Commit 23da464d authored by Kumar Kartikeya Dwivedi's avatar Kumar Kartikeya Dwivedi Committed by Alexei Starovoitov
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bpf: Allow specifying volatile type modifier for kptrs 



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: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: default avatarDavid Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20221103191013.1236066-3-memxor@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 9805af8d

include/linux/btf.h

+5 −0
Original line number Diff line number Diff line
@@ -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;

kernel/bpf/btf.c

+3 −0
Original line number Diff line number Diff line
@@ -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;