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Martin Schwidefskyc10302e2012-07-31 16:23:59 +02001/*
2 * BPF Jit compiler for s390, help functions.
3 *
Michael Holzheu05462312015-04-01 16:08:32 +02004 * Copyright IBM Corp. 2012,2015
Martin Schwidefskyc10302e2012-07-31 16:23:59 +02005 *
6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
Michael Holzheu05462312015-04-01 16:08:32 +02007 * Michael Holzheu <holzheu@linux.vnet.ibm.com>
Martin Schwidefskyc10302e2012-07-31 16:23:59 +02008 */
Michael Holzheu05462312015-04-01 16:08:32 +02009
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020010#include <linux/linkage.h>
Michael Holzheu05462312015-04-01 16:08:32 +020011#include "bpf_jit.h"
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020012
13/*
14 * Calling convention:
Michael Holzheu05462312015-04-01 16:08:32 +020015 * registers %r7-%r10, %r11,%r13, and %r15 are call saved
16 *
17 * Input (64 bit):
18 * %r3 (%b2) = offset into skb data
19 * %r6 (%b5) = return address
20 * %r7 (%b6) = skb pointer
21 * %r12 = skb data pointer
22 *
23 * Output:
24 * %r14= %b0 = return value (read skb value)
25 *
26 * Work registers: %r2,%r4,%r5,%r14
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020027 *
28 * skb_copy_bits takes 4 parameters:
29 * %r2 = skb pointer
30 * %r3 = offset into skb data
Michael Holzheudb9aa8f2015-01-15 10:20:28 +010031 * %r4 = pointer to temp buffer
32 * %r5 = length to copy
Michael Holzheu05462312015-04-01 16:08:32 +020033 * Return value in %r2: 0 = ok
34 *
35 * bpf_internal_load_pointer_neg_helper takes 3 parameters:
36 * %r2 = skb pointer
37 * %r3 = offset into data
38 * %r4 = length to copy
39 * Return value in %r2: Pointer to data
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020040 */
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020041
Michael Holzheu05462312015-04-01 16:08:32 +020042#define SKF_MAX_NEG_OFF -0x200000 /* SKF_LL_OFF from filter.h */
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020043
Michael Holzheu05462312015-04-01 16:08:32 +020044/*
45 * Load SIZE bytes from SKB
46 */
47#define sk_load_common(NAME, SIZE, LOAD) \
48ENTRY(sk_load_##NAME); \
49 ltgr %r3,%r3; /* Is offset negative? */ \
50 jl sk_load_##NAME##_slow_neg; \
51ENTRY(sk_load_##NAME##_pos); \
52 aghi %r3,SIZE; /* Offset + SIZE */ \
53 clg %r3,STK_OFF_HLEN(%r15); /* Offset + SIZE > hlen? */ \
54 jh sk_load_##NAME##_slow; \
55 LOAD %r14,-SIZE(%r3,%r12); /* Get data from skb */ \
56 b OFF_OK(%r6); /* Return */ \
57 \
58sk_load_##NAME##_slow:; \
59 lgr %r2,%r7; /* Arg1 = skb pointer */ \
60 aghi %r3,-SIZE; /* Arg2 = offset */ \
61 la %r4,STK_OFF_TMP(%r15); /* Arg3 = temp bufffer */ \
62 lghi %r5,SIZE; /* Arg4 = size */ \
63 brasl %r14,skb_copy_bits; /* Get data from skb */ \
64 LOAD %r14,STK_OFF_TMP(%r15); /* Load from temp bufffer */ \
65 ltgr %r2,%r2; /* Set cc to (%r2 != 0) */ \
66 br %r6; /* Return */
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020067
Michael Holzheu05462312015-04-01 16:08:32 +020068sk_load_common(word, 4, llgf) /* r14 = *(u32 *) (skb->data+offset) */
69sk_load_common(half, 2, llgh) /* r14 = *(u16 *) (skb->data+offset) */
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020070
Michael Holzheu05462312015-04-01 16:08:32 +020071/*
72 * Load 1 byte from SKB (optimized version)
73 */
74 /* r14 = *(u8 *) (skb->data+offset) */
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020075ENTRY(sk_load_byte)
Michael Holzheu05462312015-04-01 16:08:32 +020076 ltgr %r3,%r3 # Is offset negative?
77 jl sk_load_byte_slow_neg
78ENTRY(sk_load_byte_pos)
79 clg %r3,STK_OFF_HLEN(%r15) # Offset >= hlen?
80 jnl sk_load_byte_slow
81 llgc %r14,0(%r3,%r12) # Get byte from skb
82 b OFF_OK(%r6) # Return OK
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020083
84sk_load_byte_slow:
Michael Holzheu05462312015-04-01 16:08:32 +020085 lgr %r2,%r7 # Arg1 = skb pointer
86 # Arg2 = offset
87 la %r4,STK_OFF_TMP(%r15) # Arg3 = pointer to temp buffer
88 lghi %r5,1 # Arg4 = size (1 byte)
89 brasl %r14,skb_copy_bits # Get data from skb
90 llgc %r14,STK_OFF_TMP(%r15) # Load result from temp buffer
91 ltgr %r2,%r2 # Set cc to (%r2 != 0)
92 br %r6 # Return cc
Martin Schwidefskyc10302e2012-07-31 16:23:59 +020093
Michael Holzheu05462312015-04-01 16:08:32 +020094#define sk_negative_common(NAME, SIZE, LOAD) \
95sk_load_##NAME##_slow_neg:; \
96 cgfi %r3,SKF_MAX_NEG_OFF; \
97 jl bpf_error; \
98 lgr %r2,%r7; /* Arg1 = skb pointer */ \
99 /* Arg2 = offset */ \
100 lghi %r4,SIZE; /* Arg3 = size */ \
101 brasl %r14,bpf_internal_load_pointer_neg_helper; \
102 ltgr %r2,%r2; \
103 jz bpf_error; \
104 LOAD %r14,0(%r2); /* Get data from pointer */ \
105 xr %r3,%r3; /* Set cc to zero */ \
106 br %r6; /* Return cc */
Martin Schwidefskyc10302e2012-07-31 16:23:59 +0200107
Michael Holzheu05462312015-04-01 16:08:32 +0200108sk_negative_common(word, 4, llgf)
109sk_negative_common(half, 2, llgh)
110sk_negative_common(byte, 1, llgc)
111
112bpf_error:
113# force a return 0 from jit handler
114 ltgr %r15,%r15 # Set condition code
115 br %r6