https://github.com/riscv/riscv-elf-psabi-doc/pull/15

When we upstream glibc+linux, we should revisit this value.

This patch uses INLINE_SYSCALL_ERROR_RETURN_VALUE to avoid reading
and writing errno directly on architectures for which factoring out
the position-independent code for loading the address of errno
improves performance and/or code size in the common case.

	* sysdeps/unix/sysv/linux/generic/epoll_create.c (epoll_create):
	Use INLINE_SYSCALL_ERROR_RETURN_VALUE.
	* sysdeps/unix/sysv/linux/generic/futimesat.c (futimesat): Likewise.
	* sysdeps/unix/sysv/linux/generic/sysctl.c (sysctl): Likewise.
	* sysdeps/unix/sysv/linux/generic/ustat.c (ustat): Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/fcntl.c (do_fcntl):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/getdents.c (__getdents):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/mmap.c (__mmap):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/overflow.h
	(lseek_overflow, stat_overflow, statfs_overflow): Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/sendfile.c (sendfile):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/xmknod.c (__xmknod): Likewise.
	* sysdeps/unix/sysv/linux/generic/setegid.c (setegid): Likewise.
	* sysdeps/unix/sysv/linux/generic/seteuid.c (seteuid): Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-64/fxstat.c (__fxstat):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-64/fxstatat.c (__fxstatat):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-64/lxstat.c (__lxstat):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-64/xstat.c (__xstat):
	Likewise.

This factors out the setting of setting errno and returning -1, reducing
code size.

Forgot to add the thread pointer, derp.

This makes the common case of no error faster by avoiding clobbering
most of the caller-saved registers.

This resolves the ABI bug mentioned in #6.

Happily, falling back to the built-in versions in the no-atomic case
does the right thing (invoking sysriscv).

Since that's the only version we support, there's no reason to
support older kernel ABIs.