diff options
Diffstat (limited to 'arch/mips/net/bpf_jit_asm.S')
| -rw-r--r-- | arch/mips/net/bpf_jit_asm.S | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/arch/mips/net/bpf_jit_asm.S b/arch/mips/net/bpf_jit_asm.S new file mode 100644 index 0000000..e927260 --- /dev/null +++ b/arch/mips/net/bpf_jit_asm.S @@ -0,0 +1,238 @@ +/* + * bpf_jib_asm.S: Packet/header access helper functions for MIPS/MIPS64 BPF + * compiler. + * + * Copyright (C) 2015 Imagination Technologies Ltd. + * Author: Markos Chandras <markos.chandras@imgtec.com> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; version 2 of the License. + */ + +#include <asm/asm.h> +#include <asm/regdef.h> +#include "bpf_jit.h" + +/* ABI + * + * r_skb_hl skb header length + * r_skb_data skb data + * r_off(a1) offset register + * r_A BPF register A + * r_X PF register X + * r_skb(a0) *skb + * r_M *scratch memory + * r_skb_le skb length + * r_s0 Scratch register 0 + * r_s1 Scratch register 1 + * + * On entry: + * a0: *skb + * a1: offset (imm or imm + X) + * + * All non-BPF-ABI registers are free for use. On return, we only + * care about r_ret. The BPF-ABI registers are assumed to remain + * unmodified during the entire filter operation. + */ + +#define skb a0 +#define offset a1 +#define SKF_LL_OFF (-0x200000) /* Can't include linux/filter.h in assembly */ + + /* We know better :) so prevent assembler reordering etc */ + .set noreorder + +#define is_offset_negative(TYPE) \ + /* If offset is negative we have more work to do */ \ + slti t0, offset, 0; \ + bgtz t0, bpf_slow_path_##TYPE##_neg; \ + /* Be careful what follows in DS. */ + +#define is_offset_in_header(SIZE, TYPE) \ + /* Reading from header? */ \ + addiu $r_s0, $r_skb_hl, -SIZE; \ + slt t0, $r_s0, offset; \ + bgtz t0, bpf_slow_path_##TYPE; \ + +LEAF(sk_load_word) + is_offset_negative(word) + .globl sk_load_word_positive +sk_load_word_positive: + is_offset_in_header(4, word) + /* Offset within header boundaries */ + PTR_ADDU t1, $r_skb_data, offset + lw $r_A, 0(t1) +#ifdef CONFIG_CPU_LITTLE_ENDIAN + wsbh t0, $r_A + rotr $r_A, t0, 16 +#endif + jr $r_ra + move $r_ret, zero + END(sk_load_word) + +LEAF(sk_load_half) + is_offset_negative(half) + .globl sk_load_half_positive +sk_load_half_positive: + is_offset_in_header(2, half) + /* Offset within header boundaries */ + PTR_ADDU t1, $r_skb_data, offset + lh $r_A, 0(t1) +#ifdef CONFIG_CPU_LITTLE_ENDIAN + wsbh t0, $r_A + seh $r_A, t0 +#endif + jr $r_ra + move $r_ret, zero + END(sk_load_half) + +LEAF(sk_load_byte) + is_offset_negative(byte) + .globl sk_load_byte_positive +sk_load_byte_positive: + is_offset_in_header(1, byte) + /* Offset within header boundaries */ + PTR_ADDU t1, $r_skb_data, offset + lb $r_A, 0(t1) + jr $r_ra + move $r_ret, zero + END(sk_load_byte) + +/* + * call skb_copy_bits: + * (prototype in linux/skbuff.h) + * + * int skb_copy_bits(sk_buff *skb, int offset, void *to, int len) + * + * o32 mandates we leave 4 spaces for argument registers in case + * the callee needs to use them. Even though we don't care about + * the argument registers ourselves, we need to allocate that space + * to remain ABI compliant since the callee may want to use that space. + * We also allocate 2 more spaces for $r_ra and our return register (*to). + * + * n64 is a bit different. The *caller* will allocate the space to preserve + * the arguments. So in 64-bit kernels, we allocate the 4-arg space for no + * good reason but it does not matter that much really. + * + * (void *to) is returned in r_s0 + * + */ +#define bpf_slow_path_common(SIZE) \ + /* Quick check. Are we within reasonable boundaries? */ \ + LONG_ADDIU $r_s1, $r_skb_len, -SIZE; \ + sltu $r_s0, offset, $r_s1; \ + beqz $r_s0, fault; \ + /* Load 4th argument in DS */ \ + LONG_ADDIU a3, zero, SIZE; \ + PTR_ADDIU $r_sp, $r_sp, -(6 * SZREG); \ + PTR_LA t0, skb_copy_bits; \ + PTR_S $r_ra, (5 * SZREG)($r_sp); \ + /* Assign low slot to a2 */ \ + move a2, $r_sp; \ + jalr t0; \ + /* Reset our destination slot (DS but it's ok) */ \ + INT_S zero, (4 * SZREG)($r_sp); \ + /* \ + * skb_copy_bits returns 0 on success and -EFAULT \ + * on error. Our data live in a2. Do not bother with \ + * our data if an error has been returned. \ + */ \ + /* Restore our frame */ \ + PTR_L $r_ra, (5 * SZREG)($r_sp); \ + INT_L $r_s0, (4 * SZREG)($r_sp); \ + bltz v0, fault; \ + PTR_ADDIU $r_sp, $r_sp, 6 * SZREG; \ + move $r_ret, zero; \ + +NESTED(bpf_slow_path_word, (6 * SZREG), $r_sp) + bpf_slow_path_common(4) +#ifdef CONFIG_CPU_LITTLE_ENDIAN + wsbh t0, $r_s0 + jr $r_ra + rotr $r_A, t0, 16 +#endif + jr $r_ra + move $r_A, $r_s0 + + END(bpf_slow_path_word) + +NESTED(bpf_slow_path_half, (6 * SZREG), $r_sp) + bpf_slow_path_common(2) +#ifdef CONFIG_CPU_LITTLE_ENDIAN + jr $r_ra + wsbh $r_A, $r_s0 +#endif + jr $r_ra + move $r_A, $r_s0 + + END(bpf_slow_path_half) + +NESTED(bpf_slow_path_byte, (6 * SZREG), $r_sp) + bpf_slow_path_common(1) + jr $r_ra + move $r_A, $r_s0 + + END(bpf_slow_path_byte) + +/* + * Negative entry points + */ + .macro bpf_is_end_of_data + li t0, SKF_LL_OFF + /* Reading link layer data? */ + slt t1, offset, t0 + bgtz t1, fault + /* Be careful what follows in DS. */ + .endm +/* + * call skb_copy_bits: + * (prototype in linux/filter.h) + * + * void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb, + * int k, unsigned int size) + * + * see above (bpf_slow_path_common) for ABI restrictions + */ +#define bpf_negative_common(SIZE) \ + PTR_ADDIU $r_sp, $r_sp, -(6 * SZREG); \ + PTR_LA t0, bpf_internal_load_pointer_neg_helper; \ + PTR_S $r_ra, (5 * SZREG)($r_sp); \ + jalr t0; \ + li a2, SIZE; \ + PTR_L $r_ra, (5 * SZREG)($r_sp); \ + /* Check return pointer */ \ + beqz v0, fault; \ + PTR_ADDIU $r_sp, $r_sp, 6 * SZREG; \ + /* Preserve our pointer */ \ + move $r_s0, v0; \ + /* Set return value */ \ + move $r_ret, zero; \ + +bpf_slow_path_word_neg: + bpf_is_end_of_data +NESTED(sk_load_word_negative, (6 * SZREG), $r_sp) + bpf_negative_common(4) + jr $r_ra + lw $r_A, 0($r_s0) + END(sk_load_word_negative) + +bpf_slow_path_half_neg: + bpf_is_end_of_data +NESTED(sk_load_half_negative, (6 * SZREG), $r_sp) + bpf_negative_common(2) + jr $r_ra + lhu $r_A, 0($r_s0) + END(sk_load_half_negative) + +bpf_slow_path_byte_neg: + bpf_is_end_of_data +NESTED(sk_load_byte_negative, (6 * SZREG), $r_sp) + bpf_negative_common(1) + jr $r_ra + lbu $r_A, 0($r_s0) + END(sk_load_byte_negative) + +fault: + jr $r_ra + addiu $r_ret, zero, 1 |
