kexec-tools: i386 sys interface changes compatibility

On Wed, Dec 14, 2005 at 02:50:52PM -0600, Milton Miller wrote:

[..]
> >>(2) why do you stat the files instead of just trying to open them and
> >>check for ENOENT?
> >>
> >>milton
> >>
> >
> >I wanted to differentiate between two cases. One being sysfs not
> >mounted
> >and other being file not being present (Due to kernel bug or cpu not
> >present), hence used stat(). In case of sysfs not being mounted, we
> >simply exit after giving an error message. In other case we continue
> >to loop through other cpus and ignore cpu, which is not present.
> >
>
> Ok, but try to open the file first.  IF you want to do this diagnostic
> after the open fails, that is ok.  But don't do this check n times (n =
> number of cpus) when the file exists.
>

I have moved the sysfs mounted check in failure condition.

>
> >
> >On Tue, Dec 13, 2005 at 09:36:26AM -0800, Haren Myneni wrote:
> >>Vivek, I believe, we should push this func into arch independent code.
> >>Otherwise, we have to copy it for every platform.
> >>
> >
> >We have reworked the patch and moved this code to architecture
> >independent
> >portion.
> >
>
>
> Only the x86 code has the fallback the old name, not the genric code.
>

Only i386 port of kdump was available when crash_notes was exported
through /sys/kernel/crash_notes. Rest of the architectures see new arch-
independent percpu crash_notes sysfs interface only. Hence thought no
point copying backward compatibility code in generic code.

>
> Also, there are error paths that do not set the address, others that
> zero it.
>

The error paths which do not set address to zero are non return path. They
call die() which inturn calls exit(1) after printing appropriate error
messasge.

> What happens if the base kernel is too old for kexec-panic, where
> neiter file will exist?
>

In that case kexec will fail much earlier. There will be  no reserved
memory area for loading second kernel (crashkernel=X&Y) hence attempt to
load the second kernel will fail and control will not reach this place at
all.

Modifed patch appended.

Thanks
Vivek

o This patch moves per cpu interface to retrieve crash_notes address to
  architecture independent section. (As suggested by Haren)

o For i386, kernels older than 2.6.15-rc1-mm2 used to export crash_notes
  through /sys/kernel/crash_notes. This patch also provides backward
  compatibility with older kernel versions.

o Definition of MAX_NOTE_BYTES moved to architecture independent header
  file as everybody is using same definition.

o Definition of MAX_LINE moved to architecture independent header file.
  Seems to be a better option than defining it in many C files.

Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/kexec/crashdump.h b/kexec/crashdump.h
new file mode 100644
index 0000000..682dd53
--- /dev/null
+++ b/kexec/crashdump.h
@@ -0,0 +1,9 @@
+#ifndef CRASHDUMP_H
+#define CRASHDUMP_H
+
+extern int get_crash_notes_per_cpu(int cpu, uint64_t *addr);
+
+/* Need to find a better way to determine per cpu notes section size. */
+#define MAX_NOTE_BYTES		1024
+
+#endif /* CRASHDUMP_H */