[PATCH] get MODULES_VADDR by KERNEL_IMAGE_SIZE for x86_64

[Baoquan He]

On 09/15/14 at 02:05pm, Baoquan He wrote:
> In x86_64, since v2.6.26 the KERNEL_IMAGE_SIZE is changed to 512M, and
> according the MODULES_VADDR is changed to 0xffffffffa0000000. Before
> that, KERNEL_IMAGE_SIZE is 128M, and MODULES_VADDR is 0xffffffff88000000.
> 
> However, in v3.12 Kees Cook introduced kaslr to randomise the location
> of kernel. And the kernel text mapping addr space is enlarged from 512M
> to 1G. That means now KERNEL_IMAGE_SIZE is variable, its value is 512M
> with kaslr support not compiled in and 1G with kaslr support compiled
> in. Accordingly the MODULES_VADDR is changed too to be:

#define MODULES_VADDR    (__START_KERNEL_map + KERNEL_IMAGE_SIZE)

Sorry, the above formula is lost.

> 
> So when kaslr is compiled in and enabled, the kernel text mapping addr
> space and modules vaddr space need be adjusted. Otherwise makedumpfile
> will collapse since the addr for some symbols is not correct.
> 
> Hence KERNEL_IMAGE_SIZE need be exported to vmcoreinfo and got in
> makedumpfile to help calculate MODULES_VADDR.
> 
> Signed-off-by: Baoquan He <bhe at redhat.com>
> ---
>  makedumpfile.c | 8 ++++++++
>  makedumpfile.h | 4 +++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/makedumpfile.c b/makedumpfile.c
> index b4d43d8..48d73a8 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -1564,6 +1564,12 @@ get_value_for_old_linux(void)
>  			NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE) =
>  			PAGE_BUDDY_MAPCOUNT_VALUE_v2_6_39_to_latest_version;
>  	}
> +#ifdef __x86_64__
> +	if (NUMBER(KERNEL_IMAGE_SIZE) == NOT_FOUND_NUMBER) {
> +		if (info->kernel_version < KERNEL_VERSION(2, 6, 26))
> +			NUMBER(KERNEL_IMAGE_SIZE) = MODULES_VADDR_ORIG;
> +	}
> +#endif
>  	if (SIZE(pageflags) == NOT_FOUND_STRUCTURE) {
>  		if (info->kernel_version >= KERNEL_VERSION(2, 6, 27))
>  			SIZE(pageflags) =
> @@ -1813,6 +1819,7 @@ write_vmcoreinfo_data(void)
>  	WRITE_NUMBER("PG_hwpoison", PG_hwpoison);
>  
>  	WRITE_NUMBER("PAGE_BUDDY_MAPCOUNT_VALUE", PAGE_BUDDY_MAPCOUNT_VALUE);
> +	WRITE_NUMBER("KERNEL_IMAGE_SIZE", KERNEL_IMAGE_SIZE);
>  
>  	/*
>  	 * write the source file of 1st kernel
> @@ -2147,6 +2154,7 @@ read_vmcoreinfo(void)
>  	READ_SRCFILE("pud_t", pud_t);
>  
>  	READ_NUMBER("PAGE_BUDDY_MAPCOUNT_VALUE", PAGE_BUDDY_MAPCOUNT_VALUE);
> +	READ_NUMBER("KERNEL_IMAGE_SIZE", KERNEL_IMAGE_SIZE);
>  
>  	return TRUE;
>  }
> diff --git a/makedumpfile.h b/makedumpfile.h
> index 6493f61..28a3cac 100644
> --- a/makedumpfile.h
> +++ b/makedumpfile.h
> @@ -549,7 +549,8 @@ do { \
>  #define VMEMMAP_END_2_6_31	(0xffffeaffffffffff) /* 2.6.31, or later  */
>  
>  #define __START_KERNEL_map	(0xffffffff80000000)
> -#define MODULES_VADDR		(0xffffffff88000000)
> +#define MODULES_VADDR_ORIG	(0xffffffff88000000)
> +#define MODULES_VADDR          (__START_KERNEL_map + NUMBER(KERNEL_IMAGE_SIZE))
>  #define MODULES_END		(0xfffffffffff00000)
>  #define KVBASE			PAGE_OFFSET
>  #define _SECTION_SIZE_BITS	(27)
> @@ -1531,6 +1532,7 @@ struct number_table {
>  	long    PG_hwpoison;
>  
>  	long	PAGE_BUDDY_MAPCOUNT_VALUE;
> +	long	KERNEL_IMAGE_SIZE;
>  	long	SECTION_SIZE_BITS;
>  	long	MAX_PHYSMEM_BITS;
>  };
> -- 
> 1.8.5.3
>