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Message-ID: <20191024201524.685995-1-kafai@fb.com>
Date: Thu, 24 Oct 2019 13:15:24 -0700
From: Martin KaFai Lau <kafai@...com>
To: <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC: Alexei Starovoitov <ast@...com>,
Daniel Borkmann <daniel@...earbox.net>,
David Miller <davem@...emloft.net>, <kernel-team@...com>
Subject: [PATCH bpf-next] bpf: Prepare btf_ctx_access for non raw_tp use case.
This patch makes a few changes to btf_ctx_access() to prepare
it for non raw_tp use case.
btf_ctx_access() only needs the attach_btf_id from prog. Hence, this patch
only passes the attach_btf_id instead of passing prog. It allows other
use cases when the prog->aux->attach_btf_id may not be a typedef.
For example, in the future, a bpf_prog can attach to
"struct tcp_congestion_ops" and its attach_btf_id is
pointing to the btf_id of "struct tcp_congestion_ops".
While at it, allow btf_ctx_access to directly take a BTF_KIND_FUNC_PROTO
btf_id. It is to prepare for a later patch that does not need a "typedef"
to figure out the func_proto. For example, when attaching a bpf_prog
to an ops in "struct tcp_congestion_ops", the func_proto can be
found directly by following the members of "struct tcp_congestion_ops".
For the no typedef use case, there is no extra first arg. Hence, this
patch only limits the skip arg logic to raw_tp only.
Since a BTF_KIND_FUNC_PROTO type does not have a name (i.e. "(anon)"),
an optional name arg is added also. If specified, this name will be used
in the bpf_log() message instead of the type's name obtained from btf_id.
For example, the function pointer member name of
"struct tcp_congestion_ops" can be used.
Signed-off-by: Martin KaFai Lau <kafai@...com>
---
include/linux/bpf.h | 2 +-
kernel/bpf/btf.c | 53 ++++++++++++++++++++++++++--------------
kernel/trace/bpf_trace.c | 3 ++-
3 files changed, 38 insertions(+), 20 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2c2c29b49845..1befe59331d9 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -766,7 +766,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
const union bpf_attr *kattr,
union bpf_attr __user *uattr);
bool btf_ctx_access(int off, int size, enum bpf_access_type type,
- const struct bpf_prog *prog,
+ u32 btf_id, const char *name,
struct bpf_insn_access_aux *info);
int btf_struct_access(struct bpf_verifier_log *log,
const struct btf_type *t, int off, int size,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index f7557af39756..8c8174782675 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -346,6 +346,11 @@ static bool btf_type_is_func_proto(const struct btf_type *t)
return BTF_INFO_KIND(t->info) == BTF_KIND_FUNC_PROTO;
}
+static bool btf_type_is_typedef(const struct btf_type *t)
+{
+ return BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF;
+}
+
static bool btf_type_nosize(const struct btf_type *t)
{
return btf_type_is_void(t) || btf_type_is_fwd(t) ||
@@ -3439,16 +3444,16 @@ struct btf *btf_parse_vmlinux(void)
extern struct btf *btf_vmlinux;
bool btf_ctx_access(int off, int size, enum bpf_access_type type,
- const struct bpf_prog *prog,
+ u32 btf_id, const char *func_name,
struct bpf_insn_access_aux *info)
{
struct bpf_verifier_log *log = info->log;
- u32 btf_id = prog->aux->attach_btf_id;
const struct btf_param *args;
const struct btf_type *t;
const char prefix[] = "btf_trace_";
const char *tname;
u32 nr_args, arg;
+ bool is_raw_tp = false;
if (!btf_id)
return true;
@@ -3459,37 +3464,49 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
}
t = btf_type_by_id(btf_vmlinux, btf_id);
- if (!t || BTF_INFO_KIND(t->info) != BTF_KIND_TYPEDEF) {
+ if (!t || (!btf_type_is_typedef(t) && !btf_type_is_func_proto(t))) {
bpf_log(log, "btf_id is invalid\n");
return false;
}
tname = __btf_name_by_offset(btf_vmlinux, t->name_off);
- if (strncmp(prefix, tname, sizeof(prefix) - 1)) {
- bpf_log(log, "btf_id points to wrong type name %s\n", tname);
- return false;
+ if (btf_type_is_typedef(t)) {
+ if (strncmp(prefix, tname, sizeof(prefix) - 1)) {
+ bpf_log(log, "btf_id points to wrong type name %s\n",
+ tname);
+ return false;
+ }
+ tname += sizeof(prefix) - 1;
+
+ t = btf_type_by_id(btf_vmlinux, t->type);
+ if (!btf_type_is_ptr(t))
+ return false;
+ t = btf_type_by_id(btf_vmlinux, t->type);
+ btf_id = t->type;
+ is_raw_tp = true;
}
- tname += sizeof(prefix) - 1;
- t = btf_type_by_id(btf_vmlinux, t->type);
- if (!btf_type_is_ptr(t))
- return false;
- t = btf_type_by_id(btf_vmlinux, t->type);
if (!btf_type_is_func_proto(t))
return false;
+ if (func_name)
+ tname = func_name;
+
if (off % 8) {
- bpf_log(log, "raw_tp '%s' offset %d is not multiple of 8\n",
+ bpf_log(log, "func '%s' offset %d is not multiple of 8\n",
tname, off);
return false;
}
arg = off / 8;
args = (const struct btf_param *)(t + 1);
+ nr_args = btf_type_vlen(t);
/* skip first 'void *__data' argument in btf_trace_##name typedef */
- args++;
- nr_args = btf_type_vlen(t) - 1;
+ if (is_raw_tp) {
+ args++;
+ nr_args--;
+ }
if (arg >= nr_args) {
- bpf_log(log, "raw_tp '%s' doesn't have %d-th argument\n",
+ bpf_log(log, "func '%s' doesn't have %d-th argument\n",
tname, arg);
return false;
}
@@ -3503,7 +3520,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
return true;
if (!btf_type_is_ptr(t)) {
bpf_log(log,
- "raw_tp '%s' arg%d '%s' has type %s. Only pointer access is allowed\n",
+ "func '%s' arg%d '%s' has type %s. Only pointer access is allowed\n",
tname, arg,
__btf_name_by_offset(btf_vmlinux, t->name_off),
btf_kind_str[BTF_INFO_KIND(t->info)]);
@@ -3526,11 +3543,11 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
t = btf_type_by_id(btf_vmlinux, t->type);
if (!btf_type_is_struct(t)) {
bpf_log(log,
- "raw_tp '%s' arg%d type %s is not a struct\n",
+ "func '%s' arg%d type %s is not a struct\n",
tname, arg, btf_kind_str[BTF_INFO_KIND(t->info)]);
return false;
}
- bpf_log(log, "raw_tp '%s' arg%d has btf_id %d type %s '%s'\n",
+ bpf_log(log, "func '%s' arg%d has btf_id %d type %s '%s'\n",
tname, arg, info->btf_id, btf_kind_str[BTF_INFO_KIND(t->info)],
__btf_name_by_offset(btf_vmlinux, t->name_off));
return true;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c3240898cc44..435869b1834a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1080,7 +1080,8 @@ static bool raw_tp_prog_is_valid_access(int off, int size,
return false;
if (off % size != 0)
return false;
- return btf_ctx_access(off, size, type, prog, info);
+ return btf_ctx_access(off, size, type, prog->aux->attach_btf_id, NULL,
+ info);
}
const struct bpf_verifier_ops raw_tracepoint_verifier_ops = {
--
2.17.1
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