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Mon, 13 May 2024 14:39:16 -0400 (EDT) From: Daniel Xu To: ast@kernel.org, daniel@iogearbox.net, qmo@kernel.org, andrii@kernel.org, olsajiri@gmail.com, quentin@isovalent.com, alan.maguire@oracle.com, acme@kernel.org, eddyz87@gmail.com Cc: martin.lau@linux.dev, 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, kernel-team@meta.com Subject: [PATCH bpf-next v3 2/2] bpftool: Support dumping kfunc prototypes from BTF Date: Mon, 13 May 2024 12:38:59 -0600 Message-ID: <6b16417c2c05019e83e420240c6d9796f9324a6c.1715625447.git.dxu@dxuuu.xyz> X-Mailer: git-send-email 2.44.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net 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 optionally 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) __weak __ksym; extern void cgroup_rstat_flush(struct cgroup *cgrp) __weak __ksym; extern struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags) __weak __ksym; Signed-off-by: Daniel Xu --- tools/bpf/bpftool/btf.c | 54 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index 91fcb75babe3..884af6589f0d 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 +456,48 @@ static int dump_btf_raw(const struct btf *btf, return 0; } +static int dump_btf_kfuncs(struct btf_dump *d, const struct btf *btf) +{ + LIBBPF_OPTS(btf_dump_emit_type_decl_opts, opts); + int cnt = btf__type_cnt(btf); + int i; + + printf("\n/* BPF kfuncs */\n"); + + for (i = 1; i < cnt; i++) { + const struct btf_type *t = btf__type_by_id(btf, i); + const char *name; + int err; + + if (!btf_is_decl_tag(t)) + continue; + + if (btf_decl_tag(t)->component_idx != -1) + continue; + + name = btf__name_by_offset(btf, t->name_off); + if (strncmp(name, KFUNC_DECL_TAG, sizeof(KFUNC_DECL_TAG))) + continue; + + t = btf__type_by_id(btf, t->type); + if (!btf_is_func(t)) + continue; + + printf("extern "); + + opts.field_name = btf__name_by_offset(btf, t->name_off); + err = btf_dump__emit_type_decl(d, t->type, &opts); + if (err) + return err; + + printf(" __weak __ksym;\n"); + } + + printf("\n"); + + return 0; +} + static void __printf(2, 0) btf_dump_printf(void *ctx, const char *fmt, va_list args) { @@ -476,6 +520,12 @@ 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"); + printf("#ifndef __weak\n"); + printf("#define __weak __attribute__((weak))\n"); + printf("#endif\n\n"); if (root_type_cnt) { for (i = 0; i < root_type_cnt; i++) { @@ -491,6 +541,10 @@ static int dump_btf_c(const struct btf *btf, if (err) goto done; } + + err = dump_btf_kfuncs(d, btf); + if (err) + goto done; } printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");