[PATCH] Fix in free initrd when overlapped with crashkernel region

[PATCH] Fix in free initrd when overlapped with crashkernel region

[Haren Myneni]

[-- Attachment #1: Type: text/plain, Size: 948 bytes --]


It is possible that the reserved crashkernel region can be overlapped 
with initrd since the bootloader sets the initrd location. When the 
initrd region is freed, the second kernel memory will not be contiguous. 
The Kexec_load can cause an oops since there is no contiguous memory to 
write the second kernel or this memory could be used in the first kernel 
itself and may not be part of the dump. For example, on powerpc, the 
initrd is located at 36MB and the crashkernel starts at 32MB. The 
kexec_load caused panic since writing into non-allocated memory (after 
36MB). We could see the similar issue even on other archs.

One possibility is to move the initrd outside of crashkernel region. 
But, the initrd region will be freed anyway before the system is up.  
This patch fixes this issue and frees only regions that are not part of 
crashkernel memory in case overlaps. 

Thanks
Haren

Signed-off-by: Haren Myneni <haren@us.ibm.com>




[-- Attachment #2: kdump-initrd-overlap-fix.patch --]
[-- Type: text/x-patch, Size: 1723 bytes --]

diff -Naurp 2616-rc2.orig/include/linux/kexec.h 2616-rc2/include/linux/kexec.h
--- 2616-rc2.orig/include/linux/kexec.h	2006-02-06 19:08:01.000000000 -0800
+++ 2616-rc2/include/linux/kexec.h	2006-02-06 19:06:37.000000000 -0800
@@ -6,6 +6,7 @@
 #include <linux/list.h>
 #include <linux/linkage.h>
 #include <linux/compat.h>
+#include <linux/ioport.h>
 #include <asm/kexec.h>
 
 /* Verify architecture specific macros are defined */
diff -Naurp 2616-rc2.orig/init/initramfs.c 2616-rc2/init/initramfs.c
--- 2616-rc2.orig/init/initramfs.c	2006-02-06 19:04:42.000000000 -0800
+++ 2616-rc2/init/initramfs.c	2006-02-06 19:04:59.000000000 -0800
@@ -466,10 +466,32 @@ static char * __init unpack_to_rootfs(ch
 extern char __initramfs_start[], __initramfs_end[];
 #ifdef CONFIG_BLK_DEV_INITRD
 #include <linux/initrd.h>
+#include <linux/kexec.h>
 
 static void __init free_initrd(void)
 {
-	free_initrd_mem(initrd_start, initrd_end);
+#ifdef CONFIG_KEXEC
+	unsigned long crashk_start = (unsigned long)__va(crashk_res.start);
+	unsigned long crashk_end   = (unsigned long)__va(crashk_res.end);
+
+	/*
+	 * If the initrd region is overlapped with crashkernel reserved region,
+	 * free only memory that is not part of crashkernel region.
+	 */
+	if (initrd_start < crashk_end && initrd_end > crashk_start) {
+		/*
+		 * Initialize initrd memory region since the kexec boot does 
+		 * not do.
+		 */ 
+		memset((void *)initrd_start, 0, initrd_end - initrd_start); 
+		if (initrd_start < crashk_start)
+			free_initrd_mem(initrd_start, crashk_start); 
+		if (initrd_end > crashk_end) 
+			free_initrd_mem(crashk_end, initrd_end); 
+	} else
+#endif
+		free_initrd_mem(initrd_start, initrd_end);
+
 	initrd_start = 0;
 	initrd_end = 0;
 }

Re: [PATCH] Fix in free initrd when overlapped with crashkernel region

[Paul Mackerras]

Haren Myneni writes:

> --- 2616-rc2.orig/include/linux/kexec.h	2006-02-06 19:08:01.000000000 -0800
> +++ 2616-rc2/include/linux/kexec.h	2006-02-06 19:06:37.000000000 -0800
> @@ -6,6 +6,7 @@
>  #include <linux/list.h>
>  #include <linux/linkage.h>
>  #include <linux/compat.h>
> +#include <linux/ioport.h>
>  #include <asm/kexec.h>

What's this hunk for?

Paul.

Re: [PATCH] Fix in free initrd when overlapped with crashkernel region

[Haren Myneni]

Paul Mackerras wrote:

>Haren Myneni writes:
>
>  
>
>>--- 2616-rc2.orig/include/linux/kexec.h	2006-02-06 19:08:01.000000000 -0800
>>+++ 2616-rc2/include/linux/kexec.h	2006-02-06 19:06:37.000000000 -0800
>>@@ -6,6 +6,7 @@
>> #include <linux/list.h>
>> #include <linux/linkage.h>
>> #include <linux/compat.h>
>>+#include <linux/ioport.h>
>> #include <asm/kexec.h>
>>    
>>
>
>What's this hunk for?
>
>Paul.
>  
>

crashk_res is an extern declaration in kexec.h. Declared as "struct 
resource" which is defined in linux/ioport.h.
For other places wherever this variable is used, ioport.h got included 
through some other header file.  Whereas for initramfs.c, either we need 
to include ioport.h explicitly or include in kexec.h. Chosen the later 
one. Probably, some comment would be better to make it clear.

Paul, do you prefer to repost the patch with the comment?

Thanks
Haren

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