On Fri, Jan 18, 2019 at 8:25 AM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > This adds 21 new system calls on each ABI that has 32-bit time_t > today. All of these have the exact same semantics as their existing > counterparts, and the new ones all have macro names that end in 'time64' > for clarification. > > This gets us to the point of being able to safely use a C library > that has 64-bit time_t in user space. There are still a couple of > loose ends to tie up in various areas of the code, but this is the > big one, and should be entirely uncontroversial at this point. > > In particular, there are four system calls (getitimer, setitimer, > waitid, and getrusage) that don't have a 64-bit counterpart yet, > but these can all be safely implemented in the C library by wrapping > around the existing system calls because the 32-bit time_t they > pass only counts elapsed time, not time since the epoch. They > will be dealt with later. > > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > The one point that still needs to be agreed on is the actual > number assignment. Following the earlier patch that added > the sysv IPC calls with common numbers where possible, I also > tried the same here, using consistent numbers on all 32-bit > architectures. > > There are a couple of minor issues with this: > > - On asm-generic, we now leave the numbers from 295 to 402 > unassigned, which wastes a small amount of kernel .data > segment. Originally I had asm-generic start at 300 and > everyone else start at 400 here, which was also not > perfect, and we have gone beyond 400 already, so I ended > up just using the same numbers as the rest here. > > - Once we get to 512, we clash with the x32 numbers (unless > we remove x32 support first), and probably have to skip > a few more. I also considered using the 512..547 space > for 32-bit-only calls (which never clash with x32), but > that also seems to add a bit of complexity. I have a patch that I'll send soon to make x32 use its own table. As far as I'm concerned, 547 is *it*. 548 is just a normal number and is not special. But let's please not reuse 512..547 for other purposes on x86 variants -- that way lies even more confusion, IMO. --Andy
