From: Menglong Dong Date: Sat, 24 Jan 2026 06:19:59 +0000 (+0800) Subject: bpf: support fsession for bpf_session_is_return X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=27d89baa6da8e5e546585c53a959176d1302d46e;p=thirdparty%2Flinux.git bpf: support fsession for bpf_session_is_return If fsession exists, we will use the bit (1 << BPF_TRAMP_IS_RETURN_SHIFT) in ((u64 *)ctx)[-1] to store the "is_return" flag. The logic of bpf_session_is_return() for fsession is implemented in the verifier by inline following code: bool bpf_session_is_return(void *ctx) { return (((u64 *)ctx)[-1] >> BPF_TRAMP_IS_RETURN_SHIFT) & 1; } Signed-off-by: Menglong Dong Co-developed-by: Leon Hwang Signed-off-by: Leon Hwang Link: https://lore.kernel.org/r/20260124062008.8657-5-dongml2@chinatelecom.cn Signed-off-by: Alexei Starovoitov --- diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 41228b0add52e..29eecd79352e9 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1229,6 +1229,8 @@ enum { #endif }; +#define BPF_TRAMP_IS_RETURN_SHIFT 63 + struct bpf_tramp_links { struct bpf_tramp_link *links[BPF_MAX_TRAMP_LINKS]; int nr_links; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0fa73d56cb8ba..d04aea235a128 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -23011,6 +23011,19 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, desc->func_id == special_kfunc_list[KF_bpf_rdonly_cast]) { insn_buf[0] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1); *cnt = 1; + } else if (desc->func_id == special_kfunc_list[KF_bpf_session_is_return] && + env->prog->expected_attach_type == BPF_TRACE_FSESSION) { + /* + * inline the bpf_session_is_return() for fsession: + * bool bpf_session_is_return(void *ctx) + * { + * return (((u64 *)ctx)[-1] >> BPF_TRAMP_IS_RETURN_SHIFT) & 1; + * } + */ + insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8); + insn_buf[1] = BPF_ALU64_IMM(BPF_RSH, BPF_REG_0, BPF_TRAMP_IS_RETURN_SHIFT); + insn_buf[2] = BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 1); + *cnt = 3; } if (env->insn_aux_data[insn_idx].arg_prog) { diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 13f0a2de33b72..f7baeb8278cac 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1286,7 +1286,8 @@ static bool is_kprobe_multi(const struct bpf_prog *prog) static inline bool is_kprobe_session(const struct bpf_prog *prog) { - return prog->expected_attach_type == BPF_TRACE_KPROBE_SESSION; + return prog->type == BPF_PROG_TYPE_KPROBE && + prog->expected_attach_type == BPF_TRACE_KPROBE_SESSION; } static inline bool is_uprobe_multi(const struct bpf_prog *prog) @@ -1297,7 +1298,14 @@ static inline bool is_uprobe_multi(const struct bpf_prog *prog) static inline bool is_uprobe_session(const struct bpf_prog *prog) { - return prog->expected_attach_type == BPF_TRACE_UPROBE_SESSION; + return prog->type == BPF_PROG_TYPE_KPROBE && + prog->expected_attach_type == BPF_TRACE_UPROBE_SESSION; +} + +static inline bool is_trace_fsession(const struct bpf_prog *prog) +{ + return prog->type == BPF_PROG_TYPE_TRACING && + prog->expected_attach_type == BPF_TRACE_FSESSION; } static const struct bpf_func_proto * @@ -3341,34 +3349,39 @@ __bpf_kfunc __u64 *bpf_session_cookie(void *ctx) __bpf_kfunc_end_defs(); -BTF_KFUNCS_START(kprobe_multi_kfunc_set_ids) +BTF_KFUNCS_START(session_kfunc_set_ids) BTF_ID_FLAGS(func, bpf_session_is_return) BTF_ID_FLAGS(func, bpf_session_cookie) -BTF_KFUNCS_END(kprobe_multi_kfunc_set_ids) +BTF_KFUNCS_END(session_kfunc_set_ids) -static int bpf_kprobe_multi_filter(const struct bpf_prog *prog, u32 kfunc_id) +static int bpf_session_filter(const struct bpf_prog *prog, u32 kfunc_id) { - if (!btf_id_set8_contains(&kprobe_multi_kfunc_set_ids, kfunc_id)) + if (!btf_id_set8_contains(&session_kfunc_set_ids, kfunc_id)) return 0; - if (!is_kprobe_session(prog) && !is_uprobe_session(prog)) + if (!is_kprobe_session(prog) && !is_uprobe_session(prog) && !is_trace_fsession(prog)) return -EACCES; return 0; } -static const struct btf_kfunc_id_set bpf_kprobe_multi_kfunc_set = { +static const struct btf_kfunc_id_set bpf_session_kfunc_set = { .owner = THIS_MODULE, - .set = &kprobe_multi_kfunc_set_ids, - .filter = bpf_kprobe_multi_filter, + .set = &session_kfunc_set_ids, + .filter = bpf_session_filter, }; -static int __init bpf_kprobe_multi_kfuncs_init(void) +static int __init bpf_trace_kfuncs_init(void) { - return register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_kprobe_multi_kfunc_set); + int err = 0; + + err = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_session_kfunc_set); + err = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_session_kfunc_set); + + return err; } -late_initcall(bpf_kprobe_multi_kfuncs_init); +late_initcall(bpf_trace_kfuncs_init); typedef int (*copy_fn_t)(void *dst, const void *src, u32 size, struct task_struct *tsk);