9 files changed, 46 insertions, 11 deletions

diff --git a/arch/ia64/kernel/crash_dump.c b/arch/ia64/kernel/crash_dump.c
index da60e90..23e9129 100644
--- a/arch/ia64/kernel/crash_dump.c
+++ b/arch/ia64/kernel/crash_dump.c
@@ -8,10 +8,14 @@
 
 #include <linux/errno.h>
 #include <linux/types.h>
+#include <linux/crash_dump.h>
 
 #include <asm/page.h>
 #include <asm/uaccess.h>
 
+/* Stores the physical address of elf header of crash image. */
+unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
+
 /**
  * copy_oldmem_page - copy one page from "oldmem"
  * @pfn: page frame number to be copied
diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
index de636b2..a0286be6 100644
--- a/arch/ia64/kernel/setup.c
+++ b/arch/ia64/kernel/setup.c
@@ -478,7 +478,12 @@ static __init int setup_nomca(char *s)
 }
 early_param("nomca", setup_nomca);
 
-#ifdef CONFIG_PROC_VMCORE
+/*
+ * Note: elfcorehdr_addr is not just limited to vmcore. It is also used by
+ * is_kdump_kernel() to determine if we are booting after a panic. Hence
+ * ifdef it under CONFIG_CRASH_DUMP and not CONFIG_PROC_VMCORE.
+ */
+#ifdef CONFIG_CRASH_DUMP
 /* elfcorehdr= specifies the location of elf core header
  * stored by the crashed kernel.
  */
@@ -491,7 +496,9 @@ static int __init parse_elfcorehdr(char *arg)
 	return 0;
 }
 early_param("elfcorehdr", parse_elfcorehdr);
+#endif
 
+#ifdef CONFIG_PROC_VMCORE
 int __init reserve_elfcorehdr(unsigned long *start, unsigned long *end)
 {
 	unsigned long length;
diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index a323c9b..97e0563 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -27,6 +27,9 @@
 #define DBG(fmt...)
 #endif
 
+/* Stores the physical address of elf header of crash image. */
+unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
+
 void __init reserve_kdump_trampoline(void)
 {
 	lmb_reserve(0, KDUMP_RESERVE_LIMIT);
@@ -66,7 +69,11 @@ void __init setup_kdump_trampoline(void)
 	DBG(" <- setup_kdump_trampoline()\n");
 }
 
-#ifdef CONFIG_PROC_VMCORE
+/*
+ * Note: elfcorehdr_addr is not just limited to vmcore. It is also used by
+ * is_kdump_kernel() to determine if we are booting after a panic. Hence
+ * ifdef it under CONFIG_CRASH_DUMP and not CONFIG_PROC_VMCORE.
+ */
 static int __init parse_elfcorehdr(char *p)
 {
 	if (p)
@@ -75,7 +82,6 @@ static int __init parse_elfcorehdr(char *p)
 	return 1;
 }
 __setup("elfcorehdr=", parse_elfcorehdr);
-#endif
 
 static int __init parse_savemaxmem(char *p)
 {
diff --git a/arch/sh/kernel/crash_dump.c b/arch/sh/kernel/crash_dump.c
index 4a2ecbe..95d2162 100644
--- a/arch/sh/kernel/crash_dump.c
+++ b/arch/sh/kernel/crash_dump.c
@@ -10,6 +10,9 @@
 #include <linux/io.h>
 #include <asm/uaccess.h>
 
+/* Stores the physical address of elf header of crash image. */
+unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
+
 /**
  * copy_oldmem_page - copy one page from "oldmem"
  * @pfn: page frame number to be copied
diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c
index 72d0c56..f7cdb3b 100644
--- a/arch/x86/kernel/crash_dump_32.c
+++ b/arch/x86/kernel/crash_dump_32.c
@@ -13,6 +13,9 @@
 
 static void *kdump_buf_page;
 
+/* Stores the physical address of elf header of crash image. */
+unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
+
 /**
  * copy_oldmem_page - copy one page from "oldmem"
  * @pfn: page frame number to be copied
diff --git a/arch/x86/kernel/crash_dump_64.c b/arch/x86/kernel/crash_dump_64.c
index e90a60e..045b36c 100644
--- a/arch/x86/kernel/crash_dump_64.c
+++ b/arch/x86/kernel/crash_dump_64.c
@@ -10,6 +10,9 @@
 #include <linux/uaccess.h>
 #include <linux/io.h>
 
+/* Stores the physical address of elf header of crash image. */
+unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
+
 /**
  * copy_oldmem_page - copy one page from "oldmem"
  * @pfn: page frame number to be copied
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 2255782..b2c9787 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -561,7 +561,13 @@ static void __init reserve_standard_io_resources(void)
 
 }
 
-#ifdef CONFIG_PROC_VMCORE
+/*
+ * Note: elfcorehdr_addr is not just limited to vmcore. It is also used by
+ * is_kdump_kernel() to determine if we are booting after a panic. Hence
+ * ifdef it under CONFIG_CRASH_DUMP and not CONFIG_PROC_VMCORE.
+ */
+
+#ifdef CONFIG_CRASH_DUMP
 /* elfcorehdr= specifies the location of elf core header
  * stored by the crashed kernel. This option will be passed
  * by kexec loader to the capture kernel.
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 841368b..4c65ca4 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -32,9 +32,6 @@ static size_t elfcorebuf_sz;
 /* Total size of vmcore file. */
 static u64 vmcore_size;
 
-/* Stores the physical address of elf header of crash image. */
-unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
-
 struct proc_dir_entry *proc_vmcore = NULL;
 
 /* Reads a page from the oldmem device from given offset. */
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 025e4f5..de027d1 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -9,11 +9,7 @@
 
 #define ELFCORE_ADDR_MAX	(-1ULL)
 
-#ifdef CONFIG_PROC_VMCORE
 extern unsigned long long elfcorehdr_addr;
-#else
-static const unsigned long long elfcorehdr_addr = ELFCORE_ADDR_MAX;
-#endif
 
 extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
 						unsigned long, int);
@@ -28,6 +24,16 @@ extern struct proc_dir_entry *proc_vmcore;
 
 #define vmcore_elf_check_arch(x) (elf_check_arch(x) || vmcore_elf_check_arch_cross(x))
 
+/*
+ * is_kdump_kernel() checks whether this kernel is booting after a panic of
+ * previous kernel or not. This is determined by checking if previous kernel
+ * has passed the elf core header address on command line.
+ *
+ * This is not just a test if CONFIG_CRASH_DUMP is enabled or not. It will
+ * return 1 if CONFIG_CRASH_DUMP=y and if kernel is booting after a panic of
+ * previous kernel.
+ */
+
 static inline int is_kdump_kernel(void)
 {
 	return (elfcorehdr_addr != ELFCORE_ADDR_MAX) ? 1 : 0;