On Mon, Nov 7, 2022 at 3:10 PM Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> wrote:
>
> Currently, verifier uses MEM_ALLOC type tag to specially tag memory
> returned from bpf_ringbuf_reserve helper. However, this is currently
> only used for this purpose and there is an implicit assumption that it
> only refers to ringbuf memory (e.g. the check for ARG_PTR_TO_ALLOC_MEM
> in check_func_arg_reg_off).
>
> Hence, rename MEM_ALLOC to MEM_RINGBUF to indicate this special
> relationship and instead open the use of MEM_ALLOC for more generic
> allocations made for user types.
>
> Also, since ARG_PTR_TO_ALLOC_MEM_OR_NULL is unused, simply drop it.
>
> Finally, update selftests using 'alloc_' verifier string to 'ringbuf_'.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
Ok, so you are doing what I asked in the previous patch, nice :)
> include/linux/bpf.h | 11 ++++-------
> kernel/bpf/ringbuf.c | 6 +++---
> kernel/bpf/verifier.c | 14 +++++++-------
> tools/testing/selftests/bpf/prog_tests/dynptr.c | 2 +-
> tools/testing/selftests/bpf/verifier/ringbuf.c | 2 +-
> tools/testing/selftests/bpf/verifier/spill_fill.c | 2 +-
> 6 files changed, 17 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 2fe3ec620d54..afc1c51b59ff 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -488,10 +488,8 @@ enum bpf_type_flag {
> */
> MEM_RDONLY = BIT(1 + BPF_BASE_TYPE_BITS),
>
> - /* MEM was "allocated" from a different helper, and cannot be mixed
> - * with regular non-MEM_ALLOC'ed MEM types.
> - */
> - MEM_ALLOC = BIT(2 + BPF_BASE_TYPE_BITS),
> + /* MEM points to BPF ring buffer reservation. */
> + MEM_RINGBUF = BIT(2 + BPF_BASE_TYPE_BITS),
What do we gain by having ringbuf memory as additional modified flag
instead of its own type like PTR_TO_MAP_VALUE or PTR_TO_PACKET? It
feels like here separate register type is more justified and is less
error prone overall.
>
> /* MEM is in user address space. */
> MEM_USER = BIT(3 + BPF_BASE_TYPE_BITS),
> @@ -565,7 +563,7 @@ enum bpf_arg_type {
> ARG_PTR_TO_LONG, /* pointer to long */
> ARG_PTR_TO_SOCKET, /* pointer to bpf_sock (fullsock) */
> ARG_PTR_TO_BTF_ID, /* pointer to in-kernel struct */
> - ARG_PTR_TO_ALLOC_MEM, /* pointer to dynamically allocated memory */
> + ARG_PTR_TO_RINGBUF_MEM, /* pointer to dynamically reserved ringbuf memory */
> ARG_CONST_ALLOC_SIZE_OR_ZERO, /* number of allocated bytes requested */
> ARG_PTR_TO_BTF_ID_SOCK_COMMON, /* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */
> ARG_PTR_TO_PERCPU_BTF_ID, /* pointer to in-kernel percpu type */
[...]
