Re: [Crash-utility] [Patch] linux-2.6.22 on i386
Ken'ichi Ohmichi wrote:
Hi Dave,
I found the problem that the crash utility fails during the initialization.
This problem happened on i386 linux-2.6.22 like the following:
$ crash vmlinux vmcore
crash 4.0-4.4
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This GDB was configured as "i686-pc-linux-gnu"...
crash: invalid size request: 0 type: "__per_cpu_offset"
$
The cause is that the array number of the symbol "__per_cpu_offset"
cannot be taken. In linux-2.6.21, i386's "__per_cpu_offset" is defined
in include/asm-generic/percpu.h like the following:
extern unsigned long __per_cpu_offset[NR_CPUS];
But in linux-2.6.22, it is defined in include/asm-i386/percpu.h like
the following, and the array number is not described in the debugging
information.
extern unsigned long __per_cpu_offset[];
Here is the patch for solving the problem. If the array number is not
taken, the crash utility assumes that it is the defined value NR_CPUS.
Or, should get_array_length() be fixed to get the array number from
init/main.c ?
Ken'ichi -- thanks for tracking that down.
I don't see how get_array_length() can be "fixed" in this case -- if the
vmlinux file doesn't have the info, it doesn't have it. I'm not sure
what you mean by getting it from init/main.c?
Anyway, using NR_CPUS is probably safe, although it runs the remote
risk of reading into a non-existent section of memory or uncopied
section of dumpfile.
How about using Cliff Wickman's new get_cpus_possible() function
from his LKCD_KERNTYPES patch? Since get_cpus_possible() returns 0
on failure, your fix below should be left in place, but it might be
worth also trying get_cpus_possible() if get_array_length() returns 0?
Dave
Thanks
Ken'ichi Ohmichi
--- crash-4.0-4.4.org/kernel.c 2007-07-21 04:19:23.000000000 +0900
+++ crash-4.0-4.4/kernel.c 2007-07-24 19:51:55.000000000 +0900
@@ -170,7 +170,7 @@ kernel_init()
else
i = get_array_length("__per_cpu_offset", NULL, 0);
get_symbol_data("__per_cpu_offset",
- sizeof(long)*(i <= NR_CPUS ? i : NR_CPUS),
+ sizeof(long)*((i && (i <= NR_CPUS)) ? i : NR_CPUS),
&kt->__per_cpu_offset[0]);
kt->flags |= PER_CPU_OFF;
}
_
--
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