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SubjectRe: [RFC PATCH] kexec, x86/boot: map systab region in identity mapping before accessing it
+ hpa

On Mon, Apr 22, 2019 at 10:33:46PM +0800, Baoquan He wrote:
> On 04/19/19 at 01:36pm, Borislav Petkov wrote:
> > On Fri, Apr 19, 2019 at 01:28:01PM +0200, Borislav Petkov wrote:
> > > Read again what I said: "should all be passed through boot_params".
> > > Which means, boot_params should be extended with a field of a flag to
> > > say: "this is a kexec'ed kernel".
> >
> > And by that I mean similar to the XLF_EFI_KEXEC mechanism. The first
> > kernel or kexec(1) should prepare the info needed by the kexec'ed
> > kernel.
>
> We have set the loader type to '0x0D << 4' for kexec specifically, in both
> kexec_load and kexec_file_load. We can check this to identify if it's
> kexec-ed kernel or not.
>
> Update patch with it?
>
> static void *bzImage64_load(struct kimage *image, char *kernel,
> unsigned long kernel_len, char *initrd,
> unsigned long initrd_len, char *cmdline,
> unsigned long cmdline_len)
> {
>
> ...
> /* bootloader info. Do we need a separate ID for kexec kernel loader? */
> params->hdr.type_of_loader = 0x0D << 4;

That's already documented in Documentation/x86/boot.txt

Field name: type_of_loader
Type: write (obligatory)
Offset/size: 0x210/1
Protocol: 2.00+

...

D kexec-tools

And yes, the question in the code is still valid: do we need a separate ID.

I'd say no and we'll simply call 0xD all kernels loaded using a
kexec-type syscall.

IMO.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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