# Re: \[RFC PATCH v1 11/16\] s390/unwind\_user/sframe: Enable HAVE\_UNWIND\_USER\_SFRAME

- From: Jens Remus \<hidden\>
- Date: 2025-08-01 15:47:06 
- List: linux-trace-kernel
- Page: https://ratatoskr.run/linux-trace-kernel/2025/08/3156088
- Thread: https://ratatoskr.run/linux-trace-kernel/2025/07/3129870/t.md

```text
On 8/1/2025 2:53 PM, Heiko Carstens wrote:
> On Thu, Jul 10, 2025 at 06:35:17PM +0200, Jens Remus wrote:

>> +static inline void __s390_get_dwarf_fpr(unsigned long *val, int regnum)
>> +{
>> +	switch (regnum) {
>> +	case 16:
>> +		fpu_std(0, (freg_t *)val);
>> +		break;
> 
> ...
> 
>> +static inline int s390_unwind_user_get_reg(unsigned long *val, int regnum)
>> +{
>> +	if (0 <= regnum && regnum <= 15) {
>> +		struct pt_regs *regs = task_pt_regs(current);
>> +		*val = regs->gprs[regnum];
>> +	} else if (16 <= regnum && regnum <= 31) {
>> +		__s390_get_dwarf_fpr(val, regnum);
> 
> This won't work with other potential in-kernel fpu users. User space fpr
> contents may have been written to the current task's fpu save area and fprs
> may have been clobbered by in-kernel users; so you need to get register
> contents from the correct location. See arch/s390/include/asm/fpu.h.

Thanks!  Will implement all the review feedback and send a RFC V2 once I
am back from vacation.  Will be away from keyboard for a few weeks.

Regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303)
+49-7031-16-1128 Office
jremus@de.ibm.com

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```