Graphical desktop, l4con, mag
Leslie Zhai
lesliezhai at llvm.org.cn
Mon Jun 5 06:00:13 CEST 2017
在 2017年06月03日 04:56, Jean Wolter 写道:
> Hello Leslie,
>
> On 02/06/17 11:33, Jean Wolter wrote:
>> I replaced my "ned" binary with yours and the system boots up fine.
>>
>> Now I wonder how I could reproduce your problem. It looks like I
>>
>> * either need all binaries or
>> * need to build them the same way you are building them. I used a
>> fresh checkout from the svn repositories and use gcc version
>> 4.9.2 (Debian 4.9.2-10) to build the components.
>>
>
> Since I neither have your binaries nor know how you build them I
> thought about how you could diagnose the problem further. To
> demonstrate how to do this I intentionally added a null pointer
> dereference to ned and would like to discuss how I would diagnose this.
>
> --- ned/server/src/main.cc (revision 72)
> +++ ned/server/src/main.cc (working copy)
> @@ -35,6 +35,8 @@
> Dbg::set_level(Dbg::Warn);
> info.printf("Hello from Ned\n");
>
> + *(int *)0 = 0;
> +
> boot_info.printf("cmdline: ");
> for (int i = 0; i < argc; ++i)
> boot_info.cprintf("%s ", argv[i]);
>
> 1. Add -serial_esc -wait to kernel options in conf/modules.list
>
> --- modules.list (revision 72)
> +++ modules.list (working copy)
> @@ -80,6 +80,7 @@
> module libuc_c.so
>
> entry framebuffer-example-x86
> +kernel fiasco -serial_esc -wait
> roottask moe rom/x86-fb.cfg
> module x86-fb.cfg
> module l4re
>
> If you boot this the kernel will enter the kernel debugger before
> doing anything else. Enter the following commands:
>
> * P+ /* show every pagefault before forwarding it to the pager */
> * Prx0<space>100<space> /* restrict pagefault logging to pagefaults
> between [0-100] */.
> * g /* go */
>
> The kernel should stop when the access to 0x18 happens, then you can
> enter the kernel debugger using 'i' and can check who is responsible
> and maybe get a correct instruction pointer. If I do this here it
> looks like follows (I added -serial stdio to the qemu options):
>
> qemu-system-x86_64 -kernel
> /home/jw5/build/tmp/l4re/bin/amd64_K8/bootstrap -append "bootstrap
> -modaddr 0x01100000" -serial stdio -initrd
> "/home/jw5/build/tmp/fiasco//fiasco -serial_esc
> -wait,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/sigma0
> ,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/moe
> rom/x86-fb.cfg,/home/jw5/src/l4resvn/src/l4/conf/examples//x86-fb.cfg
> ,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/l4re
> ,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/ned
> ,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/io
> ,/home/jw5/src/l4resvn/src/l4/pkg/io/io/config//x86-legacy.devs
> ,/home/jw5/src/l4resvn/src/l4/conf/examples//x86-fb.io
> ,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/fb-drv
> ,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/mag
> ,/home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/ex_fb_spectrum_cc "
> ...
> Freeing init code/data: 49152 bytes (12 pages)
>
> Calibrating timer loop... done.
>
> ---------------------------------------------------------------------
> CPU 0 [fffffffff003df99]: Wait
> jdb: P+
> PF logging enabled
> jdb: Pr restrict to addr in [0-100] /* pressed
> Prx0<space>100<space> */
> PF logging enabled, restricted to 0000000000000000 <= pfa <=
> 0000000000000100
> jdb: g /* g does no show up in output */
> ...
> MOE: cmdline: /home/jw5/build/tmp/l4re/bin/amd64_K8/l4f/moe rom/x86-fb.cfg
> MOE: Starting: rom/ned rom/x86-fb.cfg
> MOE: loading 'rom/ned'
> pf: 0022 pfa=0000000000000000 ip=00000000010038a2 (w-)
> spc=0xffffffff807c3dd8
> /* press i */
> ---------------------------------------------------------------------
> CPU 0 [fffffffff0062116]: LOG
> jdb:
>
> Now you can use the kernel debugger to inspect the current state of
> the system. Here I simply use addr2line to find the error:
>
> addr2line -p -i -e bin/amd64_K8/l4f/ned -a 10038a2
> 0x00000000010038a2:
> /home/jw5/src/l4resvn/src/l4/pkg/l4re-core/ned/server/src/main.cc:38
> (inlined by)
> /home/jw5/src/l4resvn/src/l4/pkg/l4re-core/ned/server/src/main.cc:77
>
>
> Line 38 is the line with the null pointer dereference.
Thanks for your help! worked :)
addr2line -p -i -e bin/amd64_K8/l4f/ned -a 100398d
0x000000000100398d:
/home/zhaixiang/project/l4re/l4/pkg/l4re-core/ned/server/src/main.cc:38
(inlined by)
/home/zhaixiang/project/l4re/l4/pkg/l4re-core/ned/server/src/main.cc:77
and I need to carefully read JDB manual.
>
> I hope this helps,
> Jean
>
>
>
--
Regards,
Leslie Zhai - a LLVM hacker https://reviews.llvm.org/p/xiangzhai/
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