| Message ID | 1290153398.29509.7.camel@edumazet-laptop |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Fri, Nov 19, 2010 at 3:56 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: > Starting the translated instruction to 1 instead of 0 allows us to > remove one descrement at check time and makes codes[] array init > cleaner. > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> > --- > net/core/filter.c | 95 +++++++++++++++++++++----------------------- > 1 file changed, 47 insertions(+), 48 deletions(-) > > diff --git a/net/core/filter.c b/net/core/filter.c > index 15a545d..a1edb5d 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -39,7 +39,7 @@ > #include <linux/filter.h> > > enum { > - BPF_S_RET_K = 0, > + BPF_S_RET_K = 1, > BPF_S_RET_A, > BPF_S_ALU_ADD_K, > BPF_S_ALU_ADD_X, > @@ -436,51 +436,51 @@ int sk_chk_filter(struct sock_filter *filter, int flen) > * 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, > + [BPF_ALU|BPF_ADD|BPF_K] = BPF_S_ALU_ADD_K, > + [BPF_ALU|BPF_ADD|BPF_X] = BPF_S_ALU_ADD_X, > + [BPF_ALU|BPF_SUB|BPF_K] = BPF_S_ALU_SUB_K, > + [BPF_ALU|BPF_SUB|BPF_X] = BPF_S_ALU_SUB_X, > + [BPF_ALU|BPF_MUL|BPF_K] = BPF_S_ALU_MUL_K, > + [BPF_ALU|BPF_MUL|BPF_X] = BPF_S_ALU_MUL_X, > + [BPF_ALU|BPF_DIV|BPF_X] = BPF_S_ALU_DIV_X, > + [BPF_ALU|BPF_AND|BPF_K] = BPF_S_ALU_AND_K, > + [BPF_ALU|BPF_AND|BPF_X] = BPF_S_ALU_AND_X, > + [BPF_ALU|BPF_OR|BPF_K] = BPF_S_ALU_OR_K, > + [BPF_ALU|BPF_OR|BPF_X] = BPF_S_ALU_OR_X, > + [BPF_ALU|BPF_LSH|BPF_K] = BPF_S_ALU_LSH_K, > + [BPF_ALU|BPF_LSH|BPF_X] = BPF_S_ALU_LSH_X, > + [BPF_ALU|BPF_RSH|BPF_K] = BPF_S_ALU_RSH_K, > + [BPF_ALU|BPF_RSH|BPF_X] = BPF_S_ALU_RSH_X, > + [BPF_ALU|BPF_NEG] = BPF_S_ALU_NEG, > + [BPF_LD|BPF_W|BPF_ABS] = BPF_S_LD_W_ABS, > + [BPF_LD|BPF_H|BPF_ABS] = BPF_S_LD_H_ABS, > + [BPF_LD|BPF_B|BPF_ABS] = BPF_S_LD_B_ABS, > + [BPF_LD|BPF_W|BPF_LEN] = BPF_S_LD_W_LEN, > + [BPF_LD|BPF_W|BPF_IND] = BPF_S_LD_W_IND, > + [BPF_LD|BPF_H|BPF_IND] = BPF_S_LD_H_IND, > + [BPF_LD|BPF_B|BPF_IND] = BPF_S_LD_B_IND, > + [BPF_LD|BPF_IMM] = BPF_S_LD_IMM, > + [BPF_LDX|BPF_W|BPF_LEN] = BPF_S_LDX_W_LEN, > + [BPF_LDX|BPF_B|BPF_MSH] = BPF_S_LDX_B_MSH, > + [BPF_LDX|BPF_IMM] = BPF_S_LDX_IMM, > + [BPF_MISC|BPF_TAX] = BPF_S_MISC_TAX, > + [BPF_MISC|BPF_TXA] = BPF_S_MISC_TXA, > + [BPF_RET|BPF_K] = BPF_S_RET_K, > + [BPF_RET|BPF_A] = BPF_S_RET_A, > + [BPF_ALU|BPF_DIV|BPF_K] = BPF_S_ALU_DIV_K, > + [BPF_LD|BPF_MEM] = BPF_S_LD_MEM, > + [BPF_LDX|BPF_MEM] = BPF_S_LDX_MEM, > + [BPF_ST] = BPF_S_ST, > + [BPF_STX] = BPF_S_STX, > + [BPF_JMP|BPF_JA] = BPF_S_JMP_JA, > + [BPF_JMP|BPF_JEQ|BPF_K] = BPF_S_JMP_JEQ_K, > + [BPF_JMP|BPF_JEQ|BPF_X] = BPF_S_JMP_JEQ_X, > + [BPF_JMP|BPF_JGE|BPF_K] = BPF_S_JMP_JGE_K, > + [BPF_JMP|BPF_JGE|BPF_X] = BPF_S_JMP_JGE_X, > + [BPF_JMP|BPF_JGT|BPF_K] = BPF_S_JMP_JGT_K, > + [BPF_JMP|BPF_JGT|BPF_X] = BPF_S_JMP_JGT_X, > + [BPF_JMP|BPF_JSET|BPF_K] = BPF_S_JMP_JSET_K, > + [BPF_JMP|BPF_JSET|BPF_X] = BPF_S_JMP_JSET_X, > }; > int pc; > > @@ -495,8 +495,7 @@ int sk_chk_filter(struct sock_filter *filter, int flen) > if (code >= ARRAY_SIZE(codes)) > return -EINVAL; > code = codes[code]; > - /* Undo the '+ 1' in codes[] after validation. */ > - if (!code--) > + if (!code) > return -EINVAL; > /* Some instructions need special checks */ > switch (code) { > > > I compared the asm code of sk_run_filter. Here is the original: switch (fentry->code) { ffffffff8138c70c: 66 83 38 2c cmpw $0x2c,(%rax) /* * Process array of filter instructions. */ for (pc = 0; pc < flen; pc++) { const struct sock_filter *fentry = &filter[pc]; u32 f_k = fentry->k; ffffffff8138c710: 44 8b 78 04 mov 0x4(%rax),%r15d switch (fentry->code) { ffffffff8138c714: 0f 87 53 02 00 00 ja ffffffff8138c96d <sk_run_filter+0x2a8> ffffffff8138c71a: 0f b7 10 movzwl (%rax),%edx ffffffff8138c71d: ff 24 d5 00 00 00 00 jmpq *0x0(,%rdx,8) And here is the patched: switch (fentry->code) { ffffffff8138c708: 8b 10 mov (%rax),%edx /* * Process array of filter instructions. */ for (pc = 0; pc < flen; pc++) { const struct sock_filter *fentry = &filter[pc]; u32 f_k = fentry->k; ffffffff8138c70a: 44 8b 78 04 mov 0x4(%rax),%r15d switch (fentry->code) { ffffffff8138c70e: ff ca dec %edx ffffffff8138c710: 66 83 fa 2c cmp $0x2c,%dx ffffffff8138c714: 0f 87 53 02 00 00 ja ffffffff8138c96d <sk_run_filter+0x2ac> ffffffff8138c71a: 0f b7 d2 movzwl %dx,%edx ffffffff8138c71d: ff 24 d5 00 00 00 00 jmpq *0x0(,%rdx,8) As you see, an additional 'dec %edx' instruction is inserted. sk_chk_filter() only runs 1 times, I think we can afford the 'dec instruction' and 'dirty' code, but sk_run_filter() runs much often, this additional dec instruction isn't affordable.
Le vendredi 19 novembre 2010 à 16:38 +0800, Changli Gao a écrit : > I compared the asm code of sk_run_filter. > As you see, an additional 'dec %edx' instruction is inserted. > sk_chk_filter() only runs 1 times, I think we can afford the 'dec > instruction' and 'dirty' code, but sk_run_filter() runs much often, > this additional dec instruction isn't affordable. > Maybe on your setup. By the way, the u32 f_k = fentry->k; that David added in commit 57fe93b374a6b871 was much more a problem on arches with not enough registers. x86_32 for example : compiler use a register (%esi on my gcc-4.5.1) to store f_k, and more important A register is now stored in stack instead of a cpu register. On my compilers gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5) 64bit gcc-4.5.1 (self compiled) 32bit result code was the same, before and after patch Most probably you have "CONFIG_CC_OPTIMIZE_FOR_SIZE=y" which unfortunately is known to generate poor looking code. 39b: 49 8d 14 c6 lea (%r14,%rax,8),%rdx 39f: 66 83 3a 2d cmpw $0x2d,(%rdx) 3a3: 8b 42 04 mov 0x4(%rdx),%eax // f_k = fentry->k; 3a6: 76 28 jbe 3d0 <sk_run_filter+0x70> 3d0: 0f b7 0a movzwl (%rdx),%ecx 3d3: ff 24 cd 00 00 00 00 jmpq *0x0(,%rcx,8) 32bit code: 2e0: 8d 04 df lea (%edi,%ebx,8),%eax 2e3: 66 83 38 2d cmpw $0x2d,(%eax) 2e7: 8b 70 04 mov 0x4(%eax),%esi // f_k = fentry->k; 2ea: 76 1c jbe 308 <sk_run_filter+0x58> 308: 0f b7 10 movzwl (%eax),%edx 30b: ff 24 95 38 00 00 00 jmp *0x38(,%edx,4) DIV_X instruction : 480: 8b 45 a4 mov -0x5c(%ebp),%eax 483: 85 c0 test %eax,%eax 485: 0f 84 9d fe ff ff je 328 <sk_run_filter+0x78> 48b: 8b 45 ac mov -0x54(%ebp),%eax // A 48e: 31 d2 xor %edx,%edx 490: f7 75 a4 divl -0x5c(%ebp) 493: 89 45 ac mov %eax,-0x54(%ebp) // A 496: e9 85 fe ff ff jmp 320 <sk_run_filter+0x70> I believe we should revert the u32 f_k = fentry->k; part fentry->k as is fast as f_k if stored on stack, and avoids one instruction if fentry->k is not needed. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Nov 19, 2010 at 5:54 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: > > Most probably you have "CONFIG_CC_OPTIMIZE_FOR_SIZE=y" which > unfortunately is known to generate poor looking code. Yes. So Acked-by: Changli Gao <xiaosuo@gmail.com>
From: Changli Gao <xiaosuo@gmail.com> Date: Fri, 19 Nov 2010 20:21:57 +0800 > On Fri, Nov 19, 2010 at 5:54 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote: >> >> Most probably you have "CONFIG_CC_OPTIMIZE_FOR_SIZE=y" which >> unfortunately is known to generate poor looking code. > > Yes. So > > Acked-by: Changli Gao <xiaosuo@gmail.com> Applied. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/core/filter.c b/net/core/filter.c index 15a545d..a1edb5d 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -39,7 +39,7 @@ #include <linux/filter.h> enum { - BPF_S_RET_K = 0, + BPF_S_RET_K = 1, BPF_S_RET_A, BPF_S_ALU_ADD_K, BPF_S_ALU_ADD_X, @@ -436,51 +436,51 @@ int sk_chk_filter(struct sock_filter *filter, int flen) * 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, + [BPF_ALU|BPF_ADD|BPF_K] = BPF_S_ALU_ADD_K, + [BPF_ALU|BPF_ADD|BPF_X] = BPF_S_ALU_ADD_X, + [BPF_ALU|BPF_SUB|BPF_K] = BPF_S_ALU_SUB_K, + [BPF_ALU|BPF_SUB|BPF_X] = BPF_S_ALU_SUB_X, + [BPF_ALU|BPF_MUL|BPF_K] = BPF_S_ALU_MUL_K, + [BPF_ALU|BPF_MUL|BPF_X] = BPF_S_ALU_MUL_X, + [BPF_ALU|BPF_DIV|BPF_X] = BPF_S_ALU_DIV_X, + [BPF_ALU|BPF_AND|BPF_K] = BPF_S_ALU_AND_K, + [BPF_ALU|BPF_AND|BPF_X] = BPF_S_ALU_AND_X, + [BPF_ALU|BPF_OR|BPF_K] = BPF_S_ALU_OR_K, + [BPF_ALU|BPF_OR|BPF_X] = BPF_S_ALU_OR_X, + [BPF_ALU|BPF_LSH|BPF_K] = BPF_S_ALU_LSH_K, + [BPF_ALU|BPF_LSH|BPF_X] = BPF_S_ALU_LSH_X, + [BPF_ALU|BPF_RSH|BPF_K] = BPF_S_ALU_RSH_K, + [BPF_ALU|BPF_RSH|BPF_X] = BPF_S_ALU_RSH_X, + [BPF_ALU|BPF_NEG] = BPF_S_ALU_NEG, + [BPF_LD|BPF_W|BPF_ABS] = BPF_S_LD_W_ABS, + [BPF_LD|BPF_H|BPF_ABS] = BPF_S_LD_H_ABS, + [BPF_LD|BPF_B|BPF_ABS] = BPF_S_LD_B_ABS, + [BPF_LD|BPF_W|BPF_LEN] = BPF_S_LD_W_LEN, + [BPF_LD|BPF_W|BPF_IND] = BPF_S_LD_W_IND, + [BPF_LD|BPF_H|BPF_IND] = BPF_S_LD_H_IND, + [BPF_LD|BPF_B|BPF_IND] = BPF_S_LD_B_IND, + [BPF_LD|BPF_IMM] = BPF_S_LD_IMM, + [BPF_LDX|BPF_W|BPF_LEN] = BPF_S_LDX_W_LEN, + [BPF_LDX|BPF_B|BPF_MSH] = BPF_S_LDX_B_MSH, + [BPF_LDX|BPF_IMM] = BPF_S_LDX_IMM, + [BPF_MISC|BPF_TAX] = BPF_S_MISC_TAX, + [BPF_MISC|BPF_TXA] = BPF_S_MISC_TXA, + [BPF_RET|BPF_K] = BPF_S_RET_K, + [BPF_RET|BPF_A] = BPF_S_RET_A, + [BPF_ALU|BPF_DIV|BPF_K] = BPF_S_ALU_DIV_K, + [BPF_LD|BPF_MEM] = BPF_S_LD_MEM, + [BPF_LDX|BPF_MEM] = BPF_S_LDX_MEM, + [BPF_ST] = BPF_S_ST, + [BPF_STX] = BPF_S_STX, + [BPF_JMP|BPF_JA] = BPF_S_JMP_JA, + [BPF_JMP|BPF_JEQ|BPF_K] = BPF_S_JMP_JEQ_K, + [BPF_JMP|BPF_JEQ|BPF_X] = BPF_S_JMP_JEQ_X, + [BPF_JMP|BPF_JGE|BPF_K] = BPF_S_JMP_JGE_K, + [BPF_JMP|BPF_JGE|BPF_X] = BPF_S_JMP_JGE_X, + [BPF_JMP|BPF_JGT|BPF_K] = BPF_S_JMP_JGT_K, + [BPF_JMP|BPF_JGT|BPF_X] = BPF_S_JMP_JGT_X, + [BPF_JMP|BPF_JSET|BPF_K] = BPF_S_JMP_JSET_K, + [BPF_JMP|BPF_JSET|BPF_X] = BPF_S_JMP_JSET_X, }; int pc; @@ -495,8 +495,7 @@ int sk_chk_filter(struct sock_filter *filter, int flen) if (code >= ARRAY_SIZE(codes)) return -EINVAL; code = codes[code]; - /* Undo the '+ 1' in codes[] after validation. */ - if (!code--) + if (!code) return -EINVAL; /* Some instructions need special checks */ switch (code) {
Starting the translated instruction to 1 instead of 0 allows us to remove one descrement at check time and makes codes[] array init cleaner. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> --- net/core/filter.c | 95 +++++++++++++++++++++----------------------- 1 file changed, 47 insertions(+), 48 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html