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* [PATCH bpf-next 0/3] API to access btf_dump emit queue and print single type
@ 2024-05-16 23:04 Eduard Zingerman
  2024-05-16 23:04 ` [PATCH bpf-next 1/3] libbpf: put forward declarations to btf_dump->emit_queue Eduard Zingerman
                   ` (3 more replies)
  0 siblings, 4 replies; 6+ messages in thread
From: Eduard Zingerman @ 2024-05-16 23:04 UTC (permalink / raw)
  To: bpf, ast
  Cc: andrii, daniel, martin.lau, kernel-team, yonghong.song,
	jose.marchesi, alan.maguire, Eduard Zingerman

This is a follow-up to the following discussion:
https://lore.kernel.org/bpf/20240503111836.25275-1-jose.marchesi@oracle.com/

As suggested by Andrii, this series adds several API functions to
allow more flexibility with btf dump:
- a function to add a type and all its dependencies to the emit queue;
- functions to provide access to the emit queue owned by btf_dump object;
- a function to print a given type (skipping any dependencies).

This should allow filtering printed types and also adding
attributes / pre-processor statements to specific types.

There are several ways to add such API:
1. The simplest in terms of code changes is to refactor
   btf_dump_emit_type() to push types and forward declarations
   to the emit queue, instead of printing those directly;
2. More intrusive: refactor btf_dump_emit_type() and
   btf_dump_order_type() to avoid doing topological sorting twice and
   put forward declarations to the emit queue at once.

This series opts for (2) as it seems to simplify library code a bit.
For the sake of discussion, source code for option (1) as available at:
https://github.com/eddyz87/bpf/tree/libbpf-sort-for-dump-api-simple

Also, this series opts for the following new API function:

  int btf_dump__dump_one_type(struct btf_dump *d, __u32 id, bool fwd);

As adding _opts variant of btf_dump__dump_type seems a bit clumsy:

  struct btf_dump_opts {
	size_t sz;
	bool fwd;
	bool skip_dependencies;
	bool skip_last_semi;
  };

  int btf_dump__dump_type_opts(struct btf_dump *d, __u32 id,
			       struct btf_dump_opts *opts);

but maybe community would prefer the later variant.

Eduard Zingerman (3):
  libbpf: put forward declarations to btf_dump->emit_queue
  libbpf: API to access btf_dump emit queue and print single type
  selftests/bpf: tests for btf_dump emit queue API

 tools/lib/bpf/btf.h                           |  33 ++
 tools/lib/bpf/btf_dump.c                      | 363 ++++++++----------
 tools/lib/bpf/libbpf.map                      |   4 +
 .../selftests/bpf/prog_tests/btf_dump.c       |  86 +++++
 4 files changed, 289 insertions(+), 197 deletions(-)

-- 
2.34.1


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2024-05-16 23:04 [PATCH bpf-next 0/3] API to access btf_dump emit queue and print single type Eduard Zingerman
2024-05-16 23:04 ` [PATCH bpf-next 1/3] libbpf: put forward declarations to btf_dump->emit_queue Eduard Zingerman
2024-05-16 23:04 ` [PATCH bpf-next 2/3] libbpf: API to access btf_dump emit queue and print single type Eduard Zingerman
2024-05-16 23:04 ` [PATCH bpf-next 3/3] selftests/bpf: tests for btf_dump emit queue API Eduard Zingerman
2024-05-17  0:02 ` [PATCH bpf-next 0/3] API to access btf_dump emit queue and print single type Eduard Zingerman
2024-05-17  2:03   ` Eduard Zingerman

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