Messages in this thread | | | Date | Sun, 3 Feb 2013 21:35:39 -0800 | Subject | Re: [PATCH] arch: avr32: add dummy syscalls | From | Håvard Skinnemoen <> |
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On Sun, Feb 3, 2013 at 9:05 PM, Al Viro <viro@zeniv.linux.org.uk> wrote: > On Sun, Feb 03, 2013 at 08:52:18PM -0800, H?vard Skinnemoen wrote: > >> You're right on -- in this case, the compiler will skip r10, and do >> (r12, r11, r8:r9, stack). We pass the syscall number in r8, but we >> also unconditionally move r7 to r8 in the syscall path, so it >> shouldn't matter (libc does the opposite when necessary). >> >> I remember some talk about having the compiler reuse r10 for the next >> 32-bit argument in cases like this, but I don't think it ever >> happened. > > Umm... In case of fallocate() the next argument is 64bit one, though; > sys_fallocate() will be looking for two 32bit words on stack, so no > matter how do we pass them to syscall, we'd better push two words in > the wrapper.
Right.
> But yes, 32bit/32bit/64bit/32bit is another interesting case - > fanotify_mark is 32/32/64/32/32. From what ABI says it would seem to > be r12/r11/r8:r9/r10/stack, but if I understand you correctly, we'll > end up wanting *two* arguments on stack...
Yes, I think there may be a difference between the IAR and gcc ABI here. But I could be wrong.
Havard
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