[PATCH] Reserving backup region for kexec based crashdumps.

[Vivek Goyal]

Hi Andrew,

Following patch is against 2.6.11-rc1-mm2. 

As mentioned by following note from Eric, crashdump code is currently
broken.
> 
> The crashdump code is currently slightly broken.  I have attempted to
> minimize the breakage so things can quick be made to work again.

We have started doing changes to make crashdump up and running again.
Following are few identified items to be done.

1. Reserve the backup region (640k) during kernel bootup. 
2. Copy the data to backup region during crash.(moved to kexec user
space code, patch posted in separate mail)
3. Prepare elf headers while loading kexec panic kernel and store in
reserved memory area.
4. Pass required information to crashdump kernel, which parses it and
exports through /proc/vmcore. (may be user space utility, open to
discussion)

Following patch implements item 1) in the list. Soon we shall be rolling
out the patches for rest.

Thanks
Vivek



This patch adds support for reserving 640k memory as backup region as required
by crashdump kernel for x86. 
---


Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---

 linux-2.6.11-rc1-mm2-kexec-eric-root/arch/i386/kernel/setup.c |    8 ++++++++
 linux-2.6.11-rc1-mm2-kexec-eric-root/include/linux/kexec.h    |    6 +++++-
 linux-2.6.11-rc1-mm2-kexec-eric-root/kernel/kexec.c           |    8 ++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff -puN arch/i386/kernel/setup.c~crashdump-x86-reserve-640k-memory arch/i386/kernel/setup.c
--- linux-2.6.11-rc1-mm2-kexec-eric/arch/i386/kernel/setup.c~crashdump-x86-reserve-640k-memory	2005-01-20 13:55:33.000000000 +0530
+++ linux-2.6.11-rc1-mm2-kexec-eric-root/arch/i386/kernel/setup.c	2005-01-20 13:55:33.000000000 +0530
@@ -1159,6 +1159,13 @@ static unsigned long __init setup_memory
 #ifdef CONFIG_KEXEC
 	if (crashk_res.start != crashk_res.end) {
 		reserve_bootmem(crashk_res.start, crashk_res.end - crashk_res.start + 1);
+
+#define CRASH_DUMP_BACKUP 0xa0000
+		/* Reserve another 640Kb for crashdump backup. */
+		crashdumpk_res.start = crashk_res.end + 1;
+		crashdumpk_res.end = crashdumpk_res.start +
+					CRASH_DUMP_BACKUP -1;
+		reserve_bootmem(crashdumpk_res.start, CRASH_DUMP_BACKUP);
 	}
 #endif
 	return max_low_pfn;
@@ -1202,6 +1209,7 @@ legacy_init_iomem_resources(struct resou
 			request_resource(res, data_resource);
 #ifdef CONFIG_KEXEC
 			request_resource(res, &crashk_res);
+			request_resource(res, &crashdumpk_res);
 #endif
 		}
 	}
diff -puN include/linux/kexec.h~crashdump-x86-reserve-640k-memory include/linux/kexec.h
--- linux-2.6.11-rc1-mm2-kexec-eric/include/linux/kexec.h~crashdump-x86-reserve-640k-memory	2005-01-20 13:55:33.000000000 +0530
+++ linux-2.6.11-rc1-mm2-kexec-eric-root/include/linux/kexec.h	2005-01-20 13:55:33.000000000 +0530
@@ -79,7 +79,7 @@ struct kimage {
 	unsigned long control_page;
 
 	/* Flags to indicate special processing */
-	int type : 1;
+	unsigned int type : 1;
 #define KEXEC_TYPE_DEFAULT 0
 #define KEXEC_TYPE_CRASH   1
 };
@@ -122,6 +122,10 @@ extern struct kimage *kexec_crash_image;
  */
 extern struct resource crashk_res;
 
+/* Location of backup region to hold the crashdump kernel data.
+ */
+extern struct resource crashdumpk_res;
+
 #else /* !CONFIG_KEXEC */
 static inline void crash_kexec(void) { }
 #endif /* CONFIG_KEXEC */
diff -puN kernel/kexec.c~crashdump-x86-reserve-640k-memory kernel/kexec.c
--- linux-2.6.11-rc1-mm2-kexec-eric/kernel/kexec.c~crashdump-x86-reserve-640k-memory	2005-01-20 13:55:33.000000000 +0530
+++ linux-2.6.11-rc1-mm2-kexec-eric-root/kernel/kexec.c	2005-01-20 13:55:33.000000000 +0530
@@ -32,6 +32,14 @@ struct resource crashk_res = {
 	.flags = IORESOURCE_BUSY | IORESOURCE_MEM
 };
 
+/* Location of the backup area for the crash dump kernel */
+struct resource crashdumpk_res = {
+	.name  = "Crash Dump Backup",
+	.start = 0,
+	.end   = 0,
+	.flags = IORESOURCE_BUSY | IORESOURCE_MEM
+};
+
 /*
  * When kexec transitions to the new kernel there is a one-to-one
  * mapping between physical and virtual addresses.  On processors
_