Re: [dpdk-dev] [dpdk-stable] [PATCH] test/bpf: fix auto-test with clang fails

[David Marchand <david.marchand@redhat.com>]

On Mon, Oct 18, 2021 at 5:59 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
> Konstantin Ananyev <konstantin.ananyev@intel.com> wrote:
> > test_shift1_check() function fails with clang build.
> > The reason for that is that clang uses 64-bit shift instruction for
> > what expected to be 32-bit operation.
> > To be more specific, this C code:
> > r2 = (uint32_t)r2 >> r4;
> > With clang produces:
> > 41a4eb:       48 d3 ef                shr    %cl,%rdi
> > In that particular case it is an allowed choice, as from one side
> > left-operand value is known to fit into 32 bits, from other side
> > according to 'C' standard:
> > "...if the value of the right operand is negative or is greater than
> > or equal to the width of the promoted left operand, the behavior is
> > undefined."
> > The problem is that on x86 behavior for 64-bit and 32-bit shift
> > operation might differ.
> > The fix avoids undefined behavior by making sure
> > that right operand will not exceed width of the promoted left operand.
> >
> > Bugzilla ID: 811
> > Fixes: 9f8f9d91a701 ("test/bpf: introduce functional test")
> > Cc: stable@dpdk.org
> >
> > Reported-by: Stephen Hemminger <stephen@networkplumber.org>
> > Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> Acked-by: Stephen Hemminger <stephen@networkplumber.org>

Applied, thanks.

Probably worth adding bpf_autotest in the fast-tests list.
There are other missing tests in this list, for my todolist unless
someone wants to look at it.



-- 
David Marchand