cannot access memory errors with gdb
cannot access memory errors with gdb
- Subject: cannot access memory errors with gdb
- From: mogambo <email@hidden>
- Date: Wed, 09 Mar 2011 14:38:17 -0800
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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