diff options
| author | Yonghong Song <yhs@fb.com> | 2022-11-20 11:54:32 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-11-20 15:43:37 -0800 |
| commit | fd264ca020948a743e4c36731dfdecc4a812153c (patch) | |
| tree | 9a615b76021a3dcebdd178438bab629077e14962 /kernel/bpf/verifier.c | |
| parent | cfe1456440c8feaf6558577a400745d774418379 (diff) | |
bpf: Add a kfunc to type cast from bpf uapi ctx to kernel ctx
Implement bpf_cast_to_kern_ctx() kfunc which does a type cast
of a uapi ctx object to the corresponding kernel ctx. Previously
if users want to access some data available in kctx but not
in uapi ctx, bpf_probe_read_kernel() helper is needed.
The introduction of bpf_cast_to_kern_ctx() allows direct
memory access which makes code simpler and easier to understand.
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221120195432.3113982-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/verifier.c')
| -rw-r--r-- | kernel/bpf/verifier.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index eb090af35477..d63cc0fb0a9c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7907,6 +7907,7 @@ struct bpf_kfunc_call_arg_meta { u32 ref_obj_id; u8 release_regno; bool r0_rdonly; + u32 ret_btf_id; u64 r0_size; struct { u64 value; @@ -8151,6 +8152,7 @@ enum special_kfunc_type { KF_bpf_list_push_back, KF_bpf_list_pop_front, KF_bpf_list_pop_back, + KF_bpf_cast_to_kern_ctx, }; BTF_SET_START(special_kfunc_set) @@ -8160,6 +8162,7 @@ BTF_ID(func, bpf_list_push_front) BTF_ID(func, bpf_list_push_back) BTF_ID(func, bpf_list_pop_front) BTF_ID(func, bpf_list_pop_back) +BTF_ID(func, bpf_cast_to_kern_ctx) BTF_SET_END(special_kfunc_set) BTF_ID_LIST(special_kfunc_list) @@ -8169,6 +8172,7 @@ BTF_ID(func, bpf_list_push_front) BTF_ID(func, bpf_list_push_back) BTF_ID(func, bpf_list_pop_front) BTF_ID(func, bpf_list_pop_back) +BTF_ID(func, bpf_cast_to_kern_ctx) static enum kfunc_ptr_arg_type get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, @@ -8182,6 +8186,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, struct bpf_reg_state *reg = ®s[regno]; bool arg_mem_size = false; + if (meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) + return KF_ARG_PTR_TO_CTX; + /* In this function, we verify the kfunc's BTF as per the argument type, * leaving the rest of the verification with respect to the register * type to our caller. When a set of conditions hold in the BTF type of @@ -8668,6 +8675,13 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ verbose(env, "arg#%d expected pointer to ctx, but got %s\n", i, btf_type_str(t)); return -EINVAL; } + + if (meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) { + ret = get_kern_ctx_btf_id(&env->log, resolve_prog_type(env->prog)); + if (ret < 0) + return -EINVAL; + meta->ret_btf_id = ret; + } break; case KF_ARG_PTR_TO_ALLOC_BTF_ID: if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) { @@ -8922,6 +8936,11 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, regs[BPF_REG_0].btf = field->list_head.btf; regs[BPF_REG_0].btf_id = field->list_head.value_btf_id; regs[BPF_REG_0].off = field->list_head.node_offset; + } else if (meta.func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) { + mark_reg_known_zero(env, regs, BPF_REG_0); + regs[BPF_REG_0].type = PTR_TO_BTF_ID | PTR_TRUSTED; + regs[BPF_REG_0].btf = desc_btf; + regs[BPF_REG_0].btf_id = meta.ret_btf_id; } else { verbose(env, "kernel function %s unhandled dynamic return type\n", meta.func_name); @@ -15175,6 +15194,9 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, insn_buf[1] = addr[1]; insn_buf[2] = *insn; *cnt = 3; + } else if (desc->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) { + insn_buf[0] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1); + *cnt = 1; } return 0; } |