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

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Message-Id: <20191018150514.GB5238@oc0525413822.ibm.com>
Date:   Fri, 18 Oct 2019 08:05:14 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org,
        Mike Anderson <andmike@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
        mpe@...erman.id.au
Subject: Re:  [PATCH] powerpc/prom_init: Undo relocation before entering secure mode

On Wed, Sep 11, 2019 at 01:34:33PM -0300, Thiago Jung Bauermann wrote:
> 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>

Tested-by: Ram Pai <linuxram@...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(-)
> 
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index 409c9bfb43d9..57c229a86f08 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -175,4 +175,7 @@ do {									\
>  	ARCH_DLINFO_CACHE_GEOMETRY;					\
>  } while (0)
> 
> +/* Relocate the kernel image to @final_address */
> +void relocate(unsigned long final_address);
> +
>  #endif /* _ASM_POWERPC_ELF_H */
> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
> index 74f70f90eff0..44b1d404250e 100644
> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -3249,7 +3249,18 @@ static void setup_secure_guest(unsigned long kbase, unsigned long fdt)
>  	/* Switch to secure mode. */
>  	prom_printf("Switching to secure mode.\n");
> 
> +	/*
> +	 * 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.
> +	 */
> +	relocate(KERNELBASE);
> +
>  	ret = enter_secure_mode(kbase, fdt);
> +
> +	/* Relocate the kernel again. */
> +	relocate(kbase);
> +
>  	if (ret != U_SUCCESS) {
>  		prom_printf("Returned %d from switching to secure mode.\n", ret);
>  		prom_rtas_os_term("Switch to secure mode failed.\n");
> diff --git a/arch/powerpc/kernel/prom_init_check.sh b/arch/powerpc/kernel/prom_init_check.sh
> index 160bef0d553d..16535ccc0fa0 100644
> --- a/arch/powerpc/kernel/prom_init_check.sh
> +++ b/arch/powerpc/kernel/prom_init_check.sh
> @@ -26,7 +26,8 @@ _end enter_prom $MEM_FUNCS reloc_offset __secondary_hold
>  __secondary_hold_acknowledge __secondary_hold_spinloop __start
>  logo_linux_clut224 btext_prepare_BAT
>  reloc_got2 kernstart_addr memstart_addr linux_banner _stext
> -__prom_init_toc_start __prom_init_toc_end btext_setup_display TOC."
> +__prom_init_toc_start __prom_init_toc_end btext_setup_display TOC.
> +relocate"
> 
>  NM="$1"
>  OBJ="$2"

-- 
Ram Pai