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Thu, 23 Oct 2025 16:04:38 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E5F4B20040; Thu, 23 Oct 2025 16:04:37 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E4C6820043; Thu, 23 Oct 2025 16:04:35 +0000 (GMT) Received: from [9.111.177.23] (unknown [9.111.177.23]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 23 Oct 2025 16:04:35 +0000 (GMT) Message-ID: Date: Thu, 23 Oct 2025 18:04:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 06/15] unwind_user/sframe: Add support for reading .sframe contents To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org, Steven Rostedt Cc: Josh Poimboeuf , Masami Hiramatsu , Mathieu Desnoyers , Peter Zijlstra , Ingo Molnar , Jiri Olsa , Arnaldo Carvalho de Melo , Namhyung Kim , Thomas Gleixner , Andrii Nakryiko , Indu Bhagat , "Jose E. Marchesi" , Beau Belgrave , Linus Torvalds , Andrew Morton , Florian Weimer , Kees Cook , "Carlos O'Donell" , Sam James , Borislav Petkov , Dave Hansen , David Hildenbrand , "H. Peter Anvin" , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Heiko Carstens , Vasily Gorbik , "Steven Rostedt (Google)" References: <20251022144326.4082059-1-jremus@linux.ibm.com> <20251022144326.4082059-7-jremus@linux.ibm.com> Content-Language: en-US From: Jens Remus Organization: IBM Deutschland Research & Development GmbH In-Reply-To: <20251022144326.4082059-7-jremus@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: fgZdUdnGXaTGdSaxwNUvOB3JNAYR6LNi X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDE4MDAyMiBTYWx0ZWRfXxYbS0I7ozNJu olD9B0XrJZvSbfWDUx+3Sqi8NpgFB0qU0t9tF3zQUoxXU6konKgOnhszhPE8oKGWiHUdHJDRcxd 8ViieVm5wekdYLpFm+A73xS51SQcgkuIqX0ZHn44aDXIv9mKhhgTU+DAWt+oY3jEf9jyb+boa+4 2xXTCGYi1ry0HDJGM/YBzRGIE6ezhP4kJnR18shXPDs6fjx3gE9FoSvvMsORWfBL99cPC2Uzglh yxkGESRMvyU6jsqz+4p8osiKrJ/pnJIambuKHpfbM4t7mWotdI+baOH96LqBsK+tqCHsKUE0Ynh 69QOh0bOVtLgmzhG4Fdq55SCCx5oLsMJ1ERVjiS8s9cs0pOygX5YySe6VpgcegnZsG2yX7z2rDZ jEXEfZR1fIaRadv1ly56Js+HF/U+HA== X-Proofpoint-GUID: j-aP8M5YiDrfT85xUy7fTFBSirXnKljV X-Authority-Analysis: v=2.4 cv=SKNPlevH c=1 sm=1 tr=0 ts=68fa521b cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=s6ekHP1XpJ6eNOeT0-oA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=DXsff8QfwkrTrK3sU8N1:22 a=Z5ABNNGmrOfJ6cZ5bIyy:22 a=bWyr8ysk75zN3GCy5bjg:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-23_01,2025-10-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 suspectscore=0 clxscore=1015 priorityscore=1501 spamscore=0 impostorscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510180022 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: CCDEBC000C X-Stat-Signature: 7q169rgrshypbx7x8tfweykqedzigizr X-Rspam-User: X-HE-Tag: 1761235514-429445 X-HE-Meta: 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 MY+e8usv kLbmuKEfrEk5bfSvkb6G6gRxIDLg35YW8+stJF7T4jBFuYzbk+87Q2jSRWfMYHZTmuwu0i1+KMXm1KjZv9xhvjJC39li1RVOAtqCm336ONFkA6gGUacNSb5Mk4b4tFpJ/AOPlzyTiNt/nEBAiwQSsXvHq6Sr/c+0KaSQRkgM3s+2X7jy/+jz9O9yRCE3s8RJ0Ezh8iVFt+eiNK2Jj398xO69023BTptCU6S/B4edxI1elBmGWwj7swtkGLoXKRdkhO7ZvTKw2WMGgI4id5kJrV5RLviENXbeCJumucYLxDrGFgOlvnuLbomLIX0QlNkyUyG389acbzQwNipju7ov1/MOdSjOorEGAfOiJiHNBvpAzJ74= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Steve, et al., as discussed during yesterdays SFrame call I will be sending two RFC fixup patches shortly as POC to demonstrate how this patch and "[PATCH v11 14/15] unwind_user/sframe: Add .sframe validation option" could benefit from introducing an internal FDE representation (e.g. struct sframe_fde_internal) similar to the used internal FRE representation (struct sframe_fre). On 10/22/2025 4:43 PM, Jens Remus wrote: > diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c > +static __always_inline int __read_fde(struct sframe_section *sec, > + unsigned int fde_num, > + struct sframe_fde *fde, > + unsigned long *fde_start_base) The goal would be to eliminate the passing through of fde_start_base as well as the various computations of the effective function start address (= *fde_start_base + fde->start_addr) throughout this module. The internal FDE representation could then simply convey the effective function start address via an "unsigned long func_start_addr" field. > +{ > + unsigned long fde_addr, ip; > + > + fde_addr = sec->fdes_start + (fde_num * sizeof(struct sframe_fde)); > + unsafe_copy_from_user(fde, (void __user *)fde_addr, > + sizeof(struct sframe_fde), Efault); > + > + ip = fde_addr + fde->start_addr; > + if (ip < sec->text_start || ip > sec->text_end) > + return -EINVAL; > + > + *fde_start_base = fde_addr; > + return 0; > + > +Efault: > + return -EFAULT; > +} > + > +static __always_inline int __find_fde(struct sframe_section *sec, > + unsigned long ip, > + struct sframe_fde *fde, > + unsigned long *fde_start_base) fde_start_base would get eliminated. > +{ > + unsigned long func_addr_low = 0, func_addr_high = ULONG_MAX; > + struct sframe_fde __user *first, *low, *high, *found = NULL; > + int ret; > + > + first = (void __user *)sec->fdes_start; > + low = first; > + high = first + sec->num_fdes - 1; > + > + while (low <= high) { > + struct sframe_fde __user *mid; > + s32 func_off; > + unsigned long func_addr; > + > + mid = low + ((high - low) / 2); > + > + unsafe_get_user(func_off, (s32 __user *)mid, Efault); > + func_addr = (unsigned long)mid + func_off; > + > + if (ip >= func_addr) { > + if (func_addr < func_addr_low) > + return -EFAULT; > + > + func_addr_low = func_addr; > + > + found = mid; > + low = mid + 1; > + } else { > + if (func_addr > func_addr_high) > + return -EFAULT; > + > + func_addr_high = func_addr; > + > + high = mid - 1; > + } > + } > + > + if (!found) > + return -EINVAL; > + > + ret = __read_fde(sec, found - first, fde, fde_start_base); fde_start_base would get eliminated. > + if (ret) > + return ret; > + > + /* make sure it's not in a gap */ > + if (ip < *fde_start_base + fde->start_addr || > + ip >= *fde_start_base + fde->start_addr + fde->func_size) Would simplify to: if (ip < fde->func_start_addr || ip >= fde->func_start_addr + fde->func_size) > + return -EINVAL; > + > + return 0; > + > +Efault: > + return -EFAULT; > +} > +static __always_inline int __find_fre(struct sframe_section *sec, > + struct sframe_fde *fde, > + unsigned long fde_start_base, fde_start_base would get eliminated. > + unsigned long ip, > + struct unwind_user_frame *frame) > +{ > + unsigned char fde_type = SFRAME_FUNC_FDE_TYPE(fde->info); > + struct sframe_fre *fre, *prev_fre = NULL; > + struct sframe_fre fres[2]; > + unsigned long fre_addr; > + bool which = false; > + unsigned int i; > + u32 ip_off; > + > + ip_off = ip - (fde_start_base + fde->start_addr); Would simplify to: ip_off = ip - fde->func_start_addr; > + > + if (fde_type == SFRAME_FDE_TYPE_PCMASK) > + ip_off %= fde->rep_size; > + > + fre_addr = sec->fres_start + fde->fres_off; > + > + for (i = 0; i < fde->fres_num; i++) { > + int ret; > + > + /* > + * Alternate between the two fre_addr[] entries for 'fre' and > + * 'prev_fre'. > + */ > + fre = which ? fres : fres + 1; > + which = !which; > + > + ret = __read_fre(sec, fde, fre_addr, fre); > + if (ret) > + return ret; > + > + fre_addr += fre->size; > + > + if (prev_fre && fre->ip_off <= prev_fre->ip_off) > + return -EFAULT; > + > + if (fre->ip_off > ip_off) > + break; > + > + prev_fre = fre; > + } > + > + if (!prev_fre) > + return -EINVAL; > + fre = prev_fre; > + > + frame->cfa_off = fre->cfa_off; > + frame->ra_off = fre->ra_off; > + frame->fp_off = fre->fp_off; > + frame->use_fp = SFRAME_FRE_CFA_BASE_REG_ID(fre->info) == SFRAME_BASE_REG_FP; > + > + return 0; > +} > + > +int sframe_find(unsigned long ip, struct unwind_user_frame *frame) > +{ > + struct mm_struct *mm = current->mm; > + struct sframe_section *sec; > + struct sframe_fde fde; > + unsigned long fde_start_base; fde_start_base would get eliminated. > + int ret; > + > + if (!mm) > + return -EINVAL; > + > + guard(srcu)(&sframe_srcu); > + > + sec = mtree_load(&mm->sframe_mt, ip); > + if (!sec) > + return -EINVAL; > + > + if (!user_read_access_begin((void __user *)sec->sframe_start, > + sec->sframe_end - sec->sframe_start)) > + return -EFAULT; > + > + ret = __find_fde(sec, ip, &fde, &fde_start_base); fde_start_base would get eliminated. > + if (ret) > + goto end; > + > + ret = __find_fre(sec, &fde, fde_start_base, ip, frame); fde_start_base would get eliminated. > +end: > + user_read_access_end(); > + return ret; > +} 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/