[PATCH] get MODULES_VADDR by KERNEL_IMAGE_SIZE for x86_64

[kumagai-atsushi@xxxxxxxxxxxxxxxxx (Atsushi Kumagai)]

>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:
>
>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

This code looks wrong, the value of MODULES_VADDR will overflow as:

  MODULES_VADDR = __START_KERNEL_map + NUMBER(KERNEL_IMAGE_SIZE)
                = 0xffffffff80000000 + 0xffffffff88000000

I think the code should be fixed as:

makedumpfile.h:
    #define __START_KERNEL_map      (0xffffffff80000000)
    #define KERNEL_IMAGE_SIZE_ORIG      (0x0000000008000000) /* 2.6.25, or former */
    #define KERNEL_IMAGE_SIZE_2_6_26    (0x0000000020000000) /* 2.6.26, or later  */
    #define MODULES_VADDR          (__START_KERNEL_map + NUMBER(KERNEL_IMAGE_SIZE))

makedumpfile.c:
	if (NUMBER(KERNEL_IMAGE_SIZE) == NOT_FOUND_NUMBER) {
		if (info->kernel_version < KERNEL_VERSION(2, 6, 26))
			NUMBER(KERNEL_IMAGE_SIZE) = KERNEL_IMAGE_SIZE_ORIG;
		else
			NUMBER(KERNEL_IMAGE_SIZE) = KERNEL_IMAGE_SIZE_2_6_26;
	}


Thanks
Atsushi Kumagai

> 	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