1/*
2 * BPF Jit compiler for s390, help functions.
3 *
4 * Copyright IBM Corp. 2012,2015
5 *
6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
7 *	      Michael Holzheu <holzheu@linux.vnet.ibm.com>
8 */
9
10#include <linux/linkage.h>
11#include "bpf_jit.h"
12
13/*
14 * Calling convention:
15 * 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
27 *
28 * skb_copy_bits takes 4 parameters:
29 *   %r2 = skb pointer
30 *   %r3 = offset into skb data
31 *   %r4 = pointer to temp buffer
32 *   %r5 = length to copy
33 *   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
40 */
41
42#define SKF_MAX_NEG_OFF	-0x200000	/* SKF_LL_OFF from filter.h */
43
44/*
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 */
67
68sk_load_common(word, 4, llgf)	/* r14 = *(u32 *) (skb->data+offset) */
69sk_load_common(half, 2, llgh)	/* r14 = *(u16 *) (skb->data+offset) */
70
71/*
72 * Load 1 byte from SKB (optimized version)
73 */
74	/* r14 = *(u8 *) (skb->data+offset) */
75ENTRY(sk_load_byte)
76	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
83
84sk_load_byte_slow:
85	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
93
94#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 */
107
108sk_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
116