Add the kfunc bpf_fsession_cookie(), which is similar to bpf_session_cookie() and return the address of the session cookie. The address of the session cookie is stored after session flags, which means ctx[nr_args + 2].
Inline this kfunc in the verifier too. Signed-off-by: Menglong Dong <[email protected]> --- include/linux/bpf.h | 1 + kernel/bpf/verifier.c | 20 ++++++++++++++++++-- kernel/trace/bpf_trace.c | 10 ++++++++++ 3 files changed, 29 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 3f6cad5df2db..83d5d4d3120d 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1735,6 +1735,7 @@ struct bpf_prog { enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */ call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */ call_get_func_ip:1, /* Do we call get_func_ip() */ + call_session_cookie:1, /* Do we call bpf_fsession_cookie() */ tstamp_type_access:1, /* Accessed __sk_buff->tstamp_type */ sleepable:1; /* BPF program is sleepable */ enum bpf_prog_type type; /* Type of BPF program */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a4d0dd4440fd..ab46e5fbc7a6 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12294,6 +12294,7 @@ enum special_kfunc_type { KF_bpf_task_work_schedule_signal, KF_bpf_task_work_schedule_resume, KF_bpf_tracing_is_exit, + KF_bpf_fsession_cookie, }; BTF_ID_LIST(special_kfunc_list) @@ -12367,6 +12368,7 @@ BTF_ID(func, __bpf_trap) BTF_ID(func, bpf_task_work_schedule_signal) BTF_ID(func, bpf_task_work_schedule_resume) BTF_ID(func, bpf_tracing_is_exit) +BTF_ID(func, bpf_fsession_cookie) static bool is_task_work_add_kfunc(u32 func_id) { @@ -12422,7 +12424,8 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, bool arg_mem_size = false; if (meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] || - meta->func_id == special_kfunc_list[KF_bpf_tracing_is_exit]) + meta->func_id == special_kfunc_list[KF_bpf_tracing_is_exit] || + meta->func_id == special_kfunc_list[KF_bpf_fsession_cookie]) return KF_ARG_PTR_TO_CTX; /* In this function, we verify the kfunc's BTF as per the argument type, @@ -13915,7 +13918,8 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, } } - if (meta.func_id == special_kfunc_list[KF_bpf_session_cookie]) { + if (meta.func_id == special_kfunc_list[KF_bpf_session_cookie] || + meta.func_id == special_kfunc_list[KF_bpf_fsession_cookie]) { meta.r0_size = sizeof(u64); meta.r0_rdonly = false; } @@ -14196,6 +14200,9 @@ 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_fsession_cookie]) + env->prog->call_session_cookie = true; + return 0; } @@ -22007,6 +22014,15 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, insn_buf[4] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0); insn_buf[5] = BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 1); *cnt = 6; + } else if (desc->func_id == special_kfunc_list[KF_bpf_fsession_cookie]) { + /* Load nr_args from ctx - 8 */ + insn_buf[0] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, -8); + /* add rax, 2 */ + insn_buf[1] = BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 2); + insn_buf[2] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_0, 3); + insn_buf[3] = BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1); + insn_buf[4] = BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0); + *cnt = 5; } if (env->insn_aux_data[insn_idx].arg_prog) { diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index d0720d850621..4a8568bd654d 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -3370,10 +3370,20 @@ __bpf_kfunc bool bpf_tracing_is_exit(void *ctx) return ((u64 *)ctx)[nr_args + 1] & 1; } +__bpf_kfunc u64 *bpf_fsession_cookie(void *ctx) +{ + /* This helper call is inlined by verifier. */ + u64 nr_args = ((u64 *)ctx)[-1]; + + /* ctx[nr_args + 2] is the session cookie address */ + return (u64 *)((u64 *)ctx)[nr_args + 2]; +} + __bpf_kfunc_end_defs(); BTF_KFUNCS_START(tracing_kfunc_set_ids) BTF_ID_FLAGS(func, bpf_tracing_is_exit, KF_FASTCALL) +BTF_ID_FLAGS(func, bpf_fsession_cookie, KF_FASTCALL) BTF_KFUNCS_END(tracing_kfunc_set_ids) static int bpf_tracing_filter(const struct bpf_prog *prog, u32 kfunc_id) -- 2.51.1.dirty
