Re: [patch] crashdump: fix undefined reference to `elfcorehdr_addr'
- From: Simon Horman <horms@xxxxxxxxxxxx>
- Date: Tue, 29 Jul 2008 10:33:50 +1000
On Mon, Jul 28, 2008 at 09:31:10AM -0400, Vivek Goyal wrote:
On Mon, Jul 28, 2008 at 11:51:19AM +1000, Simon Horman wrote:
[ Updated Vivek's email address to his vgoyal@xxxxxxxxxx in CC list
Added Terry Loftin, Tony Luck, Erik Biedermann and linux-ia64 to CC list ]
[snip]
1) Always parse the elfcorehdr kernel command line option
and set elfcorehdr_addr accordingly - currently this is only
done if CONFIG_PROC_VMCORE is set.
This is nice as it won't need any modifications to kexec-tools
nor any command line bloat.
A minor difficulty is working out where to initialise elfcorehdr_addr.
Sometimes in include/linux/crash_dump.h and sometimes in
fs/proc/vmcore.c seems horrible to me.
Another problem is that would be alive and well in
code that really only uses it to check if kdump was activated or not
- a minor naming issue.
Hi Simon,
There are some kernel bits (like iommu initialization patch), which need to
take special action if they are booting after a kexec on panic (Generally we
are referring it to booting into kdump kernel) and that's why the notion
is_kdump_kernel().
To me, is_kdump_kernel() symbolizes whether I am booting after kexec on
panic and not just the fact if CONFIG_CRASH_DUMP is enabled or not in this
kernel.
So I would think that lets not rename it to kernel_has_vmcore(), instead
lets write few lines of comments before function is_kdump_kernel() to
clarify its meaning.
Secondly, we are using elfcorehdr_addr to determine whether this kernel
is booting after a panic so elfcorehdr_addr is not just limited to
CONFIG_PROC_VMCORE now and we should probably pull it out of
fs/proc/vmcore.c. How about declaring and initializing this variable in
kernel/kexec.c under CONFIG_CRASH_DUMP and always parse elfcorehdr_addr
irrespective of the setting of CONFIG_PROC_VMCORE?
Agreed. Like Eric I think that this is a reasonable solution given
the current state of things. I'll reply to your patches after looking
at them a bit more closely.
2) Add a new kernel command line option, perhaps in_kdump
This is bloat to get around elfcorehdr_addr initialisation and
naming awkwardness above.
3) Make select CONFIG_PROC_VMCORE when CONFIG_CRASH_DUMP is selected,
or perhaps even just remove CONFIG_PROC_VMCORE and only use
CONFIG_CRASH_DUMP instead. The effect would be the same either way.
Pro: One less thing to be confused about
Con: Bloat for people who want kdump without vmcore.
I wonder what usage case that is.
Argument was people can use /dev/oldmem and not use /proc/vmcore. So far
I don't know anybody who uses /dev/oldmem to capture dump and not
/proc/vmcore.
What I was getting at is that frangly the three variables
CONFIG_KEXEC, CONFIG_CRASH_DUMP and CONFIG_PROC_VMCORE seem to
confuse people. I've seen them used incorrectly several times now.
So if there is a way to simplyfy things, even slightly, I think
that would be a good idea. But if there isn't, so be it.
--
Horms
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- References:
- Re: [patch] crashdump: fix undefined reference to `elfcorehdr_addr'
- From: Simon Horman
- Re: [patch] crashdump: fix undefined reference to `elfcorehdr_addr'
- From: Simon Horman
- Re: [patch] crashdump: fix undefined reference to `elfcorehdr_addr'
- From: Vivek Goyal
- Re: [patch] crashdump: fix undefined reference to `elfcorehdr_addr'
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