[PATCH] Add support for Xtensa

[Chris Zankel]

Hi Dimitry,

On 03/22/2013 06:12 PM, Dmitry V. Levin wrote:
> On Fri, Mar 22, 2013 at 05:09:23PM -0700, Chris Zankel wrote:
>> It would be great if you could apply the attached patch to add support
>> for the Xtensa architecture. Xtensa was added to the kernel a long time
>> ago, and we have kept local patches for strace for a long time, but it
>> would be easier to support it in the mainline repository.
> [...]
>> diff --git a/linux/xtensa/syscallent.h b/linux/xtensa/syscallent.h
>> new file mode 100644
>> index 0000000..2ef4fd8
>> --- /dev/null
>> +++ b/linux/xtensa/syscallent.h
>> @@ -0,0 +1,434 @@
>> +	{ 0,	0,	printargs,		"spill"		}, /* 0 */
>> +	{ 0,	0,	printargs,		"xtensa"	}, /* 1 */
>> +	{ MA,	0,	printargs,		"SYS_2"		}, /* 2 */
>> +	{ MA,	0,	printargs,		"SYS_3"		}, /* 3 */
>> +	{ MA,	0,	printargs,		"SYS_4"		}, /* 4 */
>> +	{ MA,	0,	printargs,		"SYS_5"		}, /* 5 */
>> +	{ MA,	0,	printargs,		"SYS_6"		}, /* 6 */
>> +	{ MA,	0,	printargs,		"SYS_7"		}, /* 7 */
> In this and other similar places, please collapse blocks of undefined
> syscall entries using "[N1 ... N2] = {}" notation.
In this patch, I removed the trailing unused entries and change the
above and one other location to the [N1...N2] = {} notation.

>
> [...]
>>  		tcp->u_arg[i] = ((unsigned long *)&metag_regs.dx[3][1])[-i];
>> +#elif defined(XTENSA)
>> +	/* arg0: a6, arg1: a3, arg2: a4, arg3: a5, arg4: a8, arg5: a9 */
>> +	static const int xtensaregs[MAX_ARGS] = { 6, 3, 4, 5, 8, 9 };
>> +	for (i = 0; i < nargs; ++i)
>> +		if (upeek(tcp, REG_A_BASE + xtensaregs[i], &tcp->u_arg[i]) < 0)
>> +			return -1;
>>
>> Is there any reason to upeek one register at a time instead of fetching
>> the whole set using PTRACE_GETREGS or PTRACE_GETREGSET?
>>
>>
I checked again, but couldn't find a good way to use the regset
directly. As a recap, Xtensa is a configurable processor with a
variable  number of internal registers, and from the register set, it is
not always clear where the syscall arguments are without knowing the
configuration dependent register count. Goal is to fix it with
getregset, which is currently not supported, so we can eventually
deprecate the upeek method.

Thanks,
-Chris
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