Re: [PATCH v3 11/12] x86, boot: add fields to support load bzImageand ramdisk high

[H. Peter Anvin]

On 11/22/2012 12:50 PM, H. Peter Anvin wrote:
> On 11/22/2012 12:18 PM, Yinghai Lu wrote:
> > > If we can get the sentinel hack to work that would probably be
> > > useful, but
> > > we need to understand the exact pathology.
> >
> > for kexec bzImage --real-mode-entry, code after setup_header will be
> > executed.
> >
> > so we could clear value before setup_header after copy 16bit section
> > from bzImage...
> >
> > Index: kexec-tools/kexec/arch/i386/kexec-bzImage.c
> > ===================================================================
> > --- kexec-tools.orig/kexec/arch/i386/kexec-bzImage.c
> > +++ kexec-tools/kexec/arch/i386/kexec-bzImage.c
> > @@ -212,6 +212,16 @@ int do_bzImage_load(struct kexec_info *i
> >       setup_size = kern16_size + command_line_len +
> > PURGATORY_CMDLINE_SIZE;
> >       real_mode = xmalloc(setup_size);
> >       memcpy(real_mode, kernel, kern16_size);
> > +    /*
> > +     * clear value before header
> > +     * not not clear value after header, --real-mode-entry
> > +     * need code after header.
> > +     */
> > +    memset(real_mode, 0, 0x1f1);
> > +    if (!real_mode_entry) {
> > +        /* clear value after setup_header  */
> > +        memset((unsigned char *)real_mode + 0x290, 0, kern16_size -
> > 0x290);
> > +    }
>
> You really should move the memset() into the if() clause as well...
> doesn't matter at the moment, but that is the protocol.
>
> The limit is 0x280, not 0x290, or -- better -- you can use the byte at
> 0x201 to get the size.

Not doing so would be wrong, in fact.


--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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