From: Edward Cree <ec...@solarflare.com> Date: Wed, 7 Jun 2017 15:55:57 +0100
> This series simplifies alignment tracking, generalises bounds tracking and > fixes some bounds-tracking bugs in the BPF verifier. Pointer arithmetic on > packet pointers, stack pointers, map value pointers and context pointers has > been unified, and bounds on these pointers are only checked when the pointer > is dereferenced. > Operations on pointers which destroy all relation to the original pointer > (such as multiplies and shifts) are disallowed if !env->allow_ptr_leaks, > otherwise they convert the pointer to an unknown scalar and feed it to the > normal scalar arithmetic handling. > Pointer types have been unified with the corresponding adjusted-pointer types > where those existed (e.g. PTR_TO_MAP_VALUE[_ADJ] or FRAME_PTR vs > PTR_TO_STACK); similarly, CONST_IMM and UNKNOWN_VALUE have been unified into > SCALAR_VALUE. > Pointer types (except CONST_PTR_TO_MAP, PTR_TO_MAP_VALUE_OR_NULL and > PTR_TO_PACKET_END, which do not allow arithmetic) have a 'fixed offset' and > a 'variable offset'; the former is used when e.g. adding an immediate or a > known-constant register, as long as it does not overflow. Otherwise the > latter is used, and any operation creating a new variable offset creates a > new 'id' (and, for PTR_TO_PACKET, clears the 'range'). > SCALAR_VALUEs use the 'variable offset' fields to track the range of possible > values; the 'fixed offset' should never be set on a scalar. > > Patch 2/5 is rather on the big side, but since it changes the contents and > semantics of a fairly central data structure, I'm not really sure how to go > about splitting it up further without producing broken intermediate states. > > With the changes in patch 5/5, all tools/testing/selftests/bpf/test_verifier > tests pass. Edward, I haven't had a chance to review this yet, but I wanted to thank you for working on this. I will find some time to test your work on sparc too. Thanks again!
