| Eric Dumazet | 0a14842 | 2011-04-20 09:27:32 +0000 | [diff] [blame^] | 1 | /* bpf_jit.S : BPF JIT helper functions |
| 2 | * |
| 3 | * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com) |
| 4 | * |
| 5 | * This program is free software; you can redistribute it and/or |
| 6 | * modify it under the terms of the GNU General Public License |
| 7 | * as published by the Free Software Foundation; version 2 |
| 8 | * of the License. |
| 9 | */ |
| 10 | #include <linux/linkage.h> |
| 11 | #include <asm/dwarf2.h> |
| 12 | |
| 13 | /* |
| 14 | * Calling convention : |
| 15 | * rdi : skb pointer |
| 16 | * esi : offset of byte(s) to fetch in skb (can be scratched) |
| 17 | * r8 : copy of skb->data |
| 18 | * r9d : hlen = skb->len - skb->data_len |
| 19 | */ |
| 20 | #define SKBDATA %r8 |
| 21 | |
| 22 | sk_load_word_ind: |
| 23 | .globl sk_load_word_ind |
| 24 | |
| 25 | add %ebx,%esi /* offset += X */ |
| 26 | # test %esi,%esi /* if (offset < 0) goto bpf_error; */ |
| 27 | js bpf_error |
| 28 | |
| 29 | sk_load_word: |
| 30 | .globl sk_load_word |
| 31 | |
| 32 | mov %r9d,%eax # hlen |
| 33 | sub %esi,%eax # hlen - offset |
| 34 | cmp $3,%eax |
| 35 | jle bpf_slow_path_word |
| 36 | mov (SKBDATA,%rsi),%eax |
| 37 | bswap %eax /* ntohl() */ |
| 38 | ret |
| 39 | |
| 40 | |
| 41 | sk_load_half_ind: |
| 42 | .globl sk_load_half_ind |
| 43 | |
| 44 | add %ebx,%esi /* offset += X */ |
| 45 | js bpf_error |
| 46 | |
| 47 | sk_load_half: |
| 48 | .globl sk_load_half |
| 49 | |
| 50 | mov %r9d,%eax |
| 51 | sub %esi,%eax # hlen - offset |
| 52 | cmp $1,%eax |
| 53 | jle bpf_slow_path_half |
| 54 | movzwl (SKBDATA,%rsi),%eax |
| 55 | rol $8,%ax # ntohs() |
| 56 | ret |
| 57 | |
| 58 | sk_load_byte_ind: |
| 59 | .globl sk_load_byte_ind |
| 60 | add %ebx,%esi /* offset += X */ |
| 61 | js bpf_error |
| 62 | |
| 63 | sk_load_byte: |
| 64 | .globl sk_load_byte |
| 65 | |
| 66 | cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte */ |
| 67 | jle bpf_slow_path_byte |
| 68 | movzbl (SKBDATA,%rsi),%eax |
| 69 | ret |
| 70 | |
| 71 | /** |
| 72 | * sk_load_byte_msh - BPF_S_LDX_B_MSH helper |
| 73 | * |
| 74 | * Implements BPF_S_LDX_B_MSH : ldxb 4*([offset]&0xf) |
| 75 | * Must preserve A accumulator (%eax) |
| 76 | * Inputs : %esi is the offset value, already known positive |
| 77 | */ |
| 78 | ENTRY(sk_load_byte_msh) |
| 79 | CFI_STARTPROC |
| 80 | cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte_msh */ |
| 81 | jle bpf_slow_path_byte_msh |
| 82 | movzbl (SKBDATA,%rsi),%ebx |
| 83 | and $15,%bl |
| 84 | shl $2,%bl |
| 85 | ret |
| 86 | CFI_ENDPROC |
| 87 | ENDPROC(sk_load_byte_msh) |
| 88 | |
| 89 | bpf_error: |
| 90 | # force a return 0 from jit handler |
| 91 | xor %eax,%eax |
| 92 | mov -8(%rbp),%rbx |
| 93 | leaveq |
| 94 | ret |
| 95 | |
| 96 | /* rsi contains offset and can be scratched */ |
| 97 | #define bpf_slow_path_common(LEN) \ |
| 98 | push %rdi; /* save skb */ \ |
| 99 | push %r9; \ |
| 100 | push SKBDATA; \ |
| 101 | /* rsi already has offset */ \ |
| 102 | mov $LEN,%ecx; /* len */ \ |
| 103 | lea -12(%rbp),%rdx; \ |
| 104 | call skb_copy_bits; \ |
| 105 | test %eax,%eax; \ |
| 106 | pop SKBDATA; \ |
| 107 | pop %r9; \ |
| 108 | pop %rdi |
| 109 | |
| 110 | |
| 111 | bpf_slow_path_word: |
| 112 | bpf_slow_path_common(4) |
| 113 | js bpf_error |
| 114 | mov -12(%rbp),%eax |
| 115 | bswap %eax |
| 116 | ret |
| 117 | |
| 118 | bpf_slow_path_half: |
| 119 | bpf_slow_path_common(2) |
| 120 | js bpf_error |
| 121 | mov -12(%rbp),%ax |
| 122 | rol $8,%ax |
| 123 | movzwl %ax,%eax |
| 124 | ret |
| 125 | |
| 126 | bpf_slow_path_byte: |
| 127 | bpf_slow_path_common(1) |
| 128 | js bpf_error |
| 129 | movzbl -12(%rbp),%eax |
| 130 | ret |
| 131 | |
| 132 | bpf_slow_path_byte_msh: |
| 133 | xchg %eax,%ebx /* dont lose A , X is about to be scratched */ |
| 134 | bpf_slow_path_common(1) |
| 135 | js bpf_error |
| 136 | movzbl -12(%rbp),%eax |
| 137 | and $15,%al |
| 138 | shl $2,%al |
| 139 | xchg %eax,%ebx |
| 140 | ret |