On Wed, Aug 17, 2016 at 02:28:50PM +0200, Alexander Graf wrote: > > > On 17 Aug 2016, at 13:46, Yury Norov <yno...@caviumnetworks.com> wrote: > > > > This series enables aarch64 with ilp32 mode, and as supporting work, > > introduces ARCH_32BIT_OFF_T configuration option that is enabled for > > existing 32-bit architectures but disabled for new arches (so 64-bit > > off_t is is used by new userspace). > > > > This version is based on kernel v4.8-rc2. > > It works with glibc-2.23, and tested with LTP. > > > > This is RFC because there is still no solid understanding what type of > > registers > > top-halves delousing we prefer. In this patchset, w0-w7 are cleared for each > > syscall in assembler entry. The alternative approach is in introducing > > compat > > wrappers which is little faster for natively routed syscalls (~2.6% for > > syscall > > with no payload) but much more complicated. > > So you’re saying there are 2 options: > > 1) easy to get right, slightly slower, same ABI to user space as 2 > 2) harder to get right, minor performance benefit
No, ABI is little different. If 1) we pass off_t in a pair to syscalls, if 2) - in a single register. So if 1, we 'd take some wrappers from aarch32. See patch 12 here. > That’s an obvious pick, no? Mark it non-RFC and stay with the clearing in > assembler entry. If anyone cares about those last few percent, they can still > push the harder path upstream later if they want to, but at least we’ll have > the ABI stable, so that you can start using and developing for ilp32 on > aarch64. > > > Alex -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
