Re: cannot access memory errors with gdb
Re: cannot access memory errors with gdb
- Subject: Re: cannot access memory errors with gdb
- From: Paul Nelson <email@hidden>
- Date: Wed, 09 Mar 2011 16:48:50 -0600
You did not show show how you ran gdb. Are you running gdb -arch i386 /Volumes/KernelDebugKit/mach_kernel ?
Paul
On Mar 9, 2011, at 4:38 PM, mogambo wrote:
> Hi there,
>
> I am triaging a kernel crash caused by our vfs plugin. For some reason, the corefile was never saved on the panic server, but I have the panic log. So, I looked up the load address (0x49ea8000) of the extension from the following line in the panic log.
>
> Kernel Extensions in backtrace (with dependencies):
> com.company.kext.fsd(2.5)@0x49ea8000->0x49f65fff
>
> I ran the command to generate the symbol file with that load address: ./createsymbolfiles -s <sympath> fsd.kext
>
> I loaded the symbol file in gdb and tried to decipher the panic log:
>
> (gdb) add-symbol-file symbols/com.company.kext.fsd.sym
> :
> (gdb) add-symbol-file /Volumes/KernelDebugKit/mach_kernel
> :
> (gdb) x/i 0x49f1e3b1
> 0x49f1e3b1 <fsrwIssueRead+1663>: Cannot access memory at address 0x49f1e3b1
> :
> (gdb) disass fsrwIssueRead
> Dump of assembler code for function fsrwIssueRead:
> 0x49f1dd32 <fsrwIssueRead+0>: Cannot access memory at address 0x49f1dd32
>
> The OS X version is;
> apple$ sw_vers
> ProductName: Mac OS X
> ProductVersion: 10.6.4
> BuildVersion: 10F569
> apple$ uname -a
> Darwin MacProQA16.local 10.4.0 Darwin Kernel Version 10.4.0: Fri Apr 23 18:28:53 PDT 2010; root:xnu-1504.7.4~1/RELEASE_I386 i386
>
> apple$ file /System/Library/Extensions/fsd.kext/Contents/MacOS/fsd
> /System/Library/Extensions/fsd.kext/Contents/MacOS/fsd: Mach-O universal binary with 2 architectures
> /System/Library/Extensions/fsd.kext/Contents/MacOS/fsd (for architecture ppc): Mach-O object ppc
> /System/Library/Extensions/fsd.kext/Contents/MacOS/fsd (for architecture i386): Mach-O object i386
> apple$ file newsym/com.company.kext.fsd.sym
> newsym/com.company.kext.fsd.sym: Mach-O object i386
>
> Am I missing something? I am pretty sure I have done this before to debug a kernel crash.
>
> Thanks for your help.
> -m.
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