linux-kernel - Re: [PATCH] powerpc/prom_init: Undo relocation before entering secure mode

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Message-ID: <87o8y5dr3c.fsf@mpe.ellerman.id.au>
Date:   Fri, 25 Oct 2019 22:03:51 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org,
        Mike Anderson <andmike@...ux.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Ram Pai <linuxram@...ibm.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Subject: Re: [PATCH] powerpc/prom_init: Undo relocation before entering secure mode

Thiago Jung Bauermann <bauerman@...ux.ibm.com> writes:
> The ultravisor will do an integrity check of the kernel image but we
> relocated it so the check will fail. Restore the original image by
> relocating it back to the kernel virtual base address.
>
> This works because during build vmlinux is linked with an expected virtual
> runtime address of KERNELBASE.
>
> Fixes: 6a9c930bd775 ("powerpc/prom_init: Add the ESM call to prom_init")
> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
> ---
>  arch/powerpc/include/asm/elf.h         |  3 +++
>  arch/powerpc/kernel/prom_init.c        | 11 +++++++++++
>  arch/powerpc/kernel/prom_init_check.sh |  3 ++-
>  3 files changed, 16 insertions(+), 1 deletion(-)

This breaks the build when CONFIG_RELOCATABLE=n:

    prom_init.c:(.init.text+0x3160): undefined reference to `relocate'

See http://kisskb.ellerman.id.au/kisskb/buildresult/14004234/

cheers