On 04/25/2018 07:42 AM, Gianluca Borello wrote:
> Commit 2a5418a13fcf ("bpf: improve dead code sanitizing") replaced dead
> code with a series of ja-1 instructions, for safety. That made JIT
> compilation much more complex for some BPF programs. One instance of such
> programs is, for example:
>
> bool flag = false
> ...
> /* A bunch of other code */
> ...
> if (flag)
> do_something()
>
> In some cases llvm is not able to remove at compile time the code for
> do_something(), so the generated BPF program ends up with a large amount
> of dead instructions. In one specific real life example, there are two
> series of ~500 and ~1000 dead instructions in the program. When the
> verifier replaces them with a series of ja-1 instructions, it causes an
> interesting behavior at JIT time.
[...]
>
> Fixes: 2a5418a13fcf ("bpf: improve dead code sanitizing")
> Signed-off-by: Gianluca Borello <g.bore...@gmail.com>
I've applied this fix to bpf tree, thanks Gianluca!
