makedumpfile: ppc64: Auto-detect the correct MAX_PHYSMEM_BITS used in vmcore being analyzed.

The latest upstream kernel commit 048ee0993ec8360abb0b51bdf8f8721e9ed62ec4 adds
64TB support to ppc64 kernel and bumps the MAX_PHYSMEM_BITS from 44 to 46. This
change causes sparsemem extreme check to fail in makedumpfile.

This patch auto-detects the correct value to use for MAX_PHYSMEM_BITS by
examining the mem_section array size from the vmcore being analyzed.

This patch has been tested on upstream kernel 3.8.0-rc4 and older kernel
2.6.32.

Reported-by: Dave Anderson <anderson@redhat.com>
Reported-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
---
 arch/ppc64.c   |   27 ++++++++++++++++++++++++++-
 makedumpfile.h |    3 ++-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/makedumpfile-1.5.1/arch/ppc64.c b/makedumpfile-1.5.1/arch/ppc64.c
index 1cb69e1..afbaf55 100644
--- a/makedumpfile-1.5.1/arch/ppc64.c
+++ b/makedumpfile-1.5.1/arch/ppc64.c
@@ -25,12 +25,37 @@
 #include "../makedumpfile.h"
 
 int
+set_ppc64_max_physmem_bits(void)
+{
+	long array_len = ARRAY_LENGTH(mem_section);
+	/*
+	 * The older ppc64 kernels uses _MAX_PHYSMEM_BITS as 42 and the
+	 * newer kernels 3.7 onwards uses 46 bits.
+	 */
+
+	info->max_physmem_bits  = _MAX_PHYSMEM_BITS_ORIG ;
+	if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME()))
+		|| (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT())))
+		return TRUE;
+
+	info->max_physmem_bits  = _MAX_PHYSMEM_BITS_3_7;
+	if ((array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT_EXTREME()))
+		|| (array_len == (NR_MEM_SECTIONS() / _SECTIONS_PER_ROOT())))
+		return TRUE;
+
+	return FALSE;
+}
+
+int
 get_machdep_info_ppc64(void)
 {
 	unsigned long vmlist, vmalloc_start;
 
 	info->section_size_bits = _SECTION_SIZE_BITS;
-	info->max_physmem_bits  = _MAX_PHYSMEM_BITS;
+	if (!set_ppc64_max_physmem_bits()) {
+		ERRMSG("Can't detect max_physmem_bits.\n");
+		return FALSE;
+	}
 	info->page_offset = __PAGE_OFFSET;
 
 	if (SYMBOL(_stext) == NOT_FOUND_SYMBOL) {
diff --git a/makedumpfile-1.5.1/makedumpfile.h b/makedumpfile-1.5.1/makedumpfile.h
index d2bdc0c..d758a3c 100644
--- a/makedumpfile-1.5.1/makedumpfile.h
+++ b/makedumpfile-1.5.1/makedumpfile.h
@@ -566,7 +566,8 @@ do { \
 #define VMALLOCBASE     	(0xD000000000000000)
 #define KVBASE			(SYMBOL(_stext))
 #define _SECTION_SIZE_BITS	(24)
-#define _MAX_PHYSMEM_BITS	(44)
+#define _MAX_PHYSMEM_BITS_ORIG  (44)
+#define _MAX_PHYSMEM_BITS_3_7   (46)
 #endif
 
 #ifdef __powerpc32__