[PATCH] Add method to pass initrd through cmdline
Hui Li
lihui at loongson.cn
Mon May 2 22:50:19 PDT 2022
Hi Simon Horman,
Thanks for your review.
On 2022/4/29 下午5:40, Simon Horman wrote:
> Hi Hui Li,
>
> thanks for your patch.
>
> On Mon, Apr 18, 2022 at 09:36:59AM +0800, Hui Li wrote:
>> Problem description:
>> Under loongson platform,use command:
>> kexec -l vmlinux... --append="root=UUID=28e1..." --initrd=...
>> kexec -e
>> quick restart failed.
>>
>> The reason of this problem:
>> The kernel cannot parse the UUID,UUID is parsed in the initrd.
>> Loongson platform obtain the initrd through cmdline in kernel.
>> In kexec-tools, initrd is not added to cmdline.
>
> Is this common to other platforms?
> If not, is there a reason that Loongson takes this approach?
>
in kernel code,arch/mips/configs/loongson3_defconfig,
CONFIG_BLK_DEV_INITRD=y is defined.
In arch/mips/kernel/setup.c file, the following code：
#ifdef CONFIG_BLK_DEV_INITRD
static int __init rd_start_early(char *p)
{
unsigned long start = memparse(p, &p);
#ifdef CONFIG_64BIT
/* Guess if the sign extension was forgotten by bootloader */
if (start < XKPHYS)
start = (int)start;
#endif
initrd_start = start;
initrd_end += start;
return 0;
}
early_param("rd_start", rd_start_early);
static int __init rd_size_early(char *p)
{
initrd_end += memparse(p, &p);
return 0;
}
early_param("rd_size", rd_size_early);
...
...
...
#endif
The purpose of parsing initrd parameters through cmdline on the loongson
is to compatible with previous platforms
Maybe other platforms use DTB to parse initrd, but it can be seen that
the kernel also supports the use of cmdline to parse initrd.
>> The solution:
>> Add initrd parameter to cmdline. and add a CONFIG_LOONGSON configuration
>> to distinguish PAGE_OFFSET between different platforms under mips.
>>
>> Signed-off-by: Hui Li <lihui at loongson.cn>
>> ---
>> configure.ac | 5 ++++
>> kexec/arch/mips/crashdump-mips.h | 6 ++++-
>> kexec/arch/mips/kexec-elf-mips.c | 43 ++++++++++++++++++++++++++++++++
>> 3 files changed, 53 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure.ac b/configure.ac
>> index cf8e8a2..26bfbcd 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -111,6 +111,11 @@ AC_ARG_WITH([booke],
>> AC_DEFINE(CONFIG_BOOKE,1,
>> [Define to build for BookE]))
>>
>> +AC_ARG_WITH([loongson],
>> + AC_HELP_STRING([--with-loongson],[build for loongson]),
>> + AC_DEFINE(CONFIG_LOONGSON,1,
>> + [Define to build for LoongsoN]))
>> +
>> dnl ---Programs
>> dnl To specify a different compiler, just 'export CC=/path/to/compiler'
>> if test "${build}" != "${host}" ; then
>> diff --git a/kexec/arch/mips/crashdump-mips.h b/kexec/arch/mips/crashdump-mips.h
>> index 7edd859..d53c696 100644
>> --- a/kexec/arch/mips/crashdump-mips.h
>> +++ b/kexec/arch/mips/crashdump-mips.h
>> @@ -5,7 +5,11 @@ struct kexec_info;
>> int load_crashdump_segments(struct kexec_info *info, char *mod_cmdline,
>> unsigned long max_addr, unsigned long min_base);
>> #ifdef __mips64
>> -#define PAGE_OFFSET 0xa800000000000000ULL
>> +#ifdef CONFIG_LOONGSON
>> +#define PAGE_OFFSET 0xFFFFFFFF80000000ULL
>> +#else
>> +#define PAGE_OFFSET 0xa800000000000000ULL
>> +#endif
>
> Could this be detected at runtime?
>
> It seems awkward to set the PAGE_OFFSET at compile time and
> thus need separate builds for separate platforms (with no warning
> if the wrong one is used).
>
Thank you very much for this good suggestion.
I see that there is a way to get different platform information at
runtime via "/proc/cpuinfo", which is used to distinguish PAGE_OFFSET
for different platforms.
>> #define MAXMEM 0
>> #else
>> #define PAGE_OFFSET 0x80000000
>> diff --git a/kexec/arch/mips/kexec-elf-mips.c b/kexec/arch/mips/kexec-elf-mips.c
>> index a2d11fc..1de418e 100644
>> --- a/kexec/arch/mips/kexec-elf-mips.c
>> +++ b/kexec/arch/mips/kexec-elf-mips.c
>> @@ -40,6 +40,44 @@ static const int probe_debug = 0;
>> #define CMDLINE_PREFIX "kexec "
>> static char cmdline_buf[COMMAND_LINE_SIZE] = CMDLINE_PREFIX;
>>
>> +/* Converts unsigned long to ascii string. */
>> +static void ultoa(unsigned long i, char *str)
>> +{
>> + int j = 0, k;
>> + char tmp;
>> +
>> + do {
>> + str[j++] = i % 10 + '0';
>> + } while ((i /= 10) > 0);
>> + str[j] = '\0';
>
> Could the above be achieved using printf?
>
>> + /* Reverse the string. */
>> + for (j = 0, k = strlen(str) - 1; j < k; j++, k--) {
>> + tmp = str[k];
>> + str[k] = str[j];
>> + str[j] = tmp;
>> + }
>
> I'm confused as to why the string needs to be reversed.
> Could it be avoided by byte-swapping 'i' before rendering it to a string?
> Thanks a lot for your suggestions on these details.
ultoa() function is used in many places.I see many other platforms have
the same implementation like:
/kexec/arch/i386/crashdump-x86.c
/kexec/arch/ppc64/crashdump-ppc64.c
/kexec/arch/ppc64/crashdump-sh.c
So, Is it possible to keep the existing implementation ?
>> +}
>> +
>> +/* Adds initrd parameters to command line. */
>> +static int cmdline_add_initrd(char *cmdline, unsigned long addr, char *new_para)
>> +{
>> + int cmdlen, len;
>> + char str[30], *ptr;
>> +
>> + ptr = str;
>> + strcpy(str, new_para);
>> + ptr += strlen(str);
>> + ultoa(addr, ptr);
>> + len = strlen(str);
>> + cmdlen = strlen(cmdline) + len;
>> + if (cmdlen > (COMMAND_LINE_SIZE - 1))
>> + die("Command line overflow\n");
>> + strcat(cmdline, str);
>> +
>> + return 0;
>> +}
>> +
>> +
>> int elf_mips_probe(const char *buf, off_t len)
>> {
>> struct mem_ehdr ehdr;
>> @@ -171,6 +209,11 @@ int elf_mips_load(int argc, char **argv, const char *buf, off_t len,
>> /* Now that the buffer for initrd is prepared, update the dtb
>> * with an appropriate location */
>> dtb_set_initrd(&dtb_buf, &dtb_length, initrd_base, initrd_base + initrd_size);
>> +
>> + /* Add the initrd parameters to cmdline */
>> + cmdline_add_initrd(cmdline_buf, PAGE_OFFSET + initrd_base, " rd_start=");
>> + cmdline_add_initrd(cmdline_buf, initrd_size, " rd_size=");
>> +
>
> Will this be safe for existing use-cases?
>
This modification is safe for other existing use-cases.
Now this method is only for the loongson platform to pass the initrd
correctly. At this stage, this change is no problem to use on the
loongson platform, and it will not affect other platforms.
This part can be further constrained, only for the loongson platform.
let me think about the above and try to
find a proper way, and then I will send a v3 patch.
Thanks again for your review
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