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acme@kernel.org Red Hat Montreal, 2025 http://vger.kernel.org/~acme/prez/lsfmm-bpf-2025/ |
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root@number:/home/acme/git/pahole# tests/tests 1: Validation of BTF encoding of functions; this may take some time: Ok 2: Default BTF on a system without BTF: Ok 3: Flexible arrays accounting: Ok 4: Check that pfunct can print btf_decl_tags read from BTF: Ok 5: Pretty printing of files using DWARF type information: Ok 6: Parallel reproducible DWARF Loading/Serial BTF encoding: Ok /home/acme/git/pahole root@number:/home/acme/git/pahole#
$ pahole --running_kernel_vmlinux /usr/lib/debug/lib/modules/6.13.6-100.fc40.x86_64/vmlinux
$ perf buildid-list -k db7ce41bc9c6bdd99d5ff9508e161e3e1e078b42
$ file /usr/lib/debug/lib/modules/6.13.6-100.fc40.x86_64/vmlinux /usr/lib/debug/lib/modules/6.13.6-100.fc40.x86_64/vmlinux: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, BuildID[sha1]=db7ce41bc9c6bdd99d5ff9508e161e3e1e078b42, with debug_info, not stripped $
$ pahole --sizes --with_embedded_flexible_array | wc -l 100
$ pahole tty_bufhead
struct tty_bufhead {
struct tty_buffer * head; /* 0 8 */
struct work_struct work; /* 8 32 */
struct mutex lock; /* 40 32 */
/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
atomic_t priority; /* 72 4 */
/* XXX 4 bytes hole, try to pack */
struct tty_buffer sentinel; /* 80 32 */
/* XXX last struct has a flexible array, 1 hole */
struct llist_head free; /* 112 8 */
atomic_t mem_used; /* 120 4 */
int mem_limit; /* 124 4 */
/* --- cacheline 2 boundary (128 bytes) --- */
struct tty_buffer * tail; /* 128 8 */
/* size: 136, cachelines: 3, members: 9 */
/* sum members: 132, holes: 1, sum holes: 4 */
/* member types with holes: 1, total: 1 */
/* flexible array members: end: 1 */
/* last cacheline: 8 bytes */
};
$ pahole tty_buffer
struct tty_buffer {
union {
struct tty_buffer * next; /* 0 8 */
struct llist_node free; /* 0 8 */
}; /* 0 8 */
unsigned int used; /* 8 4 */
unsigned int size; /* 12 4 */
unsigned int commit; /* 16 4 */
unsigned int lookahead; /* 20 4 */
unsigned int read; /* 24 4 */
bool flags; /* 28 1 */
/* XXX 3 bytes hole, try to pack */
u8 data[]; /* 32 0 */
/* size: 32, cachelines: 1, members: 8 */
/* sum members: 29, holes: 1, sum holes: 3 */
/* last cacheline: 32 bytes */
};
[acme@toolbox clang+thinlto+rust]$ pahole --verbose \ --btf_encode_detached=tmp_vmlinux1.btf \ --lang_exclude=rust tmp_vmlinux1 <SNIP> Filtering CU /usr/lib/rustlib/src/rust/library/core/src/lib.rs/@/core.25793e9715209a7b-cgu.0 written in rust. Filtering CU rust/compiler_builtins.rs/@/compiler_builtins.6f57a5fc13101438-cgu.0 written in rust. Filtering CU /usr/lib/rustlib/src/rust/library/alloc/src/lib.rs/@/alloc.e373cb07bd07083a-cgu.0 written in rust. Filtering CU rust/bindings/lib.rs/@/bindings.e4a37ad9e428c652-cgu.0 written in rust. Filtering CU rust/kernel/lib.rs/@/kernel.f5c1c46b14036fc8-cgu.0 written in rust. Filtering CU rust/uapi/lib.rs/@/uapi.52e8b2f8205e89f-cgu.0 written in rust. <SNIP>
$ pahole --btf_encode_detached=/tmp/ax88796b_rust.ko.btf \ ../build/v6.14.0-rc7+/drivers/net/phy/ax88796b_rust.ko die__process_class: tag not supported 0x33 (variant_part) at <11e3e>!
$ bpftool btf dump file /tmp/ax88796b_rust.ko.btf
[16] STRUCT '{closure_env#0}<ax88796b_rust::Module>' size=8 vlen=1
'module' type_id=3081 bits_offset=0
[17] STRUCT 'InitClosure<kernel::{impl#0}::init::{closure_env#0<ax88796b_rust::Module>,
ax88796b_rust::Module, kernel::error::Error>' size=8 vlen=2
'__0' type_id=16 bits_offset=0
'__1' type_id=1682 bits_offset=64
$ pahole -F btf /tmp/ax88796b_rust.ko.btf
struct InitClosure<kernel::{impl#0}::init::{closure_env#0}<ax88796b_rust::Module>,
ax88796b_rust::Module, kernel::error::Error> {
struct {closure_env#0}<ax88796b_rust::Module> __0; /* 0 8 */
struct PhantomData<fn(*mut (kernel::error::Error, ax88796b_rust::Module)) ->
*mut (kernel::error::Error, ax88796b_rust::Module)> __1; /* 8 0 */
/* size: 8, cachelines: 1, members: 2 */
/* last cacheline: 8 bytes */
};
$ pfunct --prototype -F btf ../build/v6.13-rc2/vmlinux | grep bpf_kfunc | grep bpf_fastcall bpf_kfunc bpf_fastcall void * bpf_rdonly_cast(const void * obj__ign, u32 btf_id__k); bpf_kfunc bpf_fastcall void * bpf_cast_to_kern_ctx(void * obj); $
$ bpftool btf dump file /sys/kernel/btf/vmlinux | grep bpf_fastcall [148506] DECL_TAG 'bpf_fastcall' type_id=72111 component_idx=-1 [148508] DECL_TAG 'bpf_fastcall' type_id=73863 component_idx=-1
$ bpftool btf dump file /sys/kernel/btf/vmlinux | grep -w 72111 [72111] FUNC 'bpf_cast_to_kern_ctx' type_id=72110 linkage=static [148505] DECL_TAG 'bpf_kfunc' type_id=72111 component_idx=-1 [148506] DECL_TAG 'bpf_fastcall' type_id=72111 component_idx=-1
$ readelf -wi vmlinux | head -20 | grep DW_AT_comp_dir
<17> DW_AT_comp_dir : (indirect line string, offset: 0x21): /home/acme/git/build/v6.14-rc7+
$ pahole -j --btf_encode_detached=no_global_vars vmlinux $ stat -c "%s" no_global_vars 6115636
$ pahole -j --btf_encode_detached=global_vars --btf_features=+global_var vmlinux $ stat -c "%s" global_vars 8249077 $ echo $(((8249077 - 6115636) / 1024)) Kb 2083 Kb
$ bpftool btf dump file no_global_vars | grep -w VAR | wc -l 822
$ bpftool btf dump file global_vars | grep -w VAR | wc -l 76472
$ bpftool btf dump file no_global_vars | grep -w VAR | head -5 [3038] VAR 'kstack_offset' type_id=35, linkage=global [4135] VAR 'cpu_loops_per_jiffy' type_id=1, linkage=static [4436] VAR 'runtime_data' type_id=4391, linkage=static [4437] VAR 'sev_vmsa' type_id=4392, linkage=static [4438] VAR 'svsm_caa' type_id=4304, linkage=static
$ bpftool btf dump file global_vars | grep -w VAR | head -5 [3038] VAR '__tracepoint_initcall_level' type_id=658, linkage=global [3039] VAR '__SCK__tp_func_initcall_level' type_id=331, linkage=global [3040] VAR '__tracepoint_initcall_start' type_id=658, linkage=global [3041] VAR '__SCK__tp_func_initcall_start' type_id=331, linkage=global [3042] VAR '__tracepoint_initcall_finish' type_id=658, linkage=global
$ bpftool btf dump file global_vars | grep -w VAR | grep trace_event | wc -l 3016
$ bpftool btf dump file global_vars | grep -w VAR | grep tracepoint | wc -l 2470
$ pglobal -v -F btf global_vars | grep static_call_key | head -5 struct static_call_key __SCK____perf_guest_get_ip;; /* 0 */ struct static_call_key __SCK____perf_guest_handle_intel_pt_intr;; /* 0 */ struct static_call_key __SCK____perf_guest_state;; /* 0 */ struct static_call_key __SCK__aesni_ctr_enc_tfm;; /* 0 */ struct static_call_key __SCK__amd_pmu_branch_add;; /* 0 */
$ pglobal -v -F btf global_vars | grep static_call_key | wc -l 1143 $