Re: [PATCH qemu] x86: don't let decompressed kernel image clobber setup_data

[H. Peter Anvin]

On 12/31/22 20:55, Mika Penttilä wrote:
> > If decompression does clobber the data, then we *also* need to figure 
> > out why that is. There are basically three possibilities:
> >
> > 1. If physical KASLR is NOT used:
> >
> >      a. The boot loader doesn't honor the kernel safe area properly;
> >      b. Somewhere in the process a bug in the calculation of the
> >         kernel safe area has crept in.
> >
> > 2. If physical KASLR IS used:
> >
> >      The decompressor doesn't correctly keep track of nor relocate
> >      all the keep-out zones before picking a target address.
>
> Seems setup_data is not included in those mem_avoid regions.

[facepalm]


> > One is a bootloader bug, two is a kernel bugs. My guess is (2) is the 
> > culprit, but (1b) should be checked, too.

Correction: two are kernel bugs, i.e. (1b) and (2) are both kernel bugs.

        -hpa