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SubjectRe: [PATCH 08/62] x86/boot/compressed/64: Add IDT Infrastructure
Hi Andy,

thanks a lot for your valuable reviews!

On Tue, Feb 11, 2020 at 02:18:52PM -0800, Andy Lutomirski wrote:
> On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@8bytes.org> wrote:
> > + entry.offset_low = (u16)(address & 0xffff);
> > + entry.segment = __KERNEL_CS;
> > + entry.bits.type = GATE_TRAP;
>
> ^^^
>
> I realize we're not running a real kernel here, but GATE_TRAP is
> madness. Please use GATE_INTERRUPT.

Changed that.

> > + /* Build pt_regs */
> > + .if \error_code == 0
> > + pushq $0
> > + .endif
>
> cld

Added.

> > + popq %rdi
>
> if error_code?

The code above pushes a $0 for exceptions without an error code, so it
needs to be removed unconditionally.

> > +
> > + /* Remove error code and return */
> > + addq $8, %rsp
> > +
> > + /*
> > + * Make sure we return to __KERNEL_CS - the CS selector on
> > + * the IRET frame might still be from an old BIOS GDT
> > + */
> > + movq $__KERNEL_CS, 8(%rsp)
> > +
>
> If this actually happens, you have a major bug. Please sanitize all
> the segment registers after installing the GDT rather than hacking
> around it here.

Okay, will change that. I thought I could safe some instructions in the
head_64.S code, but you are right that its better to setup a defined
environment first.


Thanks,

Joerg

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