On Tue, Dec 22, 2015 at 3:13 AM, Borislav Petkov <bp@xxxxxxxxx> wrote: >> +#define COPY_MCHECK_ERRBIT BIT(63) > > What happened to the landing pads Andy was talking about? They sound > like cleaner design than that bit 63... I interpreted that comment as "stop playing with %rax in the fault handler ... just change the IP to point the the .fixup location" ... the target of the fixup being the "landing pad". Right now this function has only one set of fault fixups (for machine checks). When I tackle copy_from_user() it will sprout a second set for page faults, and then will look a bit more like Andy's dual landing pad example. I still need an indicator to the caller which type of fault happened since their actions will be different. So BIT(63) lives on ... but is now set in the .fixup section rather than in the machine check code. I'll move the function and #defines as you suggest - we don't need new files for these. Also will fix the assembly code. [In my defense that load immediate 0x8000000000000000 and 'or' was what gcc -O2 generates from a simple bit of C code to set bit 63 ... perhaps it is faster, or perhaps gcc is on drugs. In this case code compactness wins over possible speed difference]. -Tony -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>