linux-kernel - Re: [PATCH 07/15] binfmt_flat: use _

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Message-ID: <462a7406-19df-7910-4499-8f0acd52bc82@arm.com>
Date:   Tue, 11 Jun 2019 10:57:00 +0100
From:   Vladimir Murzin <vladimir.murzin@....com>
To:     Christoph Hellwig <hch@....de>, Greg Ungerer <gerg@...ux-m68k.org>
Cc:     uclinux-h8-devel@...ts.sourceforge.jp,
        linux-xtensa@...ux-xtensa.org, Michal Simek <monstr@...str.eu>,
        linux-c6x-dev@...ux-c6x.org, linux-sh@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 07/15] binfmt_flat: use __be32 for the on-disk format

On 6/10/19 10:20 PM, Christoph Hellwig wrote:
> So far binfmt_flat has onl been supported on 32-bit platforms, so the
			^^^^
			only
> variable size of the fields didn't matter.  But the upcoming RISC-V
> nommu port supports 64-bit CPUs, and we now have a conflict between
> the elf2flt creation tool that always uses 32-bit fields and the kernel
> that uses (unsigned) long field.  Switch to the userspace view as the
> rest of the binfmt_flat format is completely architecture neutral,
> and binfmt_flat isn't the right binary format for huge executables to
> start with.
> 
> While we're at it also ensure these fields are using __be types as
> they big endian and are byteswapped when loaded.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> 
> wip
  ^^^
Unintended?

> ---
>  include/linux/flat.h | 48 ++++++++++++++++++++++----------------------
>  1 file changed, 24 insertions(+), 24 deletions(-)


With comment message fixed:

Reviewed-by: Vladimir Murzin <vladimir.murzin@....com>

> 
> diff --git a/include/linux/flat.h b/include/linux/flat.h
> index 21d901ba191b..59e892d5fadb 100644
> --- a/include/linux/flat.h
> +++ b/include/linux/flat.h
> @@ -24,26 +24,26 @@
>   */
>  
>  struct flat_hdr {
> -	char magic[4];
> -	unsigned long rev;          /* version (as above) */
> -	unsigned long entry;        /* Offset of first executable instruction
> -	                               with text segment from beginning of file */
> -	unsigned long data_start;   /* Offset of data segment from beginning of
> -	                               file */
> -	unsigned long data_end;     /* Offset of end of data segment
> -	                               from beginning of file */
> -	unsigned long bss_end;      /* Offset of end of bss segment from beginning
> -	                               of file */
> +	char	magic[4];
> +	__be32	rev;          /* version (as above) */
> +	__be32	entry;        /* Offset of first executable instruction
> +				 with text segment from beginning of file */
> +	__be32	data_start;   /* Offset of data segment from beginning of
> +				 file */
> +	__be32	data_end;     /* Offset of end of data segment from beginning
> +				 of file */
> +	__be32	bss_end;      /* Offset of end of bss segment from beginning
> +				 of file */
>  
>  	/* (It is assumed that data_end through bss_end forms the bss segment.) */
>  
> -	unsigned long stack_size;   /* Size of stack, in bytes */
> -	unsigned long reloc_start;  /* Offset of relocation records from
> -	                               beginning of file */
> -	unsigned long reloc_count;  /* Number of relocation records */
> -	unsigned long flags;
> -	unsigned long build_date;   /* When the program/library was built */
> -	unsigned long filler[5];    /* Reservered, set to zero */
> +	__be32	stack_size;   /* Size of stack, in bytes */
> +	__be32	reloc_start;  /* Offset of relocation records from beginning of
> +				 file */
> +	__be32	reloc_count;  /* Number of relocation records */
> +	__be32	flags;
> +	__be32	build_date;   /* When the program/library was built */
> +	__u32	filler[5];    /* Reservered, set to zero */
>  };
>  
>  #define FLAT_FLAG_RAM    0x0001 /* load program entirely into RAM */
> @@ -67,19 +67,19 @@ struct flat_hdr {
>  #define OLD_FLAT_RELOC_TYPE_BSS		2
>  
>  typedef union {
> -	unsigned long	value;
> +	u32		value;
>  	struct {
>  # if defined(mc68000) && !defined(CONFIG_COLDFIRE)
> -		signed long offset : 30;
> -		unsigned long type : 2;
> +		s32	offset : 30;
> +		u32	type : 2;
>  #   	define OLD_FLAT_FLAG_RAM    0x1 /* load program entirely into RAM */
>  # elif defined(__BIG_ENDIAN_BITFIELD)
> -		unsigned long type : 2;
> -		signed long offset : 30;
> +		u32	type : 2;
> +		s32	offset : 30;
>  #   	define OLD_FLAT_FLAG_RAM    0x1 /* load program entirely into RAM */
>  # elif defined(__LITTLE_ENDIAN_BITFIELD)
> -		signed long offset : 30;
> -		unsigned long type : 2;
> +		s32	offset : 30;
> +		u32	type : 2;
>  #   	define OLD_FLAT_FLAG_RAM    0x1 /* load program entirely into RAM */
>  # else
>  #   	error "Unknown bitfield order for flat files."
>