Re: Relocation fixup during AARCH64 SEC PE-COFF generation?

[Achin Gupta <achin.gupta@arm.com>]

On Tue, Sep 13, 2016 at 03:43:41PM +0100, Ard Biesheuvel wrote:
> On 13 September 2016 at 15:12, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> > On 13 September 2016 at 15:03, Achin Gupta <achin.gupta@arm.com> wrote:
> >> Hi All,
> >>
> >> Upon entry into UEFI, the ArmPlatformPkg/PrePi/PeiUniCore.inf SEC module
> >> executes directly from within the firmware volume. The FV would typically be
> >> loaded in DRAM by ARM Trusted Firmware. The rule in ArmJuno.fdf for SEC file
> >> types converts a PE-COFF module into a stripped Terse executable as follows:
> >>
> >> [Rule.AARCH64.SEC]
> >>   FILE SEC = $(NAMED_GUID) RELOCS_STRIPPED FIXED {
> >>     TE  TE    Align = Auto              $(INF_OUTPUT)/$(MODULE_NAME).efi
> >>   }
> >>
> >> The GCC_ARM_AARCH64_DLINK_COMMON variable includes the "--emit-relocs" option
> >> when the ELF image is generated. Since the SEC module is able to "XIP" from the
> >> within FV, this means that the relocations have to be fixed up at link time
> >> before the TE image is created.
> >>
> >
> > Correct. GenFv relocates the image based on the runtime address of the
> > firmware volume.
> >
> >> It seems to me that in GenFw.c, at least the static relocations are fixed up
> >> when an ELF image is converted to PE-COFF. Can someone confirm if I am correct
> >> in understanding that dynamic relocations will be left as is in the PE-COFF
> >> image while static relocations will be fixed up?
> >>
> >
> > We usually don't emit dynamic relocations, since we are not linking
> > shared objects.
>
> ... or more specifically, all absolute static relocations are
> converted into PE/COFF base relocations, all relative static
> relocations are validated against the PE/COFF layout (which we keep
> 1:1 identical with the ELF section layout), and all dynamic
> relocations are ignored.

Thanks Ard. I expect the relative static relocations to be fixed by the PE-COFF
loader at runtime.

> Note that this implies that proxy generating
> static relocations are rejected, since --emit-relocs does not produce
> any output for the proxies.

You lost me here. What do you mean by "proxy generating static relocations"?

cheers,
Achin
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