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Subjectvmcoreinfo: add the symbol "phys_base"
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp>

upstream commit: 629c8b4cdb354518308663aff2f719e02f69ffbe

Fix the problem that makedumpfile sometimes fails on x86_64 machine.

This patch adds the symbol "phys_base" to a vmcoreinfo data. The
vmcoreinfo data has the minimum debugging information only for dump
filtering. makedumpfile (dump filtering command) gets it to distinguish
unnecessary pages, and makedumpfile creates a small dumpfile.

On x86_64 kernel which compiled with CONFIG_PHYSICAL_START=0x0 and
CONFIG_RELOCATABLE=y, makedumpfile fails like the following:

# makedumpfile -d31 /proc/vmcore dumpfile
The kernel version is not supported.
The created dumpfile may be incomplete.
_exclude_free_page: Can't get next online node.

makedumpfile Failed.
#

The cause is the lack of the symbol "phys_base" in a vmcoreinfo data.
If the symbol "phys_base" does not exist, makedumpfile considers an
x86_64 kernel as non relocatable. As the result, makedumpfile
misunderstands the physical address where the kernel is loaded, and it
cannot translate a kernel virtual address to physical address correctly.

To fix this problem, this patch adds the symbol "phys_base" to a
vmcoreinfo data.

Signed-off-by: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <stable@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
arch/x86/kernel/machine_kexec_64.c | 1 +
1 file changed, 1 insertion(+)

--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -233,6 +233,7 @@ NORET_TYPE void machine_kexec(struct kim

void arch_crash_save_vmcoreinfo(void)
{
+ VMCOREINFO_SYMBOL(phys_base);
VMCOREINFO_SYMBOL(init_level4_pgt);

#ifdef CONFIG_ARCH_DISCONTIGMEM_ENABLE
--


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