6d94e741a8
This patch adds the verifier support to recognize inlined branch conditions. The LLVM knows that the branch evaluates to the same value, but the verifier couldn't track it. Hence causing valid programs to be rejected. The potential LLVM workaround: https://reviews.llvm.org/D87428 can have undesired side effects, since LLVM doesn't know that skb->data/data_end are being compared. LLVM has to introduce extra boolean variable and use inline_asm trick to force easier for the verifier assembly. Instead teach the verifier to recognize that r1 = skb->data; r1 += 10; r2 = skb->data_end; if (r1 > r2) { here r1 points beyond packet_end and subsequent if (r1 > r2) // always evaluates to "true". } Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Tested-by: Jiri Olsa <jolsa@redhat.com> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20201111031213.25109-2-alexei.starovoitov@gmail.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.