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/* bpf_jit.S: Packet/header access helper functions
* for PPC64 BPF compiler.
*
* Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
*
* 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/ppc_asm.h>
#include "bpf_jit.h"
/*
* All of these routines are called directly from generated code,
* whose register usage is:
*
* r3 skb
* r4,r5 A,X
* r6 *** address parameter to helper ***
* r7-r10 scratch
* r14 skb->data
* r15 skb headlen
* r16-31 M[]
*/
/*
* To consider: These helpers are so small it could be better to just
* generate them inline. Inline code can do the simple headlen check
* then branch directly to slow_path_XXX if required. (In fact, could
* load a spare GPR with the address of slow_path_generic and pass size
* as an argument, making the call site a mtlr, li and bllr.)
*
* Technically, the "is addr < 0" check is unnecessary & slowing down
* the ABS path, as it's statically checked on generation.
*/
.globl sk_load_word
sk_load_word:
cmpdi r_addr, 0
blt bpf_error
/* Are we accessing past headlen? */
subi r_scratch1, r_HL, 4
cmpd r_scratch1, r_addr
blt bpf_slow_path_word
/* Nope, just hitting the header. cr0 here is eq or gt! */
lwzx r_A, r_D, r_addr
/* When big endian we don't need to byteswap. */
blr /* Return success, cr0 != LT */
.globl sk_load_half
sk_load_half:
cmpdi r_addr, 0
blt bpf_error
subi r_scratch1, r_HL, 2
cmpd r_scratch1, r_addr
blt bpf_slow_path_half
lhzx r_A, r_D, r_addr
blr
.globl sk_load_byte
sk_load_byte:
cmpdi r_addr, 0
blt bpf_error
cmpd r_HL, r_addr
ble bpf_slow_path_byte
lbzx r_A, r_D, r_addr
blr
/*
* BPF_S_LDX_B_MSH: ldxb 4*([offset]&0xf)
* r_addr is the offset value, already known positive
*/
.globl sk_load_byte_msh
sk_load_byte_msh:
cmpd r_HL, r_addr
ble bpf_slow_path_byte_msh
lbzx r_X, r_D, r_addr
rlwinm r_X, r_X, 2, 32-4-2, 31-2
blr
bpf_error:
/* Entered with cr0 = lt */
li r3, 0
/* Generated code will 'blt epilogue', returning 0. */
blr
/* Call out to skb_copy_bits:
* We'll need to back up our volatile regs first; we have
* local variable space at r1+(BPF_PPC_STACK_BASIC).
* Allocate a new stack frame here to remain ABI-compliant in
* stashing LR.
*/
#define bpf_slow_path_common(SIZE) \
mflr r0; \
std r0, 16(r1); \
/* R3 goes in parameter space of caller's frame */ \
std r_skb, (BPF_PPC_STACKFRAME+48)(r1); \
std r_A, (BPF_PPC_STACK_BASIC+(0*8))(r1); \
std r_X, (BPF_PPC_STACK_BASIC+(1*8))(r1); \
addi r5, r1, BPF_PPC_STACK_BASIC+(2*8); \
stdu r1, -BPF_PPC_SLOWPATH_FRAME(r1); \
/* R3 = r_skb, as passed */ \
mr r4, r_addr; \
li r6, SIZE; \
bl skb_copy_bits; \
/* R3 = 0 on success */ \
addi r1, r1, BPF_PPC_SLOWPATH_FRAME; \
ld r0, 16(r1); \
ld r_A, (BPF_PPC_STACK_BASIC+(0*8))(r1); \
ld r_X, (BPF_PPC_STACK_BASIC+(1*8))(r1); \
mtlr r0; \
cmpdi r3, 0; \
blt bpf_error; /* cr0 = LT */ \
ld r_skb, (BPF_PPC_STACKFRAME+48)(r1); \
/* Great success! */
bpf_slow_path_word:
bpf_slow_path_common(4)
/* Data value is on stack, and cr0 != LT */
lwz r_A, BPF_PPC_STACK_BASIC+(2*8)(r1)
blr
bpf_slow_path_half:
bpf_slow_path_common(2)
lhz r_A, BPF_PPC_STACK_BASIC+(2*8)(r1)
blr
bpf_slow_path_byte:
bpf_slow_path_common(1)
lbz r_A, BPF_PPC_STACK_BASIC+(2*8)(r1)
blr
bpf_slow_path_byte_msh:
bpf_slow_path_common(1)
lbz r_X, BPF_PPC_STACK_BASIC+(2*8)(r1)
rlwinm r_X, r_X, 2, 32-4-2, 31-2
blr
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