Re: [Crash-utility] [PATCH/RFC] Fix relocation address
----- "Simon Kagstrom" <simon.kagstrom(a)netinsight.net> wrote:
Hi!
I'm having problems getting kdumps from my relocatable kernel (2.6.31-8)
working with crash on a IA-32 board. I use makedumpfile to generate a
compressed dump, and when I try to load it with crash I get
./crash vmlinux vmcore --reloc=0x100000
crash: invalid kernel virtual address: 98 type: "present"
WARNING: cannot read cpu_present_map
crash: invalid kernel virtual address: 908bd975 type: "online"
WARNING: cannot read cpu_online_map
crash: cannot determine base kernel version
crash: vmlinux and vmcore do not match!
specifying --reloc also fails:
./crash vmlinux vmcore --reloc=0x100000
crash: seek error: kernel virtual address: c01a2108 type:
"cpu_possible_mask"
So I started looking into the code and found something which looks like
a typo in relocate() (patch below). Changing this makes crash work for me.
Actually it's not a typo -- your patch would presumably break with all kernels
that have a CONFIG_PHYSICAL_START is greater than CONFIG_PHYSICAL_ALIGN, which
is what the patch was written to handle.
What are your kernel's CONFIG_PHYSICAL_START and CONFIG_PHYSICAL_ALIGN
values? Does crash work with your kernel on the live system?
Anyway, I believe that the fix would require support for supplying a
negative --reloc value.
Great tool by the way, leaves you longing for the next kernel panic
;-)
// Simon
--- orig-crash-4.1.2/symbols.c 2009-12-09 21:37:40.000000000 +0100
+++ crash-4.1.2/symbols.c 2009-12-17 16:03:24.000000000 +0100
@@ -671,7 +671,7 @@ relocate(ulong symval, char *symname, in
break;
}
- return (symval - kt->relocate);
+ return (symval + kt->relocate);
}
/*