From: Jason Wessel on
On 07/28/2010 04:29 AM, Michal Simek wrote:
> Kgdb uses brki r16, 0x18 instruction to call
> low level _debug_exception function which save
> current state to pt_regs and call microblaze_kgdb_break
> function. _debug_exception should be called only from
> the kernel space. User space calling is not supported
> because user application debugging uses different handling.
>
> pt_regs_to_gdb_regs loads additional special registers
> which can't be changed
>
> * Enable KGDB in Kconfig
> * Remove ancient not-tested KGDB support
> * Remove ancient _debug_exception code from entry.S
>
> Only MMU KGDB support is supported.
>
>
There is only one place I saw a problem and if you fix it, you can add:

Acked-by: Jason Wessel <jason.wessel(a)windriver.com>

> +
> +int kgdb_arch_handle_exception(int vector, int signo, int err_code,
> + char *remcom_in_buffer, char *remcom_out_buffer,
> + struct pt_regs *regs)
> +{
> + char *ptr;
> + unsigned long address;
> + int cpu = smp_processor_id();
> +
> + switch (remcom_in_buffer[0]) {
> + case 's':
> + case 'c':
> + /* handle the optional parameter */
> + ptr = &remcom_in_buffer[1];
> + if (kgdb_hex2long(&ptr, &address))
> + regs->pc = address;
> + atomic_set(&kgdb_cpu_doing_single_step, -1);
> + if (remcom_in_buffer[0] == 's')
> + atomic_set(&kgdb_cpu_doing_single_step, cpu);
> +
> + return 0;
> + }
>

As far as I can see there is no code in the arch specific portion to
make use of single stepping. It needs to be implemented using hardware
assist, or a software breakpoint strategy, else you simply omit the 's'
case from statement so that kdb will not enable single stepping at run time.

Example:

switch (remcom_in_buffer[0]) {
case 'c':
/* handle the optional parameter */
ptr = &remcom_in_buffer[1];
if (kgdb_hex2long(&ptr, &address))
regs->pc = address;

return 0;
}


You can also remove the kgdb_cpu_doing_single_step operations because
this arch does not currently implement the kgdb single stepping.


Cheers,
Jason.
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From: Michal Simek on
Jason Wessel wrote:
> On 07/28/2010 04:29 AM, Michal Simek wrote:
>> Kgdb uses brki r16, 0x18 instruction to call
>> low level _debug_exception function which save
>> current state to pt_regs and call microblaze_kgdb_break
>> function. _debug_exception should be called only from
>> the kernel space. User space calling is not supported
>> because user application debugging uses different handling.
>>
>> pt_regs_to_gdb_regs loads additional special registers
>> which can't be changed
>>
>> * Enable KGDB in Kconfig
>> * Remove ancient not-tested KGDB support
>> * Remove ancient _debug_exception code from entry.S
>>
>> Only MMU KGDB support is supported.
>>
>>
> There is only one place I saw a problem and if you fix it, you can add:
>
> Acked-by: Jason Wessel <jason.wessel(a)windriver.com>
>
>> +
>> +int kgdb_arch_handle_exception(int vector, int signo, int err_code,
>> + char *remcom_in_buffer, char *remcom_out_buffer,
>> + struct pt_regs *regs)
>> +{
>> + char *ptr;
>> + unsigned long address;
>> + int cpu = smp_processor_id();
>> +
>> + switch (remcom_in_buffer[0]) {
>> + case 's':
>> + case 'c':
>> + /* handle the optional parameter */
>> + ptr = &remcom_in_buffer[1];
>> + if (kgdb_hex2long(&ptr, &address))
>> + regs->pc = address;
>> + atomic_set(&kgdb_cpu_doing_single_step, -1);
>> + if (remcom_in_buffer[0] == 's')
>> + atomic_set(&kgdb_cpu_doing_single_step, cpu);
>> +
>> + return 0;
>> + }
>>
>
> As far as I can see there is no code in the arch specific portion to
> make use of single stepping. It needs to be implemented using hardware
> assist, or a software breakpoint strategy, else you simply omit the 's'
> case from statement so that kdb will not enable single stepping at run time.
>
> Example:
>
> switch (remcom_in_buffer[0]) {
> case 'c':
> /* handle the optional parameter */
> ptr = &remcom_in_buffer[1];
> if (kgdb_hex2long(&ptr, &address))
> regs->pc = address;
>
> return 0;
> }
>
>
> You can also remove the kgdb_cpu_doing_single_step operations because
> this arch does not currently implement the kgdb single stepping.

Ok. I will remove it. I copied this part of the code from somewhere.
gdb handle single stepping and always send Z0 packet to the next
instruction or two breakpoints for branches.

Thanks,
Michal

>
>
> Cheers,
> Jason.


--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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