| Message ID | 20221103191013.1236066-3-memxor@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Commit | 23da464dd6b8935b66f4ee306ad8947fd32ccd75 |
| Delegated to: | BPF |
| Headers | show |
| Series | Local kptrs, BPF linked lists | expand |
On Fri, Nov 04, 2022 at 12:39:51AM +0530, Kumar Kartikeya Dwivedi wrote: > This is useful in particular to mark the pointer as volatile, so that > compiler treats each load and store to the field as a volatile access. > The alternative is having to define and use READ_ONCE and WRITE_ONCE in > the BPF program. > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Acked-by: David Vernet <void@manifault.com>
diff --git a/include/linux/btf.h b/include/linux/btf.h index f9aababc5d78..86aad9b2ce02 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -288,6 +288,11 @@ static inline bool btf_type_is_typedef(const struct btf_type *t) return BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF; } +static inline bool btf_type_is_volatile(const struct btf_type *t) +{ + return BTF_INFO_KIND(t->info) == BTF_KIND_VOLATILE; +} + static inline bool btf_type_is_func(const struct btf_type *t) { return BTF_INFO_KIND(t->info) == BTF_KIND_FUNC; diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 35c07afac924..f4d21eef6ebd 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3225,6 +3225,9 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t, enum bpf_kptr_type type; u32 res_id; + /* Permit modifiers on the pointer itself */ + if (btf_type_is_volatile(t)) + t = btf_type_by_id(btf, t->type); /* For PTR, sz is always == 8 */ if (!btf_type_is_ptr(t)) return BTF_FIELD_IGNORE;
This is useful in particular to mark the pointer as volatile, so that compiler treats each load and store to the field as a volatile access. The alternative is having to define and use READ_ONCE and WRITE_ONCE in the BPF program. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> --- include/linux/btf.h | 5 +++++ kernel/bpf/btf.c | 3 +++ 2 files changed, 8 insertions(+)