[Crash-utility] [PATCH] crash: arm32: a better way to identify LPAE enabled kernel

[Liu Hua]

Thanks to Dave's suggest, I impove the way to identify
LPAE enabled kernel for arm platform, for compatibility with
some old kernel.

If a vmcore santisfy one of the following conditions, It must
be generated by a LPAE enabled kernel.

(1) it has CONFIG_ARM_LPAE=y vmcore_info
(2) swapper_pg_dir and its next symbol value differ by 0x5000

Signed-off-by: Liu Hua <sdu.liu at huawei.com>
---
 arm.c     | 11 ++++++++++-
 symbols.c | 10 ++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arm.c b/arm.c
index cb7d841..76ba699 100644
--- a/arm.c
+++ b/arm.c
@@ -190,6 +190,8 @@ void
 arm_init(int when)
 {
 	ulong vaddr;
+	char *string;
+	ulong difference;
 
 #if defined(__i386__) || defined(__x86_64__)
 	if (ACTIVE())
@@ -229,8 +231,15 @@ arm_init(int when)
 		 * LPAE requires an additional page for the PGD, 
 		 * so PG_DIR_SIZE = 0x5000 for LPAE
 		 */
-		if ((symbol_value("_text") - symbol_value("swapper_pg_dir")) == 0x5000)
+		if ((string = pc->read_vmcoreinfo("CONFIG_ARM_LPAE"))) {
 			machdep->flags |= PAE;
+			free(string);
+		} else {
+			difference = next_symbol_value("swapper_pg_dir", NULL)
+					- symbol_value("swapper_pg_dir");
+			if (difference == 0x5000)
+				machdep->flags |= PAE;
+		}
 		machdep->kvbase = symbol_value("_stext") & ~KVBASE_MASK;
 		machdep->identity_map_base = machdep->kvbase;
 		machdep->is_kvaddr = arm_is_kvaddr;
diff --git a/symbols.c b/symbols.c
index a0f256e..b294cd2 100644
--- a/symbols.c
+++ b/symbols.c
@@ -4936,6 +4936,16 @@ try_get_symbol_data(char *symbol, long size, void *local)
 	return FALSE;
 }
 
+ulong
+next_symbol_value(char *symbol, struct syment *psb)
+{
+        struct syment *sp;
+
+        if (!(sp = next_symbol(symbol, psb)))
+                error(FATAL, "cannot resolve \"%s\"\n", symbol);
+        return(sp->value);
+}
+
 /*
  *  Return the value of a given symbol.
  */
-- 
1.9.0