Re: [PATCH 3/6] LoongArch/kexec_file: Add initrd loading

[Youling Tang <youling.tang@linux.dev>]

Hi, Huacai
On 2025/8/11 22:12, Huacai Chen wrote:
> Hi, Youling,
>
> On Mon, Aug 11, 2025 at 5:28 PM Youling Tang <youling.tang@linux.dev> wrote:
>> From: Youling Tang <tangyouling@kylinos.cn>
>>
>> Add inird loading support and pass it to the second kernel via the
>> cmdline 'initrd=start,size'.
> I think Patch-3 and Patch-5 should be merged into Patch-2.
Not all cases require loading initrd, so Patch-2 is a runnable basic patch.
Separating it into different patches makes it easier to understand and
review the code.

Patch-5 coming out separately can better illustrate the role of "mem"
parameters in capturing the kernel.

Youling.
>
> Huacai
>
>> Signed-off-by: Youling Tang <tangyouling@kylinos.cn>
>> ---
>>   arch/loongarch/kernel/machine_kexec_file.c | 71 ++++++++++++++++++++++
>>   1 file changed, 71 insertions(+)
>>
>> diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
>> index bc91ae0afa4c..e1240644f529 100644
>> --- a/arch/loongarch/kernel/machine_kexec_file.c
>> +++ b/arch/loongarch/kernel/machine_kexec_file.c
>> @@ -34,13 +34,84 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
>>          return kexec_image_post_load_cleanup_default(image);
>>   }
>>
>> +/* Adds the "initrd=start,size" command line parameter to command line. */
>> +static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmplen,
>> +                               char *modified_cmdline, unsigned long initrd)
>> +{
>> +       int initrd_strlen;
>> +
>> +       initrd_strlen = sprintf(modified_cmdline + (*cmdline_tmplen), "initrd=0x%lx,0x%lx ",
>> +               initrd, image->initrd_buf_len);
>> +       *cmdline_tmplen += initrd_strlen;
>> +}
>> +
>> +/*
>> + * Tries to add the initrd to the image. If it is not possible to find
>> + * valid locations, this function will undo changes to the image and return non
>> + * zero.
>> + */
>>   int load_other_segments(struct kimage *image,
>>                          unsigned long kernel_load_addr,
>>                          unsigned long kernel_size,
>>                          char *initrd, unsigned long initrd_len,
>>                          char *cmdline, unsigned long cmdline_len)
>>   {
>> +       struct kexec_buf kbuf;
>> +       unsigned long orig_segments = image->nr_segments;
>> +       char *modified_cmdline = NULL;
>> +       unsigned long cmdline_tmplen = 0;
>> +       unsigned long initrd_load_addr = 0;
>> +       int ret = 0;
>> +
>> +
>> +       kbuf.image = image;
>> +       /* not allocate anything below the kernel */
>> +       kbuf.buf_min = kernel_load_addr + kernel_size;
>> +
>> +       modified_cmdline = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
>> +       if (!modified_cmdline)
>> +               return -EINVAL;
>> +
>> +       /* Ensure it's nul terminated */
>> +       modified_cmdline[COMMAND_LINE_SIZE - 1] = '\0';
>> +
>> +       /* load initrd */
>> +       if (initrd) {
>> +               kbuf.buffer = initrd;
>> +               kbuf.bufsz = initrd_len;
>> +               kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
>> +               kbuf.memsz = initrd_len;
>> +               kbuf.buf_align = 0;
>> +               /* within 1GB-aligned window of up to 32GB in size */
>> +               kbuf.buf_max = round_down(kernel_load_addr, SZ_1G)
>> +                                               + (unsigned long)SZ_1G * 32;
>> +               kbuf.top_down = false;
>> +
>> +               ret = kexec_add_buffer(&kbuf);
>> +               if (ret)
>> +                       goto out_err;
>> +               initrd_load_addr = kbuf.mem;
>> +
>> +               kexec_dprintk("Loaded initrd at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
>> +                             initrd_load_addr, kbuf.bufsz, kbuf.memsz);
>> +
>> +               /* Add the initrd=start,size parameter to the command line */
>> +               cmdline_add_initrd(image, &cmdline_tmplen, modified_cmdline, initrd_load_addr);
>> +       }
>> +
>> +       if (cmdline_len + cmdline_tmplen > COMMAND_LINE_SIZE) {
>> +               pr_err("Appending kdump cmdline exceeds cmdline size\n");
>> +               ret = -EINVAL;
>> +               goto out_err;
>> +       }
>> +       memcpy(modified_cmdline + cmdline_tmplen, cmdline, cmdline_len);
>> +       cmdline = modified_cmdline;
>>          image->arch.cmdline_ptr = (unsigned long)cmdline;
>>
>>          return 0;
>> +
>> +out_err:
>> +       image->nr_segments = orig_segments;
>> +       kfree(modified_cmdline);
>> +       return ret;
>>   }
>> --
>> 2.34.1
>>