[Crash-utility] Re: Adding the zram decompression algorithm "lzo-rle" to support kernel versions >= 5.1

Hi Yulong, On Fri, Mar 1, 2024 at 4:25 PM tang yulong <1637403063(a)qq.com&gt; wrote: > >> Hi Yulong, >> >> Thanks for your patch! >> >> On Mon, Feb 26, 2024 at 3:20 PM Yulong TANG 汤玉龙 <yulong.tang(a)nio.com&gt; wrote: >> >> 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. > > Hi Tao, > > I discovered that there seems to be an array called ikconfig_all in kernel.c which records the kernel config status, and there is an API called get_kernel_config(char *conf_name, char **str) for obtaining kernel configuration. This might help solve the second problem you raised. > For example, adding a line: > #define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS get_kernel_config("CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS", NULL); > OK, thanks for the clarification, sounds workable. Then what do you think if we keep the "if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)" related code of the copied kernel code, but change the "if defined" macro into a runtime check like "if get_kernel_config("CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS", NULL)) == IKCONFIG_Y". So the code can be chosen whether to execute depending on the config status.