Hi YAMAZAKI, Thanks for your comments.
On Thu, Aug 7, 2025 at 11:42 PM YAMAZAKI MASAMITSU(山崎 真光) <yamazaki-m...@nec.com> wrote: > > Thank you for the suggestion. > I think it's a good idea, > but epppic needs careful consideration. Do you mean there are drawbacks of using eppic? From my side, one advantage of eppic is, users can use the kernel data structures/variables directly without redefine it, like: struct task_struct *p; p = (struct task_struct *)&init_task; Users don't need to include headers to define what task_struct looks like, and can use global variable init_task without declaring it. The callbacks of eppic can resolve these missing info via dwarf/btf/kallsyms during runtime. I think this feature can make the eppic scripts tidy and convenient. Also we can use other similar c interpreters, but I haven't encountered one with the similar feature, also considering eppic has been in makedumpfile for years, so people may already be familiar with it... > I'm sorry, but please let me check for a moment. > Sure, no problem, please take your time. Thanks, Tao Liu > Thanks, > Masa > > On 2025/08/05 12:16, Tao Liu wrote: > > Kindly ping... > > > > Any comments for this patchset? > > > > Thanks, > > Tao Liu > > > > > > On Tue, Jun 10, 2025 at 9:57 PM Tao Liu <l...@redhat.com> wrote: > >> A) This patchset will introduce the following features to makedumpfile: > >> > >> 1) Enable eppic script for memory pages filtering. > >> 2) Enable btf and kallsyms for symbol type and address resolving. > >> 3) Port maple tree data structures and functions, primarily used for > >> vma iteration. > >> > >> B) The purpose of the features are: > >> > >> 1) Currently makedumpfile filters mm pages based on page flags, because > >> flags > >> can help to determine one page's usage. But this page-flag-checking > >> method > >> lacks of flexibility in certain cases, e.g. if we want to filter > >> those mm > >> pages occupied by GPU during vmcore dumping due to: > >> > >> a) GPU may be taking a large memory and contains sensitive data; > >> b) GPU mm pages have no relations to kernel crash and useless for > >> vmcore > >> analysis. > >> > >> But there is no GPU mm page specific flags, and apparently we don't > >> need > >> to create one just for kdump use. A programmable filtering tool is > >> more > >> suitable for such cases. In addition, different GPU vendors may use > >> different ways for mm pages allocating, programmable filtering is > >> better > >> than hard coding these GPU specific logics into makedumpfile in this > >> case. > >> > >> 2) Currently makedumpfile already contains a programmable filtering > >> tool, aka > >> eppic script, which allows user to write customized code for data > >> erasing. > >> However it has the following drawbacks: > >> > >> a) cannot do mm page filtering. > >> b) need to access to debuginfo of both kernel and modules, which is > >> not > >> applicable in the 2nd kernel. > >> c) Poor performance, making vmcore dumping time unacceptable (See > >> the following performance testing). > >> > >> makedumpfile need to resolve the dwarf data from debuginfo, to get > >> symbols > >> types and addresses. In recent kernel there are dwarf alternatives > >> such > >> as btf/kallsyms which can be used for this purpose. And btf/kallsyms > >> info > >> are already packed within vmcore, so we can use it directly. > >> > >> 3) Maple tree data structures are used in recent kernels, such as vma > >> iteration. So maple tree poring is needed. > >> > >> With these, this patchset introduces an upgraded eppic, which is based > >> on > >> btf/kallsyms symbol resolving, and is programmable for mm page > >> filtering. > >> The following info shows its usage and performance, please note the > >> tests > >> are performed in 1st kernel: > >> > >> $ time ./makedumpfile -d 31 -l > >> /var/crash/127.0.0.1-2025-06-10-18\:03\:12/vmcore > >> /tmp/dwarf.out -x > >> /lib/debug/lib/modules/6.11.8-300.fc41.x86_64/vmlinux > >> --eppic eppic_scripts/filter_amdgpu_mm_pages.c > >> real 14m6.894s > >> user 4m16.900s > >> sys 9m44.695s > >> > >> $ time ./makedumpfile -d 31 -l > >> /var/crash/127.0.0.1-2025-06-10-18\:03\:12/vmcore > >> /tmp/btf.out --eppic eppic_scripts/filter_amdgpu_mm_pages.c > >> real 0m10.672s > >> user 0m9.270s > >> sys 0m1.130s > >> > >> -rw------- 1 root root 367475074 Jun 10 18:06 btf.out > >> -rw------- 1 root root 367475074 Jun 10 21:05 dwarf.out > >> -rw-rw-rw- 1 root root 387181418 Jun 10 18:03 > >> /var/crash/127.0.0.1-2025-06-10-18:03:12/vmcore > >> > >> C) Discussion: > >> > >> 1) GPU types: Currently only tested with amdgpu's mm page filtering, > >> others > >> are not tested. > >> 2) Code structure: There are some similar code shared by makedumpfile > >> and > >> crash, such as maple tree data structure, also I planed to port the > >> btf/kallsyms code to crash as well, so there are code duplications > >> for > >> crash & makedumpfile. Since I havn't working on crash poring, code > >> change > >> on btf/kallsyms is expected. How can we share the code, creating a > >> common > >> library or keep the duplication as it is? > >> 3) OS: The code can work on rhel-10+/rhel9.5+ on > >> x86_64/arm64/s390/ppc64. > >> Others are not tested. > >> > >> D) Testing: > >> > >> 1) If you don't want to create your vmcore, you can find a vmcore which > >> I > >> created with amdgpu mm pages unfiltered [1], the amdgpu mm pages are > >> allocated by program [2]. You can use the vmcore in 1st kernel to > >> filter > >> the amdgpu mm pages by the previous performance testing cmdline. To > >> verify the pages are filtered in crash: > >> > >> Unfiltered: > >> crash> search -c "!QAZXSW@#EDC" > >> ffff96b7fa800000: > >> !QAZXSW@#EDCXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX > >> ffff96b87c800000: > >> !QAZXSW@#EDCXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX > >> crash> rd ffff96b7fa800000 > >> ffff96b7fa800000: 405753585a415121 !QAZXSW@ > >> crash> rd ffff96b87c800000 > >> ffff96b87c800000: 405753585a415121 !QAZXSW@ > >> > >> Filtered: > >> crash> search -c "!QAZXSW@#EDC" > >> crash> rd ffff96b7fa800000 > >> rd: page excluded: kernel virtual address: ffff96b7fa800000 type: > >> "64-bit KVADDR" > >> crash> rd ffff96b87c800000 > >> rd: page excluded: kernel virtual address: ffff96b87c800000 type: > >> "64-bit KVADDR" > >> > >> 2) You can use eppic_scripts/print_all_vma.c against an ordinary vmcore > >> to > >> test only btf/kallsyms functions by output all VMAs if no amdgpu > >> vmcores/machine avaliable. > >> > >> [1]: https://people.redhat.com/~ltao/core/ > >> [2]: https://gist.github.com/liutgnu/a8cbce1c666452f1530e1410d1f352df > >> > >> Tao Liu (10): > >> dwarf_info: Support kernel address randomization > >> dwarf_info: Fix a infinite recursion bug for search_domain > >> Add page filtering function > >> Add btf/kallsyms support for symbol type/address resolving > >> Export necessary btf/kallsyms functions to eppic extension > >> Port the maple tree data structures and functions > >> Supporting main() as the entry of eppic script > >> Enable page filtering for dwarf eppic > >> Enable page filtering for btf/kallsyms eppic > >> Introducing 2 eppic scripts to test the dwarf/btf eppic extension > >> > >> Makefile | 6 +- > >> btf.c | 919 +++++++++++++++++++++++++ > >> btf.h | 176 +++++ > >> dwarf_info.c | 15 +- > >> eppic_maple.c | 431 ++++++++++++ > >> eppic_maple.h | 8 + > >> eppic_scripts/filter_amdgpu_mm_pages.c | 36 + > >> eppic_scripts/print_all_vma.c | 29 + > >> erase_info.c | 123 +++- > >> erase_info.h | 22 + > >> extension_btf.c | 218 ++++++ > >> extension_eppic.c | 41 +- > >> extension_eppic.h | 6 +- > >> kallsyms.c | 371 ++++++++++ > >> kallsyms.h | 42 ++ > >> makedumpfile.c | 21 +- > >> makedumpfile.h | 11 + > >> 17 files changed, 2448 insertions(+), 27 deletions(-) > >> create mode 100644 btf.c > >> create mode 100644 btf.h > >> create mode 100644 eppic_maple.c > >> create mode 100644 eppic_maple.h > >> create mode 100644 eppic_scripts/filter_amdgpu_mm_pages.c > >> create mode 100644 eppic_scripts/print_all_vma.c > >> create mode 100644 extension_btf.c > >> create mode 100644 kallsyms.c > >> create mode 100644 kallsyms.h > >> > >> -- > >> 2.47.0 > >> -- Crash-utility mailing list -- devel@lists.crash-utility.osci.io To unsubscribe send an email to devel-le...@lists.crash-utility.osci.io https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki
