net: filter: Fix some minor issues in sparc JIT.

Correct conventions comments.  %o4 and %o5 were swapped,
%g3 was not documented.

Use r_TMP instead of r_SKB_DATA + r_OFF where possible in
assembler stubs.

Correct discussion of %o4 and %o5 in one of bpf_jit_compile()'s
comments.

Based upon feedback from Richard Mortimer.
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/net/bpf_jit.h

@@ -4,13 +4,14 @@
 /* Conventions:
  *  %g1 : temporary
  *  %g2 : Secondary temporary used by SKB data helper stubs.
+ *  %g3 : packet offset passed into SKB data helper stubs.
  *  %o0 : pointer to skb (first argument given to JIT function)
  *  %o1 : BPF A accumulator
  *  %o2 : BPF X accumulator
  *  %o3 : Holds saved %o7 so we can call helper functions without needing
  *        to allocate a register window.
- *  %o4 : skb->data
- *  %o5 : skb->len - skb->data_len
+ *  %o4 : skb->len - skb->data_len
+ *  %o5 : skb->data
  */
 
 #ifndef __ASSEMBLER__

arch/sparc/net/bpf_jit_asm.S

@@ -30,7 +30,7 @@ bpf_jit_load_word_positive_offset:
 	bne	load_word_unaligned
 	 nop
 	retl
-	 ld	[r_SKB_DATA + r_OFF], r_A
+	 ld	[r_TMP], r_A
 load_word_unaligned:
 	ldub	[r_TMP + 0x0], r_OFF
 	ldub	[r_TMP + 0x1], r_TMP2
@@ -59,7 +59,7 @@ bpf_jit_load_half_positive_offset:
 	bne	load_half_unaligned
 	 nop
 	retl
-	 lduh	[r_SKB_DATA + r_OFF], r_A
+	 lduh	[r_TMP], r_A
 load_half_unaligned:
 	ldub	[r_TMP + 0x0], r_OFF
 	ldub	[r_TMP + 0x1], r_TMP2

arch/sparc/net/bpf_jit_comp.c

@@ -378,7 +378,7 @@ void bpf_jit_compile(struct sk_filter *fp)
 				emit_clear(r_X);
 
 			/* If this filter needs to access skb data,
-			 * load %o4 and %o4 with:
+			 * load %o4 and %o5 with:
 			 *  %o4 = skb->len - skb->data_len
 			 *  %o5 = skb->data
 			 * And also back up %o7 into r_saved_O7 so we can