Allocate ID for vmlinux BTF. This makes it visible when iterating over all BTF
objects in the system. To allow distinguishing vmlinux BTF (and later kernel
module BTF) from user-provided BTFs, expose extra kernel_btf flag, as well as
BTF name ("vmlinux" for vmlinux BTF, will equal to module's name for module
BTF). We might want to later allow specifying BTF name for user-provided BTFs
as well, if that makes sense. But currently this is reserved only for
in-kernel BTFs.
Having in-kernel BTFs exposed IDs will allow to extend BPF APIs that require
in-kernel BTF type with ability to specify BTF types from kernel modules, not
just vmlinux BTF. This will be implemented in a follow up patch set for
fentry/fexit/fmod_ret/lsm/etc.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 3 +++
kernel/bpf/btf.c | 43 +++++++++++++++++++++++++++++++---
tools/include/uapi/linux/bpf.h | 3 +++
3 files changed, 46 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9879d6793e90..162999b12790 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4466,6 +4466,9 @@ struct bpf_btf_info {
__aligned_u64 btf;
__u32 btf_size;
__u32 id;
+ __aligned_u64 name;
+ __u32 name_len;
+ __u32 kernel_btf;
} __attribute__((aligned(8)));
struct bpf_link_info {
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 727c1c27053f..856585db7aa7 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -214,6 +214,8 @@ struct btf {
struct btf *base_btf;
u32 start_id; /* first type ID in this BTF (0 for base BTF) */
u32 start_str_off; /* first string offset (0 for base BTF) */
+ char name[MODULE_NAME_LEN];
+ bool kernel_btf;
};
enum verifier_phase {
@@ -4429,6 +4431,8 @@ struct btf *btf_parse_vmlinux(void)
btf->data = __start_BTF;
btf->data_size = __stop_BTF - __start_BTF;
+ btf->kernel_btf = true;
+ snprintf(btf->name, sizeof(btf->name), "vmlinux");
err = btf_parse_hdr(env);
if (err)
@@ -4454,8 +4458,13 @@ struct btf *btf_parse_vmlinux(void)
bpf_struct_ops_init(btf, log);
- btf_verifier_env_free(env);
refcount_set(&btf->refcnt, 1);
+
+ err = btf_alloc_id(btf);
+ if (err)
+ goto errout;
+
+ btf_verifier_env_free(env);
return btf;
errout:
@@ -5553,7 +5562,9 @@ int btf_get_info_by_fd(const struct btf *btf,
struct bpf_btf_info info;
u32 info_copy, btf_copy;
void __user *ubtf;
- u32 uinfo_len;
+ char __user *uname;
+ u32 uinfo_len, uname_len, name_len;
+ int ret = 0;
uinfo = u64_to_user_ptr(attr->info.info);
uinfo_len = attr->info.info_len;
@@ -5570,11 +5581,37 @@ int btf_get_info_by_fd(const struct btf *btf,
return -EFAULT;
info.btf_size = btf->data_size;
+ info.kernel_btf = btf->kernel_btf;
+
+ uname = u64_to_user_ptr(info.name);
+ uname_len = info.name_len;
+ if (!uname ^ !uname_len)
+ return -EINVAL;
+
+ name_len = strlen(btf->name);
+ info.name_len = name_len;
+
+ if (uname) {
+ if (uname_len >= name_len + 1) {
+ if (copy_to_user(uname, btf->name, name_len + 1))
+ return -EFAULT;
+ } else {
+ char zero = '\0';
+
+ if (copy_to_user(uname, btf->name, uname_len - 1))
+ return -EFAULT;
+ if (put_user(zero, uname + uname_len - 1))
+ return -EFAULT;
+ /* let user-space know about too short buffer */
+ ret = -ENOSPC;
+ }
+ }
+
if (copy_to_user(uinfo, &info, info_copy) ||
put_user(info_copy, &uattr->info.info_len))
return -EFAULT;
- return 0;
+ return ret;
}
int btf_get_fd_by_id(u32 id)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 9879d6793e90..162999b12790 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4466,6 +4466,9 @@ struct bpf_btf_info {
__aligned_u64 btf;
__u32 btf_size;
__u32 id;
+ __aligned_u64 name;
+ __u32 name_len;
+ __u32 kernel_btf;
} __attribute__((aligned(8)));
struct bpf_link_info {
--
2.24.1
