Messages in this thread | | | Date | Wed, 14 Sep 2005 10:22:04 -0400 | From | Daniel Jacobowitz <> | Subject | Re: [PATCH] i386: fix stack alignment for signal handlers |
| |
On Tue, Sep 13, 2005 at 04:52:30PM -0700, Linus Torvalds wrote: > Your test program does seems to imply that gcc wants the alignment before > the return address (ie it prints out an address that is 4 bytes offset), > but on the other hand I'm not even sure how careful gcc is about this > alignment thing at all.
Very, on architectures where the ABI requires alignment. E.G. for vector register loads that require 16-byte alignment to avoid a trap.
The comment for the relevant bits of the GCC configuration says it won't assume this for x86, but I believe that comment is out of date. I think it'll assume 16-byte alignment on entrance to non-main() functions.
> In the "main()" function, gcc will actually generate a "andl $-16,%esp" to > force the alignment, but ot in the handler function. Just a gcc special > case? Random luck?
Special case. This is only done for main().
-- Daniel Jacobowitz CodeSourcery, LLC - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |