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Subject: Re: [RFC PATCH v2] powerpc: fix kexec failure on book3s/32
From:   Christophe Leroy <christophe.leroy@c-s.fr>
To:     Aaro Koskinen <aaro.koskinen@iki.fi>
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <8164abbe117d8353bb88132d7cfa8bc26a60ca66.1558677767.git.christophe.leroy@c-s.fr>
Message-ID: <8c3088b3-5fea-3cff-23f1-f6bc433d9a38@c-s.fr>
Date:   Fri, 24 May 2019 15:38:58 +0200
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Le 24/05/2019 à 08:05, Christophe Leroy a écrit :
> Fixes: 63b2bc619565 ("powerpc/mm/32s: Use BATs for STRICT_KERNEL_RWX")
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>

> ---
>   arch/powerpc/kernel/machine_kexec_32.c | 8 ++++++++
>   arch/powerpc/mm/book3s32/mmu.c         | 7 +++++--
>   arch/powerpc/mm/mmu_decl.h             | 2 ++
>   3 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/machine_kexec_32.c b/arch/powerpc/kernel/machine_kexec_32.c
> index affe5dcce7f4..83e61a8f8468 100644
> --- a/arch/powerpc/kernel/machine_kexec_32.c
> +++ b/arch/powerpc/kernel/machine_kexec_32.c
> @@ -15,6 +15,7 @@
>   #include <asm/cacheflush.h>
>   #include <asm/hw_irq.h>
>   #include <asm/io.h>
> +#include <mm/mmu_decl.h>
>   
>   typedef void (*relocate_new_kernel_t)(
>   				unsigned long indirection_page,
> @@ -35,6 +36,8 @@ void default_machine_kexec(struct kimage *image)
>   	unsigned long page_list;
>   	unsigned long reboot_code_buffer, reboot_code_buffer_phys;
>   	relocate_new_kernel_t rnk;
> +	unsigned long bat_size = 128 << 10;
> +	unsigned long bat_mask = ~(bat_size - 1);
>   
>   	/* Interrupts aren't acceptable while we reboot */
>   	local_irq_disable();
> @@ -54,6 +57,11 @@ void default_machine_kexec(struct kimage *image)
>   	memcpy((void *)reboot_code_buffer, relocate_new_kernel,
>   						relocate_new_kernel_size);
>   
> +	printk(KERN_INFO "Reboot code buffer at %lx\n", reboot_code_buffer);
> +	mtsrin(mfsrin(reboot_code_buffer) & ~SR_NX, reboot_code_buffer);
> +	setibat(7, reboot_code_buffer & bat_mask, reboot_code_buffer_phys & bat_mask,
> +		bat_size, PAGE_KERNEL_TEXT);

A call to update_bats() have to be added here after setibat()

Christophe

> +
>   	flush_icache_range(reboot_code_buffer,
>   				reboot_code_buffer + KEXEC_CONTROL_PAGE_SIZE);
>   	printk(KERN_INFO "Bye!\n");
> diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
> index fc073cb2c517..7124700edb0f 100644
> --- a/arch/powerpc/mm/book3s32/mmu.c
> +++ b/arch/powerpc/mm/book3s32/mmu.c
> @@ -124,8 +124,8 @@ static unsigned int block_size(unsigned long base, unsigned long top)
>    * of 2 between 128k and 256M.
>    * Only for 603+ ...
>    */
> -static void setibat(int index, unsigned long virt, phys_addr_t phys,
> -		    unsigned int size, pgprot_t prot)
> +void setibat(int index, unsigned long virt, phys_addr_t phys,
> +	     unsigned int size, pgprot_t prot)
>   {
>   	unsigned int bl = (size >> 17) - 1;
>   	int wimgxpp;
> @@ -197,6 +197,9 @@ void mmu_mark_initmem_nx(void)
>   	if (cpu_has_feature(CPU_FTR_601))
>   		return;
>   
> +	if (IS_ENABLED(CONFIG_KEXEC))
> +		nb--;
> +
>   	for (i = 0; i < nb - 1 && base < top && top - base > (128 << 10);) {
>   		size = block_size(base, top);
>   		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
> index 7bac0aa2026a..478584d50cf2 100644
> --- a/arch/powerpc/mm/mmu_decl.h
> +++ b/arch/powerpc/mm/mmu_decl.h
> @@ -103,6 +103,8 @@ void print_system_hash_info(void);
>   extern void mapin_ram(void);
>   extern void setbat(int index, unsigned long virt, phys_addr_t phys,
>   		   unsigned int size, pgprot_t prot);
> +void setibat(int index, unsigned long virt, phys_addr_t phys,
> +	     unsigned int size, pgprot_t prot);
>   
>   extern int __map_without_bats;
>   extern unsigned int rtas_data, rtas_size;
>