Allow struct argument in trampoline based programs where
the struct size should be <= 16 bytes. In such cases, the argument
will be put into up to 2 registers for bpf, x86_64 and arm64
architectures.
To support arch-specific trampoline manipulation,
add arg_flags for additional struct information about arguments
in btf_func_model. Such information will be used in arch specific
function arch_prepare_bpf_trampoline() to prepare argument access
properly in trampoline.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
include/linux/bpf.h | 4 ++++
kernel/bpf/btf.c | 45 +++++++++++++++++++++++++++++++++++++++------
2 files changed, 43 insertions(+), 6 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9c1674973e03..4d32f125f4af 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -727,10 +727,14 @@ enum bpf_cgroup_storage_type {
*/
#define MAX_BPF_FUNC_REG_ARGS 5
+/* The argument is a structure. */
+#define BTF_FMODEL_STRUCT_ARG BIT(0)
+
struct btf_func_model {
u8 ret_size;
u8 nr_args;
u8 arg_size[MAX_BPF_FUNC_ARGS];
+ u8 arg_flags[MAX_BPF_FUNC_ARGS];
};
/* Restore arguments before returning from trampoline to let original function
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 903719b89238..ea94527e5d70 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5328,6 +5328,34 @@ static bool is_int_ptr(struct btf *btf, const struct btf_type *t)
return btf_type_is_int(t);
}
+static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto,
+ int off)
+{
+ const struct btf_param *args;
+ const struct btf_type *t;
+ u32 offset = 0, nr_args;
+ int i;
+
+ if (!func_proto)
+ return off / 8;
+
+ nr_args = btf_type_vlen(func_proto);
+ args = (const struct btf_param *)(func_proto + 1);
+ for (i = 0; i < nr_args; i++) {
+ t = btf_type_skip_modifiers(btf, args[i].type, NULL);
+ offset += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8);
+ if (off < offset)
+ return i;
+ }
+
+ t = btf_type_skip_modifiers(btf, func_proto->type, NULL);
+ offset += btf_type_is_ptr(t) ? 8 : roundup(t->size, 8);
+ if (off < offset)
+ return nr_args;
+
+ return nr_args + 1;
+}
+
bool btf_ctx_access(int off, int size, enum bpf_access_type type,
const struct bpf_prog *prog,
struct bpf_insn_access_aux *info)
@@ -5347,7 +5375,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
tname, off);
return false;
}
- arg = off / 8;
+ arg = get_ctx_arg_idx(btf, t, off);
args = (const struct btf_param *)(t + 1);
/* if (t == NULL) Fall back to default BPF prog with
* MAX_BPF_FUNC_REG_ARGS u64 arguments.
@@ -5417,7 +5445,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
/* skip modifiers */
while (btf_type_is_modifier(t))
t = btf_type_by_id(btf, t->type);
- if (btf_type_is_small_int(t) || btf_is_any_enum(t))
+ if (btf_type_is_small_int(t) || btf_is_any_enum(t) || __btf_type_is_struct(t))
/* accessing a scalar */
return true;
if (!btf_type_is_ptr(t)) {
@@ -5881,7 +5909,7 @@ static int __get_type_size(struct btf *btf, u32 btf_id,
if (btf_type_is_ptr(t))
/* kernel size of pointer. Not BPF's size of pointer*/
return sizeof(void *);
- if (btf_type_is_int(t) || btf_is_any_enum(t))
+ if (btf_type_is_int(t) || btf_is_any_enum(t) || __btf_type_is_struct(t))
return t->size;
return -EINVAL;
}
@@ -5901,8 +5929,10 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
/* BTF function prototype doesn't match the verifier types.
* Fall back to MAX_BPF_FUNC_REG_ARGS u64 args.
*/
- for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++)
+ for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
m->arg_size[i] = 8;
+ m->arg_flags[i] = 0;
+ }
m->ret_size = 8;
m->nr_args = MAX_BPF_FUNC_REG_ARGS;
return 0;
@@ -5916,7 +5946,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
return -EINVAL;
}
ret = __get_type_size(btf, func->type, &t);
- if (ret < 0) {
+ if (ret < 0 || __btf_type_is_struct(t)) {
bpf_log(log,
"The function %s return type %s is unsupported.\n",
tname, btf_kind_str[BTF_INFO_KIND(t->info)]);
@@ -5932,7 +5962,9 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
return -EINVAL;
}
ret = __get_type_size(btf, args[i].type, &t);
- if (ret < 0) {
+
+ /* No support of struct argument size greater than 16 bytes */
+ if (ret < 0 || ret > 16) {
bpf_log(log,
"The function %s arg%d type %s is unsupported.\n",
tname, i, btf_kind_str[BTF_INFO_KIND(t->info)]);
@@ -5945,6 +5977,7 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
return -EINVAL;
}
m->arg_size[i] = ret;
+ m->arg_flags[i] = __btf_type_is_struct(t) ? BTF_FMODEL_STRUCT_ARG : 0;
}
m->nr_args = nargs;
return 0;
--
2.30.2
