Eric Lee / smarc-fsl-linux-kernel

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arch/x86/net/bpf_jit.S 2.74 KB
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0a14842f5   Eric Dumazet   net: filter: Just... 
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  /* bpf_jit.S : BPF JIT helper functions
   *
   * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.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 <linux/linkage.h>
  #include <asm/dwarf2.h>
  
  /*
   * Calling convention :
   * rdi : skb pointer
   * esi : offset of byte(s) to fetch in skb (can be scratched)
   * r8  : copy of skb->data
   * r9d : hlen = skb->len - skb->data_len
   */
  #define SKBDATA	%r8
  
  sk_load_word_ind:
  	.globl	sk_load_word_ind
  
  	add	%ebx,%esi	/* offset += X */
  #	test    %esi,%esi	/* if (offset < 0) goto bpf_error; */
  	js	bpf_error
  
  sk_load_word:
  	.globl	sk_load_word
  
  	mov	%r9d,%eax		# hlen
  	sub	%esi,%eax		# hlen - offset
  	cmp	$3,%eax
  	jle	bpf_slow_path_word
  	mov     (SKBDATA,%rsi),%eax
  	bswap   %eax  			/* ntohl() */
  	ret
  
  
  sk_load_half_ind:
  	.globl sk_load_half_ind
  
  	add	%ebx,%esi	/* offset += X */
  	js	bpf_error
  
  sk_load_half:
  	.globl	sk_load_half
  
  	mov	%r9d,%eax
  	sub	%esi,%eax		#	hlen - offset
  	cmp	$1,%eax
  	jle	bpf_slow_path_half
  	movzwl	(SKBDATA,%rsi),%eax
  	rol	$8,%ax			# ntohs()
  	ret
  
  sk_load_byte_ind:
  	.globl sk_load_byte_ind
  	add	%ebx,%esi	/* offset += X */
  	js	bpf_error
  
  sk_load_byte:
  	.globl	sk_load_byte
  
  	cmp	%esi,%r9d   /* if (offset >= hlen) goto bpf_slow_path_byte */
  	jle	bpf_slow_path_byte
  	movzbl	(SKBDATA,%rsi),%eax
  	ret
  
  /**
   * sk_load_byte_msh - BPF_S_LDX_B_MSH helper
   *
   * Implements BPF_S_LDX_B_MSH : ldxb  4*([offset]&0xf)
   * Must preserve A accumulator (%eax)
   * Inputs : %esi is the offset value, already known positive
   */
  ENTRY(sk_load_byte_msh)
  	CFI_STARTPROC
  	cmp	%esi,%r9d      /* if (offset >= hlen) goto bpf_slow_path_byte_msh */
  	jle	bpf_slow_path_byte_msh
  	movzbl	(SKBDATA,%rsi),%ebx
  	and	$15,%bl
  	shl	$2,%bl
  	ret
  	CFI_ENDPROC
  ENDPROC(sk_load_byte_msh)
  
  bpf_error:
  # force a return 0 from jit handler
  	xor		%eax,%eax
  	mov		-8(%rbp),%rbx
  	leaveq
  	ret
  
  /* rsi contains offset and can be scratched */
  #define bpf_slow_path_common(LEN)		\
  	push	%rdi;    /* save skb */		\
  	push	%r9;				\
  	push	SKBDATA;			\
  /* rsi already has offset */			\
  	mov	$LEN,%ecx;	/* len */	\
  	lea	-12(%rbp),%rdx;			\
  	call	skb_copy_bits;			\
  	test    %eax,%eax;			\
  	pop	SKBDATA;			\
  	pop	%r9;				\
  	pop	%rdi
  
  
  bpf_slow_path_word:
  	bpf_slow_path_common(4)
  	js	bpf_error
  	mov	-12(%rbp),%eax
  	bswap	%eax
  	ret
  
  bpf_slow_path_half:
  	bpf_slow_path_common(2)
  	js	bpf_error
  	mov	-12(%rbp),%ax
  	rol	$8,%ax
  	movzwl	%ax,%eax
  	ret
  
  bpf_slow_path_byte:
  	bpf_slow_path_common(1)
  	js	bpf_error
  	movzbl	-12(%rbp),%eax
  	ret
  
  bpf_slow_path_byte_msh:
  	xchg	%eax,%ebx /* dont lose A , X is about to be scratched */
  	bpf_slow_path_common(1)
  	js	bpf_error
  	movzbl	-12(%rbp),%eax
  	and	$15,%al
  	shl	$2,%al
  	xchg	%eax,%ebx
  	ret