Aurelien Jarno writes: > On Wed, Mar 05, 2008 at 11:58:34AM -0800, Joe Buck wrote: > > > > Aurelien Jarno wrote: > > > >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. > > > >... > > > >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. > > > > On Wed, Mar 05, 2008 at 08:00:42AM -0800, H. Peter Anvin wrote: > > > Linux should definitely follow the ABI. This is a bug, and a pretty > > > serious such. > > > > Unfortunately, there are a lot of kernels out there already with this > > problem, and the symptoms are likely to be subtle. So even if it is true > > that it is the kernel that is "in the wrong", I think we still are going > > to need to give users a workaround from the gcc side as well. > > > > So I think gcc at least needs an *option* to revert to the old behavior, > > and there's a good argument to make it the default for now, at least for > > x86/x86-64 on Linux. > > And for other kernels. I tested OpenBSD 4.1, FreeBSD 6.3, NetBSD 4.0, > they have the same behaviour as Linux, that is they don't clear DF > before calling the signal handler.
FWIW, Solaris 10 (both 32- and 64-bit) gets it right.
