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