This set includes some fixes in semantics and usability issues that emerged
recently, and would be good to have them in net before the next release.
In particular, ARG_CONST_SIZE_OR_ZERO semantics was recently changed in
commit 9fd29c08e520 ("bpf: improve verifier ARG_CONST_SIZE_OR_ZERO
semantics") with the goal of letting the compiler generate simpler code
that the verifier can more easily accept.
To handle this change in semantics, a few checks in some helpers were
added, like in commit 9c019e2bc4b2 ("bpf: change helper bpf_probe_read arg2
type to ARG_CONST_SIZE_OR_ZERO"), and those checks are less than ideal
because once they make it into a released kernel bpf programs can start
relying on them, preventing the possibility of being removed later on.
This patch tries to fix the issue by introducing a new argument type
ARG_PTR_TO_MEM_OR_NULL that can be used for helpers that can receive a
<NULL, 0> tuple. By doing so, we can fix the semantics of the other helpers
that don't need <NULL, 0> and can just handle <!NULL, 0>, allowing the code
to get rid of those checks.
Gianluca Borello (4):
bpf: introduce ARG_PTR_TO_MEM_OR_NULL
bpf: remove explicit handling of 0 for arg2 in bpf_probe_read
bpf: change bpf_probe_read_str arg2 type to ARG_CONST_SIZE_OR_ZERO
bpf: change bpf_perf_event_output arg5 type to ARG_CONST_SIZE_OR_ZERO
include/linux/bpf.h | 1 +
kernel/bpf/verifier.c | 4 +-
kernel/trace/bpf_trace.c | 12 +--
net/core/filter.c | 4 +-
tools/testing/selftests/bpf/test_verifier.c | 113 ++++++++++++++++++++++++++--
5 files changed, 116 insertions(+), 18 deletions(-)
--
2.14.1
