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bpf: Add bpf_skc_to_tcp6_sock() helper

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The helper is used in tracing programs to cast a socket
pointer to a tcp6_sock pointer.
The return value could be NULL if the casting is illegal.

A new helper return type RET_PTR_TO_BTF_ID_OR_NULL is added
so the verifier is able to deduce proper return types for the helper.

Different from the previous BTF_ID based helpers,
the bpf_skc_to_tcp6_sock() argument can be several possible
btf_ids. More specifically, all possible socket data structures
with sock_common appearing in the first in the memory layout.
This patch only added socket types related to tcp and udp.

All possible argument btf_id and return value btf_id
for helper bpf_skc_to_tcp6_sock() are pre-calculcated and
cached. In the future, it is even possible to precompute
these btf_id's at kernel build time.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200623230809.3988195-1-yhs@fb.com
This commit is contained in:
Yonghong Song
2020-06-23 16:08:09 -07:00
committed by Alexei Starovoitov
parent 72e2b2b66f
commit af7ec13833
8 changed files with 148 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
kernel/bpf/verifier.c
View File

@@ -3800,12 +3800,14 @@ static int int_ptr_type_to_size(enum bpf_arg_type type)
return -EINVAL;
}
static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
enum bpf_arg_type arg_type,
struct bpf_call_arg_meta *meta)
static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
struct bpf_call_arg_meta *meta,
const struct bpf_func_proto *fn)
{
u32 regno = BPF_REG_1 + arg;
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
enum bpf_reg_type expected_type, type = reg->type;
enum bpf_arg_type arg_type = fn->arg_type[arg];
int err = 0;
if (arg_type == ARG_DONTCARE)
@@ -3885,9 +3887,16 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
expected_type = PTR_TO_BTF_ID;
if (type != expected_type)
goto err_type;
if (reg->btf_id != meta->btf_id) {
verbose(env, "Helper has type %s got %s in R%d\n",
kernel_type_name(meta->btf_id),
if (!fn->check_btf_id) {
if (reg->btf_id != meta->btf_id) {
verbose(env, "Helper has type %s got %s in R%d\n",
kernel_type_name(meta->btf_id),
kernel_type_name(reg->btf_id), regno);
return -EACCES;
}
} else if (!fn->check_btf_id(reg->btf_id, arg)) {
verbose(env, "Helper does not support %s in R%d\n",
kernel_type_name(reg->btf_id), regno);
return -EACCES;
@@ -4709,10 +4718,12 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
meta.func_id = func_id;
/* check args */
for (i = 0; i < 5; i++) {
err = btf_resolve_helper_id(&env->log, fn, i);
if (err > 0)
meta.btf_id = err;
err = check_func_arg(env, BPF_REG_1 + i, fn->arg_type[i], &meta);
if (!fn->check_btf_id) {
err = btf_resolve_helper_id(&env->log, fn, i);
if (err > 0)
meta.btf_id = err;
}
err = check_func_arg(env, i, &meta, fn);
if (err)
return err;
}
@@ -4815,6 +4826,18 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
regs[BPF_REG_0].id = ++env->id_gen;
regs[BPF_REG_0].mem_size = meta.mem_size;
} else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL) {
int ret_btf_id;
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_BTF_ID_OR_NULL;
ret_btf_id = *fn->ret_btf_id;
if (ret_btf_id == 0) {
verbose(env, "invalid return type %d of func %s#%d\n",
fn->ret_type, func_id_name(func_id), func_id);
return -EINVAL;
}
regs[BPF_REG_0].btf_id = ret_btf_id;
} else {
verbose(env, "unknown return type %d of func %s#%d\n",
fn->ret_type, func_id_name(func_id), func_id);