- 08 Mar, 2023 2 commits
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Eric Dumazet authored
enum skb_drop_reason is more generic, we can adopt it instead. Provide dev_kfree_skb_irq_reason() and dev_kfree_skb_any_reason(). This means drivers can use more precise drop reasons if they want to. Signed-off-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Simon Horman <simon.horman@corigine.com> Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com> Link: https://lore.kernel.org/r/20230306204313.10492-1-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>
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Heiner Kallweit authored
cond sometimes is (val & MASK) what may result in a false positive if val is a negative errno. We shouldn't evaluate cond if val < 0. This has no functional impact here, but it's not nice. Therefore switch order of the checks. Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> Reviewed-by: Simon Horman <simon.horman@corigine.com> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Link: https://lore.kernel.org/r/6d8274ac-4344-23b4-d9a3-cad4c39517d4@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>
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- 07 Mar, 2023 1 commit
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https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-nextJakub Kicinski authored
Daniel Borkmann says: ==================== pull-request: bpf-next 2023-03-06 We've added 85 non-merge commits during the last 13 day(s) which contain a total of 131 files changed, 7102 insertions(+), 1792 deletions(-). The main changes are: 1) Add skb and XDP typed dynptrs which allow BPF programs for more ergonomic and less brittle iteration through data and variable-sized accesses, from Joanne Koong. 2) Bigger batch of BPF verifier improvements to prepare for upcoming BPF open-coded iterators allowing for less restrictive looping capabilities, from Andrii Nakryiko. 3) Rework RCU enforcement in the verifier, add kptr_rcu and enforce BPF programs to NULL-check before passing such pointers into kfunc, from Alexei Starovoitov. 4) Add support for kptrs in percpu hashmaps, percpu LRU hashmaps and in local storage maps, from Kumar Kartikeya Dwivedi. 5) Add BPF verifier support for ST instructions in convert_ctx_access() which will help new -mcpu=v4 clang flag to start emitting them, from Eduard Zingerman. 6) Make uprobe attachment Android APK aware by supporting attachment to functions inside ELF objects contained in APKs via function names, from Daniel Müller. 7) Add a new flag BPF_F_TIMER_ABS flag for bpf_timer_start() helper to start the timer with absolute expiration value instead of relative one, from Tero Kristo. 8) Add a new kfunc bpf_cgroup_from_id() to look up cgroups via id, from Tejun Heo. 9) Extend libbpf to support users manually attaching kprobes/uprobes in the legacy/perf/link mode, from Menglong Dong. 10) Implement workarounds in the mips BPF JIT for DADDI/R4000, from Jiaxun Yang. 11) Enable mixing bpf2bpf and tailcalls for the loongarch BPF JIT, from Hengqi Chen. 12) Extend BPF instruction set doc with describing the encoding of BPF instructions in terms of how bytes are stored under big/little endian, from Jose E. Marchesi. 13) Follow-up to enable kfunc support for riscv BPF JIT, from Pu Lehui. 14) Fix bpf_xdp_query() backwards compatibility on old kernels, from Yonghong Song. 15) Fix BPF selftest cross compilation with CLANG_CROSS_FLAGS, from Florent Revest. 16) Improve bpf_cpumask_ma to only allocate one bpf_mem_cache, from Hou Tao. 17) Fix BPF verifier's check_subprogs to not unnecessarily mark a subprogram with has_tail_call, from Ilya Leoshkevich. 18) Fix arm syscall regs spec in libbpf's bpf_tracing.h, from Puranjay Mohan. * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (85 commits) selftests/bpf: Add test for legacy/perf kprobe/uprobe attach mode selftests/bpf: Split test_attach_probe into multi subtests libbpf: Add support to set kprobe/uprobe attach mode tools/resolve_btfids: Add /libsubcmd to .gitignore bpf: add support for fixed-size memory pointer returns for kfuncs bpf: generalize dynptr_get_spi to be usable for iters bpf: mark PTR_TO_MEM as non-null register type bpf: move kfunc_call_arg_meta higher in the file bpf: ensure that r0 is marked scratched after any function call bpf: fix visit_insn()'s detection of BPF_FUNC_timer_set_callback helper bpf: clean up visit_insn()'s instruction processing selftests/bpf: adjust log_fixup's buffer size for proper truncation bpf: honor env->test_state_freq flag in is_state_visited() selftests/bpf: enhance align selftest's expected log matching bpf: improve regsafe() checks for PTR_TO_{MEM,BUF,TP_BUFFER} bpf: improve stack slot state printing selftests/bpf: Disassembler tests for verifier.c:convert_ctx_access() selftests/bpf: test if pointer type is tracked for BPF_ST_MEM bpf: allow ctx writes using BPF_ST_MEM instruction bpf: Use separate RCU callbacks for freeing selem ... ==================== Link: https://lore.kernel.org/r/20230307004346.27578-1-daniel@iogearbox.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>
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- 06 Mar, 2023 5 commits
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Andrii Nakryiko authored
Menglong Dong says: ==================== From: Menglong Dong <imagedong@tencent.com> By default, libbpf will attach the kprobe/uprobe BPF program in the latest mode that supported by kernel. In this series, we add the support to let users manually attach kprobe/uprobe in legacy/perf/link mode in the 1th patch. And in the 2th patch, we split the testing 'attach_probe' into multi subtests, as Andrii suggested. In the 3th patch, we add the testings for loading kprobe/uprobe in different mode. Changes since v3: - rename eBPF to BPF in the doc - use OPTS_GET() to get the value of 'force_ioctl_attach' - error out on attach mode is not supported - use test_attach_probe_manual__open_and_load() directly Changes since v2: - fix the typo in the 2th patch Changes since v1: - some small changes in the 1th patch, as Andrii suggested - split 'attach_probe' into multi subtests ==================== Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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Menglong Dong authored
Add the testing for kprobe/uprobe attaching in default, legacy, perf and link mode. And the testing passed: ./test_progs -t attach_probe $5/1 attach_probe/manual-default:OK $5/2 attach_probe/manual-legacy:OK $5/3 attach_probe/manual-perf:OK $5/4 attach_probe/manual-link:OK $5/5 attach_probe/auto:OK $5/6 attach_probe/kprobe-sleepable:OK $5/7 attach_probe/uprobe-lib:OK $5/8 attach_probe/uprobe-sleepable:OK $5/9 attach_probe/uprobe-ref_ctr:OK $5 attach_probe:OK Summary: 1/9 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Menglong Dong <imagedong@tencent.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Biao Jiang <benbjiang@tencent.com> Link: https://lore.kernel.org/bpf/20230306064833.7932-4-imagedong@tencent.com
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Menglong Dong authored
In order to adapt to the older kernel, now we split the "attach_probe" testing into multi subtests: manual // manual attach tests for kprobe/uprobe auto // auto-attach tests for kprobe and uprobe kprobe-sleepable // kprobe sleepable test uprobe-lib // uprobe tests for library function by name uprobe-sleepable // uprobe sleepable test uprobe-ref_ctr // uprobe ref_ctr test As sleepable kprobe needs to set BPF_F_SLEEPABLE flag before loading, we need to move it to a stand alone skel file, in case of it is not supported by kernel and make the whole loading fail. Therefore, we can only enable part of the subtests for older kernel. Signed-off-by: Menglong Dong <imagedong@tencent.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Biao Jiang <benbjiang@tencent.com> Link: https://lore.kernel.org/bpf/20230306064833.7932-3-imagedong@tencent.com
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Menglong Dong authored
By default, libbpf will attach the kprobe/uprobe BPF program in the latest mode that supported by kernel. In this patch, we add the support to let users manually attach kprobe/uprobe in legacy or perf mode. There are 3 mode that supported by the kernel to attach kprobe/uprobe: LEGACY: create perf event in legacy way and don't use bpf_link PERF: create perf event with perf_event_open() and don't use bpf_link Signed-off-by: Menglong Dong <imagedong@tencent.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Biao Jiang <benbjiang@tencent.com> Link: create perf event with perf_event_open() and use bpf_link Link: https://lore.kernel.org/bpf/20230113093427.1666466-1-imagedong@tencent.com/ Link: https://lore.kernel.org/bpf/20230306064833.7932-2-imagedong@tencent.com Users now can manually choose the mode with bpf_program__attach_uprobe_opts()/bpf_program__attach_kprobe_opts().
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Rong Tao authored
Add libsubcmd to .gitignore, otherwise after compiling the kernel it would result in the following: # bpf-next...bpf-next/master ?? tools/bpf/resolve_btfids/libsubcmd/ Signed-off-by: Rong Tao <rongtao@cestc.cn> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/bpf/tencent_F13D670D5D7AA9C4BD868D3220921AAC090A@qq.com
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- 04 Mar, 2023 16 commits
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Andrii Nakryiko authored
Support direct fixed-size (and for now, read-only) memory access when kfunc's return type is a pointer to non-struct type. Calculate type size and let BPF program access that many bytes directly. This is crucial for numbers iterator. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-13-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Generalize the logic of fetching special stack slot object state using spi (stack slot index). This will be used by STACK_ITER logic next. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-12-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
PTR_TO_MEM register without PTR_MAYBE_NULL is indeed non-null. This is important for BPF verifier to be able to prune guaranteed not to be taken branches. This is always the case with open-coded iterators. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-11-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Move struct bpf_kfunc_call_arg_meta higher in the file and put it next to struct bpf_call_arg_meta, so it can be used from more functions. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-10-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
r0 is important (unless called function is void-returning, but that's taken care of by print_verifier_state() anyways) in verifier logs. Currently for helpers we seem to print it in verifier log, but for kfuncs we don't. Instead of figuring out where in the maze of code we accidentally set r0 as scratched for helpers and why we don't do that for kfuncs, just enforce that after any function call r0 is marked as scratched. Also, perhaps, we should reconsider "scratched" terminology, as it's mightily confusing. "Touched" would seem more appropriate. But I left that for follow ups for now. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-9-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
It's not correct to assume that any BPF_CALL instruction is a helper call. Fix visit_insn()'s detection of bpf_timer_set_callback() helper by also checking insn->code == 0. For kfuncs insn->code would be set to BPF_PSEUDO_KFUNC_CALL, and for subprog calls it will be BPF_PSEUDO_CALL. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-8-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Instead of referencing processed instruction repeatedly as insns[t] throughout entire visit_insn() function, take a local insn pointer and work with it in a cleaner way. It makes enhancing this function further a bit easier as well. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-7-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Adjust log_fixup's expected buffer length to fix the test. It's pretty finicky in its length expectation, but it doesn't break often. So just adjust the length to work on current kernel and with follow up iterator changes as well. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-6-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
env->test_state_freq flag can be set by user by passing BPF_F_TEST_STATE_FREQ program flag. This is used in a bunch of selftests to have predictable state checkpoints at every jump and so on. Currently, bounded loop handling heuristic ignores this flag if number of processed jumps and/or number of processed instructions is below some thresholds, which throws off that reliable state checkpointing. Honor this flag in all circumstances by disabling heuristic if env->test_state_freq is set. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-5-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Allow to search for expected register state in all the verifier log output that's related to specified instruction number. See added comment for an example of possible situation that is happening due to a simple enhancement done in the next patch, which fixes handling of env->test_state_freq flag in state checkpointing logic. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-4-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Teach regsafe() logic to handle PTR_TO_MEM, PTR_TO_BUF, and PTR_TO_TP_BUFFER similarly to PTR_TO_MAP_{KEY,VALUE}. That is, instead of exact match for var_off and range, use tnum_in() and range_within() checks, allowing more general verified state to subsume more specific current state. This allows to match wider range of valid and safe states, speeding up verification and detecting wider range of equivalent states for upcoming open-coded iteration looping logic. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-3-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Andrii Nakryiko authored
Improve stack slot state printing to provide more useful and relevant information, especially for dynptrs. While previously we'd see something like: 8: (85) call bpf_ringbuf_reserve_dynptr#198 ; R0_w=scalar() fp-8_w=dddddddd fp-16_w=dddddddd refs=2 Now we'll see way more useful: 8: (85) call bpf_ringbuf_reserve_dynptr#198 ; R0_w=scalar() fp-16_w=dynptr_ringbuf(ref_id=2) refs=2 I experimented with printing the range of slots taken by dynptr, something like: fp-16..8_w=dynptr_ringbuf(ref_id=2) But it felt very awkward and pretty useless. So we print the lowest address (most negative offset) only. The general structure of this code is now also set up for easier extension and will accommodate ITER slots naturally. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230302235015.2044271-2-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Alexei Starovoitov authored
Eduard Zingerman says: ==================== Changes v1 -> v2, suggested by Alexei: - Resolved conflict with recent commit: 6fcd486b ("bpf: Refactor RCU enforcement in the verifier"); - Variable `ctx_access` removed in function `convert_ctx_accesses()`; - Macro `BPF_COPY_STORE` renamed to `BPF_EMIT_STORE` and fixed to correctly extract original store instruction class from code. Original message follows: The function verifier.c:convert_ctx_access() applies some rewrites to BPF instructions that read from or write to the BPF program context. For example, the write instruction for the `struct bpf_sockopt::retval` field: *(u32 *)(r1 + offsetof(struct bpf_sockopt, retval)) = r2 Is transformed to: *(u64 *)(r1 + offsetof(struct bpf_sockopt_kern, tmp_reg)) = r9 r9 = *(u64 *)(r1 + offsetof(struct bpf_sockopt_kern, current_task)) r9 = *(u64 *)(r9 + offsetof(struct task_struct, bpf_ctx)) *(u32 *)(r9 + offsetof(struct bpf_cg_run_ctx, retval)) = r2 r9 = *(u64 *)(r1 + offsetof(struct bpf_sockopt_kern, tmp_reg)) Currently, the verifier only supports such transformations for LDX (memory-to-register read) and STX (register-to-memory write) instructions. Error is reported for ST instructions (immediate-to-memory write). This is fine because clang does not currently emit ST instructions. However, new `-mcpu=v4` clang flag is planned, which would allow to emit ST instructions (discussed in [1]). This patch-set adjusts the verifier to support ST instructions in `verifier.c:convert_ctx_access()`. The patches #1 and #2 were previously shared as part of RFC [2]. The changes compared to that RFC are: - In patch #1, a bug in the handling of the `struct __sk_buff::queue_mapping` field was fixed. - Patch #3 is added, which is a set of disassembler-based test cases for context access rewrites. The test cases cover all fields for which the handling code is modified in patch #1. [1] Propose some new instructions for -mcpu=v4 https://lore.kernel.org/bpf/4bfe98be-5333-1c7e-2f6d-42486c8ec039@meta.com/ [2] RFC Support for BPF_ST instruction in LLVM C compiler https://lore.kernel.org/bpf/20221231163122.1360813-1-eddyz87@gmail.com/ [3] v1 https://lore.kernel.org/bpf/20230302225507.3413720-1-eddyz87@gmail.com/ ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Eduard Zingerman authored
Function verifier.c:convert_ctx_access() applies some rewrites to BPF instructions that read or write BPF program context. This commit adds machinery to allow test cases that inspect BPF program after these rewrites are applied. An example of a test case: { // Shorthand for field offset and size specification N(CGROUP_SOCKOPT, struct bpf_sockopt, retval), // Pattern generated for field read .read = "$dst = *(u64 *)($ctx + bpf_sockopt_kern::current_task);" "$dst = *(u64 *)($dst + task_struct::bpf_ctx);" "$dst = *(u32 *)($dst + bpf_cg_run_ctx::retval);", // Pattern generated for field write .write = "*(u64 *)($ctx + bpf_sockopt_kern::tmp_reg) = r9;" "r9 = *(u64 *)($ctx + bpf_sockopt_kern::current_task);" "r9 = *(u64 *)(r9 + task_struct::bpf_ctx);" "*(u32 *)(r9 + bpf_cg_run_ctx::retval) = $src;" "r9 = *(u64 *)($ctx + bpf_sockopt_kern::tmp_reg);" , }, For each test case, up to three programs are created: - One that uses BPF_LDX_MEM to read the context field. - One that uses BPF_STX_MEM to write to the context field. - One that uses BPF_ST_MEM to write to the context field. The disassembly of each program is compared with the pattern specified in the test case. Kernel code for disassembly is reused (as is in the bpftool). To keep Makefile changes to the minimum, symbolic links to `kernel/bpf/disasm.c` and `kernel/bpf/disasm.h ` are added. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20230304011247.566040-4-eddyz87@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Eduard Zingerman authored
Check that verifier tracks pointer types for BPF_ST_MEM instructions and reports error if pointer types do not match for different execution branches. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20230304011247.566040-3-eddyz87@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Eduard Zingerman authored
Lift verifier restriction to use BPF_ST_MEM instructions to write to context data structures. This requires the following changes: - verifier.c:do_check() for BPF_ST updated to: - no longer forbid writes to registers of type PTR_TO_CTX; - track dst_reg type in the env->insn_aux_data[...].ptr_type field (same way it is done for BPF_STX and BPF_LDX instructions). - verifier.c:convert_ctx_access() and various callbacks invoked by it are updated to handled BPF_ST instruction alongside BPF_STX. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20230304011247.566040-2-eddyz87@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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- 03 Mar, 2023 14 commits
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Kumar Kartikeya Dwivedi authored
Martin suggested that instead of using a byte in the hole (which he has a use for in his future patch) in bpf_local_storage_elem, we can dispatch a different call_rcu callback based on whether we need to free special fields in bpf_local_storage_elem data. The free path, described in commit 9db44fdd ("bpf: Support kptrs in local storage maps"), only waits for call_rcu callbacks when there are special (kptrs, etc.) fields in the map value, hence it is necessary that we only access smap in this case. Therefore, dispatch different RCU callbacks based on the BPF map has a valid btf_record, which dereference and use smap's btf_record only when it is valid. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20230303141542.300068-1-memxor@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>
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Daniel Borkmann authored
Alexei Starovoitov says: ==================== v4->v5: fix typos, add acks. v3->v4: - patch 3 got much cleaner after BPF_KPTR_RCU was removed as suggested by David. - make KF_RCU stronger and require that bpf program checks for NULL before passing such pointers into kfunc. The prog has to do that anyway to access fields and it aligns with BTF_TYPE_SAFE_RCU allowlist. - New patch 6: refactor RCU enforcement in the verifier. The patches 2,3,6 are part of one feature. The 2 and 3 alone are incomplete, since RCU pointers are barely useful without bpf_rcu_read_lock/unlock in GCC compiled kernel. Even if GCC lands support for btf_type_tag today it will take time to mandate that version for kernel builds. Hence go with allow list approach. See patch 6 for details. This allows to start strict enforcement of TRUSTED | UNTRUSTED in one part of PTR_TO_BTF_ID accesses. One step closer to KF_TRUSTED_ARGS by default. v2->v3: - Instead of requiring bpf progs to tag fields with __kptr_rcu teach the verifier to infer RCU properties based on the type. BPF_KPTR_RCU becomes kernel internal type of struct btf_field. - Add patch 2 to tag cgroups and dfl_cgrp as trusted. That bug was spotted by BPF CI on clang compiler kernels, since patch 3 is doing: static bool in_rcu_cs(struct bpf_verifier_env *env) { return env->cur_state->active_rcu_lock || !env->prog->aux->sleepable; } which makes all non-sleepable programs behave like they have implicit rcu_read_lock around them. Which is the case in practice. It was fine on gcc compiled kernels where task->cgroup deference was producing PTR_TO_BTF_ID, but on clang compiled kernels task->cgroup deference was producing PTR_TO_BTF_ID | MEM_RCU | MAYBE_NULL, which is more correct, but selftests were failing. Patch 2 fixes this discrepancy. With few more patches like patch 2 we can make KF_TRUSTED_ARGS default for kfuncs and helpers. - Add comment in selftest patch 5 that it's verifier only check. v1->v2: Instead of agressively allow dereferenced kptr_rcu pointers into KF_TRUSTED_ARGS kfuncs only allow them into KF_RCU funcs. The KF_RCU flag is a weaker version of KF_TRUSTED_ARGS. The kfuncs marked with KF_RCU expect either PTR_TRUSTED or MEM_RCU arguments. The verifier guarantees that the objects are valid and there is no use-after-free, but the pointers maybe NULL and pointee object's reference count could have reached zero, hence kfuncs must do != NULL check and consider refcnt==0 case when accessing such arguments. No changes in patch 1. Patches 2,3,4 adjusted with above behavior. v1: The __kptr_ref turned out to be too limited, since any "trusted" pointer access requires bpf_kptr_xchg() which is impractical when the same pointer needs to be dereferenced by multiple cpus. The __kptr "untrusted" only access isn't very useful in practice. Rename __kptr to __kptr_untrusted with eventual goal to deprecate it, and rename __kptr_ref to __kptr, since that looks to be more common use of kptrs. Introduce __kptr_rcu that can be directly dereferenced and used similar to native kernel C code. Once bpf_cpumask and task_struct kfuncs are converted to observe RCU GP when refcnt goes to zero, both __kptr and __kptr_untrusted can be deprecated and __kptr_rcu can become the only __kptr tag. ==================== Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Alexei Starovoitov authored
bpf_rcu_read_lock/unlock() are only available in clang compiled kernels. Lack of such key mechanism makes it impossible for sleepable bpf programs to use RCU pointers. Allow bpf_rcu_read_lock/unlock() in GCC compiled kernels (though GCC doesn't support btf_type_tag yet) and allowlist certain field dereferences in important data structures like tast_struct, cgroup, socket that are used by sleepable programs either as RCU pointer or full trusted pointer (which is valid outside of RCU CS). Use BTF_TYPE_SAFE_RCU and BTF_TYPE_SAFE_TRUSTED macros for such tagging. They will be removed once GCC supports btf_type_tag. With that refactor check_ptr_to_btf_access(). Make it strict in enforcing PTR_TRUSTED and PTR_UNTRUSTED while deprecating old PTR_TO_BTF_ID without modifier flags. There is a chance that this strict enforcement might break existing programs (especially on GCC compiled kernels), but this cleanup has to start sooner than later. Note PTR_TO_CTX access still yields old deprecated PTR_TO_BTF_ID. Once it's converted to strict PTR_TRUSTED or PTR_UNTRUSTED the kfuncs and helpers will be able to default to KF_TRUSTED_ARGS. KF_RCU will remain as a weaker version of KF_TRUSTED_ARGS where obj refcnt could be 0. Adjust rcu_read_lock selftest to run on gcc and clang compiled kernels. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-7-alexei.starovoitov@gmail.com
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Alexei Starovoitov authored
Adjust cgroup kfunc test to dereference RCU protected cgroup pointer as PTR_TRUSTED and pass into KF_TRUSTED_ARGS kfunc. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-6-alexei.starovoitov@gmail.com
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Alexei Starovoitov authored
Tweak existing map_kptr test to check kptr_rcu. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-5-alexei.starovoitov@gmail.com
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Alexei Starovoitov authored
The life time of certain kernel structures like 'struct cgroup' is protected by RCU. Hence it's safe to dereference them directly from __kptr tagged pointers in bpf maps. The resulting pointer is MEM_RCU and can be passed to kfuncs that expect KF_RCU. Derefrence of other kptr-s returns PTR_UNTRUSTED. For example: struct map_value { struct cgroup __kptr *cgrp; }; SEC("tp_btf/cgroup_mkdir") int BPF_PROG(test_cgrp_get_ancestors, struct cgroup *cgrp_arg, const char *path) { struct cgroup *cg, *cg2; cg = bpf_cgroup_acquire(cgrp_arg); // cg is PTR_TRUSTED and ref_obj_id > 0 bpf_kptr_xchg(&v->cgrp, cg); cg2 = v->cgrp; // This is new feature introduced by this patch. // cg2 is PTR_MAYBE_NULL | MEM_RCU. // When cg2 != NULL, it's a valid cgroup, but its percpu_ref could be zero if (cg2) bpf_cgroup_ancestor(cg2, level); // safe to do. } Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-4-alexei.starovoitov@gmail.com
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Alexei Starovoitov authored
bpf programs sometimes do: bpf_cgrp_storage_get(&map, task->cgroups->dfl_cgrp, ...); It is safe to do, because cgroups->dfl_cgrp pointer is set diring init and never changes. The task->cgroups is also never NULL. It is also set during init and will change when task switches cgroups. For any trusted task pointer dereference of cgroups and dfl_cgrp should yield trusted pointers. The verifier wasn't aware of this. Hence in gcc compiled kernels task->cgroups dereference was producing PTR_TO_BTF_ID without modifiers while in clang compiled kernels the verifier recognizes __rcu tag in cgroups field and produces PTR_TO_BTF_ID | MEM_RCU | MAYBE_NULL. Tag cgroups and dfl_cgrp as trusted to equalize clang and gcc behavior. When GCC supports btf_type_tag such tagging will done directly in the type. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/bpf/20230303041446.3630-3-alexei.starovoitov@gmail.com
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Alexei Starovoitov authored
__kptr meant to store PTR_UNTRUSTED kernel pointers inside bpf maps. The concept felt useful, but didn't get much traction, since bpf_rdonly_cast() was added soon after and bpf programs received a simpler way to access PTR_UNTRUSTED kernel pointers without going through restrictive __kptr usage. Rename __kptr_ref -> __kptr and __kptr -> __kptr_untrusted to indicate its intended usage. The main goal of __kptr_untrusted was to read/write such pointers directly while bpf_kptr_xchg was a mechanism to access refcnted kernel pointers. The next patch will allow RCU protected __kptr access with direct read. At that point __kptr_untrusted will be deprecated. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-2-alexei.starovoitov@gmail.com
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Tero Kristo authored
Add test for the absolute BPF timer under the existing timer tests. This will run the timer two times with 1us expiration time, and then re-arm the timer at ~35s in the future. At the end, it is verified that the absolute timer expired exactly two times. Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com> Link: https://lore.kernel.org/r/20230302114614.2985072-3-tero.kristo@linux.intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Tero Kristo authored
Add a new flag BPF_F_TIMER_ABS that can be passed to bpf_timer_start() to start an absolute value timer instead of the default relative value. This makes the timer expire at an exact point in time, instead of a time with latencies induced by both the BPF and timer subsystems. Suggested-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com> Link: https://lore.kernel.org/r/20230302114614.2985072-2-tero.kristo@linux.intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Dave Marchevsky authored
Per C99 standard [0], Section 6.7.8, Paragraph 10: If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. And in the same document, in appendix "J.2 Undefined behavior": The behavior is undefined in the following circumstances: [...] The value of an object with automatic storage duration is used while it is indeterminate (6.2.4, 6.7.8, 6.8). This means that use of an uninitialized stack variable is undefined behavior, and therefore that clang can choose to do a variety of scary things, such as not generating bytecode for "bunch of useful code" in the below example: void some_func() { int i; if (!i) return; // bunch of useful code } To add insult to injury, if some_func above is a helper function for some BPF program, clang can choose to not generate an "exit" insn, causing verifier to fail with "last insn is not an exit or jmp". Going from that verification failure to the root cause of uninitialized use is certain to be frustrating. This patch adds -Wuninitialized to the cflags for selftest BPF progs and fixes up existing instances of uninitialized use. [0]: https://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdfSigned-off-by: Dave Marchevsky <davemarchevsky@fb.com> Cc: David Vernet <void@manifault.com> Cc: Tejun Heo <tj@kernel.org> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230303005500.1614874-1-davemarchevsky@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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Tejun Heo authored
These helpers are safe to call from any context and there's no reason to restrict access to them. Remove them from bpf_trace and filter lists and add to bpf_base_func_proto() under perfmon_capable(). v2: After consulting with Andrii, relocated in bpf_base_func_proto() so that they require bpf_capable() but not perfomon_capable() as it doesn't read from or affect others on the system. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/ZAD8QyoszMZiTzBY@slm.duckdns.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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David Vernet authored
maps.rst in the BPF documentation links to the /userspace-api/ebpf/syscall document (Documentation/userspace-api/ebpf/syscall.rst). For some reason, if you try to reference the document with :doc:, the docs build emits the following warning: ./Documentation/bpf/maps.rst:13: WARNING: \ unknown document: '/userspace-api/ebpf/syscall' It appears that other places in the docs tree also don't support using :doc:. Elsewhere in the BPF documentation, we just reference the kernel docs page directly. Let's do that here to clean up the last remaining noise in the docs build. Signed-off-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230302183918.54190-2-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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David Vernet authored
The BPF devel Q&A documentation page makes frequent reference to the netdev-QA page via the netdev-FAQ rst link. This link is currently broken, as is evidenced by the build output when making BPF docs: ./Documentation/bpf/bpf_devel_QA.rst:150: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:206: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:231: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:396: WARNING: undefined label: 'netdev-faq' ./Documentation/bpf/bpf_devel_QA.rst:412: WARNING: undefined label: 'netdev-faq' Fix the links to point to the actual netdev-faq page. Signed-off-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230302183918.54190-1-void@manifault.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>
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- 02 Mar, 2023 2 commits
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Joanne Koong authored
Change bpf_dynptr_slice and bpf_dynptr_slice_rdwr to return NULL instead of 0, in accordance with the codebase guidelines. Fixes: 66e3a13e ("bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr") Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Joanne Koong <joannelkoong@gmail.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20230302053014.1726219-1-joannelkoong@gmail.com
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Andrii Nakryiko authored
Daniel Müller says: ==================== On Android, APKs (android packages; zip packages with somewhat prescriptive contents) are first class citizens in the system: the shared objects contained in them don't exist in unpacked form on the file system. Rather, they are mmaped directly from within the archive and the archive is also what the kernel is aware of. For users that complicates the process of attaching a uprobe to a function contained in a shared object in one such APK: they'd have to find the byte offset of said function from the beginning of the archive. That is cumbersome to do manually and can be fragile, because various changes could invalidate said offset. That is why for uprobes inside ELF files (not inside an APK), commit d112c9ce249b ("libbpf: Support function name-based attach uprobes") added support for attaching to symbols by name. On Android, that mechanism currently does not work, because this logic is not APK aware. This patch set introduces first class support for attaching uprobes to functions inside ELF objects contained in APKs via function names. We add support for recognizing the following syntax for a binary path: <archive>!/<binary-in-archive> (e.g., /system/app/test-app.apk!/lib/arm64-v8a/libc++.so) This syntax is common in the Android eco system and used by tools such as simpleperf. It is also what is being proposed for bcc [0]. If the user provides such a binary path, we find <binary-in-archive> (lib/arm64-v8a/libc++.so in the example) inside of <archive> (/system/app/test-app.apk). We perform the regular ELF offset search inside the binary and add that to the offset within the archive itself, to retrieve the offset at which to attach the uprobe. [0] https://github.com/iovisor/bcc/pull/4440 Changelog --------- v3->v4: - use ERR_PTR instead of libbpf_err_ptr() in zip_archive_open() - eliminated err variable from elf_find_func_offset_from_archive() v2->v3: - adjusted zip_archive_open() to report errno - fixed provided libbpf_strlcpy() buffer size argument - adjusted find_cd() to handle errors better - use fewer local variables in get_entry_at_offset() v1->v2: - removed unaligned_* types - switched to using __u32 and __u16 - switched to using errno constants instead of hard-coded negative values - added another pr_debug() message - shortened central_directory_* to cd_* - inlined cd_file_header_at_offset() function - bunch of syntactical changes ==================== Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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