On Wed, May 11, 2016 at 09:30:07PM +0200, Arnd Bergmann wrote: > On Wednesday 11 May 2016 17:59:01 Catalin Marinas wrote: > > On Wed, May 11, 2016 at 12:55:01PM +0200, Arnd Bergmann wrote: > > > On Wednesday 11 May 2016 11:04:38 Yury Norov wrote: > > > > On Wed, May 11, 2016 at 10:04:16AM +0800, Zhangjian (Bamvor) wrote: > > > > [...] > > > > > > > > > >>Ok, I will test the ltp syscall test. > > > > > >>With this changes, the issue I mentioned should be fixed. But we still > > > > > >>use mmap2 syscall for ILP32 application when we pass the offset instead > > > > > >>of page offset. Is it correct? > > > > > > > > > > > >I don't remember. It's probably not important whether we have the shift > > > > > >in there, as long as it's independent of the actual kernel page size and > > > > > >user space and kernel agree on the calling conventions. > > > > > Well. I am ok with where to shift the pages size because we get the same > > > > > result. I was just thinking if we should get rid of the name of mmap2 in our > > > > > ILP32 porting. Actually, it is mmap but we name it as mmap2. User may confused > > > > > if they do not know the implementations. > > > > > > > > > > > > > This is what generic unistd.h does. If you want to change it, you'd > > > > change each arch that uses generic unistd.h. > > > > > > Generic unistd.h has this: > > > > > > #ifdef __SYSCALL_COMPAT > > > #define __SC_COMP_3264(_nr, _32, _64, _comp) __SYSCALL(_nr, _comp) > > > #else > > > #define __SC_COMP_3264(_nr, _32, _64, _comp) __SC_3264(_nr, _32, _64) > > > #endif > > > > > > #define __NR3264_mmap 222 > > > __SC_3264(__NR3264_mmap, sys_mmap2, sys_mmap) > > > > > > > > > #if __BITS_PER_LONG == 64 && !defined(__SYSCALL_COMPAT) > > > #define __NR_mmap __NR3264_mmap > > > #else > > > #define __NR_mmap2 __NR3264_mmap > > > #endif > > > > > > So by default we get __NR_mmap2 and sys_mmap2 on 32-bit ABIs, but > > > __NR_mmap and sys_mmap on 64-bit ABIs, as it should be. > > > > > > The problem is that arch/arm64/kernel/sys_ilp32.c now overrides > > > this to use __NR_mmap2 with sys_mmap, so we have a mismatch. I think > > > we should either override both the implementation and the number, > > > or neither of them. > > > > I would vote for "neither of them" (so we use __NR_mmap2 and sys_mmap2) > > to keep it close to new 32-bit architectures, even though we would have > > some shifts by 12 in both glibc and kernel. > > I don't think the shifts are a problem, the main downside would be > the limit to 44 bits of file offsets (16TB files), but it's also > unclear if that is a practical problem at all. If it is, we run > into the same problem on all other 32-bit architectures too. I hope people are seriously thinking of moving to an LP64 ABI if they have such large file offset needs. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
