linux-kernel - Re: [PATCH V3 2/3] ARM: net: bpf_jit: make code generation less dependent on struct sk

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Date:	Fri, 26 Apr 2013 21:47:46 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Arnd Bergmann <arnd@...db.de>,
	Nicolas Schichan <nschichan@...ebox.fr>,
	Will Drewry <wad@...omium.org>,
	Mircea Gherzan <mgherzan@...il.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Daniel Borkmann <daniel.borkmann@....ee.ethz.ch>,
	netdev@...r.kernel.org
Subject: Re: [PATCH V3 2/3] ARM: net: bpf_jit: make code generation less dependent
 on struct sk_filter.

On 04/26/2013 09:26 PM, Andrew Morton wrote:
> On Fri, 26 Apr 2013 16:04:44 +0200 Arnd Bergmann <arnd@...db.de> wrote:
>> On Wednesday 24 April 2013 19:27:08 Nicolas Schichan wrote:
>>> @@ -858,7 +858,7 @@ b_epilogue:
>>>   }
>>>
>>>
>>> -void bpf_jit_compile(struct sk_filter *fp)
>>> +static void __bpf_jit_compile(struct jit_ctx *out_ctx)
>>>   {
>>>          struct jit_ctx ctx;
>>>          unsigned tmp_idx;
>>> @@ -867,11 +867,10 @@ void bpf_jit_compile(struct sk_filter *fp)
>>>          if (!bpf_jit_enable)
>>>                  return;
>>>
>>> -       memset(&ctx, 0, sizeof(ctx));
>>> -       ctx.skf         = fp;
>>> +       ctx = *out_ctx;
>>>          ctx.ret0_fp_idx = -1;
>>>
>>> -       ctx.offsets = kzalloc(4 * (ctx.skf->len + 1), GFP_KERNEL);
>>> +       ctx.offsets = kzalloc(4 * (ctx.prog_len + 1), GFP_KERNEL);
>>>          if (ctx.offsets == NULL)
>>>                  return;
>>>
>>> @@ -921,13 +920,26 @@ void bpf_jit_compile(struct sk_filter *fp)
>>>                  print_hex_dump(KERN_INFO, "BPF JIT code: ",
>>>                                 DUMP_PREFIX_ADDRESS, 16, 4, ctx.target,
>>>                                 alloc_size, false);
>>> -
>>> -       fp->bpf_func = (void *)ctx.target;
>>>   out:
>>>          kfree(ctx.offsets);
>>> +
>>> +       *out_ctx = ctx;
>>>          return;
>>
>> This part of the patch, in combination with 79617801e "filter: bpf_jit_comp:
>> refactor and unify BPF JIT image dump output" is now causing build errors
>> in linux-next:
>>
>> arch/arm/net/bpf_jit_32.c: In function '__bpf_jit_compile':
>> arch/arm/net/bpf_jit_32.c:930:16: error: 'fp' undeclared (first use in this function)
>>     bpf_jit_dump(fp->len, alloc_size, 2, ctx.target);
>
> Thanks, I did this.  There may be a smarter way...

I think also seccomp_jit_compile() would need this change then, otherwise the build
with CONFIG_SECCOMP_FILTER_JIT might break.

I can fix this up for you if not already applied. I presume it's against
linux-next tree?

> --- a/arch/arm/net/bpf_jit_32.c~arm-net-bpf_jit-make-code-generation-less-dependent-on-struct-sk_filter-fix
> +++ a/arch/arm/net/bpf_jit_32.c
> @@ -858,7 +858,7 @@ b_epilogue:
>   }
>
>
> -static void __bpf_jit_compile(struct jit_ctx *out_ctx)
> +static void __bpf_jit_compile(struct sk_filter *fp, struct jit_ctx *out_ctx)
>   {
>   	struct jit_ctx ctx;
>   	unsigned tmp_idx;
> @@ -934,7 +934,7 @@ void bpf_jit_compile(struct sk_filter *f
>   	ctx.prog_len = fp->len;
>   	ctx.prog_insns = fp->insns;
>
> -	__bpf_jit_compile(&ctx);
> +	__bpf_jit_compile(fp, &ctx);
>   	if (ctx.target)
>   		fp->bpf_func = (void *)ctx.target;
>   }
> _
>
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