Messages in this thread |  | | | Date | Wed, 26 May 2010 08:59:26 +0200 | | Subject | Re: [PATCH] FLAT: allow arches to declare a larger alignment than the slab | | From | Geert Uytterhoeven <> |
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On Wed, May 26, 2010 at 04:23, Jie Zhang <jie@codesourcery.com> wrote: > On 05/26/2010 07:17 AM, Mike Frysinger wrote: >> >> i do not believe that is the reason for this, but unfortunately Jie is >> about the only one atm who knows the inner details as for why shared >> FLAT libraries requires 0x20 rather than just 0x4 alignment. i do >> know that there are some gcc fortran tests that fail otherwise. >> hopefully he can remember details ;). >> > I encountered this issue when investigating some GCC test failures when > using FLAT. I don't remember if they were in GCC Fortran testsuite. Some > variables in those test cases were required to be aligned at a large > boundary, for example 16-byte. I found 0x20 was a reasonably large alignment > to fix all such failures in GCC testsuite.
I'm no FLAT expert (except for the AmigaOS HUNK loader :-), but isn't the core of the issue that alignment requirements in the object file are no longer fulfilled after loading, as a FLAT segment in memory is just allocated using kmalloc(), which may now return 4-byte aligned blocks?
From looking at <linux/flat.h>, it looks like the FLAT binary format doesn't contain any alignment information? So if I put __attribute__((aligned(4096))) in a file, there's still no guarantee it will actually be in memory at a 4Ki-aligned address?
Gr{oetje,eeting}s, Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
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