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io: Refactor close_range and closefrom

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Now that Hurd implementis both close_range and closefrom (f2c996597d),
we can make close_range() a base ABI, and make the default closefrom()
implementation on top of close_range().

The generic closefrom() implementation based on __getdtablesize() is
moved to generic close_range().  On Linux it will be overriden by
the auto-generation syscall while on Hurd it will be a system specific
implementation.

The closefrom() now calls close_range() and __closefrom_fallback().
Since on Hurd close_range() does not fail, __closefrom_fallback() is an
empty static inline function set by__ASSUME_CLOSE_RANGE.

The __ASSUME_CLOSE_RANGE also allows optimize Linux
__closefrom_fallback() implementation when --enable-kernel=5.9 or
higher is used.

Finally the Linux specific tst-close_range.c is moved to io and
enabled as default.  The Linuxism and CLOSE_RANGE_UNSHARE are
guarded so it can be built for Hurd (I have not actually test it).

Checked on x86_64-linux-gnu, i686-linux-gnu, and with a i686-gnu
build.
This commit is contained in:
Adhemerval Zanella
2021-11-08 10:20:23 -03:00
parent e186fc5a31
commit 456b3c08b6
15 changed files with 76 additions and 68 deletions
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8
sysdeps/unix/sysv/linux/kernel-features.h
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@@ -220,6 +220,14 @@
# define __ASSUME_FACCESSAT2 0
#endif
/* The close_range system call was introduced across all architectures
in Linux 5.9. */
#if __LINUX_KERNEL_VERSION >= 0x050900
# define __ASSUME_CLOSE_RANGE 1
#else
# define __ASSUME_CLOSE_RANGE 0
#endif
/* The FUTEX_LOCK_PI2 operation was introduced across all architectures in Linux
5.14. */
#if __LINUX_KERNEL_VERSION >= 0x050e00