Messages in this thread | | | Date | Wed, 05 Mar 2008 08:00:42 -0800 | From | "H. Peter Anvin" <> | Subject | Re: Linux doesn't follow x86/x86-64 ABI wrt direction flag |
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Aurelien Jarno wrote: > Hi all, > > Since version 4.3, gcc changed its behaviour concerning the x86/x86-64 > ABI and the direction flag, that is it now assumes that the direction > flag is cleared at the entry of a function and it doesn't clear once > more if needed. > > This causes some problems with the Linux kernel which does not clear > the direction flag when entering a signal handler. The small code below > (for x86-64) demonstrates that. > > If the signal handler is using code that need the direction flag cleared > (for example bzero() or memset()), the code is incorrectly executed. > > I guess this has to be fixed on the kernel side, but also gcc-4.3 could > revert back to the old behaviour, that is clearing the direction flag > when entering a routine that touches it until most people are running a > fixed kernel. >
Linux should definitely follow the ABI. This is a bug, and a pretty serious such.
-hpa
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