On 15/02/2018 at 21:44:53 +0100, Alexandre Belloni wrote: > On 15/02/2018 at 19:36:14 +0000, Colin King wrote: > > From: Colin Ian King <[email protected]> > > > > The shifting of buf[5] by 24 bits to the left will be promoted to > > a 32 bit signed int and then sign-extended to an unsigned long. If > > the top bit of buf[5] is set then all then all the upper bits sec > > end up as also being set because of the sign-extension. Fix this by > > casting buf[5] to an unsigned long before the shift. > > > > The timing of the discovery of this issue is suspicious. I believe it is > because I just enabled COMPILE_TEST on that driver and now this gets > compiled on a 64bit architecture. > > Can I ask on which architecture this is an issue? I don't think (and a > small test program confirms) x86 does the sign extension because both > sec and buf are unsigned. >
Actually, my test program was wrong and you are right. -- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering http://bootlin.com
