[DTrace-devel] [PATCH 2/2] Fix copy from user space when accessing high-number pid entry args

[Nick Alcock]

On 15 Apr 2022, eugene loh told this:

> +/*
> + * Set dt_bpf_func_max_id.  While it should be __BPF_FUNC_MAX_ID from
> + * /usr/include/linux/bpf.h,

That assumption is just not justified at all. /usr/include/linux is the
kernel headers against which *glibc* was built: it need have no
relationship with the running kernel at all. It's often older, if RH is
using an older kernel than we are; it is also often newer, because when
building glibc you are (or were, historically: see below) supposed to
use the newest headers possible so that glibc can enable every kernel
feature it supports (iff the running kernel is new enough).

In glibc 2.33 (IIRC) this whole dance is dropped in favour of just
copying in definitions out of the /usr/include/linux header files, and
distros can finally start treating the kernel headers in a somewhat more
reasonable fashion (and upgrading them more often).

Projects that use kernel headers (like we do) are expected to copy them
into their source tree. Shame we can't do that because we're the wrong
license :/