[PATCH 1/3] Support BE8 mode kernel modules relocation

[Catalin Marinas]

On 18 January 2011 01:22, Stanley.Miao <stanleymiao at gmail.com> wrote:
> 2011/1/17 Catalin Marinas <catalin.marinas at arm.com>:
>> On 17 January 2011 08:42, Stanley.Miao <stanley.miao at windriver.com> wrote:
>>> The code section in BE8 kernel modules is in little-endian while data
>>> section is in big-endian. When reading code from memory in the relocation
>>> procedure, these instructions are read according to big-endian, so they
>>> need to be inverted before writing to memory and after reading from memory.
>> [...]
>>> --- a/arch/arm/include/asm/io.h
>>> +++ b/arch/arm/include/asm/io.h
>>> @@ -233,6 +233,18 @@ extern void _memset_io(volatile void __iomem *, int, size_t);
>>>
>>>  #endif /* __mem_pci */
>>>
>>> +#ifdef CONFIG_CPU_ENDIAN_BE8
>>> +#define read_instr32(c)                        __swab32(*(u32 *)c)
>>> +#define read_instr16(c)                        __swab16(*(u16 *)c)
>>> +#define write_instr32(v,a)             (*(u32 *)(a) = __swab32((__force __u32)(v)))
>>> +#define write_instr16(v,a)             (*(u16 *)(a) = __swab16((__force __u16)(v)))
>>> +#else
>>> +#define read_instr32(c)                        (*(u32 *)c)
>>> +#define read_instr16(c)                        (*(u16 *)c)
>>> +#define write_instr32(v,a)             (*(u32 *)(a) = (v))
>>> +#define write_instr16(v,a)             (*(u16 *)(a) = (v))
>>> +#endif
>>
>> Can we not use cpu_to_le32 etc in here (and as Russell said, they are
>> not really IO)?
>
> Except moving these definition to arch/arm/kernel/module.c, do I need
> to do other modifications ?

Just personal preference (not important), I'd rather have a "u32
instr" variable set by read_instr32() than this kind of functional
style (in C code, I'm fine with it otherwise):

> +                       write_instr32((read_instr32(loc) & 0xff000000) |
> +                                               (offset & 0x00ffffff), loc);

BTW (not related to modules, but since you are looking at this), when
we copy the sigreturn_codes to the vectors page in early_trap_init(),
do they get there in little endian form (as required by BE8)?

-- 
Catalin