[RFC bpf-next v4 2/6] bpf: Parse and support "uptr" tag.

Kui-Feng Lee
2024-08-16T19:12:20Z

Parse "uptr" tag from BTF, map it to BPF_UPTR, and support it in related
functions. "uptr" tag is used to annotate a field in a struct type is a
uptr, which is used to share a block memory between user programs and BPF
programs.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
---
kernel/bpf/btf.c | 5 +++++
kernel/bpf/syscall.c | 2 ++
2 files changed, 7 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ab3c9f592c9f..f61bad288385 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3356,6 +3356,8 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
type = BPF_KPTR_REF;
else if (!strcmp("percpu_kptr", __btf_name_by_offset(btf, t->name_off)))
type = BPF_KPTR_PERCPU;
+ else if (!strcmp("uptr", __btf_name_by_offset(btf, t->name_off)))
+ type = BPF_UPTR;
else
return -EINVAL;

@@ -3533,6 +3535,7 @@ static int btf_repeat_fields(struct btf_field_info *info,
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
+ case BPF_UPTR:
case BPF_LIST_HEAD:
case BPF_RB_ROOT:
break;
@@ -3659,6 +3662,7 @@ static int btf_find_field_one(const struct btf *btf,
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
+ case BPF_UPTR:
ret = btf_find_kptr(btf, var_type, off, sz,
info_cnt ? &info[0] : &tmp);
if (ret < 0)
@@ -3983,6 +3987,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
+ case BPF_UPTR:
ret = btf_parse_kptr(btf, &rec->fields[i], &info_arr[i]);
if (ret < 0)
goto end;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 65dcd92d0b2c..fed4a2145f81 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -548,6 +548,7 @@ void btf_record_free(struct btf_record *rec)
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
+ case BPF_UPTR:
if (rec->fields[i].kptr.module)
module_put(rec->fields[i].kptr.module);
btf_put(rec->fields[i].kptr.btf);
@@ -596,6 +597,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec)
case BPF_KPTR_UNREF:
case BPF_KPTR_REF:
case BPF_KPTR_PERCPU:
+ case BPF_UPTR:
btf_get(fields[i].kptr.btf);
if (fields[i].kptr.module && !try_module_get(fields[i].kptr.module)) {
ret = -ENXIO;
--
2.34.1