On Fri, Jun 08, 2018 at 03:33:51PM -0700, Palmer Dabbelt wrote: > On Fri, 08 Jun 2018 10:32:07 PDT (-0700), catalin.marinas@xxxxxxx wrote: > > On Wed, May 16, 2018 at 11:18:49AM +0300, Yury Norov wrote: > > > diff --git a/arch/Kconfig b/arch/Kconfig > > > index 76c0b54443b1..ee079244dc3c 100644 > > > --- a/arch/Kconfig > > > +++ b/arch/Kconfig > > > @@ -264,6 +264,21 @@ config ARCH_THREAD_STACK_ALLOCATOR > > > config ARCH_WANTS_DYNAMIC_TASK_STRUCT > > > bool > > > > > > +config ARCH_32BIT_OFF_T > > > + bool > > > + depends on !64BIT > > > + help > > > + All new 32-bit architectures should have 64-bit off_t type on > > > + userspace side which corresponds to the loff_t kernel type. This > > > + is the requirement for modern ABIs. Some existing architectures > > > + already have 32-bit off_t. This option is enabled for all such > > > + architectures explicitly. Namely: arc, arm, blackfin, cris, frv, > > > + h8300, hexagon, m32r, m68k, metag, microblaze, mips32, mn10300, > > > + nios2, openrisc, parisc32, powerpc32, score, sh, sparc, tile32, > > > + unicore32, x86_32 and xtensa. This is the complete list. Any > > > + new 32-bit architecture should declare 64-bit off_t type on user > > > + side and so should not enable this option. > > > > Do you know if this is the case for riscv and nds32, merged in the > > meantime? If not, I suggest you drop this patch altogether and just > > define force_o_largefile() for arm64/ilp32 as we don't seem to stick to > > "all new 32-bit architectures should have 64-bit off_t". > > We (RISC-V) don't have support for rv32i in glibc yet, so there really isn't > a fixed ABI there yet. From my understanding the rv32i port as it currently > stands has a 32-bit off_t (via __kernel_off_t being defined as long), so > this change would technically be a kernel ABI break. > > Since we don't have rv32i glibc yet I'm not fundamentally opposed to an ABI > break. Is there a concrete advantage to this? One obvious advantage is manipulating large files - if file is greater than 2G, you cannot easily mmap(), lseek() etc with 32-bit offset. Another point is unification of layuots for structures like struct stat between 32- and 64-bit worlds. On glibc side it helps to unify 32-bit and 64-bit versions of syscalls. Refer, for example this commit: 3c7f1f59cd161 (Consolidate lseek/lseek64/llseek implementations). Yury
