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0c5d187828
The entire bpf_jit_asm.S is written in noreorder mode because "we know better" according to a comment. This also prevented the assembler from throwing in the required NOPs for MIPS I processors which have no load-use interlock, thus the load's consumer might end up using the old value of the register from prior to the load. Fixed by putting the assembler in reorder mode for just the affected load instructions. This is not enough for gas to actually try to be clever by looking at the next instruction and inserting a nop only when needed but as the comment said "we know better", so getting gas to unconditionally emit a NOP is just right in this case and prevents adding further ifdefery. Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
283 lines
6.8 KiB
ArmAsm
283 lines
6.8 KiB
ArmAsm
/*
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* bpf_jib_asm.S: Packet/header access helper functions for MIPS/MIPS64 BPF
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* compiler.
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*
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* Copyright (C) 2015 Imagination Technologies Ltd.
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* Author: Markos Chandras <markos.chandras@imgtec.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; version 2 of the License.
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*/
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#include <asm/asm.h>
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#include <asm/regdef.h>
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#include "bpf_jit.h"
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/* ABI
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*
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* r_skb_hl skb header length
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* r_skb_data skb data
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* r_off(a1) offset register
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* r_A BPF register A
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* r_X PF register X
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* r_skb(a0) *skb
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* r_M *scratch memory
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* r_skb_le skb length
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* r_s0 Scratch register 0
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* r_s1 Scratch register 1
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*
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* On entry:
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* a0: *skb
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* a1: offset (imm or imm + X)
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*
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* All non-BPF-ABI registers are free for use. On return, we only
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* care about r_ret. The BPF-ABI registers are assumed to remain
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* unmodified during the entire filter operation.
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*/
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#define skb a0
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#define offset a1
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#define SKF_LL_OFF (-0x200000) /* Can't include linux/filter.h in assembly */
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/* We know better :) so prevent assembler reordering etc */
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.set noreorder
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#define is_offset_negative(TYPE) \
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/* If offset is negative we have more work to do */ \
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slti t0, offset, 0; \
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bgtz t0, bpf_slow_path_##TYPE##_neg; \
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/* Be careful what follows in DS. */
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#define is_offset_in_header(SIZE, TYPE) \
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/* Reading from header? */ \
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addiu $r_s0, $r_skb_hl, -SIZE; \
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slt t0, $r_s0, offset; \
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bgtz t0, bpf_slow_path_##TYPE; \
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LEAF(sk_load_word)
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is_offset_negative(word)
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FEXPORT(sk_load_word_positive)
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is_offset_in_header(4, word)
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/* Offset within header boundaries */
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PTR_ADDU t1, $r_skb_data, offset
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.set reorder
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lw $r_A, 0(t1)
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.set noreorder
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#ifdef CONFIG_CPU_LITTLE_ENDIAN
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# if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
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wsbh t0, $r_A
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rotr $r_A, t0, 16
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# else
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sll t0, $r_A, 24
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srl t1, $r_A, 24
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srl t2, $r_A, 8
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or t0, t0, t1
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andi t2, t2, 0xff00
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andi t1, $r_A, 0xff00
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or t0, t0, t2
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sll t1, t1, 8
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or $r_A, t0, t1
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# endif
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#endif
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jr $r_ra
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move $r_ret, zero
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END(sk_load_word)
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LEAF(sk_load_half)
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is_offset_negative(half)
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FEXPORT(sk_load_half_positive)
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is_offset_in_header(2, half)
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/* Offset within header boundaries */
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PTR_ADDU t1, $r_skb_data, offset
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.set reorder
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lh $r_A, 0(t1)
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.set noreorder
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#ifdef CONFIG_CPU_LITTLE_ENDIAN
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# if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
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wsbh t0, $r_A
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seh $r_A, t0
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# else
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sll t0, $r_A, 24
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andi t1, $r_A, 0xff00
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sra t0, t0, 16
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srl t1, t1, 8
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or $r_A, t0, t1
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# endif
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#endif
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jr $r_ra
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move $r_ret, zero
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END(sk_load_half)
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LEAF(sk_load_byte)
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is_offset_negative(byte)
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FEXPORT(sk_load_byte_positive)
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is_offset_in_header(1, byte)
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/* Offset within header boundaries */
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PTR_ADDU t1, $r_skb_data, offset
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lb $r_A, 0(t1)
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jr $r_ra
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move $r_ret, zero
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END(sk_load_byte)
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/*
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* call skb_copy_bits:
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* (prototype in linux/skbuff.h)
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*
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* int skb_copy_bits(sk_buff *skb, int offset, void *to, int len)
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*
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* o32 mandates we leave 4 spaces for argument registers in case
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* the callee needs to use them. Even though we don't care about
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* the argument registers ourselves, we need to allocate that space
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* to remain ABI compliant since the callee may want to use that space.
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* We also allocate 2 more spaces for $r_ra and our return register (*to).
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*
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* n64 is a bit different. The *caller* will allocate the space to preserve
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* the arguments. So in 64-bit kernels, we allocate the 4-arg space for no
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* good reason but it does not matter that much really.
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*
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* (void *to) is returned in r_s0
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*
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*/
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#define bpf_slow_path_common(SIZE) \
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/* Quick check. Are we within reasonable boundaries? */ \
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LONG_ADDIU $r_s1, $r_skb_len, -SIZE; \
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sltu $r_s0, offset, $r_s1; \
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beqz $r_s0, fault; \
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/* Load 4th argument in DS */ \
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LONG_ADDIU a3, zero, SIZE; \
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PTR_ADDIU $r_sp, $r_sp, -(6 * SZREG); \
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PTR_LA t0, skb_copy_bits; \
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PTR_S $r_ra, (5 * SZREG)($r_sp); \
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/* Assign low slot to a2 */ \
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move a2, $r_sp; \
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jalr t0; \
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/* Reset our destination slot (DS but it's ok) */ \
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INT_S zero, (4 * SZREG)($r_sp); \
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/* \
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* skb_copy_bits returns 0 on success and -EFAULT \
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* on error. Our data live in a2. Do not bother with \
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* our data if an error has been returned. \
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*/ \
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/* Restore our frame */ \
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PTR_L $r_ra, (5 * SZREG)($r_sp); \
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INT_L $r_s0, (4 * SZREG)($r_sp); \
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bltz v0, fault; \
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PTR_ADDIU $r_sp, $r_sp, 6 * SZREG; \
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move $r_ret, zero; \
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NESTED(bpf_slow_path_word, (6 * SZREG), $r_sp)
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bpf_slow_path_common(4)
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#ifdef CONFIG_CPU_LITTLE_ENDIAN
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# if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
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wsbh t0, $r_s0
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jr $r_ra
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rotr $r_A, t0, 16
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# else
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sll t0, $r_s0, 24
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srl t1, $r_s0, 24
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srl t2, $r_s0, 8
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or t0, t0, t1
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andi t2, t2, 0xff00
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andi t1, $r_s0, 0xff00
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or t0, t0, t2
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sll t1, t1, 8
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jr $r_ra
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or $r_A, t0, t1
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# endif
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#else
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jr $r_ra
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move $r_A, $r_s0
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#endif
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END(bpf_slow_path_word)
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NESTED(bpf_slow_path_half, (6 * SZREG), $r_sp)
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bpf_slow_path_common(2)
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#ifdef CONFIG_CPU_LITTLE_ENDIAN
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# if defined(__mips_isa_rev) && (__mips_isa_rev >= 2)
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jr $r_ra
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wsbh $r_A, $r_s0
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# else
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sll t0, $r_s0, 8
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andi t1, $r_s0, 0xff00
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andi t0, t0, 0xff00
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srl t1, t1, 8
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jr $r_ra
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or $r_A, t0, t1
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# endif
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#else
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jr $r_ra
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move $r_A, $r_s0
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#endif
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END(bpf_slow_path_half)
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NESTED(bpf_slow_path_byte, (6 * SZREG), $r_sp)
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bpf_slow_path_common(1)
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jr $r_ra
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move $r_A, $r_s0
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END(bpf_slow_path_byte)
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/*
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* Negative entry points
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*/
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.macro bpf_is_end_of_data
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li t0, SKF_LL_OFF
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/* Reading link layer data? */
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slt t1, offset, t0
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bgtz t1, fault
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/* Be careful what follows in DS. */
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.endm
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/*
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* call skb_copy_bits:
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* (prototype in linux/filter.h)
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*
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* void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb,
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* int k, unsigned int size)
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*
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* see above (bpf_slow_path_common) for ABI restrictions
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*/
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#define bpf_negative_common(SIZE) \
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PTR_ADDIU $r_sp, $r_sp, -(6 * SZREG); \
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PTR_LA t0, bpf_internal_load_pointer_neg_helper; \
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PTR_S $r_ra, (5 * SZREG)($r_sp); \
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jalr t0; \
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li a2, SIZE; \
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PTR_L $r_ra, (5 * SZREG)($r_sp); \
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/* Check return pointer */ \
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beqz v0, fault; \
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PTR_ADDIU $r_sp, $r_sp, 6 * SZREG; \
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/* Preserve our pointer */ \
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move $r_s0, v0; \
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/* Set return value */ \
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move $r_ret, zero; \
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bpf_slow_path_word_neg:
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bpf_is_end_of_data
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NESTED(sk_load_word_negative, (6 * SZREG), $r_sp)
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bpf_negative_common(4)
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jr $r_ra
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lw $r_A, 0($r_s0)
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END(sk_load_word_negative)
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bpf_slow_path_half_neg:
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bpf_is_end_of_data
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NESTED(sk_load_half_negative, (6 * SZREG), $r_sp)
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bpf_negative_common(2)
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jr $r_ra
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lhu $r_A, 0($r_s0)
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END(sk_load_half_negative)
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bpf_slow_path_byte_neg:
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bpf_is_end_of_data
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NESTED(sk_load_byte_negative, (6 * SZREG), $r_sp)
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bpf_negative_common(1)
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jr $r_ra
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lbu $r_A, 0($r_s0)
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END(sk_load_byte_negative)
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fault:
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jr $r_ra
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addiu $r_ret, zero, 1
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