[POWERPC] Oprofile enhanced instruction sampling support

Oprofile enhanced instruction sampling support.

When performing instruction sampling, the mmcra[SLOT] field can be used to
more accurately identify the address of the sampled instruction.

Tested on power4, js20, power5 and power5+.
Signed-off-by: Will Schmidt <will_schmidt@vnet.ibm.com>
cc: Maynard Johnson <maynardj@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/oprofile/op_model_power4.c

 /*
  * Copyright (C) 2004 Anton Blanchard <anton@au.ibm.com>, IBM
+ * Added mmcra[slot] support:
+ * Copyright (C) 2006-2007 Will Schmidt <willschm@us.ibm.com>, IBM
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -181,11 +183,17 @@ static void __attribute_used__ kernel_unknown_bucket(void)
  * On GQ and newer the MMCRA stores the HV and PR bits at the time
  * the SIAR was sampled. We use that to work out if the SIAR was sampled in
  * the hypervisor, our exception vectors or RTAS.
+ * If the MMCRA_SAMPLE_ENABLE bit is set, we can use the MMCRA[slot] bits
+ * to more accurately identify the address of the sampled instruction. The
+ * mmcra[slot] bits represent the slot number of a sampled instruction
+ * within an instruction group.  The slot will contain a value between 1
+ * and 5 if MMCRA_SAMPLE_ENABLE is set, otherwise 0.
  */
 static unsigned long get_pc(struct pt_regs *regs)
 {
 	unsigned long pc = mfspr(SPRN_SIAR);
 	unsigned long mmcra;
+	unsigned long slot;
 
 	/* Cant do much about it */
 	if (!cur_cpu_spec->oprofile_mmcra_sihv)
@@ -193,6 +201,12 @@ static unsigned long get_pc(struct pt_regs *regs)
 
 	mmcra = mfspr(SPRN_MMCRA);
 
+	if (mmcra & MMCRA_SAMPLE_ENABLE) {
+		slot = ((mmcra & MMCRA_SLOT) >> MMCRA_SLOT_SHIFT);
+		if (slot > 1)
+			pc += 4 * (slot - 1);
+	}
+
 	/* Were we in the hypervisor? */
 	if (firmware_has_feature(FW_FEATURE_LPAR) &&
 	    (mmcra & cur_cpu_spec->oprofile_mmcra_sihv))

include/asm-powerpc/reg.h

@@ -453,6 +453,8 @@
 #define SPRN_MMCRA	0x312
 #define   MMCRA_SIHV	0x10000000UL /* state of MSR HV when SIAR set */
 #define   MMCRA_SIPR	0x08000000UL /* state of MSR PR when SIAR set */
+#define   MMCRA_SLOT	0x07000000UL /* SLOT bits (37-39) */
+#define   MMCRA_SLOT_SHIFT	24
 #define   MMCRA_SAMPLE_ENABLE 0x00000001UL /* enable sampling */
 #define   POWER6_MMCRA_SIHV   0x0000040000000000ULL
 #define   POWER6_MMCRA_SIPR   0x0000020000000000ULL