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SubjectRe: [PATCH 07/15] binfmt_flat: use __be32 for the on-disk format
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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@lst.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@arm.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."
>

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