netdev - Re: [PATCH net] ebpf, x86: fix general protection fault when tail call is invoked

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Date:	Tue, 28 Jul 2015 10:02:08 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Daniel Borkmann <daniel@...earbox.net>, davem@...emloft.net
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net] ebpf, x86: fix general protection fault when tail
 call is invoked

On 7/28/15 6:26 AM, Daniel Borkmann wrote:
> After patch, disassembly:
>
>    [...]
>    9e:   lea    0x80(%rsi,%rdx,8),%rax   <--- CONFIG_LOCKDEP/CONFIG_LOCK_STAT
>          48 8d 84 d6 80 00 00 00
>    a6:   mov    (%rax),%rax
>          48 8b 00
>    [...]
>
>    [...]
>    9e:   lea    0x50(%rsi,%rdx,8),%rax   <--- No CONFIG_LOCKDEP
>          48 8d 84 d6 50 00 00 00
>    a6:   mov    (%rax),%rax
>          48 8b 00
>    [...]
>
> Fixes: b52f00e6a715 ("x86: bpf_jit: implement bpf_tail_call() helper")
> Signed-off-by: Daniel Borkmann<daniel@...earbox.net>

Thanks for fixing it.
Most of my development is actually with LOCKDEP on, but I don't ever
turn LOCK_STAT on, so sadly missed this 48 byte increase of 80 byte
structure :(

Acked-by: Alexei Starovoitov <ast@...mgrid.com>

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