user/sven/linux.git/include/uapi/linux/bpf.h, branch v5.5.14

bpf: Add mmap() support for BPF_MAP_TYPE_ARRAY

2019-11-18T10:41:59Z

Add ability to memory-map contents of BPF array map. This is extremely useful for working with BPF global data from userspace programs. It allows to avoid typical bpf_map_{lookup,update}_elem operations, improving both performance and usability. There had to be special considerations for map freezing, to avoid having writable memory view into a frozen map. To solve this issue, map freezing and mmap-ing is happening under mutex now: - if map is already frozen, no writable mapping is allowed; - if map has writable memory mappings active (accounted in map->writecnt), map freezing will keep failing with -EBUSY; - once number of writable memory mappings drops to zero, map freezing can be performed again. Only non-per-CPU plain arrays are supported right now. Maps with spinlocks can't be memory mapped either. For BPF_F_MMAPABLE array, memory allocation has to be done through vmalloc() to be mmap()'able. We also need to make sure that array data memory is page-sized and page-aligned, so we over-allocate memory in such a way that struct bpf_array is at the end of a single page of memory with array->value being aligned with the start of the second page. On deallocation we need to accomodate this memory arrangement to free vmalloc()'ed memory correctly. One important consideration regarding how memory-mapping subsystem functions. Memory-mapping subsystem provides few optional callbacks, among them open() and close(). close() is called for each memory region that is unmapped, so that users can decrease their reference counters and free up resources, if necessary. open() is *almost* symmetrical: it's called for each memory region that is being mapped, **except** the very first one. So bpf_map_mmap does initial refcnt bump, while open() will do any extra ones after that. Thus number of close() calls is equal to number of open() calls plus one more. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Song Liu Acked-by: John Fastabend Acked-by: Johannes Weiner Link: https://lore.kernel.org/bpf/20191117172806.2195367-4-andriin@fb.com

bpf: Support attaching tracing BPF program to other BPF programs

2019-11-15T22:45:24Z

Allow FENTRY/FEXIT BPF programs to attach to other BPF programs of any type including their subprograms. This feature allows snooping on input and output packets in XDP, TC programs including their return values. In order to do that the verifier needs to track types not only of vmlinux, but types of other BPF programs as well. The verifier also needs to translate uapi/linux/bpf.h types used by networking programs into kernel internal BTF types used by FENTRY/FEXIT BPF programs. In some cases LLVM optimizations can remove arguments from BPF subprograms without adjusting BTF info that LLVM backend knows. When BTF info disagrees with actual types that the verifiers sees the BPF trampoline has to fallback to conservative and treat all arguments as u64. The FENTRY/FEXIT program can still attach to such subprograms, but it won't be able to recognize pointer types like 'struct sk_buff *' and it won't be able to pass them to bpf_skb_output() for dumping packets to user space. The FENTRY/FEXIT program would need to use bpf_probe_read_kernel() instead. The BPF_PROG_LOAD command is extended with attach_prog_fd field. When it's set to zero the attach_btf_id is one vmlinux BTF type ids. When attach_prog_fd points to previously loaded BPF program the attach_btf_id is BTF type id of main function or one of its subprograms. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20191114185720.1641606-18-ast@kernel.org

bpf: Introduce BPF trampoline

2019-11-15T22:41:51Z

Introduce BPF trampoline concept to allow kernel code to call into BPF programs with practically zero overhead. The trampoline generation logic is architecture dependent. It's converting native calling convention into BPF calling convention. BPF ISA is 64-bit (even on 32-bit architectures). The registers R1 to R5 are used to pass arguments into BPF functions. The main BPF program accepts only single argument "ctx" in R1. Whereas CPU native calling convention is different. x86-64 is passing first 6 arguments in registers and the rest on the stack. x86-32 is passing first 3 arguments in registers. sparc64 is passing first 6 in registers. And so on. The trampolines between BPF and kernel already exist. BPF_CALL_x macros in include/linux/filter.h statically compile trampolines from BPF into kernel helpers. They convert up to five u64 arguments into kernel C pointers and integers. On 64-bit architectures this BPF_to_kernel trampolines are nops. On 32-bit architecture they're meaningful. The opposite job kernel_to_BPF trampolines is done by CAST_TO_U64 macros and __bpf_trace_##call() shim functions in include/trace/bpf_probe.h. They convert kernel function arguments into array of u64s that BPF program consumes via R1=ctx pointer. This patch set is doing the same job as __bpf_trace_##call() static trampolines, but dynamically for any kernel function. There are ~22k global kernel functions that are attachable via nop at function entry. The function arguments and types are described in BTF. The job of btf_distill_func_proto() function is to extract useful information from BTF into "function model" that architecture dependent trampoline generators will use to generate assembly code to cast kernel function arguments into array of u64s. For example the kernel function eth_type_trans has two pointers. They will be casted to u64 and stored into stack of generated trampoline. The pointer to that stack space will be passed into BPF program in R1. On x86-64 such generated trampoline will consume 16 bytes of stack and two stores of %rdi and %rsi into stack. The verifier will make sure that only two u64 are accessed read-only by BPF program. The verifier will also recognize the precise type of the pointers being accessed and will not allow typecasting of the pointer to a different type within BPF program. The tracing use case in the datacenter demonstrated that certain key kernel functions have (like tcp_retransmit_skb) have 2 or more kprobes that are always active. Other functions have both kprobe and kretprobe. So it is essential to keep both kernel code and BPF programs executing at maximum speed. Hence generated BPF trampoline is re-generated every time new program is attached or detached to maintain maximum performance. To avoid the high cost of retpoline the attached BPF programs are called directly. __bpf_prog_enter/exit() are used to support per-program execution stats. In the future this logic will be optimized further by adding support for bpf_stats_enabled_key inside generated assembly code. Introduction of preemptible and sleepable BPF programs will completely remove the need to call to __bpf_prog_enter/exit(). Detach of a BPF program from the trampoline should not fail. To avoid memory allocation in detach path the half of the page is used as a reserve and flipped after each attach/detach. 2k bytes is enough to call 40+ BPF programs directly which is enough for BPF tracing use cases. This limit can be increased in the future. BPF_TRACE_FENTRY programs have access to raw kernel function arguments while BPF_TRACE_FEXIT programs have access to kernel return value as well. Often kprobe BPF program remembers function arguments in a map while kretprobe fetches arguments from a map and analyzes them together with return value. BPF_TRACE_FEXIT accelerates this typical use case. Recursion prevention for kprobe BPF programs is done via per-cpu bpf_prog_active counter. In practice that turned out to be a mistake. It caused programs to randomly skip execution. The tracing tools missed results they were looking for. Hence BPF trampoline doesn't provide builtin recursion prevention. It's a job of BPF program itself and will be addressed in the follow up patches. BPF trampoline is intended to be used beyond tracing and fentry/fexit use cases in the future. For example to remove retpoline cost from XDP programs. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20191114185720.1641606-5-ast@kernel.org

bpf: Add probe_read_{user, kernel} and probe_read_{user, kernel}_str helpers

2019-11-02T19:39:12Z

The current bpf_probe_read() and bpf_probe_read_str() helpers are broken in that they assume they can be used for probing memory access for kernel space addresses /as well as/ user space addresses. However, plain use of probe_kernel_read() for both cases will attempt to always access kernel space address space given access is performed under KERNEL_DS and some archs in-fact have overlapping address spaces where a kernel pointer and user pointer would have the /same/ address value and therefore accessing application memory via bpf_probe_read{,_str}() would read garbage values. Lets fix BPF side by making use of recently added 3d7081822f7f ("uaccess: Add non-pagefault user-space read functions"). Unfortunately, the only way to fix this status quo is to add dedicated bpf_probe_read_{user,kernel}() and bpf_probe_read_{user,kernel}_str() helpers. The bpf_probe_read{,_str}() helpers are kept as-is to retain their current behavior. The two *_user() variants attempt the access always under USER_DS set, the two *_kernel() variants will -EFAULT when accessing user memory if the underlying architecture has non-overlapping address ranges, also avoiding throwing the kernel warning via 00c42373d397 ("x86-64: add warning for non-canonical user access address dereferences"). Fixes: a5e8c07059d0 ("bpf: add bpf_probe_read_str helper") Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes") Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/796ee46e948bc808d54891a1108435f8652c6ca4.1572649915.git.daniel@iogearbox.net

bpf: Replace prog_raw_tp+btf_id with prog_tracing

2019-10-31T14:16:59Z

The bpf program type raw_tp together with 'expected_attach_type' was the most appropriate api to indicate BTF-enabled raw_tp programs. But during development it became apparent that 'expected_attach_type' cannot be used and new 'attach_btf_id' field had to be introduced. Which means that the information is duplicated in two fields where one of them is ignored. Clean it up by introducing new program type where both 'expected_attach_type' and 'attach_btf_id' fields have specific meaning. In the future 'expected_attach_type' will be extended with other attach points that have similar semantics to raw_tp. This patch is replacing BTF-enabled BPF_PROG_TYPE_RAW_TRACEPOINT with prog_type = BPF_RPOG_TYPE_TRACING expected_attach_type = BPF_TRACE_RAW_TP attach_btf_id = btf_id of raw tracepoint inside the kernel Future patches will add expected_attach_type = BPF_TRACE_FENTRY or BPF_TRACE_FEXIT where programs have the same input context and the same helpers, but different attach points. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20191030223212.953010-2-ast@kernel.org

bpf: Check types of arguments passed into helpers

2019-10-17T14:44:36Z

Introduce new helper that reuses existing skb perf_event output implementation, but can be called from raw_tracepoint programs that receive 'struct sk_buff *' as tracepoint argument or can walk other kernel data structures to skb pointer. In order to do that teach verifier to resolve true C types of bpf helpers into in-kernel BTF ids. The type of kernel pointer passed by raw tracepoint into bpf program will be tracked by the verifier all the way until it's passed into helper function. For example: kfree_skb() kernel function calls trace_kfree_skb(skb, loc); bpf programs receives that skb pointer and may eventually pass it into bpf_skb_output() bpf helper which in-kernel is implemented via bpf_skb_event_output() kernel function. Its first argument in the kernel is 'struct sk_buff *'. The verifier makes sure that types match all the way. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20191016032505.2089704-11-ast@kernel.org

bpf: Add attach_btf_id attribute to program load

2019-10-17T14:44:35Z

Add attach_btf_id attribute to prog_load command. It's similar to existing expected_attach_type attribute which is used in several cgroup based program types. Unfortunately expected_attach_type is ignored for tracing programs and cannot be reused for new purpose. Hence introduce attach_btf_id to verify bpf programs against given in-kernel BTF type id at load time. It is strictly checked to be valid for raw_tp programs only. In a later patches it will become: btf_id == 0 semantics of existing raw_tp progs. btd_id > 0 raw_tp with BTF and additional type safety. Signed-off-by: Alexei Starovoitov Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20191016032505.2089704-5-ast@kernel.org

uapi/bpf: fix helper docs

2019-10-07T05:29:36Z

Various small fixes to BPF helper documentation comments, enabling automatic header generation with a list of BPF helpers. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2019-09-06T14:49:17Z

Daniel Borkmann says: ==================== The following pull-request contains BPF updates for your *net-next* tree. The main changes are: 1) Add the ability to use unaligned chunks in the AF_XDP umem. By relaxing where the chunks can be placed, it allows to use an arbitrary buffer size and place whenever there is a free address in the umem. Helps more seamless DPDK AF_XDP driver integration. Support for i40e, ixgbe and mlx5e, from Kevin and Maxim. 2) Addition of a wakeup flag for AF_XDP tx and fill rings so the application can wake up the kernel for rx/tx processing which avoids busy-spinning of the latter, useful when app and driver is located on the same core. Support for i40e, ixgbe and mlx5e, from Magnus and Maxim. 3) bpftool fixes for printf()-like functions so compiler can actually enforce checks, bpftool build system improvements for custom output directories, and addition of 'bpftool map freeze' command, from Quentin. 4) Support attaching/detaching XDP programs from 'bpftool net' command, from Daniel. 5) Automatic xskmap cleanup when AF_XDP socket is released, and several barrier/{read,write}_once fixes in AF_XDP code, from Björn. 6) Relicense of bpf_helpers.h/bpf_endian.h for future libbpf inclusion as well as libbpf versioning improvements, from Andrii. 7) Several new BPF kselftests for verifier precision tracking, from Alexei. 8) Several BPF kselftest fixes wrt endianess to run on s390x, from Ilya. 9) And more BPF kselftest improvements all over the place, from Stanislav. 10) Add simple BPF map op cache for nfp driver to batch dumps, from Jakub. 11) AF_XDP socket umem mapping improvements for 32bit archs, from Ivan. 12) Add BPF-to-BPF call and BTF line info support for s390x JIT, from Yauheni. 13) Small optimization in arm64 JIT to spare 1 insns for BPF_MOD, from Jerin. 14) Fix an error check in bpf_tcp_gen_syncookie() helper, from Petar. 15) Various minor fixes and cleanups, from Nathan, Masahiro, Masanari, Peter, Wei, Yue. ==================== Signed-off-by: David S. Miller

bpf: introduce verifier internal test flag

2019-08-27T22:30:11Z

Introduce BPF_F_TEST_STATE_FREQ flag to stress test parentage chain and state pruning. Signed-off-by: Alexei Starovoitov Acked-by: Song Liu Signed-off-by: Daniel Borkmann