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Marchesi" , Beau Belgrave , Linus Torvalds , Andrew Morton , Florian Weimer , Kees Cook , "Carlos O'Donell" , Sam James , Dylan Hatch References: <20251208171559.2029709-1-jremus@linux.ibm.com> <20251208171559.2029709-15-jremus@linux.ibm.com> <20251210151012.40732B79-hca@linux.ibm.com> Content-Language: en-US From: Jens Remus Organization: IBM Deutschland Research & Development GmbH In-Reply-To: <20251210151012.40732B79-hca@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: OEvpXfclAQ9iQ829_WXTZ7y3JxA1yP13 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjExMDA2MSBTYWx0ZWRfX7cwJ/2FTxbOK JGde00bzjEu9AlLbFNhQ6noZTmjVvTRBrYo4EsCH/SrF2Q00lVkRE35E9CyNnCnLKs4Pp/BHXeH fX57/LxEdTxrYs0lXUaFefsSbnFoffcoS6ZKQ0knYvSabcR2fFsN9Gl5tmoni+k8P/wC+tlPlG+ kRu/0l1Tne1MoUmMaVSr+MvbRBBwC9nRzKrL1c6MlPQfQgE8V9XUsEPF0j0bGTG2Qt8O1LT363/ QjRKgoqiE2zmZeipWxF0/UPvxc1nHBQKxNh1vzamLOsxEW7oW5vecRuMtA/Zri0B6PIBXXswhGf pliB88rrSlsqU7/VxV0Gv+epvbQUCCEIPqhrydZnZg4HfKgbFMpfHo5SLEHmCmEV6fKg1iCICNW F8qZpFLon4TeEz4sXcHqeuk+VU2bRA== X-Proofpoint-GUID: KvxoyagGqrDnoujMKLzUDAEemsy768bn X-Authority-Analysis: v=2.4 cv=F5xat6hN c=1 sm=1 tr=0 ts=693bcef3 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=jPGRhfdHIWHQ-jYqdAYA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-12_01,2025-12-11_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 spamscore=0 bulkscore=0 impostorscore=0 phishscore=0 clxscore=1015 lowpriorityscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2512110061 Hello Heiko, thank you for the feedback! On 12/10/2025 4:10 PM, Heiko Carstens wrote: > On Mon, Dec 08, 2025 at 06:15:56PM +0100, Jens Remus wrote: >> +static inline int __s390_get_dwarf_fpr(unsigned long *val, int regnum) >> +{ >> + switch (regnum) { >> + case 16: >> + fpu_std(0, (freg_t *)val); >> + break; >> + case 17: >> + fpu_std(2, (freg_t *)val); >> + break; >> + case 18: >> + fpu_std(4, (freg_t *)val); >> + break; >> + case 19: >> + fpu_std(6, (freg_t *)val); >> + break; >> + case 20: >> + fpu_std(1, (freg_t *)val); >> + break; > > IIRC, I mentioned this already last time. But it is not correct to access user > space floating point register contents like this. Due to in-kernel fpu/vector > register usage the user space register contents may have been saved away to > the per-thread vxrs save area, and registers may have been used for in-kernel > usage instead. > Read: the above code could access lazy register contents of in-kernel usage. > > Change the above to something like: > > struct fpu *fpu = ¤t->thread.ufpu; > > save_user_fpu_regs(); > switch (regnum) { > case 16: return fpu->vxrs[0].high; > case 17: return fpu->vxrs[2].high; > case 18: return fpu->vxrs[4].high; > case 19: return fpu->vxrs[6].high; > case 20: return fpu->vxrs[1].high; > ... > > save_user_fpu_regs() will write all user space fpu/vector register contents to > the per-thread save area (if not already saved), and then it is possible to > read contents from there. Thanks! I have changed the code accordingly. Works fine. > I'll see if I can provide something better for this use case, since this code > needs to access only the first 16 registers; so no need to write contents of > all registers to the save area. Ok. Regards, Jens -- Jens Remus Linux on Z Development (D3303) +49-7031-16-1128 Office jremus@de.ibm.com IBM IBM Deutschland Research & Development GmbH; Vorsitzender des Aufsichtsrats: Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der Gesellschaft: Böblingen; Registergericht: Amtsgericht Stuttgart, HRB 243294 IBM Data Privacy Statement: https://www.ibm.com/privacy/