linux-kernel - Re: [PATCH v2 05/10] powerpc/fsl_booke/32: introduce reloc_kernel

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Message-ID: <a1159f8e-ba34-5568-aef0-31f3a8b65449@c-s.fr>
Date:   Tue, 30 Jul 2019 11:26:23 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Jason Yan <yanaijie@...wei.com>, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com,
        benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        keescook@...omium.org, kernel-hardening@...ts.openwall.com
Cc:     linux-kernel@...r.kernel.org, wangkefeng.wang@...wei.com,
        yebin10@...wei.com, thunder.leizhen@...wei.com,
        jingxiangfeng@...wei.com, fanchengyang@...wei.com,
        zhaohongjiang@...wei.com
Subject: Re: [PATCH v2 05/10] powerpc/fsl_booke/32: introduce
 reloc_kernel_entry() helper



Le 30/07/2019 à 09:42, Jason Yan a écrit :
> Add a new helper reloc_kernel_entry() to jump back to the start of the
> new kernel. After we put the new kernel in a randomized place we can use
> this new helper to enter the kernel and begin to relocate again.
> 
> Signed-off-by: Jason Yan <yanaijie@...wei.com>
> Cc: Diana Craciun <diana.craciun@....com>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Christophe Leroy <christophe.leroy@....fr>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: Kees Cook <keescook@...omium.org>

Reviewed-by: Christophe Leroy <christophe.leroy@....fr>

> ---
>   arch/powerpc/kernel/head_fsl_booke.S | 13 +++++++++++++
>   arch/powerpc/mm/mmu_decl.h           |  1 +
>   2 files changed, 14 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
> index 04d124fee17d..2083382dd662 100644
> --- a/arch/powerpc/kernel/head_fsl_booke.S
> +++ b/arch/powerpc/kernel/head_fsl_booke.S
> @@ -1143,6 +1143,19 @@ _GLOBAL(create_tlb_entry)
>   	sync
>   	blr
>   
> +/*
> + * Return to the start of the relocated kernel and run again
> + * r3 - virtual address of fdt
> + * r4 - entry of the kernel
> + */
> +_GLOBAL(reloc_kernel_entry)
> +	mfmsr	r7
> +	rlwinm	r7, r7, 0, ~(MSR_IS | MSR_DS)
> +
> +	mtspr	SPRN_SRR0,r4
> +	mtspr	SPRN_SRR1,r7
> +	rfi
> +
>   /*
>    * Create a tlb entry with the same effective and physical address as
>    * the tlb entry used by the current running code. But set the TS to 1.
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index a09f89d3aa0f..804da298beb3 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -143,6 +143,7 @@ extern void adjust_total_lowmem(void);
>   extern int switch_to_as1(void);
>   extern void restore_to_as0(int esel, int offset, void *dt_ptr, int bootcpu);
>   void create_tlb_entry(phys_addr_t phys, unsigned long virt, int entry);
> +void reloc_kernel_entry(void *fdt, int addr);
>   #endif
>   extern void loadcam_entry(unsigned int index);
>   extern void loadcam_multi(int first_idx, int num, int tmp_idx);
>