From 935dee7a7ec7063e48e1fbe9cc0b65801e70973b Mon Sep 17 00:00:00 2001
From: Simon Horman <horms@verge.net.au>
Date: Sat, 18 Oct 2008 20:28:29 -0700
Subject: [PATCH] --- yaml --- r: 115952 b: refs/heads/master c:
 85a0ee342e0c06c19d78fdf48307211c6cf18fcb h: refs/heads/master v: v3

---
 [refs]                           |  2 +-
 trunk/arch/ia64/kernel/setup.c   |  4 ++--
 trunk/fs/proc/vmcore.c           |  2 +-
 trunk/include/linux/crash_dump.h | 24 ++++++++++++++++++++++++
 4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index 5d57aa2dbe24..470d54a5bc9b 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 630bf20747e27391b20f137a5be2edb4235ca8fa
+refs/heads/master: 85a0ee342e0c06c19d78fdf48307211c6cf18fcb
diff --git a/trunk/arch/ia64/kernel/setup.c b/trunk/arch/ia64/kernel/setup.c
index a0286be6c235..60286522d54a 100644
--- a/trunk/arch/ia64/kernel/setup.c
+++ b/trunk/arch/ia64/kernel/setup.c
@@ -509,11 +509,11 @@ int __init reserve_elfcorehdr(unsigned long *start, unsigned long *end)
 	 * to work properly.
 	 */
 
-	if (elfcorehdr_addr >= ELFCORE_ADDR_MAX)
+	if (!is_vmcore_usable())
 		return -EINVAL;
 
 	if ((length = vmcore_find_descriptor_size(elfcorehdr_addr)) == 0) {
-		elfcorehdr_addr = ELFCORE_ADDR_MAX;
+		vmcore_unusable();
 		return -EINVAL;
 	}
 
diff --git a/trunk/fs/proc/vmcore.c b/trunk/fs/proc/vmcore.c
index 4c65ca432d30..cd9ca67f841b 100644
--- a/trunk/fs/proc/vmcore.c
+++ b/trunk/fs/proc/vmcore.c
@@ -644,7 +644,7 @@ static int __init vmcore_init(void)
 	int rc = 0;
 
 	/* If elfcorehdr= has been passed in cmdline, then capture the dump.*/
-	if (!(elfcorehdr_addr < ELFCORE_ADDR_MAX))
+	if (!(is_vmcore_usable()))
 		return rc;
 	rc = parse_crash_elf_headers();
 	if (rc) {
diff --git a/trunk/include/linux/crash_dump.h b/trunk/include/linux/crash_dump.h
index de027d1db745..0acf3b737e2e 100644
--- a/trunk/include/linux/crash_dump.h
+++ b/trunk/include/linux/crash_dump.h
@@ -8,6 +8,7 @@
 #include <linux/proc_fs.h>
 
 #define ELFCORE_ADDR_MAX	(-1ULL)
+#define ELFCORE_ADDR_ERR	(-2ULL)
 
 extern unsigned long long elfcorehdr_addr;
 
@@ -38,6 +39,29 @@ static inline int is_kdump_kernel(void)
 {
 	return (elfcorehdr_addr != ELFCORE_ADDR_MAX) ? 1 : 0;
 }
+
+/* is_vmcore_usable() checks if the kernel is booting after a panic and
+ * the vmcore region is usable.
+ *
+ * This makes use of the fact that due to alignment -2ULL is not
+ * a valid pointer, much in the vain of IS_ERR(), except
+ * dealing directly with an unsigned long long rather than a pointer.
+ */
+
+static inline int is_vmcore_usable(void)
+{
+	return is_kdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
+}
+
+/* vmcore_unusable() marks the vmcore as unusable,
+ * without disturbing the logic of is_kdump_kernel()
+ */
+
+static inline void vmcore_unusable(void)
+{
+	if (is_kdump_kernel())
+		elfcorehdr_addr = ELFCORE_ADDR_ERR;
+}
 #else /* !CONFIG_CRASH_DUMP */
 static inline int is_kdump_kernel(void) { return 0; }
 #endif /* CONFIG_CRASH_DUMP */