From: Mykyta Yatsenko DECLARE_EVENT_CLASS emitted __bpf_trace_btf_ids_ through BTF_ID_LIST_GLOBAL, i.e. a global symbol named after the event class. The class name is not unique across the kernel, so the symbol multiply-defines whenever two translation units instantiate the same class. Switch to the file-local BTF_ID_LIST: the list is reached only through the event_class_.btf_ids pointer, initialised in the same unit, so tracefs readers never reference the symbol by name and resolve_btfids still fills the now-local .BTF_ids entries. The handcrafted syscall classes are the one cross-unit consumer: give them their own local BTF_ID_LIST rather than importing the generated sys_{enter,exit} lists, which are now file-local. Fixes: eadc0725ab8d3 ("tracing: Expose tracepoint BTF ids via tracefs") Reported-by: Mark Brown Closes: https://lore.kernel.org/all/ff58b01c-3f5e-4d55-be82-609d2faaf12e@sirena.org.uk/ Signed-off-by: Mykyta Yatsenko --- include/trace/trace_events.h | 6 ++++-- kernel/trace/trace_syscalls.c | 22 ++++++++++++++-------- 2 files changed, 18 insertions(+), 10 deletions(-) diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h index 09ad57ac4b73..45ffbe04b580 100644 --- a/include/trace/trace_events.h +++ b/include/trace/trace_events.h @@ -404,10 +404,12 @@ static inline notrace int trace_event_get_offsets_##call( \ * [0] FUNC __bpf_trace_ (the BPF dispatcher) * [1] STRUCT trace_event_raw_ (the ring-buffer record) * Exposed via the events///btf_ids tracefs file. + * + * File-local: the class name is not unique, so a global symbol would + * clash across translation units. */ #define _TRACE_BTF_IDS_DECLARE(call) \ - extern u32 __bpf_trace_btf_ids_##call[]; \ - BTF_ID_LIST_GLOBAL(__bpf_trace_btf_ids_##call, 2) \ + BTF_ID_LIST(__bpf_trace_btf_ids_##call) \ BTF_ID(func, __bpf_trace_##call) \ BTF_ID(struct, trace_event_raw_##call) diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c index 48ef1a93e576..9b5931f2f280 100644 --- a/kernel/trace/trace_syscalls.c +++ b/kernel/trace/trace_syscalls.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include "trace_output.h" @@ -1305,13 +1306,18 @@ struct trace_event_functions exit_syscall_print_funcs = { #ifdef CONFIG_BPF_EVENTS /* - * BTF id lists generated by DECLARE_EVENT_CLASS for the sys_enter and - * sys_exit tracepoints. The auto-generated event_class_sys_{enter,exit} - * is unused (per-syscall events share the handcrafted classes below), - * but the id lists themselves are global and reusable. + * BTF id lists for the shared sys_enter/sys_exit dispatcher tracepoints, + * resolved by resolve_btfids. Defined locally rather than importing the + * DECLARE_EVENT_CLASS-generated lists, which are now file-local to the + * translation unit that instantiates the tracepoint. */ -extern u32 __bpf_trace_btf_ids_sys_enter[]; -extern u32 __bpf_trace_btf_ids_sys_exit[]; +BTF_ID_LIST(syscall_enter_btf_ids) +BTF_ID(func, __bpf_trace_sys_enter) +BTF_ID(struct, trace_event_raw_sys_enter) + +BTF_ID_LIST(syscall_exit_btf_ids) +BTF_ID(func, __bpf_trace_sys_exit) +BTF_ID(struct, trace_event_raw_sys_exit) #endif struct trace_event_class __refdata event_class_syscall_enter = { @@ -1321,7 +1327,7 @@ struct trace_event_class __refdata event_class_syscall_enter = { .get_fields = syscall_get_enter_fields, .raw_init = init_syscall_trace, #ifdef CONFIG_BPF_EVENTS - .btf_ids = __bpf_trace_btf_ids_sys_enter, + .btf_ids = syscall_enter_btf_ids, #endif }; @@ -1336,7 +1342,7 @@ struct trace_event_class __refdata event_class_syscall_exit = { .fields = LIST_HEAD_INIT(event_class_syscall_exit.fields), .raw_init = init_syscall_trace, #ifdef CONFIG_BPF_EVENTS - .btf_ids = __bpf_trace_btf_ids_sys_exit, + .btf_ids = syscall_exit_btf_ids, #endif }; --- base-commit: eadc0725ab8d38c05148fce49f8d5c6a0e01f062 change-id: 20260730-b4-fix_btf_tracefs-fdafda5fdb5b Best regards, -- Mykyta Yatsenko