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

2011/1/18 Catalin Marinas [off-list ref]:

On 18 January 2011 01:22, Stanley.Miao [off-list ref] wrote:

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2011/1/17 Catalin Marinas [off-list ref]:

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On 17 January 2011 08:42, Stanley.Miao [off-list ref] wrote:

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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.

[...]

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--- 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):

upper, lower and offset are used. It looks we don't need another "instr".

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+ ? ? ? ? ? ? ? ? ? ? ? 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)?

No, they get there in big endian.They are read as data in the function
setup_return().

retcode = KERN_SIGRETURN_CODE + (idx << 2) + thumb;


Stanley.

--
Catalin