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Mon, 12 Oct 2026 06:12:06 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.87.85.9]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 12 Oct 2026 06:12:06 +0000 (GMT) From: Sven Schnelle To: Heiko Carstens Cc: Alexander Gordeev , Vasily Gorbik , Christian Borntraeger , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH] s390/ptrace: Preserve ILC when updating system call number In-Reply-To: <20261009152132.1113325-1-hca@linux.ibm.com> (Heiko Carstens's message of "Fri, 9 Oct 2026 17:21:31 +0200") References: <20261009152132.1113325-1-hca@linux.ibm.com> Date: Mon, 12 Oct 2026 08:12:06 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDEyMDAyMiBTYWx0ZWRfX03Rta/ed0FPz c5kW9+hgGEEO8gbwJvL/5DgDPKVgFDWFNVbbzmHR5aY7v+IsLJHWJt3qPALaLVVZ+RcejppIsI0 qdmCnMNM3EQTkbp7YKB69U1hiULtkng= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDEyMDAyMiBTYWx0ZWRfXwPMTVoO0lkkK /U/1uKBiT6HZgZk9y53+LdTsirCPx4sWUjCr1tuWrPt8ulFurVmDfnbCLKNirwURD7QOzQQzBnb tAHyo4dH3r+wh0Pjc/s/lrQKAHukZy9FsRWPLnn9Nd/5O7+UIkYV+M7pXtUhXxu6fU8lLKY/67l /8WmkQbuQ/Spb3Dv58WmPSoPTfYwv3S6409smA05uOIoSPCGSzpkbg0Aj2HPKkXu+OHRmBKk7HL lCRrOVV38+yiTEDnkZMNhEFWtL6u5Gn1LEvg1cPE1wLGZAxcpWmuZy96vsHKTKihuFLVKiGDQGy afEVAigxiBSHMb7cn+3NxbUoC+yN+eIa7hN0MkLSQxKjBEBvDaCm4+zx8/BdZ3LN7+nytxzATOU 0eeTMVzPs/Q+Pi8OcyHJNJjGi5c5zdtcHDfYE/+RLOV+jXtB0wV0ohLDcdwG+jUVdIeg+rdaxC6 Ec66sDGWkv30zbAH1nw== X-Authority-Analysis: v=2.4 cv=E6pYNqdl c=1 sm=1 tr=0 ts=6acc7a3b cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=31u72ZEnUxVqjmpZp2QA:9 X-Proofpoint-ORIG-GUID: srHuSWHhLNOzFUnmMXEsaJ0LsLguDThK X-Proofpoint-GUID: srHuSWHhLNOzFUnmMXEsaJ0LsLguDThK X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-12_02,2026-10-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 spamscore=0 adultscore=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610120022 Heiko Carstens writes: > When an attached debugger changes gpr2 via PTRACE_POKEUSR while the > traced process has PIF_SYSCALL set, the int_code in pt_regs is also > updated. In case of an svc it contains the instruction length code > (ILC), as well as the system call number. > > The ptrace code sets the ILC unconditionally to a value which matches the > svc instruction. However the svc instruction also may have been executed > via the execute or execute relative long instruction, which have a > different length. Therefore preserve the ILC and only change the system > call number using syscall_set_nr(). > > This makes sure that in case of a PSW rewind the instruction address > points to the correct instruction. > > Fixes: 56e62a737028 ("s390: convert to generic entry") > Signed-off-by: Heiko Carstens > --- > arch/s390/kernel/ptrace.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c > index 125ca4c4e30c..d8d5e843859c 100644 > --- a/arch/s390/kernel/ptrace.c > +++ b/arch/s390/kernel/ptrace.c > @@ -34,6 +34,7 @@ > #include > #include > #include > +#include > > #include "entry.h" > > @@ -345,11 +346,9 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data) > return -EINVAL; > } > > - if (test_pt_regs_flag(regs, PIF_SYSCALL) && > - addr == offsetof(struct user, regs.gprs[2])) { > - struct pt_regs *regs = task_pt_regs(child); > - > - regs->int_code = 0x20000 | (data & 0xffff); > + if (addr == offsetof(struct user, regs.gprs[2])) { > + if (test_pt_regs_flag(regs, PIF_SYSCALL)) > + syscall_set_nr(child, regs, data); > } > *(addr_t *)((addr_t) ®s->psw + addr) = data; > } else if (addr < offsetof(struct user, regs.orig_gpr2)) { Reviewed-by: Sven Schnelle