On Tue, May 05, 2015 at 06:09:57PM +0100, André Hentschel wrote: > Am 05.05.2015 um 12:51 schrieb Will Deacon: > > On Sun, May 03, 2015 at 05:24:18PM +0100, André Hentschel wrote: > >> From: André Hentschel <nerv@xxxxxxxxxxx> > >> > >> Since commit a4780adeefd042482f624f5e0d577bf9cdcbb760 the user writeable TLS > >> register on ARM is preserved per thread. > >> > >> This patch does it analogous to the ARM patch, but for compat mode on ARM64. > >> > >> Signed-off-by: André Hentschel <nerv@xxxxxxxxxxx> > >> Cc: Will Deacon <will.deacon@xxxxxxx> > >> Cc: Jonathan Austin <jonathan.austin@xxxxxxx> > >> > >> --- > >> This patch is against Linux 4.1-rc1 (b787f68c36d49bb1d9236f403813641efa74a031) > > > > Curious, but why do you need this? iirc, we added this for arch/arm/ because > > of some windows rt (?) emulation in wine. Is that still the case here and is > > anybody actually using that? > > Yes, Windows ARM binaries are the well known use case, but also the compat > mode should do what the arm kernel is doing I’d think and the code wasn't > adjusted yet. Sure, I was just curious. > What i'm curious about is why the main TLS register on arm64 is the user > writeable, I'm not an security expert but this looks odd. I could easily > provoke a crash by writing to it... You've probably got the wrong TLS. Allowing a program to clobber it's own thread-local storage is no worse than allowing it to write to its general purpose registers, pc, etc. I'm assuming the crash you saw was just a userspace crash, rather than the kernel? Will -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
