On 2024/03/01 9:29, HAGIO KAZUHITO(萩尾 一仁) wrote: > On 2024/02/29 19:08, Tao Liu wrote: >> Hi Yulong, >> >> Thanks for your patch! >> >> On Mon, Feb 26, 2024 at 3:20 PM Yulong TANG 汤玉龙 <yulong.tang@xxxxxxx> wrote: >>> >>> In Linux 5.1, the ZRAM block driver has changed its default compressor from "lzo" to "lzo-rle" to enhance LZO compression support. However, crash does not support the improved LZO algorithm, resulting in failure when reading memory. >>> >>> change default compressor : ce82f19fd5809f0cf87ea9f753c5cc65ca0673d6 >>> >>> >>> The issue was discovered when using the extension 'gcore' to generate a process coredump, which was found to be incomplete and unable to be opened properly with gdb. >>> >>> >>> This patch is for Crash-utility tool, it enables the Crash-utility to support decompression of the "lzo-rle" compression algorithm used in zram. The patch has been tested with vmcore files from kernel version 5.4, and successfully allows reading of memory compressed with the zram compression algorithm. >> >> I have no objection to the lzo-rle decompression feature for crash. >> However I have some concern of your patch: >> >> The patch you attached is a "lzorle_decompress_safe" implementation >> which is copied from kernel source code. One of the drawbacks of >> copying kernel source code is, kernel is constantly evolving, the code >> you copied here today maybe updated someday later, and in support of >> different kernel versions, we need to keep a bunch of >> switch(kernel_version) and case code to keep the compatibility, which >> is what we are trying to avoid. >> >> In addition, the code you copied has deliberately deleted the "if >> defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)" part, which may also >> cause some problem, and as far as I know, there is no good way in >> crash to determine the kernel config status, please feel free to >> correct me if I'm wrong. >> >> I'm thinking of another way to implement this, by copying the related >> kernel function's binary to crash and execute it in crash, of course >> the kernel function needs to meet some limitations, but at least it >> can work for some simple functions as my test. So could you please >> give the following trial patch some modification and try? > > Hi Tao, > > That's an interesting idea, but I'm very afraid of copying a function > from data (vmcore) and executing it, for security. Maybe it's not > impossible that someone sends a crafted vmcore to your support team.. > > Also, with that, we cannot handle a vmcore of another architecture, e.g. > arm64 vmcores with x86_64 crash with target=ARM64. > > sorry I still haven't check Yulong's patch, but if lzo-rle library is > not available, maybe we need to import the code..? seeing lib/lzo/ in the kernel source, lzo-rle is not far from lzo, the lzo library will not support lzo-rle? Thanks, Kazu -- Crash-utility mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxxxxxx https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki
