Hi All, Looks like pahole fails to deduplicate BTF when kernel and kernel module are built with gcc-14. I see this issue with various kernel .config-s on bpf and bpf-next trees. I tried pahole 1.28 and the latest master. Same issues. BTF in bpf_testmod.ko built with gcc-14 has 2849 types. When built with gcc-13 it has 454 types. So something is confusing dedup logic. Would be great if dedup experts can take a look, since this dedup issue is breaking a lot of selftests/bpf. Also vmlinux.h generated out of the kernel compiled with gcc-13 and out of the kernel compiled with gcc-14 shows these differences: --- vmlinux13.h 2025-04-24 21:33:50.556884372 -0700 +++ vmlinux14.h 2025-04-24 21:39:10.310488992 -0700 @@ -148815,7 +148815,6 @@ extern int hid_bpf_input_report(struct hid_bpf_ctx *ctx, enum hid_report_type type, u8 *buf, const size_t buf__sz) __weak __ksym; extern void hid_bpf_release_context(struct hid_bpf_ctx *ctx) __weak __ksym; extern int hid_bpf_try_input_report(struct hid_bpf_ctx *ctx, enum hid_report_type type, u8 *buf, const size_t buf__sz) __weak __ksym; -extern bool scx_bpf_consume(u64 dsq_id) __weak __ksym; extern int scx_bpf_cpu_node(s32 cpu) __weak __ksym; extern struct rq *scx_bpf_cpu_rq(s32 cpu) __weak __ksym; extern u32 scx_bpf_cpuperf_cap(s32 cpu) __weak __ksym; @@ -148825,12 +148824,8 @@ extern void scx_bpf_destroy_dsq(u64 dsq_id) __weak __ksym; extern void scx_bpf_dispatch(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __weak __ksym; extern void scx_bpf_dispatch_cancel(void) __weak __ksym; -extern bool scx_bpf_dispatch_from_dsq(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __weak __ksym; -extern void scx_bpf_dispatch_from_dsq_set_slice(struct bpf_iter_scx_dsq *it__iter, u64 slice) __weak __ksym; extern void scx_bpf_dispatch_from_dsq_set_vtime(struct bpf_iter_scx_dsq *it__iter, u64 vtime) __weak __ksym; extern u32 scx_bpf_dispatch_nr_slots(void) __weak __ksym; -extern void scx_bpf_dispatch_vtime(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime, u64 enq_flags) __weak __ksym; -extern bool scx_bpf_dispatch_vtime_from_dsq(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __weak __ksym; extern void scx_bpf_dsq_insert(struct task_struct *p, u64 dsq_id, u64 slice, u64 enq_flags) __weak __ksym; extern void scx_bpf_dsq_insert_vtime(struct task_struct *p, u64 dsq_id, u64 slice, u64 vtime, u64 enq_flags) __weak __ksym; extern bool scx_bpf_dsq_move(struct bpf_iter_scx_dsq *it__iter, struct task_struct *p, u64 dsq_id, u64 enq_flags) __weak __ksym; gcc-14's kernel is clearly wrong. These 5 kfuncs still exist in the kernel. I manually checked there is no if __GNUC__ > 13 in the code. Also: nm bld/vmlinux|grep -w scx_bpf_consume ffffffff8159d4b0 T scx_bpf_consume ffffffff8120ea81 t scx_bpf_consume.cold I suspect the second issue is not related to the dedup problem. All 5 missing kfuncs have ".cold" optimized bodies. But ".cold" maybe a red herring, since nm bld/vmlinux|grep -w scx_bpf_dispatch ffffffff8159d020 T scx_bpf_dispatch ffffffff8120ea0f t scx_bpf_dispatch.cold but this kfunc is present in vmlinux14.h If it makes a difference I have these configs: # CONFIG_DEBUG_INFO_DWARF4 is not set # CONFIG_DEBUG_INFO_DWARF5 is not set # CONFIG_DEBUG_INFO_REDUCED is not set CONFIG_DEBUG_INFO_COMPRESSED_NONE=y # CONFIG_DEBUG_INFO_COMPRESSED_ZLIB is not set # CONFIG_DEBUG_INFO_SPLIT is not set CONFIG_DEBUG_INFO_BTF=y CONFIG_PAHOLE_HAS_SPLIT_BTF=y CONFIG_DEBUG_INFO_BTF_MODULES=y
