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SubjectRe: scripts/mod/file2alias.c cross compile problem
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On Sat, 2007-07-28 at 03:39 +0200, Adrian Bunk wrote:
> On Fri, Jul 27, 2007 at 04:21:47PM -0700, Luck, Tony wrote:
> > > So it seems on ia64 with gcc 3.3.6 there's some 8 byte alignment of the
> > > array members?
> > >
> > > Sam and the ia64 maintainers Cc'ed - they might know better what's going
> > > on here.
> >
> > This ia64 maintainer is baffled ... but I don't see the problem here (perhaps
> > because my build machine has gcc 3.4.6).
>
>
> I found what causes this problem, and it only occurs during cross
> compilation.
>
>
> The struct is:
>
> #define ACPI_ID_LEN 9
>
> struct acpi_device_id {
> __u8 id[ACPI_ID_LEN];
> kernel_ulong_t driver_data;
> };
>
>
> When compiling for ia64, this results in:
>
> struct acpi_device_id {
> __u8 id[9];
> uint64_t driver_data;
> };
>
>
> sizeof(struct acpi_device_id) for ia64 is due to different padding
> after id[] 20 bytes on i386 but 24 bytes on ia64.
>
> scripts/mod/file2alias.c is compiled with HOSTCC and ensures that
> kernel_ulong_t is correct (in this case uint64_t for ia64), but it can't
> cope with different padding on different architectures.

This one should workaround it. Is this acceptable for now?
Don't know how to fix this in a cleaner way (but I am sure it's
possible... ). Maybe an IA64 guy who is more used to such things has a
better idea and could have a look at this if there is time...

Thomas

-------------
Cross-compilation between e.g. i386 -> 64bit could break -> work around it

Adrian Bunk: scripts/mod/file2alias.c is compiled with HOSTCC and ensures that
kernel_ulong_t is correct, but it can't cope with different padding on
different architectures.
---
include/linux/mod_devicetable.h | 2 ++
1 file changed, 2 insertions(+)
Index: torvalds/include/linux/mod_devicetable.h
===================================================================
--- torvalds.orig/include/linux/mod_devicetable.h
+++ torvalds/include/linux/mod_devicetable.h
@@ -160,9 +160,11 @@ struct ap_device_id {
#define AP_DEVICE_ID_MATCH_DEVICE_TYPE 0x01

#define ACPI_ID_LEN 9
+#define FILLUP_LEN 7 /* dirty fix for i386 -> 64bit cross-compilation */

struct acpi_device_id {
__u8 id[ACPI_ID_LEN];
+ __u8 dummy[FILLUP_LEN];
kernel_ulong_t driver_data;
};


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