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Some subsystems only have bare tracepoints (a tracepoint with no associated trace event) to avoid the problem of trace events being an ABI that can't be changed. >From bpf presepective, bare tracepoints are what it calls RAW_TRACEPOINT(). Since bpf assumed there's 1:1 mapping, it relied on hooking to DEFINE_EVENT() macro to create bpf mapping of the tracepoints. Since bare tracepoints use DECLARE_TRACE() to create the tracepoint, bpf had no knowledge about their existence. By teaching bpf_probe.h to parse DECLARE_TRACE() in a similar fashion to DEFINE_EVENT(), bpf can find and attach to the new raw tracepoints. Enabling that comes with the contract that changes to raw tracepoints don't constitute a regression if they break existing bpf programs. We need the ability to continue to morph and modify these raw tracepoints without worrying about any ABI. Update Documentation/bpf/bpf_design_QA.rst to document this contract. Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20210119122237.2426878-2-qais.yousef@arm.com
129 lines
4.2 KiB
C
129 lines
4.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#undef TRACE_SYSTEM_VAR
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#ifdef CONFIG_BPF_EVENTS
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#undef __entry
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#define __entry entry
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#undef __get_dynamic_array
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#define __get_dynamic_array(field) \
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((void *)__entry + (__entry->__data_loc_##field & 0xffff))
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#undef __get_dynamic_array_len
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#define __get_dynamic_array_len(field) \
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((__entry->__data_loc_##field >> 16) & 0xffff)
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#undef __get_str
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#define __get_str(field) ((char *)__get_dynamic_array(field))
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#undef __get_bitmask
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#define __get_bitmask(field) (char *)__get_dynamic_array(field)
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#undef __perf_count
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#define __perf_count(c) (c)
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#undef __perf_task
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#define __perf_task(t) (t)
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/* cast any integer, pointer, or small struct to u64 */
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#define UINTTYPE(size) \
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__typeof__(__builtin_choose_expr(size == 1, (u8)1, \
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__builtin_choose_expr(size == 2, (u16)2, \
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__builtin_choose_expr(size == 4, (u32)3, \
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__builtin_choose_expr(size == 8, (u64)4, \
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(void)5)))))
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#define __CAST_TO_U64(x) ({ \
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typeof(x) __src = (x); \
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UINTTYPE(sizeof(x)) __dst; \
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memcpy(&__dst, &__src, sizeof(__dst)); \
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(u64)__dst; })
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#define __CAST1(a,...) __CAST_TO_U64(a)
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#define __CAST2(a,...) __CAST_TO_U64(a), __CAST1(__VA_ARGS__)
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#define __CAST3(a,...) __CAST_TO_U64(a), __CAST2(__VA_ARGS__)
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#define __CAST4(a,...) __CAST_TO_U64(a), __CAST3(__VA_ARGS__)
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#define __CAST5(a,...) __CAST_TO_U64(a), __CAST4(__VA_ARGS__)
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#define __CAST6(a,...) __CAST_TO_U64(a), __CAST5(__VA_ARGS__)
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#define __CAST7(a,...) __CAST_TO_U64(a), __CAST6(__VA_ARGS__)
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#define __CAST8(a,...) __CAST_TO_U64(a), __CAST7(__VA_ARGS__)
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#define __CAST9(a,...) __CAST_TO_U64(a), __CAST8(__VA_ARGS__)
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#define __CAST10(a,...) __CAST_TO_U64(a), __CAST9(__VA_ARGS__)
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#define __CAST11(a,...) __CAST_TO_U64(a), __CAST10(__VA_ARGS__)
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#define __CAST12(a,...) __CAST_TO_U64(a), __CAST11(__VA_ARGS__)
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/* tracepoints with more than 12 arguments will hit build error */
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#define CAST_TO_U64(...) CONCATENATE(__CAST, COUNT_ARGS(__VA_ARGS__))(__VA_ARGS__)
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#define __BPF_DECLARE_TRACE(call, proto, args) \
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static notrace void \
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__bpf_trace_##call(void *__data, proto) \
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{ \
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struct bpf_prog *prog = __data; \
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CONCATENATE(bpf_trace_run, COUNT_ARGS(args))(prog, CAST_TO_U64(args)); \
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}
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#undef DECLARE_EVENT_CLASS
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#define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print) \
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__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args))
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/*
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* This part is compiled out, it is only here as a build time check
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* to make sure that if the tracepoint handling changes, the
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* bpf probe will fail to compile unless it too is updated.
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*/
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#define __DEFINE_EVENT(template, call, proto, args, size) \
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static inline void bpf_test_probe_##call(void) \
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{ \
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check_trace_callback_type_##call(__bpf_trace_##template); \
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} \
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typedef void (*btf_trace_##call)(void *__data, proto); \
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static union { \
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struct bpf_raw_event_map event; \
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btf_trace_##call handler; \
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} __bpf_trace_tp_map_##call __used \
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__section("__bpf_raw_tp_map") = { \
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.event = { \
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.tp = &__tracepoint_##call, \
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.bpf_func = __bpf_trace_##template, \
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.num_args = COUNT_ARGS(args), \
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.writable_size = size, \
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}, \
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};
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#define FIRST(x, ...) x
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#undef DEFINE_EVENT_WRITABLE
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#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \
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static inline void bpf_test_buffer_##call(void) \
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{ \
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/* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \
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* BUILD_BUG_ON_ZERO() uses a different mechanism that is not \
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* dead-code-eliminated. \
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*/ \
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FIRST(proto); \
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(void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \
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} \
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__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size)
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#undef DEFINE_EVENT
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#define DEFINE_EVENT(template, call, proto, args) \
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__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), 0)
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#undef DEFINE_EVENT_PRINT
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#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
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DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
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#undef DECLARE_TRACE
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#define DECLARE_TRACE(call, proto, args) \
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__BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \
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__DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), 0)
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#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
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#undef DEFINE_EVENT_WRITABLE
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#undef __DEFINE_EVENT
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#undef FIRST
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#endif /* CONFIG_BPF_EVENTS */
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