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Mon, 12 Oct 2026 15:07:52 +0000 (GMT) Received: from [0.0.0.0] (unknown [9.87.157.242]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 12 Oct 2026 15:07:52 +0000 (GMT) Message-ID: Date: Mon, 12 Oct 2026 17:07:52 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/32] s390/bug: Indicate modified PSW in disassembly To: Heiko Carstens , Alexander Gordeev , Sven Schnelle , Vasily Gorbik , Christian Borntraeger , Niklas Schnelle , Matthew Rosato , Gerald Schaefer , Vineeth Vijayan , Peter Oberparleiter , Harald Freudenberger , Holger Dengler , Stefan Haberland , Jan Hoeppner , Janosch Frank , Claudio Imbrenda Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org References: <20261001103247.1989111-1-hca@linux.ibm.com> <20261001103247.1989111-5-hca@linux.ibm.com> Content-Language: en-US From: Ilya Leoshkevich In-Reply-To: <20261001103247.1989111-5-hca@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Cr0q4X4D c=1 sm=1 tr=0 ts=6accf7cf cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=BX07Cdk8x4Z_pagRTk8A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: cH6VSp2Li-NEBrazbPR15VLP614VqHJO X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDEyMDA1OCBTYWx0ZWRfX1NAKRBVa1oAj KLzpXqoB/7eC/1rM4F5K1kqG+tANeDB1KoFUiwPKhjCwjvIUULDd9VZ6iyOnqlaXFfSd2xgqF4g UjJEKxbgFtWklevnfBEH12EdeOeQzowE6CN+EGumURvVVnYiYPGm8Anur14JpP7sN5KYq4CTsS/ Xu7HL5245ofIARY3xm4RuyhWlc7xSL+PwzsnhXXyIUjWDM273bWWvs0Sxog8wq5M51nPocRQ3cQ rzl236jPeHPR7r+w5KLiH/i5vdak4m+1j2tGyhHw2XU4fQrcVJIBLwaThxBzKm2nJAKjSXGerBM P+gL/N+K46Ko994SL+vbvbeDs+v1AHPcwWum83Xyxxtxx4mgAG2g3fAadsJMIJobQqBr9VK8h1n 1y9NdnjbzZ7XM/gbTXZjtY9TGU28Xyak4euFmaxlhDdZDN+u3jZlqO2d6oU6dfWQe+zq6NttpTJ /3gfG6YCLc4iw5Ol7JA== X-Proofpoint-Spam-Info: AW1haW4tMjYxMDEyMDA1OCBTYWx0ZWRfXxctiS+6MBHBq 8K+bRTDuqh+9upz9qXJfsPt//A6SIAq1pBFxNi3NG+FZl/fzLwbtJCU04zoFFyYyB0loIq5ju5U Z2RwrkHGYkfyLH80orjXe0rZwnXlsWg= X-Proofpoint-ORIG-GUID: cH6VSp2Li-NEBrazbPR15VLP614VqHJO 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_04,2026-10-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 adultscore=0 priorityscore=1501 suspectscore=0 malwarescore=0 clxscore=1015 impostorscore=0 lowpriorityscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610120058 On 10/1/26 12:32, Heiko Carstens wrote: > With [1] the PSW address is set to the return address of the calling > __WARN_trap() function in order to provide a more useful disassembly of > the caller rather than the helper itself. > > However, since regs->psw.addr is modified, regs->int_code has nothing to > do with the exception. In order to make that more obvious change the > disassembler output. > > Introduce a new PIF_WARN_TRAP_SKIPPED pt_regs flag and set it whenever > __WARN_trap() is skipped. In the disassembler output print a "WARN RET" > prefix to make it obvious that the PSW points to the return address of > the warning trap function. > > Also do not print the interruption code and instruction length code for > this case, since they have nothing to do with the modified PSW. > > Example output: > > Krnl Code: > 000003ffe185bc1c: e3f0ff98ff71 lay %r15,-104(%r15) > 000003ffe185bc22: e3e0f0980024 stg %r14,152(%r15) > 000003ffe185bc28: c0e5ff45ed94 brasl %r14,000003ffe0119750 > WARN RET >000003ffe185bc2e: c0e5ffa052b9 brasl %r14,000003ffe0c661a0 > 000003ffe185bc34: c020fffe86d6 larl %r2,000003ffe182c9e0 > 000003ffe185bc3a: e548f0a80006 mvghi 168(%r15),6 > 000003ffe185bc40: e548f0a00005 mvghi 160(%r15),5 > 000003ffe185bc46: a7690004 lghi %r6,4 > > [1] 79996065cfa2 ("s390/bug: Skip __WARN_trap() in call traces") > > Signed-off-by: Heiko Carstens > --- > arch/s390/include/asm/ptrace.h | 2 ++ > arch/s390/kernel/dis.c | 23 ++++++++++------------- > arch/s390/kernel/dumpstack.c | 7 +++++-- > arch/s390/kernel/early.c | 9 +++++++-- > arch/s390/kernel/traps.c | 1 + > 5 files changed, 25 insertions(+), 17 deletions(-) > > diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h > index 6411e3584283..c844b8aa0fd9 100644 > --- a/arch/s390/include/asm/ptrace.h > +++ b/arch/s390/include/asm/ptrace.h > @@ -17,11 +17,13 @@ > #define PIF_PSW_ADDR_ADJUSTED 1 /* psw address has been adjusted */ > #define PIF_SYSCALL_RET_SET 2 /* return value was set via ptrace */ > #define PIF_FTRACE_FULL_REGS 3 /* all register contents valid (ftrace) */ > +#define PIF_WARN_TRAP_SKIPPED 4 /* __WARN_trap() was skipped */ > > #define _PIF_SYSCALL BIT(PIF_SYSCALL) > #define _PIF_ADDR_PSW_ADJUSTED BIT(PIF_PSW_ADDR_ADJUSTED) > #define _PIF_SYSCALL_RET_SET BIT(PIF_SYSCALL_RET_SET) > #define _PIF_FTRACE_FULL_REGS BIT(PIF_FTRACE_FULL_REGS) > +#define _PIF_WARN_TRAP_SKIPPED BIT(PIF_WARN_TRAP_SKIPPED) > > #define PSW32_MASK_PER _AC(0x40000000, UL) > #define PSW32_MASK_DAT _AC(0x04000000, UL) > diff --git a/arch/s390/kernel/dis.c b/arch/s390/kernel/dis.c > index 1cec93895b3a..5a1a24d211c3 100644 > --- a/arch/s390/kernel/dis.c > +++ b/arch/s390/kernel/dis.c > @@ -540,34 +540,31 @@ void show_code(struct pt_regs *regs) > start += 2; > } > /* Decode the instructions. */ > - ptr = buffer; > - ptr += sprintf(ptr, "%s Code:", mode); > + printk("%s Code:\n", mode); > hops = 0; > while (start < end && hops < 8) { > + ptr = buffer; > opsize = insn_length(code[start]); > - if (start + opsize == 32) > - *ptr++ = '*'; > + if (start == 32 && test_pt_regs_flag(regs, PIF_WARN_TRAP_SKIPPED)) > + ptr += sprintf(ptr, " WARN RET >"); > + else if (start + opsize == 32 && !test_pt_regs_flag(regs, PIF_WARN_TRAP_SKIPPED)) > + ptr += sprintf(ptr, " *"); > else if (start == 32) > - *ptr++ = '>'; > + ptr += sprintf(ptr, " >"); > else > - *ptr++ = ' '; > + ptr += sprintf(ptr, " "); > addr = pswaddr + start - 32; > ptr += sprintf(ptr, "%px: ", (void *)addr); > if (start + opsize >= end) > break; > for (i = 0; i < opsize; i++) > ptr += sprintf(ptr, "%02x", code[start + i]); > - *ptr++ = '\t'; > - if (i < 6) > - *ptr++ = '\t'; > + ptr += sprintf(ptr, "%*s", 13 - 2 * opsize, " "); > ptr += print_insn(ptr, code + start, addr); > start += opsize; > - pr_cont("%s", buffer); > - ptr = buffer; > - ptr += sprintf(ptr, "\n "); > + pr_cont("%s\n", buffer); Should this really be pr_cont() and not printk()? The KERN_CONT doc says: only done after a line that had no enclosing \n and the new code prints everything line-by-line.