linux-kernel - Re: [PATCH] ARM: xip: Use correct symbol for end of ROM marker

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Message-ID: <5644836B.2050608@hurleysoftware.com>
Date:	Thu, 12 Nov 2015 07:17:47 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Chris Brandt <chris.brandt@...esas.com>, linux@....linux.org.uk,
	arnd@...db.de
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-sh@...r.kernel.org
Subject: Re: [PATCH] ARM: xip: Use correct symbol for end of ROM marker

On 11/11/2015 09:17 AM, Chris Brandt wrote:
> For an XIP build, _edata_loc, not _etext, represents the end of the
> binary image that will be programmed into ROM and mapped into the
> MODULES_VADDR area.
> With an XIP kernel, nothing is loaded into RAM before boot, meaning
> you have to take into account the size of the entire binary image
> that was programmed, including the init data values that will be copied
> to RAM during kernel boot.
> 
> This fixes the bug where you might lose the end of your kernel area
> after page table setup is complete.
> 
> 
> Signed-off-by: Chris Brandt <chris.brandt@...esas.com>
> ---
>  arch/arm/mm/mmu.c              |    4 ++--
>  include/asm-generic/sections.h |    2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 4867f5d..dd5a56b 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -1210,7 +1210,7 @@ static inline void prepare_page_table(void)
>  
>  #ifdef CONFIG_XIP_KERNEL
>  	/* The XIP kernel is mapped in the module area -- skip over it */
> -	addr = ((unsigned long)_etext + PMD_SIZE - 1) & PMD_MASK;
> +	addr = ((unsigned long)_edata_loc + PMD_SIZE - 1) & PMD_MASK;
>  #endif
>  	for ( ; addr < PAGE_OFFSET; addr += PMD_SIZE)
>  		pmd_clear(pmd_off_k(addr));
> @@ -1292,7 +1292,7 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
>  #ifdef CONFIG_XIP_KERNEL
>  	map.pfn = __phys_to_pfn(CONFIG_XIP_PHYS_ADDR & SECTION_MASK);
>  	map.virtual = MODULES_VADDR;
> -	map.length = ((unsigned long)_etext - map.virtual + ~SECTION_MASK) & SECTION_MASK;
> +	map.length = ((unsigned long)_edata_loc - map.virtual + ~SECTION_MASK) & SECTION_MASK;
>  	map.type = MT_ROM;
>  	create_mapping(&map);
>  #endif
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index b58fd66..195554d 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -26,7 +26,7 @@
>   *	__ctors_start, __ctors_end
>   */
>  extern char _text[], _stext[], _etext[];
> -extern char _data[], _sdata[], _edata[];
> +extern char _data[], _sdata[], _edata[], _edata_loc[];
>  extern char __bss_start[], __bss_stop[];
>  extern char __init_begin[], __init_end[];
>  extern char _sinittext[], _einittext[];
> 

I think below is required as well.

--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -34,7 +36,7 @@
  * recompiling the whole kernel when CONFIG_XIP_KERNEL is turned on/off.
  */
 #undef MODULES_VADDR
-#define MODULES_VADDR	(((unsigned long)_etext + ~PMD_MASK) & PMD_MASK)
+#define MODULES_VADDR	(((unsigned long)_edata_loc + ~PMD_MASK) & PMD_MASK)
 #endif
 
Regards,
Peter Hurley

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