel.org/all/20241028160917.1380714-1-alexander.shishkin@lin… Maciej Wieczor-Retman (3): selftests/lam: Move cpu_has_la57() to use cpuinfo flag selftests/lam: Skip test if LAM is disabled selftests/lam: Test get_user() LAM pointer handling tools/testing/selftests/x86/lam.c | 120 ++++++++++++++++++++++++++++-- 1 file changed, 115 insertions(+), 5 deletions(-) -- 2.47.1

7 months, 3 weeks

3
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"stty sane" in kunit.py

by Brendan Jackman

Hi all, Does anyone know what the 'stty sane' invocation in kunit.py is about? The other day I ran into an issue when running it via watchexec[1]. At the time I believed that it was there to clean up after the firmware that QEMU runs potentially messed up the terminal. However, I just realised I'm not sure if that makes sense - stty is about setting terminal settings via ioctl. I don't think QEMU or its guests are messing up the terminal with ioctls, they're just writing funny control characters. What's going on here? I guess one of: 1. Terminal is messed up with ctrl chars but ioctls are the easiest/only way to reliably clean it up. 2. Nobody thought about this unimportant detail so hard before and there's no particular rationale in place here. 3. I made bad assumptions about why the `stty sane` is there. If it's 1 or 2 I wonder if there's an alternative way to clean up without getting the SIGTTOU issue. Or, maybe it doesn't matter and the fact that this was ever a problem is just a bug in watchexec (maybe you can tell I haven't actually taken the time to research the SIGTTOU thing properly). But thought I'd raise it in case this points to issues people might have using kunit.py in CI. [1] https://github.com/watchexec/watchexec/issues/874 [2] https://gist.github.com/bjackman/27fd9980d87c5556c20e67a6ed891500

7 months, 4 weeks

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[PATCH RFC v3 00/27] KVM: arm64: Implement support for SME in non-protected guests

by Mark Brown

Given the time of year and point in the release cycle this is an RFC series, there's a few areas where I'm particularly expecting that people might have feedback: - The userspace ABI, in particular: - The vector length used for the SVE registers, access to the SVE registers and access to ZA and (if available) ZT0 depending on the current state of PSTATE.{SM,ZA}. - The use of a single finalisation for both SVE and SME. - The addition of control for enabling fine grained traps in a similar manner to FGU but without the UNDEF, I'm not clear if this is desired at all and at present this requires symmetric read and write traps like FGU. That seemed like it might be desired from an implementation point of view but we already have one case where we enable an asymmetric trap (for ARM64_WORKAROUND_AMPERE_AC03_CPU_38) and it seems generally useful to enable asymmetrically. There is some nested virtualisation support in the code but it is not enabled or complete, this will be completed before the RFC tag is removed. I am anticipating having a vastly better test environment soon which will make this much easier to complete and there is no SME specific ABI for nested virtualisation. This series implements support for SME use in non-protected KVM guests. Much of this is very similar to SVE, the main additional challenge that SME presents is that it introduces a new vector length similar to the SVE vector length and two new controls which change the registers seen by guests: - PSTATE.ZA enables the ZA matrix register and, if SME2 is supported, the ZT0 LUT register. - PSTATE.SM enables streaming mode, a new floating point mode which uses the SVE register set with the separately configured SME vector length. In streaming mode implementation of the FFR register is optional. It is also permitted to build systems which support SME without SVE, in this case when not in streaming mode no SVE registers or instructions are available. Further, there is no requirement that there be any overlap in the set of vector lengths supported by SVE and SME in a system, this is expected to be a common situation in practical systems. Since there is a new vector length to configure we introduce a new feature parallel to the existing SVE one with a new pseudo register for the streaming mode vector length. Due to the overlap with SVE caused by streaming mode rather than finalising SME as a separate feature we use the existing SVE finalisation to also finalise SME, a new define KVM_ARM_VCPU_VEC is provided to help make user code clearer. Finalising SVE and SME separately would introduce complication with register access since finalising SVE makes the SVE regsiters writeable by userspace and doing multiple finalisations results in an error being reported. Dealing with a state where the SVE registers are writeable due to one of SVE or SME being finalised but may have their VL changed by the other being finalised seems like needless complexity with minimal practical utility, it seems clearer to just express directly that only one finalisation can be done in the ABI. Access to the floating point registers follows the architecture: - When both SVE and SME are present: - If PSTATE.SM == 0 the vector length used for the Z and P registers is the SVE vector length. - If PSTATE.SM == 1 the vector length used for the Z and P registers is the SME vector length. - If only SME is present: - If PSTATE.SM == 0 the Z and P registers are inaccessible and the floating point state accessed via the encodings for the V registers. - If PSTATE.SM == 1 the vector length used for the Z and P registers - The SME specific ZA and ZT0 registers are only accessible if SVCR.ZA is 1. The VMM must understand this, in particular when loading state SVCR should be configured before other state. There are a large number of subfeatures for SME, most of which only offer additional instructions but some of which (SME2 and FA64) add architectural state. These are configured via the ID registers as per usual. The new KVM_ARM_VCPU_VEC feature and ZA and ZT0 registers have not been added to the get-reg-list selftest, the idea of supporting additional features there without restructuring the program to generate all possible feature combinations has been rejected. I will post a separate series which does that restructuring. No support is present for protected guests, this is expected to be added separately. The series is based on Fuad's series: https://lore.kernel.org/r/20241216105057.579031-1-tabba@google.com/ It will need a rebase on: https://lore.kernel.org/r/20241219173351.1123087-1-maz@kernel.org (as will Fuad's.) Signed-off-by: Mark Brown <broonie(a)kernel.org> --- Changes in v3: - Rebase onto v6.12-rc2. - Link to v2: https://lore.kernel.org/r/20231222-kvm-arm64-sme-v2-0-da226cb180bb@kernel.o… Changes in v2: - Rebase onto v6.7-rc3. - Configure subfeatures based on host system only. - Complete nVHE support. - There was some snafu with sending v1 out, it didn't make it to the lists but in case it hit people's inboxes I'm sending as v2. --- Mark Brown (27): arm64/fpsimd: Update FA64 and ZT0 enables when loading SME state arm64/fpsimd: Decide to save ZT0 and streaming mode FFR at bind time arm64/fpsimd: Check enable bit for FA64 when saving EFI state arm64/fpsimd: Determine maximum virtualisable SME vector length KVM: arm64: Introduce non-UNDEF FGT control KVM: arm64: Pull ctxt_has_ helpers to start of sysreg-sr.h KVM: arm64: Convert cpacr_clear_set() to a static inline KVM: arm64: Move SVE state access macros after feature test macros KVM: arm64: Factor SVE guest exit handling out into a function KVM: arm64: Rename SVE finalization constants to be more general KVM: arm64: Document the KVM ABI for SME KVM: arm64: Define internal features for SME KVM: arm64: Rename sve_state_reg_region KVM: arm64: Store vector lengths in an array KVM: arm64: Implement SME vector length configuration KVM: arm64: Add definitions for SME control register KVM: arm64: Support TPIDR2_EL0 KVM: arm64: Support SMIDR_EL1 for guests KVM: arm64: Support SME priority registers KVM: arm64: Provide assembly for SME state restore KVM: arm64: Support Z and P registers in streaming mode KVM: arm64: Expose SME specific state to userspace KVM: arm64: Context switch SME state for normal guests KVM: arm64: Handle SME exceptions KVM: arm64: Provide interface for configuring and enabling SME for guests KVM: arm64: selftests: Add SME system registers to get-reg-list KVM: arm64: selftests: Add SME to set_id_regs test Documentation/virt/kvm/api.rst | 117 ++++++--- arch/arm64/include/asm/fpsimd.h | 22 ++ arch/arm64/include/asm/kvm_emulate.h | 37 ++- arch/arm64/include/asm/kvm_host.h | 135 ++++++++--- arch/arm64/include/asm/kvm_hyp.h | 4 +- arch/arm64/include/asm/kvm_pkvm.h | 2 +- arch/arm64/include/asm/vncr_mapping.h | 2 + arch/arm64/include/uapi/asm/kvm.h | 33 +++ arch/arm64/kernel/cpufeature.c | 2 - arch/arm64/kernel/fpsimd.c | 86 ++++--- arch/arm64/kvm/arm.c | 10 + arch/arm64/kvm/fpsimd.c | 156 +++++++----- arch/arm64/kvm/guest.c | 262 ++++++++++++++++++--- arch/arm64/kvm/handle_exit.c | 14 ++ arch/arm64/kvm/hyp/fpsimd.S | 16 ++ arch/arm64/kvm/hyp/include/hyp/switch.h | 104 ++++++-- arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 47 ++-- arch/arm64/kvm/hyp/nvhe/hyp-main.c | 17 +- arch/arm64/kvm/hyp/nvhe/pkvm.c | 4 +- arch/arm64/kvm/hyp/nvhe/switch.c | 11 +- arch/arm64/kvm/hyp/vhe/switch.c | 21 +- arch/arm64/kvm/reset.c | 154 +++++++++--- arch/arm64/kvm/sys_regs.c | 118 +++++++++- include/uapi/linux/kvm.h | 1 + tools/testing/selftests/kvm/aarch64/get-reg-list.c | 32 ++- tools/testing/selftests/kvm/aarch64/set_id_regs.c | 29 ++- 26 files changed, 1117 insertions(+), 319 deletions(-) --- base-commit: e32a80927434907f973f38a88cd19d7e51991d24 change-id: 20230301-kvm-arm64-sme-06a1246d3636 prerequisite-message-id: 20241216105057.579031-1-tabba(a)google.com prerequisite-patch-id: 10a23279fc1aa942c363d66df0e95414342b614b prerequisite-patch-id: 670db72b1987d2591e23db072fd27db7f65ffb0f prerequisite-patch-id: c6bc6f799cebe5010bf3d734eb06e39d5dfab0d6 prerequisite-patch-id: 5555cde0b025483c2318d006a0324fd95bd06268 prerequisite-patch-id: a73738d5bbc5e694c92b7a5654f78eb79ed23c09 prerequisite-patch-id: 6194857db22ccaefe13e88b3155b6e761c9b7692 prerequisite-patch-id: 5dca3992c2ffa5bf2edb45f68be45edfae9b41b3 prerequisite-patch-id: b048e799d816c9c6750ed4f264fd38cb6e31f968 prerequisite-patch-id: 07fea6c2207f8cd2d35d4c171a97d28397db9a79 prerequisite-patch-id: f330e82665af9f223e838511bd4a95faad56e3ac prerequisite-patch-id: 060a6061eaedb7fd02c18e898bfd9652c991b9af prerequisite-patch-id: fc31d9f0e7812a8f962876fdb311414122895389 prerequisite-patch-id: ae675f63215a211c42a497789ee5e092fd461279 prerequisite-patch-id: ff3c533043a1fa3a13827ea5c70459b228aa95ee prerequisite-patch-id: de489d2d73f49d74b75c628828a6b56dbac751e2 prerequisite-patch-id: 92f4a1249e3a1ff32eb16c25af56930762c5697d prerequisite-patch-id: ac1248b4e10dce15672e02b366a359d634297877 Best regards, -- Mark Brown <broonie(a)kernel.org>

7 months, 4 weeks

3
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[PATCH v6 00/15] integrity: Introduce the Integrity Digest Cache

by Roberto Sassu

From: Roberto Sassu <roberto.sassu(a)huawei.com> Integrity detection and protection has long been a desirable feature, to reach a large user base and mitigate the risk of flaws in the software and attacks. However, while solutions exist, they struggle to reach a large user base, due to requiring higher than desired constraints on performance, flexibility and configurability, that only security conscious people are willing to accept. For example, IMA measurement requires the target platform to collect integrity measurements, and to protect them with the TPM, which introduces a noticeable overhead (up to 10x slower in a microbenchmark) on frequently used system calls, like the open(). IMA Appraisal currently requires individual files to be signed and verified, and Linux distributions to rebuild all packages to include file signatures (this approach has been adopted from Fedora 39+). Like a TPM, also signature verification introduces a significant overhead, especially if it is used to check the integrity of many files. This is where the new Integrity Digest Cache comes into play, it offers additional support for new and existing integrity solutions, to make them faster and easier to deploy. The Integrity Digest Cache can help IMA to reduce the number of TPM operations and to make them happen in a deterministic way. If IMA knows that a file comes from a Linux distribution, it can measure files in a different way: measure the list of digests coming from the distribution (e.g. RPM package headers), and subsequently measure a file if it is not found in that list. The performance improvement comes at the cost of IMA not reporting which files from installed packages were accessed, and in which temporal sequence. This approach might not be suitable for all use cases. The Integrity Digest Cache can also help IMA for appraisal. IMA can simply lookup the calculated digest of an accessed file in the list of digests extracted from package headers, after verifying the header signature. It is sufficient to verify only one signature for all files in the package, as opposed to verifying a signature for each file. The same approach can be followed by other LSMs, such as Integrity Policy Enforcement (IPE), and BPF LSM. The Integrity Digest Cache is not tied to a specific package format. The kernel supports a TLV-based digest list format. More can be added through third-party kernel modules. The TLV parser has been verified for memory safety with the Frama-C static analyzer. The version with the Frama-C assertions is available here: https://github.com/robertosassu/rpm-formal/blob/main/validate_tlv.c Integrating the Integrity Digest Cache in IMA brings significant performance improvements: up to 67% and 79% for measurement respectively in sequential and parallel file reads; up to 65% and 43% for appraisal respectively in sequential and parallel file reads. The performance can be further enhanced by using fsverity digests instead of conventional file digests, which would make IMA verify only the portion of the file to be read. However, at the moment, fsverity digests are not included in RPM packages. In this case, once rpm is extended to include them, Linux distributions still have to rebuild their packages. The Integrity Digest Cache can support both digest types, so that the functionality is immediately available without waiting for Linux distributions to do the transition. This patch set only includes the patches necessary to extract digests from a TLV-based data format, and exposes an API for LSMs to query them. A separate patch set will be provided to integrate it in IMA. This patch set and the follow-up IMA integration can be tested by following the instructions at: https://github.com/linux-integrity/digest-cache-tools This patch set applies on top of: https://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity.git/l… with commit 08ae3e5f5fc8 ("integrity: Use static_assert() to check struct sizes"). Changelog v5: - Remove the RPM parser and selftests (suggested by Linus) - Return digest cache pointer from digest_cache_lookup() - Export new Parser API, and allow registration of third-party digest list parsers (suggested by Mimi) - Reduce sizes in TLV format and remove TLV header (suggested by Jani Nikula) - Introduce new DIGEST_LIST_NUM_ENTRIES TLV field - Pass file descriptor instead of dentry in digest_cache_get() to properly detect potential deadlocks - Introduce digest_cache_opened_fd() to tell lockdep when it is safe to nest a mutex if digest_cache_get() is called with that mutex held - Add new patch to introduce ksys_finit_module() - Make the TLV parser as configurable (Y/N/m) with Kconfig (suggested by Mimi) - Don't store the path structure in the digest cache and pass it between creation and initialization of the digest cache - Remove digest_cache_dir_update_dig_user() and keep the digest cache retrieved during digest_cache_get() - Fail with an error pointer in digest_cache_dir_lookup_digest() if the current and passed directory digest cache don't match, or the digest cache was reset - Handle num_digest = 0 in digest_cache_htable_init() - Accept -EOPNOTSUPP error in digest_cache_new() - Implement inode_free_security_rcu LSM hook instead of inode_free_security - Move reservation of file descriptor security blob inside the #ifdef in init_ima_lsm() - Add test file_reset_again to check the error pointer returned by digest_cache_lookup() - Remove TLV_FAILURE_HDR_LEN TLV error test - Add missing MODULE_DESCRIPTION in kselftest kernel module (suggested by Jeff Johnson) - Replace dentry_open() with kernel_file_open() in populate.c and dir.c - Skip affected tests when CONFIG_DYNAMIC_FTRACE_WITH_ARGS=n v4: - Rename digest_cache LSM to Integrity Digest Cache (suggested by Paul Moore) - Update documentation - Remove forward declaration of struct digest_cache in include/linux/digest_cache.h (suggested by Jarkko) - Add DIGEST_CACHE_FREE digest cache event for notification - Remove digest_cache_found_t typedef and use uintptr_t instead - Add header callback in TLV parser and unexport tlv_parse_hdr() and tlv_parse_data() - Plug the Integrity Digest Cache into the 'ima' LSM - Switch from constructor to zeroing the object cache - Remove notifier and detect digest cache changes by comparing pointers - Rename digest_cache_dir_create() to digest_cache_dir_add_entries() - Introduce digest_cache_dir_create() to create and initialize a directory digest cache - Introduce digest_cache_dir_update_dig_user() to update dig_user with a file digest cache on positive digest lookup - Use up to date directory digest cache, to take into account possible inode eviction for the old ones - Introduce digest_cache_dir_prefetch() to prefetch digest lists - Adjust component name in debug messages (suggested by Jarkko) - Add FILE_PREFETCH and FILE_READ digest cache flags, remove RESET_USER - Reintroduce spin lock for digest cache verification data (needed for the selftests) - Get inode and file descriptor security blob offsets from outside (IMA) - Avoid user-after-free in digest_cache_unref() by decrementing the ref. count after printing the debug message - Check for digest list lookup loops also for the parent directory - Put and clear dig_owner directly in digest_cache_reset_clear_owner() - Move digest cache initialization code from digest_cache_create() to digest_cache_init() - Hold the digest list path until the digest cache is initialized (to avoid premature inode eviction) - Avoid race condition on setting DIR_PREFETCH in the directory digest cache - Introduce digest_cache_dir_prefetch() and do it between digest cache creation and initialization (to avoid lock inversion) - Avoid unnecessary length check in digest_list_parse_rpm() - Declare arrays of strings in tlv parser as static - Emit reset for parent directory on directory entry modification - Rename digest_cache_reset_owner() to digest_cache_reset_clear_owner() and digest_cache_reset_user() to digest_cache_clear_user() - Execute digest_cache_file_release() either if FMODE_WRITE or FMODE_CREATED are set in the file descriptor f_mode - Determine in digest_cache_verif_set() which gfp flag to use depending on verifier ID - Update selftests v3: - Rewrite documentation, and remove the installation instructions since they are now included in the README of digest-cache-tools - Add digest cache event notifier - Drop digest_cache_was_reset(), and send instead to asynchronous notifications - Fix digest_cache LSM Kconfig style issues (suggested by Randy Dunlap) - Propagate digest cache reset to directory entries - Destroy per directory entry mutex - Introduce RESET_USER bit, to clear the dig_user pointer on set/removexattr - Replace 'file content' with 'file data' (suggested by Mimi) - Introduce per digest cache mutex and replace verif_data_lock spinlock - Track changes of security.digest_list xattr - Stop tracking file_open and use file_release instead also for file writes - Add error messages in digest_cache_create() - Load/unload testing kernel module automatically during execution of test - Add tests for digest cache event notifier - Add test for ftruncate() - Remove DIGEST_CACHE_RESET_PREFETCH_BUF command in test and clear the buffer on read instead v2: - Include the TLV parser in this patch set (from user asymmetric keys and signatures) - Move from IMA and make an independent LSM - Remove IMA-specific stuff from this patch set - Add per algorithm hash table - Expect all digest lists to be in the same directory and allow changing the default directory - Support digest lookup on directories, when there is no security.digest_list xattr - Add seq num to digest list file name, to impose ordering on directory iteration - Add a new data type DIGEST_LIST_ENTRY_DATA for the nested data in the tlv digest list format - Add the concept of verification data attached to digest caches - Add the reset mechanism to track changes on digest lists and directory containing the digest lists - Add kernel selftests v1: - Add documentation in Documentation/security/integrity-digest-cache.rst - Pass the mask of IMA actions to digest_cache_alloc() - Add a reference count to the digest cache - Remove the path parameter from digest_cache_get(), and rely on the reference count to avoid the digest cache disappearing while being used - Rename the dentry_to_check parameter of digest_cache_get() to dentry - Rename digest_cache_get() to digest_cache_new() and add digest_cache_get() to set the digest cache in the iint of the inode for which the digest cache was requested - Add dig_owner and dig_user to the iint, to distinguish from which inode the digest cache was created from, and which is using it; consequently it makes the digest cache usable to measure/appraise other digest caches (support not yet enabled) - Add dig_owner_mutex and dig_user_mutex to serialize accesses to dig_owner and dig_user until they are initialized - Enforce strong synchronization and make the contenders wait until dig_owner and dig_user are assigned to the iint the first time - Move checking IMA actions on the digest list earlier, and fail if no action were performed (digest cache not usable) - Remove digest_cache_put(), not needed anymore with the introduction of the reference count - Fail immediately in digest_cache_lookup() if the digest algorithm is not set in the digest cache - Use 64 bit mask for IMA actions on the digest list instead of 8 bit - Return NULL in the inline version of digest_cache_get() - Use list_add_tail() instead of list_add() in the iterator - Copy the digest list path to a separate buffer in digest_cache_iter_dir() - Use digest list parsers verified with Frama-C - Explicitly disable (for now) the possibility in the IMA policy to use the digest cache to measure/appraise other digest lists - Replace exit(<value>) with return <value> in manage_digest_lists.c Roberto Sassu (15): lib: Add TLV parser module: Introduce ksys_finit_module() integrity: Introduce the Integrity Digest Cache digest_cache: Initialize digest caches digest_cache: Add securityfs interface digest_cache: Add hash tables and operations digest_cache: Allow registration of digest list parsers digest_cache: Parse tlv digest lists digest_cache: Populate the digest cache from a digest list digest_cache: Add management of verification data digest_cache: Add support for directories digest cache: Prefetch digest lists if requested digest_cache: Reset digest cache on file/directory change selftests/digest_cache: Add selftests for the Integrity Digest Cache docs: Add documentation of the Integrity Digest Cache Documentation/security/digest_cache.rst | 850 ++++++++++++++++++ Documentation/security/index.rst | 1 + MAINTAINERS | 10 + include/linux/digest_cache.h | 131 +++ include/linux/kernel_read_file.h | 1 + include/linux/syscalls.h | 10 + include/linux/tlv_parser.h | 32 + include/uapi/linux/tlv_digest_list.h | 47 + include/uapi/linux/tlv_parser.h | 41 + include/uapi/linux/xattr.h | 6 + kernel/module/main.c | 43 +- lib/Kconfig | 3 + lib/Makefile | 2 + lib/tlv_parser.c | 87 ++ lib/tlv_parser.h | 18 + security/integrity/Kconfig | 1 + security/integrity/Makefile | 1 + security/integrity/digest_cache/Kconfig | 43 + security/integrity/digest_cache/Makefile | 11 + security/integrity/digest_cache/dir.c | 400 +++++++++ security/integrity/digest_cache/htable.c | 260 ++++++ security/integrity/digest_cache/internal.h | 283 ++++++ security/integrity/digest_cache/main.c | 597 ++++++++++++ security/integrity/digest_cache/modsig.c | 66 ++ security/integrity/digest_cache/parsers.c | 257 ++++++ security/integrity/digest_cache/parsers/tlv.c | 341 +++++++ security/integrity/digest_cache/populate.c | 104 +++ security/integrity/digest_cache/reset.c | 227 +++++ security/integrity/digest_cache/secfs.c | 104 +++ security/integrity/digest_cache/verif.c | 135 +++ security/integrity/ima/ima.h | 1 + security/integrity/ima/ima_fs.c | 6 + security/integrity/ima/ima_main.c | 10 +- tools/testing/selftests/Makefile | 1 + .../testing/selftests/digest_cache/.gitignore | 3 + tools/testing/selftests/digest_cache/Makefile | 24 + .../testing/selftests/digest_cache/all_test.c | 769 ++++++++++++++++ tools/testing/selftests/digest_cache/common.c | 78 ++ tools/testing/selftests/digest_cache/common.h | 93 ++ .../selftests/digest_cache/common_user.c | 33 + .../selftests/digest_cache/common_user.h | 15 + tools/testing/selftests/digest_cache/config | 2 + .../selftests/digest_cache/generators.c | 130 +++ .../selftests/digest_cache/generators.h | 16 + .../selftests/digest_cache/testmod/Makefile | 16 + .../selftests/digest_cache/testmod/kern.c | 551 ++++++++++++ 46 files changed, 5849 insertions(+), 11 deletions(-) create mode 100644 Documentation/security/digest_cache.rst create mode 100644 include/linux/digest_cache.h create mode 100644 include/linux/tlv_parser.h create mode 100644 include/uapi/linux/tlv_digest_list.h create mode 100644 include/uapi/linux/tlv_parser.h create mode 100644 lib/tlv_parser.c create mode 100644 lib/tlv_parser.h create mode 100644 security/integrity/digest_cache/Kconfig create mode 100644 security/integrity/digest_cache/Makefile create mode 100644 security/integrity/digest_cache/dir.c create mode 100644 security/integrity/digest_cache/htable.c create mode 100644 security/integrity/digest_cache/internal.h create mode 100644 security/integrity/digest_cache/main.c create mode 100644 security/integrity/digest_cache/modsig.c create mode 100644 security/integrity/digest_cache/parsers.c create mode 100644 security/integrity/digest_cache/parsers/tlv.c create mode 100644 security/integrity/digest_cache/populate.c create mode 100644 security/integrity/digest_cache/reset.c create mode 100644 security/integrity/digest_cache/secfs.c create mode 100644 security/integrity/digest_cache/verif.c create mode 100644 tools/testing/selftests/digest_cache/.gitignore create mode 100644 tools/testing/selftests/digest_cache/Makefile create mode 100644 tools/testing/selftests/digest_cache/all_test.c create mode 100644 tools/testing/selftests/digest_cache/common.c create mode 100644 tools/testing/selftests/digest_cache/common.h create mode 100644 tools/testing/selftests/digest_cache/common_user.c create mode 100644 tools/testing/selftests/digest_cache/common_user.h create mode 100644 tools/testing/selftests/digest_cache/config create mode 100644 tools/testing/selftests/digest_cache/generators.c create mode 100644 tools/testing/selftests/digest_cache/generators.h create mode 100644 tools/testing/selftests/digest_cache/testmod/Makefile create mode 100644 tools/testing/selftests/digest_cache/testmod/kern.c -- 2.47.0.118.gfd3785337b

7 months, 4 weeks

7
53
0 0

[PATCH v2 0/6] Extend pmu_counters_test to AMD CPUs

by Colton Lewis

Extend pmu_counters_test to AMD CPUs. As the AMD PMU is quite different from Intel with different events and feature sets, this series introduces a new code path to test it, specifically focusing on the core counters including the PerfCtrExtCore and PerfMonV2 features. Northbridge counters and cache counters exist, but are not as important and can be deferred to a later series. The first patch is a bug fix that could be submitted separately. The series has been tested on both Intel and AMD machines, but I have not found an AMD machine old enough to lack PerfCtrExtCore. I have made efforts that no part of the code has any dependency on its presence. I am aware of similar work in this direction done by Jinrong Liang [1]. He told me he is not working on it currently and I am not intruding by making my own submission. [1] https://lore.kernel.org/kvm/20231121115457.76269-1-cloudliang@tencent.com/ v2: * Test all combinations of VM setup rather than only the maximum allowed by hardware * Add fixes tag to bug fix in patch 1 * Refine some names v1: https://lore.kernel.org/kvm/20240813164244.751597-1-coltonlewis@google.com/ Colton Lewis (6): KVM: x86: selftests: Fix typos in macro variable use KVM: x86: selftests: Define AMD PMU CPUID leaves KVM: x86: selftests: Set up AMD VM in pmu_counters_test KVM: x86: selftests: Test read/write core counters KVM: x86: selftests: Test core events KVM: x86: selftests: Test PerfMonV2 .../selftests/kvm/include/x86_64/processor.h | 7 + .../selftests/kvm/x86_64/pmu_counters_test.c | 304 ++++++++++++++++-- 2 files changed, 277 insertions(+), 34 deletions(-) base-commit: da3ea35007d0af457a0afc87e84fddaebc4e0b63 -- 2.46.0.662.g92d0881bb0-goog

8 months

2
20
0 0

[PATCH v10 00/14] riscv: Add support for xtheadvector

by Charlie Jenkins

xtheadvector is a custom extension that is based upon riscv vector version 0.7.1 [1]. All of the vector routines have been modified to support this alternative vector version based upon whether xtheadvector was determined to be supported at boot. vlenb is not supported on the existing xtheadvector hardware, so a devicetree property thead,vlenb is added to provide the vlenb to Linux. There is a new hwprobe key RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0 that is used to request which thead vendor extensions are supported on the current platform. This allows future vendors to allocate hwprobe keys for their vendor. Support for xtheadvector is also added to the vector kselftests. Signed-off-by: Charlie Jenkins <charlie(a)rivosinc.com> [1] https://github.com/T-head-Semi/thead-extension-spec/blob/95358cb2cca9489361… --- This series is a continuation of a different series that was fragmented into two other series in an attempt to get part of it merged in the 6.10 merge window. The split-off series did not get merged due to a NAK on the series that added the generic riscv,vlenb devicetree entry. This series has converted riscv,vlenb to thead,vlenb to remedy this issue. The original series is titled "riscv: Support vendor extensions and xtheadvector" [3]. The series titled "riscv: Extend cpufeature.c to detect vendor extensions" is still under development and this series is based on that series! [4] I have tested this with an Allwinner Nezha board. I used SkiffOS [1] to manage building the image, but upgraded the U-Boot version to Samuel Holland's more up-to-date version [2] and changed out the device tree used by U-Boot with the device trees that are present in upstream linux and this series. Thank you Samuel for all of the work you did to make this task possible. [1] https://github.com/skiffos/SkiffOS/tree/master/configs/allwinner/nezha [2] https://github.com/smaeul/u-boot/commit/2e89b706f5c956a70c989cd31665f1429e9… [3] https://lore.kernel.org/all/20240503-dev-charlie-support_thead_vector_6_9-v… [4] https://lore.kernel.org/lkml/20240719-support_vendor_extensions-v3-4-0af758… --- Changes in v10: - In DT probing disable vector with new function to clear vendor extension bits for xtheadvector - Add ghostwrite mitigations for c9xx CPUs. This disables xtheadvector unless mitigations=off is set as a kernel boot arg - Link to v9: https://lore.kernel.org/r/20240806-xtheadvector-v9-0-62a56d2da5d0@rivosinc.… Changes in v9: - Rebase onto palmer's for-next - Fix sparse error in arch/riscv/kernel/vendor_extensions/thead.c - Fix maybe-uninitialized warning in arch/riscv/include/asm/vendor_extensions/vendor_hwprobe.h - Wrap some long lines - Link to v8: https://lore.kernel.org/r/20240724-xtheadvector-v8-0-cf043168e137@rivosinc.… Changes in v8: - Rebase onto palmer's for-next - Link to v7: https://lore.kernel.org/r/20240724-xtheadvector-v7-0-b741910ada3e@rivosinc.… Changes in v7: - Add defs for has_xtheadvector_no_alternatives() and has_xtheadvector() when vector disabled. (Palmer) - Link to v6: https://lore.kernel.org/r/20240722-xtheadvector-v6-0-c9af0130fa00@rivosinc.… Changes in v6: - Fix return type of is_vector_supported()/is_xthead_supported() to be bool - Link to v5: https://lore.kernel.org/r/20240719-xtheadvector-v5-0-4b485fc7d55f@rivosinc.… Changes in v5: - Rebase on for-next - Link to v4: https://lore.kernel.org/r/20240702-xtheadvector-v4-0-2bad6820db11@rivosinc.… Changes in v4: - Replace inline asm with C (Samuel) - Rename VCSRs to CSRs (Samuel) - Replace .insn directives with .4byte directives - Link to v3: https://lore.kernel.org/r/20240619-xtheadvector-v3-0-bff39eb9668e@rivosinc.… Changes in v3: - Add back Heiko's signed-off-by (Conor) - Mark RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0 as a bitmask - Link to v2: https://lore.kernel.org/r/20240610-xtheadvector-v2-0-97a48613ad64@rivosinc.… Changes in v2: - Removed extraneous references to "riscv,vlenb" (Jess) - Moved declaration of "thead,vlenb" into cpus.yaml and added restriction that it's only applicable to thead cores (Conor) - Check CONFIG_RISCV_ISA_XTHEADVECTOR instead of CONFIG_RISCV_ISA_V for thead,vlenb (Jess) - Fix naming of hwprobe variables (Evan) - Link to v1: https://lore.kernel.org/r/20240609-xtheadvector-v1-0-3fe591d7f109@rivosinc.… --- Charlie Jenkins (13): dt-bindings: riscv: Add xtheadvector ISA extension description dt-bindings: cpus: add a thead vlen register length property riscv: dts: allwinner: Add xtheadvector to the D1/D1s devicetree riscv: Add thead and xtheadvector as a vendor extension riscv: vector: Use vlenb from DT for thead riscv: csr: Add CSR encodings for CSR_VXRM/CSR_VXSAT riscv: Add xtheadvector instruction definitions riscv: vector: Support xtheadvector save/restore riscv: hwprobe: Add thead vendor extension probing riscv: hwprobe: Document thead vendor extensions and xtheadvector extension selftests: riscv: Fix vector tests selftests: riscv: Support xtheadvector in vector tests riscv: Add ghostwrite vulnerability Heiko Stuebner (1): RISC-V: define the elements of the VCSR vector CSR Documentation/arch/riscv/hwprobe.rst | 10 + Documentation/devicetree/bindings/riscv/cpus.yaml | 19 ++ .../devicetree/bindings/riscv/extensions.yaml | 10 + arch/riscv/Kconfig.errata | 11 + arch/riscv/Kconfig.vendor | 26 ++ arch/riscv/boot/dts/allwinner/sun20i-d1s.dtsi | 3 +- arch/riscv/errata/thead/errata.c | 28 ++ arch/riscv/include/asm/bugs.h | 22 ++ arch/riscv/include/asm/cpufeature.h | 2 + arch/riscv/include/asm/csr.h | 15 + arch/riscv/include/asm/errata_list.h | 3 +- arch/riscv/include/asm/hwprobe.h | 3 +- arch/riscv/include/asm/switch_to.h | 2 +- arch/riscv/include/asm/vector.h | 225 +++++++++++---- arch/riscv/include/asm/vendor_extensions/thead.h | 48 ++++ .../include/asm/vendor_extensions/thead_hwprobe.h | 19 ++ .../include/asm/vendor_extensions/vendor_hwprobe.h | 37 +++ arch/riscv/include/uapi/asm/hwprobe.h | 3 +- arch/riscv/include/uapi/asm/vendor/thead.h | 3 + arch/riscv/kernel/Makefile | 2 + arch/riscv/kernel/bugs.c | 55 ++++ arch/riscv/kernel/cpufeature.c | 58 +++- arch/riscv/kernel/kernel_mode_vector.c | 8 +- arch/riscv/kernel/process.c | 4 +- arch/riscv/kernel/signal.c | 6 +- arch/riscv/kernel/sys_hwprobe.c | 5 + arch/riscv/kernel/vector.c | 24 +- arch/riscv/kernel/vendor_extensions.c | 10 + arch/riscv/kernel/vendor_extensions/Makefile | 2 + arch/riscv/kernel/vendor_extensions/thead.c | 29 ++ .../riscv/kernel/vendor_extensions/thead_hwprobe.c | 19 ++ drivers/base/cpu.c | 3 + include/linux/cpu.h | 1 + tools/testing/selftests/riscv/vector/.gitignore | 3 +- tools/testing/selftests/riscv/vector/Makefile | 17 +- .../selftests/riscv/vector/v_exec_initval_nolibc.c | 94 +++++++ tools/testing/selftests/riscv/vector/v_helpers.c | 68 +++++ tools/testing/selftests/riscv/vector/v_helpers.h | 8 + tools/testing/selftests/riscv/vector/v_initval.c | 22 ++ .../selftests/riscv/vector/v_initval_nolibc.c | 68 ----- .../selftests/riscv/vector/vstate_exec_nolibc.c | 20 +- .../testing/selftests/riscv/vector/vstate_prctl.c | 305 +++++++++++++-------- 42 files changed, 1048 insertions(+), 272 deletions(-) --- base-commit: 0e3f3649d44bf1b388a7613ade14c29cbdedf075 change-id: 20240530-xtheadvector-833d3d17b423 -- - Charlie

8 months

9
35
0 0

[PATCH RFC v3 00/10] extensible syscalls: CHECK_FIELDS to allow for easier feature detection

by Aleksa Sarai

This is something that I've been thinking about for a while. We had a discussion at LPC 2020 about this[1] but the proposals suggested there never materialised. In short, it is quite difficult for userspace to detect the feature capability of syscalls at runtime. This is something a lot of programs want to do, but they are forced to create elaborate scenarios to try to figure out if a feature is supported without causing damage to the system. For the vast majority of cases, each individual feature also needs to be tested individually (because syscall results are all-or-nothing), so testing even a single syscall's feature set can easily inflate the startup time of programs. This patchset implements the fairly minimal design I proposed in this talk[2] and in some old LKML threads (though I can't find the exact references ATM). The general flow looks like: 1. Userspace will indicate to the kernel that a syscall should a be no-op by setting the top bit of the extensible struct size argument. We will almost certainly never support exabyte sized structs, so the top bits are free for us to use as makeshift flag bits. This is preferable to using the per-syscall flag field inside the structure because seccomp can easily detect the bit in the flag and allow the probe or forcefully return -EEXTSYS_NOOP. 2. The kernel will then fill the provided structure with every valid bit pattern that the current kernel understands. For flags or other bitflag-like fields, this is the set of valid flags or bits. For pointer fields or fields that take an arbitrary value, the field has every bit set (0xFF... to fill the field) to indicate that any value is valid in the field. 3. The syscall then returns -EEXTSYS_NOOP which is an errno that will only ever be used for this purpose (so userspace can be sure that the request succeeded). On older kernels, the syscall will return a different error (usually -E2BIG or -EFAULT) and userspace can do their old-fashioned checks. 4. Userspace can then check which flags and fields are supported by looking at the fields in the returned structure. Flags are checked by doing an AND with the flags field, and field support can checked by comparing to 0. In principle you could just AND the entire structure if you wanted to do this check generically without caring about the structure contents (this is what libraries might consider doing). Userspace can even find out the internal kernel structure size by passing a PAGE_SIZE buffer and seeing how many bytes are non-zero. As with copy_struct_from_user(), this is designed to be forward- and backwards- compatible. This allows programas to get a one-shot understanding of what features a syscall supports without having to do any elaborate setups or tricks to detect support for destructive features. Flags can simply be ANDed to check if they are in the supported set, and fields can just be checked to see if they are non-zero. This patchset is IMHO the simplest way we can add the ability to introspect the feature set of extensible struct (copy_struct_from_user) syscalls. It doesn't preclude the chance of a more generic mechanism being added later. The intended way of using this interface to get feature information looks something like the following (imagine that openat2 has gained a new field and a new flag in the future): static bool openat2_no_automount_supported; static bool openat2_cwd_fd_supported; int check_openat2_support(void) { int err; struct open_how how = {}; err = openat2(AT_FDCWD, ".", &how, CHECK_FIELDS | sizeof(how)); assert(err < 0); switch (errno) { case EFAULT: case E2BIG: /* Old kernel... */ check_support_the_old_way(); break; case EEXTSYS_NOOP: openat2_no_automount_supported = (how.flags & RESOLVE_NO_AUTOMOUNT); openat2_cwd_fd_supported = (how.cwd_fd != 0); break; } } This series adds CHECK_FIELDS support for the following extensible struct syscalls, as they are quite likely to grow flags in the near future: * openat2 * clone3 * mount_setattr [1]: https://lwn.net/Articles/830666/ [2]: https://youtu.be/ggD-eb3yPVs Signed-off-by: Aleksa Sarai <cyphar(a)cyphar.com> --- Changes in v3: - Fix copy_struct_to_user() return values in case of clear_user() failure. - v2: <https://lore.kernel.org/r/20240906-extensible-structs-check_fields-v2-0-0f4…> Changes in v2: - Add CHECK_FIELDS support to mount_setattr(2). - Fix build failure on architectures with custom errno values. - Rework selftests to use the tools/ uAPI headers rather than custom defining EEXTSYS_NOOP. - Make sure we return -EINVAL and -E2BIG for invalid sizes even if CHECK_FIELDS is set, and add some tests for that. - v1: <https://lore.kernel.org/r/20240902-extensible-structs-check_fields-v1-0-545…> --- Aleksa Sarai (10): uaccess: add copy_struct_to_user helper sched_getattr: port to copy_struct_to_user openat2: explicitly return -E2BIG for (usize > PAGE_SIZE) openat2: add CHECK_FIELDS flag to usize argument selftests: openat2: add 0xFF poisoned data after misaligned struct selftests: openat2: add CHECK_FIELDS selftests clone3: add CHECK_FIELDS flag to usize argument selftests: clone3: add CHECK_FIELDS selftests mount_setattr: add CHECK_FIELDS flag to usize argument selftests: mount_setattr: add CHECK_FIELDS selftest arch/alpha/include/uapi/asm/errno.h | 3 + arch/mips/include/uapi/asm/errno.h | 3 + arch/parisc/include/uapi/asm/errno.h | 3 + arch/sparc/include/uapi/asm/errno.h | 3 + fs/namespace.c | 17 ++ fs/open.c | 18 ++ include/linux/uaccess.h | 97 ++++++++ include/uapi/asm-generic/errno.h | 3 + include/uapi/linux/openat2.h | 2 + kernel/fork.c | 30 ++- kernel/sched/syscalls.c | 42 +--- tools/arch/alpha/include/uapi/asm/errno.h | 3 + tools/arch/mips/include/uapi/asm/errno.h | 3 + tools/arch/parisc/include/uapi/asm/errno.h | 3 + tools/arch/sparc/include/uapi/asm/errno.h | 3 + tools/include/uapi/asm-generic/errno.h | 3 + tools/include/uapi/asm-generic/posix_types.h | 101 ++++++++ tools/testing/selftests/clone3/.gitignore | 1 + tools/testing/selftests/clone3/Makefile | 4 +- .../testing/selftests/clone3/clone3_check_fields.c | 264 +++++++++++++++++++++ tools/testing/selftests/mount_setattr/Makefile | 2 +- .../selftests/mount_setattr/mount_setattr_test.c | 53 ++++- tools/testing/selftests/openat2/Makefile | 2 + tools/testing/selftests/openat2/openat2_test.c | 165 ++++++++++++- 24 files changed, 777 insertions(+), 51 deletions(-) --- base-commit: 98f7e32f20d28ec452afb208f9cffc08448a2652 change-id: 20240803-extensible-structs-check_fields-a47e94cef691 Best regards, -- Aleksa Sarai <cyphar(a)cyphar.com>

8 months

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[PATCH 0/1] selftests: Clear -Wimplicit-function-declaration warnings

by Ariel Otilibili

Hello, This patch clears out warnings seen while compiling the tests; at the time, it closes a test report. Thank you, Link: https://lore.kernel.org/oe-kbuild-all/202412222015.lMBH62zB-lkp@intel.com/ Ariel Otilibili (1): selftests: Clear -Wimplicit-function-declaration warnings tools/testing/selftests/pid_namespace/pid_max.c | 1 + tools/testing/selftests/pidfd/pidfd_fdinfo_test.c | 1 + 2 files changed, 2 insertions(+) -- 2.43.0

8 months

2
2
0 0

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Linux-kselftest-mirror December 2024