On Tue, Dec 22, 2015 at 10:44:14PM +0100, Arnd Bergmann wrote: > On Tuesday 22 December 2015, Catalin Marinas wrote: > > > + > > > +ENTRY(compat_sys_statfs64_wrapper) > > > + mov w3, #84 > > > + cmp w1, #88 > > > + csel w1, w3, w1, eq > > > + b compat_sys_statfs64 > > > +ENDPROC(compat_sys_statfs64_wrapper) > > > + > > > +ENTRY(compat_sys_fstatfs64_wrapper) > > > + mov w3, #84 > > > + cmp w1, #88 > > > + csel w1, w3, w1, eq > > > + b compat_sys_fstatfs64 > > > +ENDPROC(compat_sys_fstatfs64_wrapper) > > > > I'm not convinced we need these wrappers for ILP32. They've been > > introduced on arch/arm many years ago by commit Fixes: 713c481519f1 > > ([ARM] 3108/2: old ABI compat: statfs64 and fstatfs64) to deal with user > > space passing a size of 88 (the EABI size of struct compat_statfs64 > > without the packing and alignment attribute). Since that commit, the > > sizeof(struct compat_statfs64) is 84 already. This should be the case > > with the new ILP32 exported headers (no backwards compatibility), so > > user space should never pass 88 as size. Therefore we could call > > compat_sys_(f)statfs64 directly without wrappers. > > That means we have to set ARCH_PACK_STATFS64 in the arm64 header files > though, and propagate the OABI alignment to arm64/ilp32 as well, rather > than using the 88-byte version that every other 32-bit architecture > except for x86-32 and arm32 has.
Yuri replied that for EABI glibc, sizeof(struct statfs64) is already 88. If that's correct and the packing attribute is ignored by glibc, we could drop ARCH_PACK_COMPAT_STATFS64 as well (OABI not supported by arm64). But I would be slightly worried since glibc is not the only user of the kernel ABI. For ILP32, I think we can skip defining ARCH_PACK_STATFS64 (of course, only if __ILP32__) and state that sizeof(struct statfs64) is 88 (unpacked). In which case we need the wrappers above to be able to reuse the compat_sys_statfs64 code. > Another option would be to set "#define __statfs_word __u64" and use > the 64-bit statfs call, instead of compat_sys_statfs64, but that in turn > requires special-casing statfs in libc. I wouldn't go this route as we kind of agreed that ILP32 should look like any other 32-bit ABI. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/