[PATCH 4/5] xen: Try hard to get max_cpus value

[daniel.kiper@xxxxxxxxxx (Daniel Kiper)]

This patch improves max_cpus value calculation. First
xen_hyper_get_cpu_info() tries to get it from nr_cpu_ids
variable. If nr_cpu_ids does not exist then it attempts
to read max_cpus variable. If it is not available estimate
max_cpus value on the base of cpumask_t size.

Signed-off-by: Daniel Kiper <daniel.kiper at oracle.com>

diff -Npru crash-6.1.0.orig/xen_hyper.c crash-6.1.0/xen_hyper.c
--- crash-6.1.0.orig/xen_hyper.c	2012-11-13 15:02:34.000000000 +0100
+++ crash-6.1.0/xen_hyper.c	2012-11-13 15:07:40.000000000 +0100
@@ -1883,13 +1883,28 @@ xen_hyper_get_uptime_hyper(void)
 void
 xen_hyper_get_cpu_info(void)
 {
-	ulong addr;
+	ulong addr, init_begin, init_end;
 	ulong *cpumask;
 	uint *cpu_idx;
 	int i, j, cpus;
 
 	XEN_HYPER_STRUCT_SIZE_INIT(cpumask_t, "cpumask_t");
-	xht->max_cpus = XEN_HYPER_SIZE(cpumask_t) * 8;
+
+	if (symbol_exists("nr_cpu_ids"))
+		get_symbol_data("nr_cpu_ids", sizeof(uint), &xht->max_cpus);
+	else {
+		init_begin = symbol_value("__init_begin");
+		init_end = symbol_value("__init_end");
+		addr = symbol_value("max_cpus");
+
+		if (addr >= init_begin && addr < init_end)
+			xht->max_cpus = XEN_HYPER_SIZE(cpumask_t) * 8;
+		else {
+			get_symbol_data("max_cpus", sizeof(xht->max_cpus), &xht->max_cpus);
+			if (XEN_HYPER_SIZE(cpumask_t) * 8 > xht->max_cpus)
+				xht->max_cpus = XEN_HYPER_SIZE(cpumask_t) * 8;
+		}
+	}
 
 	if (xht->cpumask) {
 		free(xht->cpumask);