201 строка
4.1 KiB
ArmAsm
201 строка
4.1 KiB
ArmAsm
/* bpf_jit.S : BPF JIT helper functions
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*
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* Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*/
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#include <linux/linkage.h>
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#include <asm/dwarf2.h>
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/*
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* Calling convention :
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* rdi : skb pointer
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* esi : offset of byte(s) to fetch in skb (can be scratched)
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* r8 : copy of skb->data
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* r9d : hlen = skb->len - skb->data_len
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*/
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#define SKBDATA %r8
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#define SKF_MAX_NEG_OFF $(-0x200000) /* SKF_LL_OFF from filter.h */
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sk_load_word:
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.globl sk_load_word
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test %esi,%esi
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js bpf_slow_path_word_neg
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sk_load_word_positive_offset:
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.globl sk_load_word_positive_offset
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mov %r9d,%eax # hlen
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sub %esi,%eax # hlen - offset
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cmp $3,%eax
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jle bpf_slow_path_word
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mov (SKBDATA,%rsi),%eax
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bswap %eax /* ntohl() */
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ret
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sk_load_half:
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.globl sk_load_half
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test %esi,%esi
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js bpf_slow_path_half_neg
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sk_load_half_positive_offset:
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.globl sk_load_half_positive_offset
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mov %r9d,%eax
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sub %esi,%eax # hlen - offset
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cmp $1,%eax
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jle bpf_slow_path_half
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movzwl (SKBDATA,%rsi),%eax
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rol $8,%ax # ntohs()
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ret
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sk_load_byte:
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.globl sk_load_byte
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test %esi,%esi
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js bpf_slow_path_byte_neg
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sk_load_byte_positive_offset:
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.globl sk_load_byte_positive_offset
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cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte */
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jle bpf_slow_path_byte
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movzbl (SKBDATA,%rsi),%eax
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ret
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/**
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* sk_load_byte_msh - BPF_S_LDX_B_MSH helper
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*
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* Implements BPF_S_LDX_B_MSH : ldxb 4*([offset]&0xf)
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* Must preserve A accumulator (%eax)
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* Inputs : %esi is the offset value
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*/
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sk_load_byte_msh:
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.globl sk_load_byte_msh
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test %esi,%esi
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js bpf_slow_path_byte_msh_neg
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sk_load_byte_msh_positive_offset:
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.globl sk_load_byte_msh_positive_offset
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cmp %esi,%r9d /* if (offset >= hlen) goto bpf_slow_path_byte_msh */
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jle bpf_slow_path_byte_msh
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movzbl (SKBDATA,%rsi),%ebx
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and $15,%bl
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shl $2,%bl
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ret
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/* rsi contains offset and can be scratched */
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#define bpf_slow_path_common(LEN) \
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push %rdi; /* save skb */ \
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push %r9; \
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push SKBDATA; \
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/* rsi already has offset */ \
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mov $LEN,%ecx; /* len */ \
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lea -12(%rbp),%rdx; \
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call skb_copy_bits; \
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test %eax,%eax; \
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pop SKBDATA; \
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pop %r9; \
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pop %rdi
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bpf_slow_path_word:
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bpf_slow_path_common(4)
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js bpf_error
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mov -12(%rbp),%eax
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bswap %eax
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ret
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bpf_slow_path_half:
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bpf_slow_path_common(2)
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js bpf_error
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mov -12(%rbp),%ax
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rol $8,%ax
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movzwl %ax,%eax
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ret
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bpf_slow_path_byte:
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bpf_slow_path_common(1)
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js bpf_error
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movzbl -12(%rbp),%eax
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ret
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bpf_slow_path_byte_msh:
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xchg %eax,%ebx /* dont lose A , X is about to be scratched */
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bpf_slow_path_common(1)
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js bpf_error
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movzbl -12(%rbp),%eax
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and $15,%al
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shl $2,%al
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xchg %eax,%ebx
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ret
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#define sk_negative_common(SIZE) \
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push %rdi; /* save skb */ \
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push %r9; \
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push SKBDATA; \
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/* rsi already has offset */ \
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mov $SIZE,%ecx; /* size */ \
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call bpf_internal_load_pointer_neg_helper; \
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test %rax,%rax; \
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pop SKBDATA; \
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pop %r9; \
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pop %rdi; \
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jz bpf_error
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bpf_slow_path_word_neg:
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cmp SKF_MAX_NEG_OFF, %esi /* test range */
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jl bpf_error /* offset lower -> error */
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sk_load_word_negative_offset:
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.globl sk_load_word_negative_offset
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sk_negative_common(4)
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mov (%rax), %eax
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bswap %eax
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ret
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bpf_slow_path_half_neg:
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cmp SKF_MAX_NEG_OFF, %esi
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jl bpf_error
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sk_load_half_negative_offset:
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.globl sk_load_half_negative_offset
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sk_negative_common(2)
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mov (%rax),%ax
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rol $8,%ax
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movzwl %ax,%eax
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ret
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bpf_slow_path_byte_neg:
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cmp SKF_MAX_NEG_OFF, %esi
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jl bpf_error
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sk_load_byte_negative_offset:
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.globl sk_load_byte_negative_offset
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sk_negative_common(1)
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movzbl (%rax), %eax
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ret
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bpf_slow_path_byte_msh_neg:
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cmp SKF_MAX_NEG_OFF, %esi
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jl bpf_error
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sk_load_byte_msh_negative_offset:
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.globl sk_load_byte_msh_negative_offset
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xchg %eax,%ebx /* dont lose A , X is about to be scratched */
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sk_negative_common(1)
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movzbl (%rax),%eax
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and $15,%al
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shl $2,%al
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xchg %eax,%ebx
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ret
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bpf_error:
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# force a return 0 from jit handler
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xor %eax,%eax
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mov -8(%rbp),%rbx
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leaveq
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ret
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