Messages in this thread | | | From | Chen Yu <> | Date | Fri, 13 Nov 2020 08:49:57 +0800 | Subject | Re: bootconfig length parse error in kernel |
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On Thu, Nov 12, 2020 at 11:36 PM Masami Hiramatsu <mhiramat@kernel.org> wrote: > > On Thu, 12 Nov 2020 14:49:16 +0800 > Chen Yu <yu.chen.surf@gmail.com> wrote: > > > On Thu, Nov 12, 2020 at 1:50 PM Masami Hiramatsu <mhiramat@kernel.org> wrote: > > > > > > Hi Chen, > > > > > > On Thu, 12 Nov 2020 12:34:36 +0800 > > > Chen Yu <yu.chen.surf@gmail.com> wrote: > > > > > > > Hi Masami, > > > > > > > > On Wed, Nov 11, 2020 at 5:37 PM Masami Hiramatsu <mhiramat@kernel.org> wrote: > > > > > > > > > > Hi Chen, > > > > > > > > > > On Tue, 10 Nov 2020 23:39:53 +0800 > > > > > Chen Yu <yu.chen.surf@gmail.com> wrote: > > > > > > > > > > > Hi Masami, > > > > > > Thanks for writing bootconfig and it is useful for boot up trace event > > > > > > debugging. > > > > > > > > > > Thanks for testing! > > > > > > > > > > > However it was found that on 5.10-rc2 the bootconfig does not work and it shows > > > > > > "'bootconfig' found on command line, but no bootconfig found" > > > > > > And the reason for this is the kernel found the magic number to be incorrect. > > > > > > I've added some hack in kernel to dump the first 12 bytes, it shows: > > > > > > "OTCONFIG". So printed more content ahead we can find > > > > > > "#BOOTCONFIG" ahead. So it looks that there is some alignment during > > > > > > initrd load, and get_boot_config_from_initrd() might also deal with it. That is > > > > > > to say: > > > > > > data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN; > > > > > > might do some alignment? > > > > > > > > > > Hrm, interesting. So initrd_end might be aligned. Could you print out the > > > > > actuall address of initrd_end? > > > > I've done some investigation, it looks like this issue is not related > > > > to alignment, but related to > > > > the bootloader that has provided an inaccurate ramdisk size via > > > > boot_params.hdr.ramdisk_size. > > > > > > Yeah, it seems to happen. bootloader can pass wrong (bigger) size > > > to kernel. BTW, what bootloader would you use? > > > > > It is > > $ grub-install --version > > grub-install (GRUB) 2.04-1ubuntu26.2 > > > > The actual size of initrd is: > > > > ls /boot/initrd.img-5.10.0-rc3-e1000e-hw+ -l > > > > -rw-r--r-- 1 root root 48689230 11月 12 00:08 > > > > /boot/initrd.img-5.10.0-rc3-e1000e-hw+ > > > > while the ramdisk size provided by bootloader via > > > > boot_params.hdr.ramdisk_size is > > > > 48689232, which is 2 bytes bigger than the actual size, and this is > > > > why the initrd_end > > > > is bigger than expected and causing the missmatch of magic number. > > > > > > OK. It seems that the bootloader might cut it up to 16 bytes > > > aligned. (But I think that's wrong behavior, there is no reason > > > to do it) > > Agree. > > > > > > > Since there is no guarantee that bootloader provides the accurate > > > > ramdisk size, an compromised > > > > proposal might be that to search for the magic number a little ahead. > > > > > > If the bootloader does such wrong behavior, there is no guarantee > > > that the size is "a little" bigger. IOW, it can be aligned to the > > > page size (4KB-) > > > > > Right. How about inserting the bootconfig at initrd_start if > > initrd_end could not be trusted? > > > > For example, the > > > > following patch works for me: > > > > diff --git a/init/main.c b/init/main.c > > > > index 130376ec10ba..60fb125d44f4 100644 > > > > --- a/init/main.c > > > > +++ b/init/main.c > > > > @@ -273,7 +273,10 @@ static void * __init > > > > get_boot_config_from_initrd(u32 *_size, u32 *_csum) > > > > if (!initrd_end) > > > > return NULL; > > > > > > > > - data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN; > > > > + data = memchr((char *)initrd_end - 2 * BOOTCONFIG_MAGIC_LEN, > > > > + '#', BOOTCONFIG_MAGIC_LEN); > > > > + if (!data) > > > > + return NULL; > > > > > > So this also does not guarantee that we can find "#" in BOOTCONFIG_MAGIC_LEN. > > > We need to find actual code in the bootloader, what it does. > > > > > Indeed. > > > > if (memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN)) > > > > return NULL; > > > > > > > > > > > > > And could you tell me which platform are you tested? > > > > > > > > > It is HP ZHAN 99 Mobile Workstation G1 with i5-8300H, Ubuntu 20.04. > > > > > > Hmm, this means x86 Grub2 does this change. Let me check it. > > > > > I found the 4 byte alignment code in the grub > (grub_initrd_init()grub-core/loader/linux.c), but that seems to happen > only when load a file with newc:/PACKAGE/FILE format. (And this is not > documented.) At a glance, u-boot may not do that (but of course user > can pass different size directly by command), EDK2 doesn't too. > So, we should check at least 3 byte back for grub. > > BTW, just out of curious, what is your "initrd" command line in grub.conf? :) > It is: linux /boot/vmlinuz-5.10.0-rc3-e1000e-hw+ root=UUID=21f729c7-4ab0-40a9-b8cf-6f22b3851b9f ro ignore_loglevel no_console_suspend bootconfig initrd /boot/initrd.img-5.10.0-rc3-e1000e-hw+ Thanks, Chenyu
> Thank you, > > -- > Masami Hiramatsu <mhiramat@kernel.org>
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