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Sun, 28 Jan 2024 20:35:38 -0500 (EST) From: Daniel Xu To: quentin@isovalent.com, daniel@iogearbox.net, ast@kernel.org, andrii@kernel.org, alexei.starovoitov@gmail.com, olsajiri@gmail.com, alan.maguire@oracle.com, memxor@gmail.com Cc: martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next] bpftool: Support dumping kfunc prototypes from BTF Date: Sun, 28 Jan 2024 18:35:33 -0700 Message-ID: <373d86f4c26c0ebf5046b6627c8988fa75ea7a1d.1706492080.git.dxu@dxuuu.xyz> X-Mailer: git-send-email 2.42.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1789386726392030218 X-GMAIL-MSGID: 1789386726392030218 This patch enables dumping kfunc prototypes from bpftool. This is useful b/c with this patch, end users will no longer have to manually define kfunc prototypes. For the kernel tree, this also means we can drop kfunc prototypes from: tools/testing/selftests/bpf/bpf_kfuncs.h tools/testing/selftests/bpf/bpf_experimental.h Example usage: $ make PAHOLE=/home/dxu/dev/pahole/build/pahole -j30 vmlinux $ ./tools/bpf/bpftool/bpftool btf dump file ./vmlinux format c | rg "__ksym;" | head -3 extern void cgroup_rstat_updated(struct cgroup * cgrp, int cpu) __ksym; extern void cgroup_rstat_flush(struct cgroup * cgrp) __ksym; extern struct bpf_key * bpf_lookup_user_key(u32 serial, u64 flags) __ksym; Note that this patch is only effective after enabling pahole [0] and kernel [1] changes are merged. [0]: https://lore.kernel.org/bpf/0f25134ec999e368478c4ca993b3b729c2a03383.1706491733.git.dxu@dxuuu.xyz/ [1]: https://lore.kernel.org/bpf/cover.1706491398.git.dxu@dxuuu.xyz/ Signed-off-by: Daniel Xu --- tools/bpf/bpftool/btf.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index 91fcb75babe3..9ab26ed12733 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -20,6 +20,8 @@ #include "json_writer.h" #include "main.h" +#define KFUNC_DECL_TAG "bpf_kfunc" + static const char * const btf_kind_str[NR_BTF_KINDS] = { [BTF_KIND_UNKN] = "UNKNOWN", [BTF_KIND_INT] = "INT", @@ -454,6 +456,28 @@ static int dump_btf_raw(const struct btf *btf, return 0; } +static void dump_btf_kfuncs(const struct btf *btf) +{ + int cnt = btf__type_cnt(btf); + int i; + + for (i = 1; i < cnt; i++) { + const struct btf_type *t = btf__type_by_id(btf, i); + char kfunc_sig[1024]; + const char *name; + + if (!btf_is_decl_tag(t)) + continue; + + name = btf__name_by_offset(btf, t->name_off); + if (strncmp(name, KFUNC_DECL_TAG, sizeof(KFUNC_DECL_TAG))) + continue; + + btf_dumper_type_only(btf, t->type, kfunc_sig, sizeof(kfunc_sig)); + printf("extern %s __ksym;\n\n", kfunc_sig); + } +} + static void __printf(2, 0) btf_dump_printf(void *ctx, const char *fmt, va_list args) { @@ -476,6 +500,9 @@ static int dump_btf_c(const struct btf *btf, printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n"); printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n"); printf("#endif\n\n"); + printf("#ifndef __ksym\n"); + printf("#define __ksym __attribute__((section(\".ksyms\")))\n"); + printf("#endif\n\n"); if (root_type_cnt) { for (i = 0; i < root_type_cnt; i++) { @@ -491,6 +518,8 @@ static int dump_btf_c(const struct btf *btf, if (err) goto done; } + + dump_btf_kfuncs(btf); } printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");