On 2025/11/24 13:46, Tao Liu wrote: > Kindly ping... Any comments on this?
Hi Tao, I'm sorry for the delay. I think I can look into this next month. Thanks, Kazu > > Thanks, > Tao Liu > > On Tue, Oct 21, 2025 at 11:24 AM Tao Liu <[email protected]> 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. >> >> 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. >> >> 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) 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 >> >> v2 -> v1: >> >> 1) Moved maple tree related code(for VMA iteration) into eppic script, so we >> don't need to port maple tree code to makedumpfile. >> >> 2) Reorganized the patchset as follows: >> >> --- <common modification> --- >> 1.Add page filtering function >> 2.Supporting main() as the entry of eppic script >> >> --- <dwarf related modification> --- >> 3.dwarf_info: Support kernel address randomization >> 4.dwarf_info: Fix a infinite recursion bug for rust >> 5.eppic dwarf: support anonymous structs member resolving >> 6.Enable page filtering for dwarf eppic >> >> --- <btf & kallsyms related modification> --- >> 7.Implement kernel kallsyms resolving >> 8.Implement kernel btf resolving >> 9.Implement kernel module's kallsyms resolving >> 10.Implement kernel module's btf resolving >> 11.Export necessary btf/kallsyms functions to eppic extension >> 12.Enable page filtering for btf/kallsyms eppic >> 13.Docs: Update eppic related entries >> >> --- <only for test purpose, don't merge> --- >> 14.Introducing 2 eppic scripts to test the dwarf/btf eppic extension >> >> The modification on dwarf is primary for comparision purpose, that >> for the same eppic program, mm page filtering should get exact same >> outputs for dwarf & kallsyms/btf based approaches. If outputs unmatch, >> this indicates bugs. In fact, we will never take dwarf mm pages filtering >> in real use, due to its poor performance as well as inaccessibility >> of debuginfo during kdump in 2nd kernel. So patch 3/4/5 won't affect >> the function of btf/kallsyms eppic mm page filtering, but there are >> functions shared in patch 6, so it is a must-have one. Patch 14 is >> only for test purpose, to demonstrate how to write eppic script for >> mm page filtering, so it isn't a must-have patch. >> >> Please note, in patch 14, I have deliberately converted all array >> operation into pointer operation, e.g. modified "node->slot[i]" into >> "*((unsigned long *)&(node->slot) + i)". This is because there are >> bugs for array operation support in extension_eppic.c. I didn't have >> effort to test and fix them all because as I mentioned previously, >> mm page filtering in dwarf side is only for comparision and will >> never be used in real use. There is no such issue for kallsyms/btf >> eppic side. >> >> 3) Since we ported maple tree code to eppic script, several bugs found >> both for eppic library & eppic btf support. Please use master branch >> of eppic library to co-compile with this patchset. >> >> Tao Liu (14): >> Add page filtering function >> Supporting main() as the entry of eppic script >> dwarf_info: Support kernel address randomization >> dwarf_info: Fix a infinite recursion bug for rust >> eppic dwarf: support anonymous structs member resolving >> Enable page filtering for dwarf eppic >> Implement kernel kallsyms resolving >> Implement kernel btf resolving >> Implement kernel module's kallsyms resolving >> Implement kernel module's btf resolving >> Export necessary btf/kallsyms functions to eppic extension >> Enable page filtering for btf/kallsyms eppic >> Docs: Update eppic related entries >> Introducing 2 eppic scripts to test the dwarf/btf eppic extension >> >> Makefile | 6 +- >> btf.c | 919 +++++++++++++++++++++++++ >> btf.h | 177 +++++ >> dwarf_info.c | 7 + >> eppic_scripts/filter_amdgpu_mm_pages.c | 255 +++++++ >> eppic_scripts/print_all_vma.c | 239 +++++++ >> erase_info.c | 120 +++- >> erase_info.h | 19 + >> extension_btf.c | 258 +++++++ >> extension_eppic.c | 106 ++- >> extension_eppic.h | 6 +- >> kallsyms.c | 392 +++++++++++ >> kallsyms.h | 41 ++ >> makedumpfile.8.in | 24 +- >> makedumpfile.c | 21 +- >> makedumpfile.h | 11 + >> print_info.c | 11 +- >> 17 files changed, 2550 insertions(+), 62 deletions(-) >> create mode 100644 btf.c >> create mode 100644 btf.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 >>
