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filter: Optimize instruction revalidation code.
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Since repeating u16 value to u8 value conversion using switch() clause's
case statement is wasteful, this patch introduces u16 to u8 mapping table
and removes most of case statements. As a result, the size of net/core/filter.o
is reduced by about 29% on x86.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Tetsuo Handa authored and David S. Miller committed Nov 18, 2010
1 parent 9e50e3a commit cba328f
Showing 1 changed file with 72 additions and 159 deletions.
231 changes: 72 additions & 159 deletions net/core/filter.c
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Original file line number Diff line number Diff line change
Expand Up @@ -383,185 +383,97 @@ EXPORT_SYMBOL(sk_run_filter);
*/
int sk_chk_filter(struct sock_filter *filter, int flen)
{
struct sock_filter *ftest;
/*
* Valid instructions are initialized to non-0.
* Invalid instructions are initialized to 0.
*/
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,
};
int pc;

if (flen == 0 || flen > BPF_MAXINSNS)
return -EINVAL;

/* check the filter code now */
for (pc = 0; pc < flen; pc++) {
ftest = &filter[pc];

/* Only allow valid instructions */
switch (ftest->code) {
case BPF_ALU|BPF_ADD|BPF_K:
ftest->code = BPF_S_ALU_ADD_K;
break;
case BPF_ALU|BPF_ADD|BPF_X:
ftest->code = BPF_S_ALU_ADD_X;
break;
case BPF_ALU|BPF_SUB|BPF_K:
ftest->code = BPF_S_ALU_SUB_K;
break;
case BPF_ALU|BPF_SUB|BPF_X:
ftest->code = BPF_S_ALU_SUB_X;
break;
case BPF_ALU|BPF_MUL|BPF_K:
ftest->code = BPF_S_ALU_MUL_K;
break;
case BPF_ALU|BPF_MUL|BPF_X:
ftest->code = BPF_S_ALU_MUL_X;
break;
case BPF_ALU|BPF_DIV|BPF_X:
ftest->code = BPF_S_ALU_DIV_X;
break;
case BPF_ALU|BPF_AND|BPF_K:
ftest->code = BPF_S_ALU_AND_K;
break;
case BPF_ALU|BPF_AND|BPF_X:
ftest->code = BPF_S_ALU_AND_X;
break;
case BPF_ALU|BPF_OR|BPF_K:
ftest->code = BPF_S_ALU_OR_K;
break;
case BPF_ALU|BPF_OR|BPF_X:
ftest->code = BPF_S_ALU_OR_X;
break;
case BPF_ALU|BPF_LSH|BPF_K:
ftest->code = BPF_S_ALU_LSH_K;
break;
case BPF_ALU|BPF_LSH|BPF_X:
ftest->code = BPF_S_ALU_LSH_X;
break;
case BPF_ALU|BPF_RSH|BPF_K:
ftest->code = BPF_S_ALU_RSH_K;
break;
case BPF_ALU|BPF_RSH|BPF_X:
ftest->code = BPF_S_ALU_RSH_X;
break;
case BPF_ALU|BPF_NEG:
ftest->code = BPF_S_ALU_NEG;
break;
case BPF_LD|BPF_W|BPF_ABS:
ftest->code = BPF_S_LD_W_ABS;
break;
case BPF_LD|BPF_H|BPF_ABS:
ftest->code = BPF_S_LD_H_ABS;
break;
case BPF_LD|BPF_B|BPF_ABS:
ftest->code = BPF_S_LD_B_ABS;
break;
case BPF_LD|BPF_W|BPF_LEN:
ftest->code = BPF_S_LD_W_LEN;
break;
case BPF_LD|BPF_W|BPF_IND:
ftest->code = BPF_S_LD_W_IND;
break;
case BPF_LD|BPF_H|BPF_IND:
ftest->code = BPF_S_LD_H_IND;
break;
case BPF_LD|BPF_B|BPF_IND:
ftest->code = BPF_S_LD_B_IND;
break;
case BPF_LD|BPF_IMM:
ftest->code = BPF_S_LD_IMM;
break;
case BPF_LDX|BPF_W|BPF_LEN:
ftest->code = BPF_S_LDX_W_LEN;
break;
case BPF_LDX|BPF_B|BPF_MSH:
ftest->code = BPF_S_LDX_B_MSH;
break;
case BPF_LDX|BPF_IMM:
ftest->code = BPF_S_LDX_IMM;
break;
case BPF_MISC|BPF_TAX:
ftest->code = BPF_S_MISC_TAX;
break;
case BPF_MISC|BPF_TXA:
ftest->code = BPF_S_MISC_TXA;
break;
case BPF_RET|BPF_K:
ftest->code = BPF_S_RET_K;
break;
case BPF_RET|BPF_A:
ftest->code = BPF_S_RET_A;
break;
struct sock_filter *ftest = &filter[pc];
u16 code = ftest->code;

if (code >= ARRAY_SIZE(codes))
return -EINVAL;
code = codes[code];
/* Undo the '+ 1' in codes[] after validation. */
if (!code--)
return -EINVAL;
/* Some instructions need special checks */

switch (code) {
case BPF_S_ALU_DIV_K:
/* check for division by zero */
case BPF_ALU|BPF_DIV|BPF_K:
if (ftest->k == 0)
return -EINVAL;
ftest->code = BPF_S_ALU_DIV_K;
break;

/* check for invalid memory addresses */
case BPF_LD|BPF_MEM:
if (ftest->k >= BPF_MEMWORDS)
return -EINVAL;
ftest->code = BPF_S_LD_MEM;
break;
case BPF_LDX|BPF_MEM:
if (ftest->k >= BPF_MEMWORDS)
return -EINVAL;
ftest->code = BPF_S_LDX_MEM;
break;
case BPF_ST:
if (ftest->k >= BPF_MEMWORDS)
return -EINVAL;
ftest->code = BPF_S_ST;
break;
case BPF_STX:
case BPF_S_LD_MEM:
case BPF_S_LDX_MEM:
case BPF_S_ST:
case BPF_S_STX:
/* check for invalid memory addresses */
if (ftest->k >= BPF_MEMWORDS)
return -EINVAL;
ftest->code = BPF_S_STX;
break;

case BPF_JMP|BPF_JA:
case BPF_S_JMP_JA:
/*
* Note, the large ftest->k might cause loops.
* Compare this with conditional jumps below,
* where offsets are limited. --ANK (981016)
*/
if (ftest->k >= (unsigned)(flen-pc-1))
return -EINVAL;
ftest->code = BPF_S_JMP_JA;
break;

case BPF_JMP|BPF_JEQ|BPF_K:
ftest->code = BPF_S_JMP_JEQ_K;
break;
case BPF_JMP|BPF_JEQ|BPF_X:
ftest->code = BPF_S_JMP_JEQ_X;
break;
case BPF_JMP|BPF_JGE|BPF_K:
ftest->code = BPF_S_JMP_JGE_K;
break;
case BPF_JMP|BPF_JGE|BPF_X:
ftest->code = BPF_S_JMP_JGE_X;
break;
case BPF_JMP|BPF_JGT|BPF_K:
ftest->code = BPF_S_JMP_JGT_K;
break;
case BPF_JMP|BPF_JGT|BPF_X:
ftest->code = BPF_S_JMP_JGT_X;
break;
case BPF_JMP|BPF_JSET|BPF_K:
ftest->code = BPF_S_JMP_JSET_K;
break;
case BPF_JMP|BPF_JSET|BPF_X:
ftest->code = BPF_S_JMP_JSET_X;
break;

default:
return -EINVAL;
}

/* for conditionals both must be safe */
switch (ftest->code) {
case BPF_S_JMP_JEQ_K:
case BPF_S_JMP_JEQ_X:
case BPF_S_JMP_JGE_K:
Expand All @@ -570,21 +482,22 @@ int sk_chk_filter(struct sock_filter *filter, int flen)
case BPF_S_JMP_JGT_X:
case BPF_S_JMP_JSET_X:
case BPF_S_JMP_JSET_K:
/* for conditionals both must be safe */
if (pc + ftest->jt + 1 >= flen ||
pc + ftest->jf + 1 >= flen)
return -EINVAL;
break;
}
ftest->code = code;
}

/* last instruction must be a RET code */
switch (filter[flen - 1].code) {
case BPF_S_RET_K:
case BPF_S_RET_A:
return 0;
break;
default:
return -EINVAL;
}
}
return -EINVAL;
}
EXPORT_SYMBOL(sk_chk_filter);

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