Dominic Sweetman wrote: > > > > The __access_ok macro in include/asm-mips64/uaccess.h and the > > > > check_axs macro in arch/mips64/kernel/unaligned.c ... is a copy > > > > from the 32-bit kernel... > > > > > > > > The area between USEG (XUSEG) and KSEG0 will in 64-bit > > > > addressing mode generate an address error, if accessed. > > I'd like to be clear about the consequences of this. Presumably the > 'access_ok()' macro is used to check addresses which were (originally) > provided by a user program's system call. > > Carsten, are you saying that if such an address is set to say 2**41 in > a CPU supporting 40-bit user virtual addresses, that the kernel will > crash? Yes, that's the case. It's been a while since I fixed it locally, but if I ran something like crashme, I could end up, in a situation where the kernel tries (on the behalf of the user) to access an address like 2**41 in a CPU supporting 40-bit user virtual addresses, which generate an address error and because we are in kernel mode we die. > > If so, that seems to require a fix, even if we don't know a very > efficient one. But perhaps any problem is a bit more subtle than > that? > > -- > Dominic Sweetman > MIPS Technologies > The Fruit Farm, Ely Road, Chittering, CAMBS CB5 9PH, ENGLAND > phone +44 1223 706205/fax +44 1223 706250/swbrd +44 1223 706200 > http://www.algor.co.uk -- _ _ ____ ___ Carsten Langgaard Mailto:carstenl@mips.com |\ /|||___)(___ MIPS Denmark Direct: +45 4486 5527 | \/ ||| ____) Lautrupvang 4B Switch: +45 4486 5555 TECHNOLOGIES 2750 Ballerup Fax...: +45 4486 5556 Denmark http://www.mips.com
