Re: [PATCH 0/2] x86/kexec: Implement crash kexec for Secure Boot

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 04/06/2026 8:46 pm, Kevin Lampis wrote:
>> You have identified that bzimage is x86 specific, and for that reason it
>> should not be included in common/kexec.c.
> I believe Ross moved the definition of setup_header out of kexec.c because
> kimage.c also needs to use it now.

Moving the definition is fine.  But it's still x86 specific and cannot
be in common code, because you'll break ARM, RISC-V and PPC by doing so.

>
>> We are going to need an
>> architecture specific way of figuring out the alignment, but looking at
>> kimage_find_kernel_entry_maddr(), why can't we just use the EFI header?
> "Going to need" like "it would be nice" or "we absolutely can't merge this"?

The latter.  But really it depends on "why can't we just use the EFI
header?"

The EFI header is common across architectures, so if we can use that,
its easy.  If we can't use the EFI header and are forced to inspect the
bzImage header, then getting the adequate alignment needs abstracting
properly for the common <-> arch split.

>> Why is it [digest checks] tied to
>> KEXEC_TYPE_CRASH_EFI?  It's applicable to all kexec types.  This ought
>> to be first first in the series so it's not tied to EFI.
> I can do KEXEC_TYPE_CRASH_EFI and KEXEC_TYPE_CRASH but there's an extra layer
> of complexity with normal kexec.
>
> kimage_load_normal_segment() copies the segments data into temporary,
> non-contiguous buffers and then sets up a relocation table which kexec_reloc.S
> uses to copy the segments data into the correct place before jumping to the 
> new
> kernel. Calculating and verifying the digest for normal kexec would mean new
> code to walk the relocation table to find every temporary buffer.

Oh - we can calculate the digest easily when it's loaded, but we can't
check the digest easily at kexec time while we've still got the ability
to fail the action.

In which case lets do it only for the crash types in the short term. 
They're the important ones to check.

It's ok to "return 0; /* TODO, non-crash types */" or equivalent.

~Andrew