Differences between version 10 and predecessor to the previous major change of KernelDevelopment.
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| Newer page: | version 10 | Last edited on Saturday, October 15, 2005 2:27:36 pm | by IanMcDonald | Revert |
| Older page: | version 9 | Last edited on Monday, September 19, 2005 9:45:24 am | by IanMcDonald | Revert |
@@ -2,8 +2,46 @@
There are useful tools for kernel development available such as [Ostra] and [Sparse].
Today most KernelDevelopment is done with [Git]. See KernelDevelopmentWithGit for more details.
+
+To debug a kernel crash you can use objdump to show the assembler for the routine shown and if debug symbols from kernel hacking menu are turned on then you can see the C code also. There will be a hex offset in the crash output and just use that to find the valid line of code/assembler. For example:
+<tt>
+objdump -r -S -l --disassemble net/dccp/ipv4.o
+</tt>
+
+NB. You need to be at the top level of the kernel tree for this to pick up your C files.
+
+If you don't have access to the code you can also debug on some crash dumps e.g. crash dump output as shown by Dave Miller.
+<verbatim>
+EIP is at ip_queue_xmit+0x14/0x4c0
+ ...
+Code: 44 24 04 e8 6f 05 00 00 e9 e8 fe ff ff 8d 76 00 8d bc 27 00 00
+00 00 55 57 56 53 81 ec bc 00 00 00 8b ac 24 d0 00 00 00 8b 5d 08
+<8b> 83 3c 01 00 00 89 44 24 14 8b 45 28 85 c0 89 44 24 18 0f 85
+
+Put the bytes into a "foo.s" file like this:
+
+ .text
+ .globl foo
+foo:
+ .byte .... /* bytes from Code: part of OOPS dump */
+
+Compile it with "gcc -c -o foo.o foo.s" then look at the output
+of "objdump --disassemble foo.o".
+
+Output:
+
+ip_queue_xmit:
+ push %ebp
+ push %edi
+ push %esi
+ push %ebx
+ sub $0xbc, %esp
+ mov 0xd0(%esp), %ebp ! %ebp = arg0 (skb)
+ mov 0x8(%ebp), %ebx ! %ebx = skb->sk
+ mov 0x13c(%ebx), %eax ! %eax = inet_sk(sk)->opt
+</verbatim>
A couple of useful articles for kernel development from [IBM]: %%%
http://www-128.ibm.com/developerworks/linux/edu/l-dw-linux-kernelhack1-i.html %%%
http://www-128.ibm.com/developerworks/linux/edu/l-dw-linux-kernelhack2-i.html %%%
