bpf: btf: add btf print functionality
This consumes functionality exported in the previous patch. It does the main job of printing with BTF data. This is used in the following patch to provide a more readable output of a map's dump. It relies on json_writer to do json printing. Below is sample output where map keys are ints and values are of type struct A: typedef int int_type; enum E { E0, E1, }; struct B { int x; int y; }; struct A { int m; unsigned long long n; char o; int p[8]; int q[4][8]; enum E r; void *s; struct B t; const int u; int_type v; unsigned int w1: 3; unsigned int w2: 3; }; $ sudo bpftool map dump id 14 [{ "key": 0, "value": { "m": 1, "n": 2, "o": "c", "p": [15,16,17,18,15,16,17,18 ], "q": [[25,26,27,28,25,26,27,28 ],[35,36,37,38,35,36,37,38 ],[45,46,47,48,45,46,47,48 ],[55,56,57,58,55,56,57,58 ] ], "r": 1, "s": 0x7ffd80531cf8, "t": { "x": 5, "y": 10 }, "u": 100, "v": 20, "w1": 0x7, "w2": 0x3 } } ] This patch uses json's {} and [] to imply struct/union and array. More explicit information can be added later. For example, a command line option can be introduced to print whether a key or value is struct or union, name of a struct etc. This will however come at the expense of duplicating info when, for example, printing an array of structs. enums are printed as ints without their names. Signed-off-by: NOkash Khawaja <osk@fb.com> Acked-by: NMartin KaFai Lau <kafai@fb.com> Reviewed-by: NJakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
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tools/bpf/bpftool/btf_dumper.c
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