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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/s390/net/bpf_jit.S
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+/*
+ * 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