bianbu-repo-mirror/bianbu-linux-6.6
1
0
Fork 0
mirror of https://gitee.com/bianbu-linux/linux-6.6 synced 2025-04-24 14:07:52 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

libbpf: Add BPF_CORE_READ/BPF_CORE_READ_INTO helpers

Browse source 
Add few macros simplifying BCC-like multi-level probe reads, while also
emitting CO-RE relocations for each read.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20191008175942.1769476-7-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2019-10-08 10:59:41 -07:00 • committed by Daniel Borkmann
parent e01a75c159
commit 7db3822ab9
12 changed files with 187 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

32
tools/lib/bpf/bpf_helpers.h
View file

@ -7,7 +7,7 @@
#define __uint(name, val) int (*name)[val]
#define __type(name, val) typeof(val) *name
/* helper macro to print out debug messages */
/* Helper macro to print out debug messages */
#define bpf_printk(fmt, ...) \
({ \
char ____fmt[] = fmt; \
@ -15,13 +15,19 @@
##__VA_ARGS__); \
})
/* helper macro to place programs, maps, license in
/*
* Helper macro to place programs, maps, license in
* different sections in elf_bpf file. Section names
* are interpreted by elf_bpf loader
*/
#define SEC(NAME) __attribute__((section(NAME), used))
/* a helper structure used by eBPF C program
#ifndef __always_inline
#define __always_inline __attribute__((always_inline))
#endif
/*
* Helper structure used by eBPF C program
* to describe BPF map attributes to libbpf loader
*/
struct bpf_map_def {
@ -32,24 +38,4 @@ struct bpf_map_def {
unsigned int map_flags;
};
/*
* bpf_core_read() abstracts away bpf_probe_read() call and captures offset
* relocation for source address using __builtin_preserve_access_index()
* built-in, provided by Clang.
*
* __builtin_preserve_access_index() takes as an argument an expression of
* taking an address of a field within struct/union. It makes compiler emit
* a relocation, which records BTF type ID describing root struct/union and an
* accessor string which describes exact embedded field that was used to take
* an address. See detailed description of this relocation format and
* semantics in comments to struct bpf_offset_reloc in libbpf_internal.h.
*
* This relocation allows libbpf to adjust BPF instruction to use correct
* actual field offset, based on target kernel BTF type that matches original
* (local) BTF, used to record relocation.
*/
#define bpf_core_read(dst, sz, src) \
bpf_probe_read(dst, sz, \
(const void *)__builtin_preserve_access_index(src))
#endif