From eeee4239dbb155a98f8ba737324ac081acde8417 Mon Sep 17 00:00:00 2001 From: Menglong Dong Date: Sat, 24 Jan 2026 14:20:00 +0800 Subject: bpf: support fsession for bpf_session_cookie Implement session cookie for fsession. The session cookies will be stored in the stack, and the layout of the stack will look like this: return value -> 8 bytes argN -> 8 bytes ... arg1 -> 8 bytes nr_args -> 8 bytes ip (optional) -> 8 bytes cookie2 -> 8 bytes cookie1 -> 8 bytes The offset of the cookie for the current bpf program, which is in 8-byte units, is stored in the "(((u64 *)ctx)[-1] >> BPF_TRAMP_COOKIE_INDEX_SHIFT) & 0xFF". Therefore, we can get the session cookie with ((u64 *)ctx)[-offset]. Implement and inline the bpf_session_cookie() for the fsession in the verifier. Signed-off-by: Menglong Dong Link: https://lore.kernel.org/r/20260124062008.8657-6-dongml2@chinatelecom.cn Signed-off-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'kernel') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d04aea235a12..c2f2650db9fd 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -14406,6 +14406,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, return err; } + if (meta.func_id == special_kfunc_list[KF_bpf_session_cookie]) + env->prog->call_session_cookie = true; + return 0; } @@ -23024,6 +23027,23 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, 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; + } else if (desc->func_id == special_kfunc_list[KF_bpf_session_cookie] && + env->prog->expected_attach_type == BPF_TRACE_FSESSION) { + /* + * inline bpf_session_cookie() for fsession: + * __u64 *bpf_session_cookie(void *ctx) + * { + * u64 off = (((u64 *)ctx)[-1] >> BPF_TRAMP_COOKIE_INDEX_SHIFT) & 0xFF; + * return &((u64 *)ctx)[-off]; + * } + */ + 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_COOKIE_INDEX_SHIFT); + insn_buf[2] = BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xFF); + insn_buf[3] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_0, 3); + insn_buf[4] = BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1); + insn_buf[5] = BPF_ALU64_IMM(BPF_NEG, BPF_REG_0, 0); + *cnt = 6; } if (env->insn_aux_data[insn_idx].arg_prog) { -- cgit v1.2.3