[IA64] Merge overlapping reserved regions at boot

While working on the upcoming SLES11 SP2, I ran into an issue with booting the
panic kernel on a kernel crash. In the first iteration I found out that the
initial register backing store gets overwritten with zeroes, causing a kernel
crash shortly afterwards.

Further investigation revealed that rsvd_region[] contains overlapping
entries: find_memmap_space() returns a pointer which lies between KERNEL_START
and _end. This is correct with the EFI memmap as patched by the kexec
purgatory code. That code removes vmlinux LOAD segments from the usable map,
but there is a pretty large hole between the gate section and the per-cpu
section.

This happens because reserve_memory() blindly marks [KERNEL_START, __end]
as reserved, even though there is a free block in the middle in the kexec
case because it noticed a large gap between sections and modified the
efi_memory_map to account for this.
Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/setup.c

@@ -220,6 +220,23 @@ sort_regions (struct rsvd_region *rsvd_region, int max)
 	}
 }
 
+/* merge overlaps */
+static int __init
+merge_regions (struct rsvd_region *rsvd_region, int max)
+{
+	int i;
+	for (i = 1; i < max; ++i) {
+		if (rsvd_region[i].start >= rsvd_region[i-1].end)
+			continue;
+		if (rsvd_region[i].end > rsvd_region[i-1].end)
+			rsvd_region[i-1].end = rsvd_region[i].end;
+		--max;
+		memmove(&rsvd_region[i], &rsvd_region[i+1],
+			(max - i) * sizeof(struct rsvd_region));
+	}
+	return max;
+}
+
 /*
  * Request address space for all standard resources
  */
@@ -270,6 +287,7 @@ static void __init setup_crashkernel(unsigned long total, int *n)
 	if (ret == 0 && size > 0) {
 		if (!base) {
 			sort_regions(rsvd_region, *n);
+			*n = merge_regions(rsvd_region, *n);
 			base = kdump_find_rsvd_region(size,
 					rsvd_region, *n);
 		}
@@ -373,6 +391,7 @@ reserve_memory (void)
 	BUG_ON(IA64_MAX_RSVD_REGIONS + 1 < n);
 
 	sort_regions(rsvd_region, num_rsvd_regions);
+	num_rsvd_regions = merge_regions(rsvd_region, num_rsvd_regions);
 }