Incomplete read marks debug #8655

eddyz87 · 2025-03-11T23:02:37Z

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…istat' Mykyta Yatsenko says: ==================== selftests/bpf: implement setting global variables in veristat From: Mykyta Yatsenko <[email protected]> To better verify some complex BPF programs by veristat, it would be useful to preset global variables. This patch set implements this functionality and introduces tests for veristat. v4->v5 * Rework parsing to use sscanf for integers * Addressing nits v3->v4: * Fixing bug in set_global_var introduced by refactoring in previous patch set * Addressed nits from Eduard v2->v3: * Reworked parsing of the presets, using sscanf to split into variable and value, but still use strtoll/strtoull to support range checks when parsing integers * Fix test failures for no_alu32 & cpuv4 by checking if veristat binary is in parent folder * Introduce __CHECK_STR macro for simplifying checks in test * Modify tests into sub-tests ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Andrii Nakryiko <[email protected]>

Refactor bpf_dynptr_read and bpf_dynptr_write helpers: extract code into the static functions namely __bpf_dynptr_read and __bpf_dynptr_write, this allows calling these without compiler warnings. Signed-off-by: Mykyta Yatsenko <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]

Introducing bpf_dynptr_copy kfunc allowing copying data from one dynptr to another. This functionality is useful in scenarios such as capturing XDP data to a ring buffer. The implementation consists of 4 branches: * A fast branch for contiguous buffer capacity in both source and destination dynptrs * 3 branches utilizing __bpf_dynptr_read and __bpf_dynptr_write to copy data to/from non-contiguous buffer Signed-off-by: Mykyta Yatsenko <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]

Add XDP setup type for dynptr tests, enabling testing for non-contiguous buffer. Add 2 tests: - test_dynptr_copy - verify correctness for the fast (contiguous buffer) code path. - test_dynptr_copy_xdp - verifies code paths that handle non-contiguous buffer. Signed-off-by: Mykyta Yatsenko <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]

Mykyta Yatsenko says: ==================== introduce bpf_dynptr_copy kfunc From: Mykyta Yatsenko <[email protected]> Introduce a new kfunc, bpf_dynptr_copy, which enables copying of data from one dynptr to another. This functionality may be useful in scenarios such as capturing XDP data to a ring buffer. The patch set is split into 3 patches: 1. Refactor bpf_dynptr_read and bpf_dynptr_write by extracting code into static functions, that allows calling them with no compiler warnings 2. Introduce bpf_dynptr_copy 3. Add tests for bpf_dynptr_copy v2->v3: * Implemented bpf_memcmp in dynptr_success.c test, as __builtin_memcmp was not inlined on GCC-BPF. ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Andrii Nakryiko <[email protected]>

Allow auto port binding for cgroup connect test to avoid binding conflict. Result: ./test_progs -a cgroup_v1v2 59 cgroup_v1v2:OK Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Jiayuan Chen <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Allow auto port binding for bpf nf test to avoid binding conflict. ./test_progs -a bpf_nf 24/1 bpf_nf/xdp-ct:OK 24/2 bpf_nf/tc-bpf-ct:OK 24/3 bpf_nf/alloc_release:OK 24/4 bpf_nf/insert_insert:OK 24/5 bpf_nf/lookup_insert:OK 24/6 bpf_nf/set_timeout_after_insert:OK 24/7 bpf_nf/set_status_after_insert:OK 24/8 bpf_nf/change_timeout_after_alloc:OK 24/9 bpf_nf/change_status_after_alloc:OK 24/10 bpf_nf/write_not_allowlisted_field:OK 24 bpf_nf:OK Summary: 1/10 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Jiayuan Chen <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

BPF CI has failed 3 times in the last 24 hours. Add retry for ENOMEM. It's similar to the optimization plan: commit 2f553b0 ("selftsets/bpf: Retry map update for non-preallocated per-cpu map") Failed CI: https://github.com/kernel-patches/bpf/actions/runs/13549227497/job/37868926343 https://github.com/kernel-patches/bpf/actions/runs/13548089029/job/37865812030 https://github.com/kernel-patches/bpf/actions/runs/13553536268/job/37883329296 selftests/bpf: Fixes for test_maps test Fork 100 tasks to 'test_update_delete' Fork 100 tasks to 'test_update_delete' Fork 100 tasks to 'test_update_delete' Fork 100 tasks to 'test_update_delete' ...... test_task_storage_map_stress_lookup:PASS test_maps: OK, 0 SKIPPED Signed-off-by: Jiayuan Chen <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Jiayuan Chen says: ==================== Optimize bpf selftest to increase CI success rate 1. Optimized some static bound port selftests to avoid port occupation when running test_progs -j. 2. Optimized the retry logic for test_maps. Some Failed CI: https://github.com/kernel-patches/bpf/actions/runs/13275542359/job/37064974076 https://github.com/kernel-patches/bpf/actions/runs/13549227497/job/37868926343 https://github.com/kernel-patches/bpf/actions/runs/13548089029/job/37865812030 https://github.com/kernel-patches/bpf/actions/runs/13553536268/job/37883329296 (Perhaps it's due to the large number of pull requests requiring CI runs?) ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Currently for bpf progs in a cgroup hierarchy, the effective prog array is computed from bottom cgroup to upper cgroups (post-ordering). For example, the following cgroup hierarchy root cgroup: p1, p2 subcgroup: p3, p4 have BPF_F_ALLOW_MULTI for both cgroup levels. The effective cgroup array ordering looks like p3 p4 p1 p2 and at run time, progs will execute based on that order. But in some cases, it is desirable to have root prog executes earlier than children progs (pre-ordering). For example, - prog p1 intends to collect original pkt dest addresses. - prog p3 will modify original pkt dest addresses to a proxy address for security reason. The end result is that prog p1 gets proxy address which is not what it wants. Putting p1 to every child cgroup is not desirable either as it will duplicate itself in many child cgroups. And this is exactly a use case we are encountering in Meta. To fix this issue, let us introduce a flag BPF_F_PREORDER. If the flag is specified at attachment time, the prog has higher priority and the ordering with that flag will be from top to bottom (pre-ordering). For example, in the above example, root cgroup: p1, p2 subcgroup: p3, p4 Let us say p2 and p4 are marked with BPF_F_PREORDER. The final effective array ordering will be p2 p4 p3 p1 Suggested-by: Andrii Nakryiko <[email protected]> Acked-by: Andrii Nakryiko <[email protected]> Signed-off-by: Yonghong Song <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Add a few selftests with cgroup prog pre-ordering. Signed-off-by: Yonghong Song <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

In !PREEMPT_RT local_lock_irqsave() disables interrupts to protect critical section, but it doesn't prevent NMI, so the fully reentrant code cannot use local_lock_irqsave() for exclusive access. Introduce localtry_lock_t and localtry_lock_irqsave() that disables interrupts and sets acquired=1, so localtry_lock_irqsave() from NMI attempting to acquire the same lock will return false. In PREEMPT_RT local_lock_irqsave() maps to preemptible spin_lock(). Map localtry_lock_irqsave() to preemptible spin_trylock(). When in hard IRQ or NMI return false right away, since spin_trylock() is not safe due to explicit locking in the underneath rt_spin_trylock() implementation. Removing this explicit locking and attempting only "trylock" is undesired due to PI implications. Note there is no need to use local_inc for acquired variable, since it's a percpu variable with strict nesting scopes. Acked-by: Davidlohr Bueso <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Vlastimil Babka <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Tracing BPF programs execute from tracepoints and kprobes where running context is unknown, but they need to request additional memory. The prior workarounds were using pre-allocated memory and BPF specific freelists to satisfy such allocation requests. Instead, introduce gfpflags_allow_spinning() condition that signals to the allocator that running context is unknown. Then rely on percpu free list of pages to allocate a page. try_alloc_pages() -> get_page_from_freelist() -> rmqueue() -> rmqueue_pcplist() will spin_trylock to grab the page from percpu free list. If it fails (due to re-entrancy or list being empty) then rmqueue_bulk()/rmqueue_buddy() will attempt to spin_trylock zone->lock and grab the page from there. spin_trylock() is not safe in PREEMPT_RT when in NMI or in hard IRQ. Bailout early in such case. The support for gfpflags_allow_spinning() mode for free_page and memcg comes in the next patches. This is a first step towards supporting BPF requirements in SLUB and getting rid of bpf_mem_alloc. That goal was discussed at LSFMM: https://lwn.net/Articles/974138/ Acked-by: Michal Hocko <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Acked-by: Sebastian Andrzej Siewior <[email protected]> Reviewed-by: Shakeel Butt <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Introduce free_pages_nolock() that can free pages without taking locks. It relies on trylock and can be called from any context. Since spin_trylock() cannot be used in PREEMPT_RT from hard IRQ or NMI it uses lockless link list to stash the pages which will be freed by subsequent free_pages() from good context. Do not use llist unconditionally. BPF maps continuously allocate/free, so we cannot unconditionally delay the freeing to llist. When the memory becomes free make it available to the kernel and BPF users right away if possible, and fallback to llist as the last resort. Acked-by: Vlastimil Babka <[email protected]> Acked-by: Sebastian Andrzej Siewior <[email protected]> Reviewed-by: Shakeel Butt <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Teach memcg to operate under trylock conditions when spinning locks cannot be used. localtry_trylock might fail and this would lead to charge cache bypass if the calling context doesn't allow spinning (gfpflags_allow_spinning). In those cases charge the memcg counter directly and fail early if that is not possible. This might cause a pre-mature charge failing but it will allow an opportunistic charging that is safe from try_alloc_pages path. Acked-by: Michal Hocko <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Acked-by: Shakeel Butt <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Unconditionally use __GFP_ACCOUNT in try_alloc_pages(). The caller is responsible to setup memcg correctly. All BPF memory accounting is memcg based. Acked-by: Vlastimil Babka <[email protected]> Acked-by: Shakeel Butt <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Use try_alloc_pages() and free_pages_nolock() for BPF needs when context doesn't allow using normal alloc_pages. This is a prerequisite for further work. Signed-off-by: Alexei Starovoitov <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Alexei Starovoitov says: ==================== The main motivation is to make alloc page and slab reentrant and remove bpf_mem_alloc. v8->v9: - Squash Vlastimil's fix/feature for localtry_trylock, and udpate commit log as suggested by Sebastian. - Drop _noprof suffix in try_alloc_pages kdoc - rebase v8: https://lore.kernel.org/bpf/[email protected]/ v7->v8: - rebase: s/free_unref_page/free_frozen_page/ v6->v7: - Took Sebastian's patch for localtry_lock_t as-is with minor addition of local_trylock_acquire() for proper LOCKDEP. Kept his authorship. - Adjusted patch 4 to use it. The rest is unchanged. v6: https://lore.kernel.org/bpf/[email protected]/ v5->v6: - Addressed comments from Sebastian, Vlastimil - New approach for local_lock_t in patch 3. Instead of unconditionally increasing local_lock_t size to 4 bytes introduce local_trylock_t and use _Generic() tricks to manipulate active field. - Address stackdepot reentrance issues. alloc part in patch 1 and free part in patch 2. - Inlined mem_cgroup_cancel_charge() in patch 4 since this helper is being removed. - Added Acks. - Dropped failslab, kfence, kmemleak patch. - Improved bpf_map_alloc_pages() in patch 6 a bit to demo intended usage. It will be refactored further. - Considered using __GFP_COMP in try_alloc_pages to simplify free_pages_nolock a bit, but then decided to make it work for all types of pages, since free_pages_nolock() is used by stackdepot and currently it's using non-compound order 2. I felt it's best to leave it as-is and make free_pages_nolock() support all pages. v5: https://lore.kernel.org/all/[email protected]/ v4->v5: - Fixed patch 1 and 4 commit logs and comments per Michal suggestions. Added Acks. - Added patch 6 to make failslab, kfence, kmemleak complaint with trylock mode. It's a prerequisite for reentrant slab patches. v4: https://lore.kernel.org/bpf/[email protected]/ v3->v4: Addressed feedback from Michal and Shakeel: - GFP_TRYLOCK flag is gone. gfpflags_allow_spinning() is used instead. - Improved comments and commit logs. v3: https://lore.kernel.org/bpf/[email protected]/ v2->v3: To address the issues spotted by Sebastian, Vlastimil, Steven: - Made GFP_TRYLOCK internal to mm/internal.h try_alloc_pages() and free_pages_nolock() are the only interfaces. - Since spin_trylock() is not safe in RT from hard IRQ and NMI disable such usage in lock_trylock and in try_alloc_pages(). In such case free_pages_nolock() falls back to llist right away. - Process trylock_free_pages llist when preemptible. - Check for things like unaccepted memory and order <= 3 early. - Don't call into __alloc_pages_slowpath() at all. - Inspired by Vlastimil's struct local_tryirq_lock adopted it in local_lock_t. Extra 4 bytes in !RT in local_lock_t shouldn't affect any of the current local_lock_t users. This is patch 3. - Tested with bpf selftests in RT and !RT and realized how much more work is necessary on bpf side to play nice with RT. The urgency of this work got higher. The alternative is to convert bpf bits left and right to bpf_mem_alloc. v2: https://lore.kernel.org/bpf/[email protected]/ v1->v2: - fixed buggy try_alloc_pages_noprof() in PREEMPT_RT. Thanks Peter. - optimize all paths by doing spin_trylock_irqsave() first and only then check for gfp_flags & __GFP_TRYLOCK. Then spin_lock_irqsave() if it's a regular mode. So new gfp flag will not add performance overhead. - patches 2-5 are new. They introduce lockless and/or trylock free_pages_nolock() and memcg support. So it's in usable shape for bpf in patch 6. v1: https://lore.kernel.org/bpf/[email protected]/ ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Merge try_alloc_pages feature branch into bpf-next/master. Signed-off-by: Alexei Starovoitov <[email protected]>

test_select_reuseport_kern.c is currently including <stdlib.h>, but it does not use any definition from there. Remove stdlib.h inclusion from test_select_reuseport_kern.c Signed-off-by: Alexis Lothoré (eBPF Foundation) <[email protected]> Signed-off-by: Martin KaFai Lau <[email protected]> Link: https://patch.msgid.link/[email protected]

The verifier currently does not permit global subprog calls when a lock is held, preemption is disabled, or when IRQs are disabled. This is because we don't know whether the global subprog calls sleepable functions or not. In case of locks, there's an additional reason: functions called by the global subprog may hold additional locks etc. The verifier won't know while verifying the global subprog whether it was called in context where a spin lock is already held by the program. Perform summarization of the sleepable nature of a global subprog just like changes_pkt_data and then allow calls to global subprogs for non-sleepable ones from atomic context. While making this change, I noticed that RCU read sections had no protection against sleepable global subprog calls, include it in the checks and fix this while we're at it. Care needs to be taken to not allow global subprog calls when regular bpf_spin_lock is held. When resilient spin locks is held, we want to potentially have this check relaxed, but not for now. Also make sure extensions freplacing global functions cannot do so in case the target is non-sleepable, but the extension is. The other combination is ok. Tests are included in the next patch to handle all special conditions. Fixes: 9bb00b2 ("bpf: Add kfunc bpf_rcu_read_lock/unlock()") Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Add tests for rejecting sleepable and accepting non-sleepable global function calls in atomic contexts. For spin locks, we still reject all global function calls. Once resilient spin locks land, we will carefully lift in cases where we deem it safe. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Add tests for freplace behavior with the combination of sleepable and non-sleepable global subprogs. The changes_pkt_data selftest did all the hardwork, so simply rename it and include new support for more summarization tests for might_sleep bit. Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Kumar Kartikeya Dwivedi says: ==================== Global subprogs in RCU/{preempt,irq}-disabled sections Small change to allow non-sleepable global subprogs in RCU, preempt-disabled, and irq-disabled sections. For now, we don't lift the limitation for locks as it requires more analysis, and will do this one resilient spin locks land. This surfaced a bug where sleepable global subprogs were allowed in RCU read sections, that has been fixed. Tests have been added to cover various cases. Changelog: ---------- v2 -> v3 v2: https://lore.kernel.org/bpf/[email protected] * Fix broken to_be_replaced argument in the selftest. * Adjust selftest program type. v1 -> v2 v1: https://lore.kernel.org/bpf/[email protected] * Rename subprog_info[i].sleepable to might_sleep, which more accurately reflects the nature of the bit. 'sleepable' means whether a given context is allowed to, while might_sleep captures if it does. * Disallow extensions that might sleep to attach to targets that don't sleep, since they'd be permitted to be called in atomic contexts. (Eduard) * Add tests for mixing non-sleepable and sleepable global function calls, and extensions attaching to non-sleepable global functions. (Eduard) * Rename changes_pkt_data -> summarization ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

bpf_sk_storage_clone() is the only caller of bpf_map_inc_not_zero() and is holding rcu_read_lock(). map_idr_lock does not add any protection, just remove the cost for passive TCP flows. Signed-off-by: Eric Dumazet <[email protected]> Cc: Kui-Feng Lee <[email protected]> Cc: Martin KaFai Lau <[email protected]> Acked-by: Stanislav Fomichev <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Factor out atomic_ptr_type_ok() as a helper function to be used later. Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/e5ef8b3116f3fffce78117a14060ddce05eba52a.1740978603.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

Currently, check_atomic() only handles atomic read-modify-write (RMW) instructions. Since we are planning to introduce other types of atomic instructions (i.e., atomic load/store), extract the existing RMW handling logic into its own function named check_atomic_rmw(). Remove the @insn_idx parameter as it is not really necessary. Use 'env->insn_idx' instead, as in other places in verifier.c. Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/6323ac8e73a10a1c8ee547c77ed68cf8eb6b90e1.1740978603.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

Extract BPF_LDX and most non-ATOMIC BPF_STX instruction handling logic in do_check() into helper functions to be used later. While we are here, make that comment about "reserved fields" more specific. Suggested-by: Eduard Zingerman <[email protected]> Acked-by: Eduard Zingerman <[email protected]> Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/8b39c94eac2bb7389ff12392ca666f939124ec4f.1740978603.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

Allow reading object file list from file. E.g. the following command: ./veristat @list.txt Is equivalent to the following invocation: ./veristat line-1 line-2 ... line-N Where line-i corresponds to lines from list.txt. Lines starting with '#' are ignored. Signed-off-by: Eduard Zingerman <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Acked-by: Mykyta Yatsenko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]

@foobar

Before: ./veristat -G @foobar iters.bpf.o Failed to open presets in 'foobar': Unknown error -2 ... After: ./veristat -G @foobar iters.bpf.o Failed to open presets in 'foobar': No such file or directory ... Signed-off-by: Eduard Zingerman <[email protected]> Signed-off-by: Andrii Nakryiko <[email protected]> Acked-by: Mykyta Yatsenko <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]

We are planning to add load-acquire (LDAR{,B,H}) and store-release (STLR{,B,H}) instructions to insn.{c,h}; add BIT(23) to mask of load_ex and store_ex to prevent aarch64_insn_is_{load,store}_ex() from returning false-positives for load-acquire and store-release instructions. Reference: Arm Architecture Reference Manual (ARM DDI 0487K.a, ID032224), * C6.2.228 LDXR * C6.2.165 LDAXR * C6.2.161 LDAR * C6.2.393 STXR * C6.2.360 STLXR * C6.2.353 STLR Acked-by: Xu Kuohai <[email protected]> Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/5a4d2a52b2cc022bf86d0b572789f0b3bc3d5162.1741049567.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

Add load-acquire ("load_acq", LDAR{,B,H}) and store-release ("store_rel", STLR{,B,H}) instructions. Breakdown of encoding: size L (Rs) o0 (Rt2) Rn Rt mask (0x3fdffc00): 00 111111 1 1 0 11111 1 11111 00000 00000 value, load_acq (0x08dffc00): 00 001000 1 1 0 11111 1 11111 00000 00000 value, store_rel (0x089ffc00): 00 001000 1 0 0 11111 1 11111 00000 00000 As suggested by Xu [1], include all Should-Be-One (SBO) bits ("Rs" and "Rt2" fields) in the "mask" and "value" numbers. It is worth noting that we are adding the "no offset" variant of STLR instead of the "pre-index" variant, which has a different encoding. Reference: Arm Architecture Reference Manual (ARM DDI 0487K.a, ID032224), * C6.2.161 LDAR * C6.2.353 STLR [1] https://lore.kernel.org/bpf/[email protected]/ Acked-by: Xu Kuohai <[email protected]> Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/ba92057b7502ce4c9c9b03b7d637abe5e178134e.1741049567.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

Support BPF load-acquire (BPF_LOAD_ACQ) and store-release (BPF_STORE_REL) instructions in the arm64 JIT compiler. For example (assuming little-endian): db 10 00 00 00 01 00 00 r0 = load_acquire((u64 *)(r1 + 0x0)) 95 00 00 00 00 00 00 00 exit opcode (0xdb): BPF_ATOMIC | BPF_DW | BPF_STX imm (0x00000100): BPF_LOAD_ACQ The JIT compiler would emit an LDAR instruction for the above, e.g.: ldar x7, [x0] Similarly, consider the following 16-bit store-release: cb 21 00 00 10 01 00 00 store_release((u16 *)(r1 + 0x0), w2) 95 00 00 00 00 00 00 00 exit opcode (0xcb): BPF_ATOMIC | BPF_H | BPF_STX imm (0x00000110): BPF_STORE_REL An STLRH instruction would be emitted, e.g.: stlrh w1, [x0] For a complete mapping: load-acquire 8-bit LDARB (BPF_LOAD_ACQ) 16-bit LDARH 32-bit LDAR (32-bit) 64-bit LDAR (64-bit) store-release 8-bit STLRB (BPF_STORE_REL) 16-bit STLRH 32-bit STLR (32-bit) 64-bit STLR (64-bit) Arena accesses are supported. bpf_jit_supports_insn(..., /*in_arena=*/true) always returns true for BPF_LOAD_ACQ and BPF_STORE_REL instructions, as they don't depend on ARM64_HAS_LSE_ATOMICS. Acked-by: Xu Kuohai <[email protected]> Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/51664a1300710238ba2d4d95142b57a52c4f0cae.1741049567.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

Recently we introduced BPF load-acquire (BPF_LOAD_ACQ) and store-release (BPF_STORE_REL) instructions. For x86-64, simply implement them as regular BPF_LDX/BPF_STX loads and stores. The verifier always rejects misaligned load-acquires/store-releases (even if BPF_F_ANY_ALIGNMENT is set), so emitted MOV* instructions are guaranteed to be atomic. Arena accesses are supported. 8- and 16-bit load-acquires are zero-extending (i.e., MOVZBQ, MOVZWQ). Rename emit_atomic{,_index}() to emit_atomic_rmw{,_index}() to make it clear that they only handle read-modify-write atomics, and extend their @atomic_op parameter from u8 to u32, since we are starting to use more than the lowest 8 bits of the 'imm' field. Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/d22bb3c69f126af1d962b7314f3489eff606a3b7.1741049567.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

…uctions Add several ./test_progs tests: - arena_atomics/load_acquire - arena_atomics/store_release - verifier_load_acquire/* - verifier_store_release/* - verifier_precision/bpf_load_acquire - verifier_precision/bpf_store_release The last two tests are added to check if backtrack_insn() handles the new instructions correctly. Additionally, the last test also makes sure that the verifier "remembers" the value (in src_reg) we store-release into e.g. a stack slot. For example, if we take a look at the test program: #0: r1 = 8; /* store_release((u64 *)(r10 - 8), r1); */ #1: .8byte %[store_release]; #2: r1 = *(u64 *)(r10 - 8); kernel-patches#3: r2 = r10; kernel-patches#4: r2 += r1; kernel-patches#5: r0 = 0; kernel-patches#6: exit; At #1, if the verifier doesn't remember that we wrote 8 to the stack, then later at kernel-patches#4 we would be adding an unbounded scalar value to the stack pointer, which would cause the program to be rejected: VERIFIER LOG: ============= ... math between fp pointer and register with unbounded min value is not allowed For easier CI integration, instead of using built-ins like __atomic_{load,store}_n() which depend on the new __BPF_FEATURE_LOAD_ACQ_STORE_REL pre-defined macro, manually craft load-acquire/store-release instructions using __imm_insn(), as suggested by Eduard. All new tests depend on: (1) Clang major version >= 18, and (2) ENABLE_ATOMICS_TESTS is defined (currently implies -mcpu=v3 or v4), and (3) JIT supports load-acquire/store-release (currently arm64 and x86-64) In .../progs/arena_atomics.c: /* 8-byte-aligned */ __u8 __arena_global load_acquire8_value = 0x12; /* 1-byte hole */ __u16 __arena_global load_acquire16_value = 0x1234; That 1-byte hole in the .addr_space.1 ELF section caused clang-17 to crash: fatal error: error in backend: unable to write nop sequence of 1 bytes To work around such llvm-17 CI job failures, conditionally define __arena_global variables as 64-bit if __clang_major__ < 18, to make sure .addr_space.1 has no holes. Ideally we should avoid compiling this file using clang-17 at all (arena tests depend on __BPF_FEATURE_ADDR_SPACE_CAST, and are skipped for llvm-17 anyway), but that is a separate topic. Acked-by: Eduard Zingerman <[email protected]> Signed-off-by: Peilin Ye <[email protected]> Link: https://lore.kernel.org/r/1b46c6feaf0f1b6984d9ec80e500cc7383e9da1a.1741049567.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <[email protected]>

Peilin Ye says: ==================== Introduce load-acquire and store-release BPF instructions This patchset adds kernel support for BPF load-acquire and store-release instructions (for background, please see [1]), including core/verifier and arm64/x86-64 JIT compiler changes, as well as selftests. riscv64 is also planned to be supported. The corresponding LLVM changes can be found at: llvm/llvm-project#108636 The first 3 patches from v4 have already been applied: - [bpf-next,v4,01/10] bpf/verifier: Factor out atomic_ptr_type_ok() https://git.kernel.org/bpf/bpf-next/c/b2d9ef71d4c9 - [bpf-next,v4,02/10] bpf/verifier: Factor out check_atomic_rmw() https://git.kernel.org/bpf/bpf-next/c/d430c46c7580 - [bpf-next,v4,03/10] bpf/verifier: Factor out check_load_mem() and check_store_reg() https://git.kernel.org/bpf/bpf-next/c/d38ad248fb7a Please refer to the LLVM PR and individual kernel patches for details. Thanks! v5: https://lore.kernel.org/all/[email protected]/ v5..v6 change: o (Alexei) avoid using #ifndef in verifier.c v4: https://lore.kernel.org/bpf/[email protected]/ v4..v5 notable changes: o (kernel test robot) for 32-bit arches: make the verifier reject 64-bit load-acquires/store-releases, and fix build error in interpreter changes * tested ARCH=arc build following instructions from kernel test robot o (Alexei) drop Documentation/ patch (v4 10/10) for now v3: https://lore.kernel.org/bpf/[email protected]/ v3..v4 notable changes: o (Alexei) add x86-64 JIT support (including arena) o add Acked-by: tags from Xu v2: https://lore.kernel.org/bpf/[email protected]/ v2..v3 notable changes: o (Alexei) change encoding to BPF_LOAD_ACQ=0x100, BPF_STORE_REL=0x110 o add Acked-by: tags from Ilya and Eduard o make new selftests depend on: * __clang_major__ >= 18, and * ENABLE_ATOMICS_TESTS is defined (currently this means -mcpu=v3 or v4), and * JIT supports load_acq/store_rel (currenty only arm64) o work around llvm-17 CI job failure by conditionally define __arena_global variables as 64-bit if __clang_major__ < 18, to make sure .addr_space.1 has no holes o add Google copyright notice in new files v1: https://lore.kernel.org/all/[email protected]/ v1..v2 notable changes: o (Eduard) for x86 and s390, make bpf_jit_supports_insn(..., /*in_arena=*/true) return false for load_acq/store_rel o add Eduard's Acked-by: tag o (Eduard) extract LDX and non-ATOMIC STX handling into helpers, see PATCH v2 3/9 o allow unpriv programs to store-release pointers to stack o (Alexei) make it clearer in the interpreter code (PATCH v2 4/9) that only W and DW are supported for atomic RMW o test misaligned load_acq/store_rel o (Eduard) other selftests/ changes: * test load_acq/store_rel with !atomic_ptr_type_ok() pointers: - PTR_TO_CTX, for is_ctx_reg() - PTR_TO_PACKET, for is_pkt_reg() - PTR_TO_FLOW_KEYS, for is_flow_key_reg() - PTR_TO_SOCKET, for is_sk_reg() * drop atomics/ tests * delete unnecessary 'pid' checks from arena_atomics/ tests * avoid depending on __BPF_FEATURE_LOAD_ACQ_STORE_REL, use __imm_insn() and inline asm macros instead RFC v1: https://lore.kernel.org/all/[email protected] RFC v1..v1 notable changes: o 1-2/8: minor verifier.c refactoring patches o 3/8: core/verifier changes * (Eduard) handle load-acquire properly in backtrack_insn() * (Eduard) avoid skipping checks (e.g., bpf_jit_supports_insn()) for load-acquires * track the value stored by store-releases, just like how non-atomic STX instructions are handled * (Eduard) add missing link in commit message * (Eduard) always print 'r' for disasm.c changes o 4/8: arm64/insn: avoid treating load_acq/store_rel as load_ex/store_ex o 5/8: arm64/insn: add load_acq/store_rel * (Xu) include Should-Be-One (SBO) bits in "mask" and "value", to avoid setting fixed bits during runtime (JIT-compile time) o 6/8: arm64 JIT compiler changes * (Xu) use emit_a64_add_i() for "pointer + offset" to optimize code emission o 7/8: selftests * (Eduard) avoid adding new tests to the 'test_verifier' runner * add more tests, e.g., checking mark_precise logic o 8/8: instruction-set.rst changes [1] https://lore.kernel.org/all/[email protected]/ Thanks, ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Extract two utility functions: - One BPF jump instruction uses .imm field to encode jump offset, while the rest use .off. Encapsulate this detail as jmp_offset() function. - Avoid duplicating instruction printing callback definitions by defining a verbose_insn() function, which disassembles an instruction into the verifier log while hiding this detail. These functions will be used in the next patch. Signed-off-by: Eduard Zingerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Refactor mark_fastcall_pattern_for_call() to extract a utility function get_call_summary(). For a helper or kfunc call this function fills the following information: {num_params, is_void, fastcall}. This function would be used in the next patch in order to get number of parameters of a helper or kfunc call. Signed-off-by: Eduard Zingerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Compute may-live registers before each instruction in the program. The register is live before the instruction I if it is read by I or some instruction S following I during program execution and is not overwritten between I and S. This information would be used in the next patch as a hint in func_states_equal(). Use a simple algorithm described in [1] to compute this information: - define the following: - I.use : a set of all registers read by instruction I; - I.def : a set of all registers written by instruction I; - I.in : a set of all registers that may be alive before I execution; - I.out : a set of all registers that may be alive after I execution; - I.successors : a set of instructions S that might immediately follow I for some program execution; - associate separate empty sets 'I.in' and 'I.out' with each instruction; - visit each instruction in a postorder and update corresponding 'I.in' and 'I.out' sets as follows: I.out = U [S.in for S in I.successors] I.in = (I.out / I.def) U I.use (where U stands for set union, / stands for set difference) - repeat the computation while I.{in,out} changes for any instruction. On implementation side keep things as simple, as possible: - check_cfg() already marks instructions EXPLORED in post-order, modify it to save the index of each EXPLORED instruction in a vector; - represent I.{in,out,use,def} as bitmasks; - don't split the program into basic blocks and don't maintain the work queue, instead: - do fixed-point computation by visiting each instruction; - maintain a simple 'changed' flag if I.{in,out} for any instruction change; Measurements show that even such simplistic implementation does not add measurable verification time overhead (for selftests, at-least). Note on check_cfg() ex_insn_beg/ex_done change: To avoid out of bounds access to env->cfg.insn_postorder array, it should be guaranteed that instruction transitions to EXPLORED state only once. Previously this was not the fact for incorrect programs with direct calls to exception callbacks. The 'align' selftest needs adjustment to skip computed insn/live registers printout. Otherwise it matches lines from the live registers printout. [1] https://en.wikipedia.org/wiki/Live-variable_analysis Signed-off-by: Eduard Zingerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Liveness analysis DFA computes a set of registers live before each instruction. Leverage this information to skip comparison of dead registers in func_states_equal(). This helps with convergance of iterator processing loops, as bpf_reg_state->live marks can't be used when loops are processed. This has certain performance impact for selftests, here is a veristat listing using `-f "insns_pct>5" -f "!insns<200"` selftests: File Program States (A) States (B) States (DIFF) -------------------- ----------------------------- ---------- ---------- -------------- arena_htab.bpf.o arena_htab_llvm 37 35 -2 (-5.41%) arena_htab_asm.bpf.o arena_htab_asm 37 33 -4 (-10.81%) arena_list.bpf.o arena_list_add 37 22 -15 (-40.54%) dynptr_success.bpf.o test_dynptr_copy 22 16 -6 (-27.27%) dynptr_success.bpf.o test_dynptr_copy_xdp 68 58 -10 (-14.71%) iters.bpf.o checkpoint_states_deletion 918 40 -878 (-95.64%) iters.bpf.o clean_live_states 136 66 -70 (-51.47%) iters.bpf.o iter_nested_deeply_iters 43 37 -6 (-13.95%) iters.bpf.o iter_nested_iters 72 62 -10 (-13.89%) iters.bpf.o iter_pass_iter_ptr_to_subprog 30 26 -4 (-13.33%) iters.bpf.o iter_subprog_iters 68 59 -9 (-13.24%) iters.bpf.o loop_state_deps2 35 32 -3 (-8.57%) iters_css.bpf.o iter_css_for_each 32 29 -3 (-9.38%) pyperf600_iter.bpf.o on_event 286 192 -94 (-32.87%) Total progs: 3578 Old success: 2061 New success: 2061 States diff min: -95.64% States diff max: 0.00% -100 .. -90 %: 1 -55 .. -45 %: 3 -45 .. -35 %: 2 -35 .. -25 %: 5 -20 .. -10 %: 12 -10 .. 0 %: 6 sched_ext: File Program States (A) States (B) States (DIFF) ----------------- ---------------------- ---------- ---------- --------------- bpf.bpf.o lavd_dispatch 8950 7065 -1885 (-21.06%) bpf.bpf.o lavd_init 516 480 -36 (-6.98%) bpf.bpf.o layered_dispatch 662 501 -161 (-24.32%) bpf.bpf.o layered_dump 298 237 -61 (-20.47%) bpf.bpf.o layered_init 523 423 -100 (-19.12%) bpf.bpf.o layered_init_task 24 22 -2 (-8.33%) bpf.bpf.o layered_runnable 151 125 -26 (-17.22%) bpf.bpf.o p2dq_dispatch 66 53 -13 (-19.70%) bpf.bpf.o p2dq_init 170 142 -28 (-16.47%) bpf.bpf.o refresh_layer_cpumasks 120 78 -42 (-35.00%) bpf.bpf.o rustland_init 37 34 -3 (-8.11%) bpf.bpf.o rustland_init 37 34 -3 (-8.11%) bpf.bpf.o rusty_select_cpu 125 108 -17 (-13.60%) scx_central.bpf.o central_dispatch 59 43 -16 (-27.12%) scx_central.bpf.o central_init 39 28 -11 (-28.21%) scx_nest.bpf.o nest_init 58 51 -7 (-12.07%) scx_pair.bpf.o pair_dispatch 142 111 -31 (-21.83%) scx_qmap.bpf.o qmap_dispatch 174 141 -33 (-18.97%) scx_qmap.bpf.o qmap_init 768 654 -114 (-14.84%) Total progs: 216 Old success: 186 New success: 186 States diff min: -35.00% States diff max: 0.00% -35 .. -25 %: 3 -25 .. -20 %: 6 -20 .. -15 %: 6 -15 .. -5 %: 7 -5 .. 0 %: 6 Signed-off-by: Eduard Zingerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Cover instructions from each kind: - assignment - arithmetic - store/load - endian conversion - atomics - branches, conditional branches, may_goto, calls - LD_ABS/LD_IND - address_space_cast Signed-off-by: Eduard Zingerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Eduard Zingerman says: ==================== bpf: simple DFA-based live registers analysis This patch-set introduces a simple live registers DFA analysis. Analysis is done as a separate step before main verification pass. Results are stored in the env->insn_aux_data for each instruction. The change helps with iterator/callback based loops handling, as regular register liveness marks are not finalized while loops are processed. See veristat results in patch #2. Note: for regular subprogram calls analysis conservatively assumes that r1-r5 are used, and r0 is used at each 'exit' instruction. Experiments show that adding logic handling these cases precisely has no impact on verification performance. The patch set was tested by disabling the current register parentage chain liveness computation, using DFA-based liveness for registers while assuming all stack slots as live. See discussion in [1]. Changes v2 -> v3: - added support for BPF_LOAD_ACQ, BPF_STORE_REL atomics (Alexei); - correct use marks for r0 for BPF_CMPXCHG. Changes v1 -> v2: - added a refactoring commit extracting utility functions: jmp_offset(), verbose_insn() (Alexei); - added a refactoring commit extracting utility function get_call_summary() in order to share helper/kfunc related code with mark_fastcall_pattern_for_call() (Alexei); - comment in the compute_insn_live_regs() extended (Alexei). Changes RFC -> v1: - parameter count for helpers and kfuncs is taken into account; - copy_verifier_state() bugfix had been merged as a separate patch-set and is no longer a part of this patch set. RFC: https://lore.kernel.org/bpf/[email protected]/ v1: https://lore.kernel.org/bpf/[email protected]/ v2: https://lore.kernel.org/bpf/[email protected]/ [1] https://lore.kernel.org/bpf/[email protected]/ ==================== Link: https://patch.msgid.link/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

may_goto instruction does not use any registers, but in compute_insn_live_regs() it was treated as a regular conditional jump of kind BPF_K with r0 as source register. Thus unnecessarily marking r0 as used. Fixes: 7dad036 ("bpf: simple DFA-based live registers analysis") Signed-off-by: Eduard Zingerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

This file was renamed from bpf_iter_task_vma.c. Fixes: 45b3894 ("selftests/bpf: Rename bpf_iter_task_vma.c to bpf_iter_task_vmas.c") Signed-off-by: T.J. Mercier <[email protected]> Acked-by: Song Liu <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Suppose the verifier state exploration graph looks as follows: .-> A --. Suppose: | | | - state A is at iterator 'next'; | v v - path A -> B -> A is verified first; '-- B C - path A -> C is verified next; - B does not impose a read mark for register R1; - C imposes a read mark for register R1; Under such conditions: - when B is explored and A is identified as its loop entry, the read marks are copied from A to B by propagate_liveness(), but these marks do not include R1; - when C is explored, the read mark for R1 is propagated to A, but not to B. - at this point, state A has its branch count at zero, but state B has incomplete read marks. The same logic applies to precision marks. This means that states with a loop entry can have incomplete read and precision marks, regardless of whether the loop entry itself has branches. The current verification logic does not account for this. An example of an unsafe program accepted by the verifier is the selftest included in the next patch. Fix this by removing bpf_verifier_state->branches checks for loop entries in clean_live_states() and is_state_visited(). Verification performance impact for selftests and sched_ext: ========= selftests: master vs patch ========= File Program States (A) States (B) States (DIFF) ---------------------------------- ----------------- ---------- ---------- ------------- iters.bpf.o clean_live_states 66 67 +1 (+1.52%) verifier_iterating_callbacks.bpf.o cond_break2 10 13 +3 (+30.00%) Total progs: 3579 Old success: 2061 New success: 2061 States diff min: 0.00% States diff max: 30.00% 0 .. 5 %: 3578 30 .. 35 %: 1 ========= sched_ext: master vs patch ========= File Program States (A) States (B) States (DIFF) -------------- ---------------- ---------- ---------- ------------- bpf.bpf.o layered_dispatch 501 516 +15 (+2.99%) bpf.bpf.o layered_dump 237 252 +15 (+6.33%) bpf.bpf.o layered_init 423 432 +9 (+2.13%) bpf.bpf.o p2dq_init 142 144 +2 (+1.41%) scx_pair.bpf.o pair_dispatch 111 138 +27 (+24.32%) scx_qmap.bpf.o qmap_dump 22 30 +8 (+36.36%) scx_qmap.bpf.o qmap_init 654 656 +2 (+0.31%) Total progs: 216 Old success: 186 New success: 186 States diff min: 0.00% States diff max: 36.36% 0 .. 5 %: 213 5 .. 15 %: 1 20 .. 30 %: 1 35 .. 40 %: 1 Fixes: 2a09928 ("bpf: correct loop detection for iterators convergence") Signed-off-by: Eduard Zingerman <[email protected]>

The test case is equivalent of the following C program: 1: r8 = bpf_get_prandom_u32(); 2: r6 = -32; 3: bpf_iter_num_new(&fp[-8], 0, 10); 4: if (unlikely(bpf_get_prandom_u32())) 5: r6 = -31; 6: for (;;) { 7: if (!bpf_iter_num_next(&fp[-8])) 8: break; 9: if (unlikely(bpf_get_prandom_u32())) 10: *(u64 *)(fp + r6) = 7; 11: } 12: bpf_iter_num_destroy(&fp[-8]); 13: return 0; W/o a fix that instructs verifier to ignore branches count for loop entries verification proceeds as follows: - 1-4, state is {r6=-32,fp-8=active}; - 6, checkpoint A is created with {r6=-32,fp-8=active}; - 7, checkpoint B is created with {r6=-32,fp-8=active}, push state {r6=-32,fp-8=active} from 7 to 9; - 8,12,13, {r6=-32,fp-8=drained}, exit; - pop state with {r6=-32,fp-8=active} from 7 to 9; - 9, push state {r6=-32,fp-8=active} from 9 to 10; - 6, checkpoint C is created with {r6=-32,fp-8=active}; - 7, checkpoint A is hit, no precision or propagated for r6 to C; - pop state {r6=-32,fp-8=active} from 9 to 10; - 10, state is {r6=-31,fp-8=active}, r6 is marked as read and precise, these marks are propagated to checkpoints A and B (but not C, as it is not the parent of current state; - 6, {r6=-31,fp-8=active} checkpoint C is hit, because r6 is not marked precise for this checkpoint; - the program is accepted, despite a possibility of unaligned u64 stack access at offset -31. Signed-off-by: Eduard Zingerman <[email protected]>

kernel-patches-daemon-bpf · 2025-03-18T23:18:07Z

Automatically cleaning up stale PR; feel free to reopen if needed

anakryiko and others added 30 commits February 26, 2025 10:45

selftests/bpf: Add selftests allowing cgroup prog pre-ordering

42c5e6d

Add a few selftests with cgroup prog pre-ordering. Signed-off-by: Yonghong Song <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>

Merge branch 'bpf-next/try_alloc_pages' into bpf-next/master

e4d68c0

Merge try_alloc_pages feature branch into bpf-next/master. Signed-off-by: Alexei Starovoitov <[email protected]>

peilin-ye and others added 16 commits March 3, 2025 21:00

eddyz87 force-pushed the incomplete-read-marks-debug branch from 60e8048 to 3e1f38e Compare March 11, 2025 23:16

kernel-patches-daemon-bpf bot force-pushed the bpf-next_base branch 11 times, most recently from e14a0d8 to 503edd4 Compare March 18, 2025 17:29

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