CONFIG_COMPAT_32BIT_TIME in the kernel, x86 ABI on x86-64

[Andreas K. Huettel]

Dear all, 

one of my Gentoo colleagues (Mike Gilbert, floppym) found this, so I'm forwarding
his notes:

===
Using utimensat as an example, the kernel interface is as follows:

When CONFIG_COMPAT_32BIT_TIME is enabled, the kernel provides both the legact 
32-bit interface (utimensat) and the 64-bit interface (utimensat_time64).
When CONFIG_COMPAT_32BIT_TIME is disabled, only the 64-bit interface 
(utimensat_time64) is provided. utimensat gives ENOSYS.

Behavior of utimensat64 libc function before b286eca5d4117b3e17c939e3df56e132ae623df1:

1. Try utimensat_time64
2. If ENOSYS, fall back to utimensat if the arguments are small enough to fit in 32-bits

Behavior of utimensat64 libc function after b286eca5d4117b3e17c939e3df56e132ae623df1:

1. If the arguments are small enough to fit in 32-bits, use utimensat
2. If the arguments are too large, use utimensat_time64

The new behavior fails when CONFIG_COMPAT_32BIT_TIME is disabled, since utimensat is 
unavailable.

Several other glibc functions were updated with similar behavior changes.
===

What's to do?

Cheers,
Andreas

-- 
Andreas K. Hüttel
dilfridge@gentoo.org
Gentoo Linux developer
(council, toolchain, base-system, perl, libreoffice)
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