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SubjectRe: PROBLEM: zstd bzImage decompression fails for some x86_32 config on 5.9-rc1
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> On Sep 28, 2020, at 1:55 AM, Feng Tang <feng.tang@intel.com> wrote:
>
> Hi Nick,
>
> 0day has found some kernel decomprssion failure case since 5.9-rc1 (X86_32
> build), and it could be related with ZSTD code, though initially we bisected
> to some other commits.
>
> The error messages are:
>
> early console in setup code
> Wrong EFI loader signature.
> early console in extract_kernel
> input_data: 0x046f50b4
> input_len: 0x01ebbeb6
> output: 0x01000000
> output_len: 0x04fc535c
> kernel_total_size: 0x055f5000
> needed_size: 0x055f5000
>
> Decompressing Linux...
>
> ZSTD-compressed data is corrupt
>
> This could be reproduced by compiling the kernel with attached config,
> and use QEMU to boot it.
>
> We suspect it could be related with the kernel size, as we only see
> it on big kernel, and some more info are:
>
> * If we remove a lot of kernel config to build a much smaller kernel,
> it will boot fine
>
> * If we change the zstd algorithm from zstd22 to zstd19, the kernel will
> boot fine with below patch
>
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 3962f59..8fe71ba 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -147,7 +147,7 @@ $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE
> $(obj)/vmlinux.bin.zst: $(vmlinux.bin.all-y) FORCE
> - $(call if_changed,zstd22)
> + $(call if_changed,zstd)
>
>
> Please let me know if you need more info, and sorry for the late report
> as we just tracked down to this point.

Thanks for the report, I will look into it today.

Best,
Nick

> Thanks,
> Feng
>
>
>
> <zstd_x86_32.config>

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