On Mon, Oct 19, 2020 at 04:51:53PM +0200, Daniel Kiper wrote:
> On Fri, Oct 16, 2020 at 04:51:51PM -0400, Arvind Sankar wrote:
> > On Thu, Oct 15, 2020 at 08:26:54PM +0200, Daniel Kiper wrote:
> > >
> > > I am discussing with Ross the other option. We can create
> > > .rodata.mle_header section and put it at fixed offset as
> > > kernel_info is. So, we would have, e.g.:
> > >
> > > arch/x86/boot/compressed/vmlinux.lds.S:
> > > .rodata.kernel_info KERNEL_INFO_OFFSET : {
> > > *(.rodata.kernel_info)
> > > }
> > > ASSERT(ABSOLUTE(kernel_info) == KERNEL_INFO_OFFSET, "kernel_info
> > > at bad address!")
> > >
> > > .rodata.mle_header MLE_HEADER_OFFSET : {
> > > *(.rodata.mle_header)
> > > }
> > > ASSERT(ABSOLUTE(mle_header) == MLE_HEADER_OFFSET, "mle_header at
> > > bad address!")
> > >
> > > arch/x86/boot/compressed/sl_stub.S:
> > > #define mleh_rva(X) (((X) - mle_header) + MLE_HEADER_OFFSET)
> > >
> > > .section ".rodata.mle_header", "a"
> > >
> > > SYM_DATA_START(mle_header)
> > > .long 0x9082ac5a /* UUID0 */
> > > .long 0x74a7476f /* UUID1 */
> > > .long 0xa2555c0f /* UUID2 */
> > > .long 0x42b651cb /* UUID3 */
> > > .long 0x00000034 /* MLE header size */
> > > .long 0x00020002 /* MLE version 2.2 */
> > > .long mleh_rva(sl_stub_entry) /* Linear entry point of MLE
> > > (virt. address) */
> > > .long 0x00000000 /* First valid page of MLE */
> > > .long 0x00000000 /* Offset within binary of first byte of
> > > MLE */
> > > .long 0x00000000 /* Offset within binary of last byte + 1 of
> > > MLE */
> > > .long 0x00000223 /* Bit vector of MLE-supported capabilities
> > > */
> > > .long 0x00000000 /* Starting linear address of command line
> > > (unused) */
> > > .long 0x00000000 /* Ending linear address of command line
> > > (unused) */
> > > SYM_DATA_END(mle_header)
> > >
> > > Of course MLE_HEADER_OFFSET has to be defined as a constant somewhere.
> > > Anyway, is it acceptable?
>
> What do you think about my MLE_HEADER_OFFSET and related stuff proposal?
>
I'm wondering if it would be easier to just allow relocations in these
special "header" sections. I need to check how easy/hard it is to do
that without triggering linker warnings.
Thanks.
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