Re: GDB get wrong debug infos on TI DSP architecture extension

[casmac]

Hi,

   Thank you for forwarding my question to developers and sharing the C6x implementation.

   Perhaps I should follow up with another problem I encountered. The senerio is the  emulator keeps running eventhough the program it emulates has already exited. And it keeps retrieving instructions which are all zero "instruction"(0x00000000).

   It looks to me that in function cpu_exec(CPUState *cpu), the following loop never terminate:

   while (!cpu_handle_exception(cpu, &ret)) {
        TranslationBlock *last_tb = NULL;
        int tb_exit = 0;
        while (!cpu_handle_interrupt(cpu, &last_tb)) { ... }

   Is it because cpu->exit_request remains 0 ?

   At what point should we make cpu->exit_request=1 ?

   Thanks again!!

regards

xiaolei

------------------ Original ------------------

From: "Philippe Mathieu-Daud?"<f4bug@amsat.org>;

Date: Wed, May 27, 2020 03:19 PM

To: "casmac"<1482995675@qq.com>;"qemu-devel"<qemu-devel@nongnu.org>;

Cc: "Taylor Simpson"<tsimpson@quicinc.com>;"Alex Benn?e"<alex.bennee@linaro.org>;"Luc Michel"<luc.michel@greensocs.com>;

Subject: Re: GDB get wrong debug infos on TI DSP architecture extension

Hi Xiaolei,

Cc'ing more developers who might answer you.

On 5/27/20 8:48 AM, casmac wrote:
> Hi all,
>    I am working on a TI DSP architecture extension for QEMU.

FYI you can find the TI TMS320C6x target implemented here:
https://github.com/philmd/qemu/releases/tag/target-c6x-2.4

I started rebasing it to QEMU 4.2 but then got distracted.

> Now, we are
> adding GDB debugging features.
>    We have done the following, but not sure we are on the right track :
>    - add a xml description file in gdb-xml, without understanding the
> purpose of the file, why some architectures don't provide such xml file?
>    - add ***_cpu_gdb_read_register(), ***_cpu_gdb_write_register();
>    - added  dsp_cpu_get_phys_page_attrs_debug(), but uncertain about
> what to return
>      dsp_cpu_get_phys_page_attrs_debug(CPUState *cs, vaddr addr,
> MemTxAttrs *attrs)
>      {
>         return addr & TARGET_PAGE_MASK;  
>      }
>   
>    We run QEMU with the these arguments
>    qemu-system-dsp ... -kernel filename.out -S -s
>   
>    It turns out that gdb reads incorrect register values, and complains
> : "warning: Target-supplied registers are not supported by the current
> architecture".
>   
>    Something is missing here, or we do it in a wrong way.  Any advise
> would be helpful to us.
>   
>    Thanks.
>    
> xiaolei
>
>    ----- ti_dsp.xml  -----
>   
>    <?xml version="1.0"?>
> <!DOCTYPE feature SYSTEM "gdb-target.dtd">
> <feature name="org.gnu.gdb.tic3x.core">
>     <reg name="r0"  bitsize="32"></reg>
>  <reg name="r1"  bitsize="32"/>
>  <reg name="r2"  bitsize="32"></reg>
>  <reg name="r3"  bitsize="32"/>
>  <reg name="r4"  bitsize="32"/>
>  <reg name="r5"  bitsize="32"/>
>  <reg name="r6"  bitsize="32"/>
>  <reg name="r7"  bitsize="32"/>
>  <reg name="ar0" bitsize="32"/>
>  <reg name="ar1" bitsize="32"/>
>  <reg name="ar2" bitsize="32"/>
>  <reg name="ar3" bitsize="32"/>
>  <reg name="ar4" bitsize="32"/>
>  <reg name="ar5" bitsize="32"/>
>  <reg name="ar6" bitsize="32"/>
>  <reg name="ar7" bitsize="32"/>
>  <reg name="dp"  bitsize="32"/>
>  <reg name="ir0" bitsize="32"/>
>  <reg name="ir1" bitsize="32"/>
>  <reg name="bk"  bitsize="32"/>
>  <reg name="sp"  bitsize="32" type="data_ptr"/>
>  <reg name="st"  bitsize="32"></reg>
>  <reg name="ie"  bitsize="32"/>
>  <reg name="if"  bitsize="32"/>
>  <reg name="iof" bitsize="32"/>
>  <reg name="rs"  bitsize="32"/>
>  <reg name="re"  bitsize="32"/>
>  <reg name="rc"  bitsize="32"/>
>  <reg name="pc"  bitsize="32" type="data_ptr"/>
>  <reg name="clk"  bitsize="32"/>
> </feature>
>