netdev - Re: [PATCH v3] filter: Optimize instruction revalidation code.

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Date:	Wed, 17 Nov 2010 09:18:05 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, mjt@....msk.ru,
	davem@...emloft.net, drosenberg@...curity.com, hagen@...u.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH v3] filter: Optimize instruction revalidation code.

Le mercredi 17 novembre 2010 à 15:54 +0800, Changli Gao a écrit :
> On Wed, Nov 17, 2010 at 3:48 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> >
> > Acked-by: Eric Dumazet <eric.dumazet@...il.com>
> >
> > Please repost it when Changli patch is accepted by David
> > (if accepted :)), to get rid of the "+ 1"
> >
> 
> Oh. No need, if David accepts this patch first, otherwise, there is
> just some offset, and patch can handle it. :)
> 
> 


I was speaking of all the "+ 1" in codes[] init

+       static const u8 codes[] = {
+               [BPF_ALU|BPF_ADD|BPF_K]  = BPF_S_ALU_ADD_K + 1,
+               [BPF_ALU|BPF_ADD|BPF_X]  = BPF_S_ALU_ADD_X + 1,
+               [BPF_ALU|BPF_SUB|BPF_K]  = BPF_S_ALU_SUB_K + 1,
+               [BPF_ALU|BPF_SUB|BPF_X]  = BPF_S_ALU_SUB_X + 1,
+               [BPF_ALU|BPF_MUL|BPF_K]  = BPF_S_ALU_MUL_K + 1,
+               [BPF_ALU|BPF_MUL|BPF_X]  = BPF_S_ALU_MUL_X + 1,
+               [BPF_ALU|BPF_DIV|BPF_X]  = BPF_S_ALU_DIV_X + 1,
+               [BPF_ALU|BPF_AND|BPF_K]  = BPF_S_ALU_AND_K + 1,
+               [BPF_ALU|BPF_AND|BPF_X]  = BPF_S_ALU_AND_X + 1,
+               [BPF_ALU|BPF_OR|BPF_K]   = BPF_S_ALU_OR_K + 1,
+               [BPF_ALU|BPF_OR|BPF_X]   = BPF_S_ALU_OR_X + 1,
+               [BPF_ALU|BPF_LSH|BPF_K]  = BPF_S_ALU_LSH_K + 1,
+               [BPF_ALU|BPF_LSH|BPF_X]  = BPF_S_ALU_LSH_X + 1,
+               [BPF_ALU|BPF_RSH|BPF_K]  = BPF_S_ALU_RSH_K + 1,
+               [BPF_ALU|BPF_RSH|BPF_X]  = BPF_S_ALU_RSH_X + 1,
+               [BPF_ALU|BPF_NEG]        = BPF_S_ALU_NEG + 1,
+               [BPF_LD|BPF_W|BPF_ABS]   = BPF_S_LD_W_ABS + 1,
+               [BPF_LD|BPF_H|BPF_ABS]   = BPF_S_LD_H_ABS + 1,
+               [BPF_LD|BPF_B|BPF_ABS]   = BPF_S_LD_B_ABS + 1,
+               [BPF_LD|BPF_W|BPF_LEN]   = BPF_S_LD_W_LEN + 1,
+               [BPF_LD|BPF_W|BPF_IND]   = BPF_S_LD_W_IND + 1,
+               [BPF_LD|BPF_H|BPF_IND]   = BPF_S_LD_H_IND + 1,
+               [BPF_LD|BPF_B|BPF_IND]   = BPF_S_LD_B_IND + 1,
+               [BPF_LD|BPF_IMM]         = BPF_S_LD_IMM + 1,
+               [BPF_LDX|BPF_W|BPF_LEN]  = BPF_S_LDX_W_LEN + 1,
+               [BPF_LDX|BPF_B|BPF_MSH]  = BPF_S_LDX_B_MSH + 1,
+               [BPF_LDX|BPF_IMM]        = BPF_S_LDX_IMM + 1,
+               [BPF_MISC|BPF_TAX]       = BPF_S_MISC_TAX + 1,
+               [BPF_MISC|BPF_TXA]       = BPF_S_MISC_TXA + 1,
+               [BPF_RET|BPF_K]          = BPF_S_RET_K + 1,
+               [BPF_RET|BPF_A]          = BPF_S_RET_A + 1,
+               [BPF_ALU|BPF_DIV|BPF_K]  = BPF_S_ALU_DIV_K + 1,
+               [BPF_LD|BPF_MEM]         = BPF_S_LD_MEM + 1,
+               [BPF_LDX|BPF_MEM]        = BPF_S_LDX_MEM + 1,
+               [BPF_ST]                 = BPF_S_ST + 1,
+               [BPF_STX]                = BPF_S_STX + 1,
+               [BPF_JMP|BPF_JA]         = BPF_S_JMP_JA + 1,
+               [BPF_JMP|BPF_JEQ|BPF_K]  = BPF_S_JMP_JEQ_K + 1,
+               [BPF_JMP|BPF_JEQ|BPF_X]  = BPF_S_JMP_JEQ_X + 1,
+               [BPF_JMP|BPF_JGE|BPF_K]  = BPF_S_JMP_JGE_K + 1,
+               [BPF_JMP|BPF_JGE|BPF_X]  = BPF_S_JMP_JGE_X + 1,
+               [BPF_JMP|BPF_JGT|BPF_K]  = BPF_S_JMP_JGT_K + 1,
+               [BPF_JMP|BPF_JGT|BPF_X]  = BPF_S_JMP_JGT_X + 1,
+               [BPF_JMP|BPF_JSET|BPF_K] = BPF_S_JMP_JSET_K + 1,
+               [BPF_JMP|BPF_JSET|BPF_X] = BPF_S_JMP_JSET_X + 1,
+       };

This was needed because the translated instructions were begining from 0

If we change them to start at offset 1, we can avoid all the "+ 1" :

and avoid the bit ugly :

if (!code--) ...




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