/*
* BPF Jit compiler for s390, help functions.
*
* Copyright IBM Corp. 2012,2015
*
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
* Michael Holzheu <holzheu@linux.vnet.ibm.com>
*/
#include <linux/linkage.h>
#include "bpf_jit.h"
/*
* Calling convention:
* registers %r7-%r10, %r11,%r13, and %r15 are call saved
*
* Input (64 bit):
* %r3 (%b2) = offset into skb data
* %r6 (%b5) = return address
* %r7 (%b6) = skb pointer
* %r12 = skb data pointer
*
* Output:
* %r14= %b0 = return value (read skb value)
*
* Work registers: %r2,%r4,%r5,%r14
*
* skb_copy_bits takes 4 parameters:
* %r2 = skb pointer
* %r3 = offset into skb data
* %r4 = pointer to temp buffer
* %r5 = length to copy
* Return value in %r2: 0 = ok
*
* bpf_internal_load_pointer_neg_helper takes 3 parameters:
* %r2 = skb pointer
* %r3 = offset into data
* %r4 = length to copy
* Return value in %r2: Pointer to data
*/
#define SKF_MAX_NEG_OFF -0x200000 /* SKF_LL_OFF from filter.h */
/*
* Load SIZE bytes from SKB
*/
#define sk_load_common(NAME, SIZE, LOAD) \
ENTRY(sk_load_##NAME); \
ltgr %r3,%r3; /* Is offset negative? */ \
jl sk_load_##NAME##_slow_neg; \
ENTRY(sk_load_##NAME##_pos); \
aghi %r3,SIZE; /* Offset + SIZE */ \
clg %r3,STK_OFF_HLEN(%r15); /* Offset + SIZE > hlen? */ \
jh sk_load_##NAME##_slow; \
LOAD %r14,-SIZE(%r3,%r12); /* Get data from skb */ \
b OFF_OK(%r6); /* Return */ \
\
sk_load_##NAME##_slow:; \
lgr %r2,%r7; /* Arg1 = skb pointer */ \
aghi %r3,-SIZE; /* Arg2 = offset */ \
la %r4,STK_OFF_TMP(%r15); /* Arg3 = temp bufffer */ \
lghi %r5,SIZE; /* Arg4 = size */ \
brasl %r14,skb_copy_bits; /* Get data from skb */ \
LOAD %r14,STK_OFF_TMP(%r15); /* Load from temp bufffer */ \
ltgr %r2,%r2; /* Set cc to (%r2 != 0) */ \
br %r6; /* Return */
sk_load_common(word, 4, llgf) /* r14 = *(u32 *) (skb->data+offset) */
sk_load_common(half, 2, llgh) /* r14 = *(u16 *) (skb->data+offset) */
/*
* Load 1 byte from SKB (optimized version)
*/
/* r14 = *(u8 *) (skb->data+offset) */
ENTRY(sk_load_byte)
ltgr %r3,%r3 # Is offset negative?
jl sk_load_byte_slow_neg
ENTRY(sk_load_byte_pos)
clg %r3,STK_OFF_HLEN(%r15) # Offset >= hlen?
jnl sk_load_byte_slow
llgc %r14,0(%r3,%r12) # Get byte from skb
b OFF_OK(%r6) # Return OK
sk_load_byte_slow:
lgr %r2,%r7 # Arg1 = skb pointer
# Arg2 = offset
la %r4,STK_OFF_TMP(%r15) # Arg3 = pointer to temp buffer
lghi %r5,1 # Arg4 = size (1 byte)
brasl %r14,skb_copy_bits # Get data from skb
llgc %r14,STK_OFF_TMP(%r15) # Load result from temp buffer
ltgr %r2,%r2 # Set cc to (%r2 != 0)
br %r6 # Return cc
#define sk_negative_common(NAME, SIZE, LOAD) \
sk_load_##NAME##_slow_neg:; \
cgfi %r3,SKF_MAX_NEG_OFF; \
jl bpf_error; \
lgr %r2,%r7; /* Arg1 = skb pointer */ \
/* Arg2 = offset */ \
lghi %r4,SIZE; /* Arg3 = size */ \
brasl %r14,bpf_internal_load_pointer_neg_helper; \
ltgr %r2,%r2; \
jz bpf_error; \
LOAD %r14,0(%r2); /* Get data from pointer */ \
xr %r3,%r3; /* Set cc to zero */ \
br %r6; /* Return cc */
sk_negative_common(word, 4, llgf)
sk_negative_common(half, 2, llgh)
sk_negative_common(byte, 1, llgc)
bpf_error:
# force a return 0 from jit handler
ltgr %r15,%r15 # Set condition code
br %r6
