Beginning with the upcoming 4.1 release, Linux on a subset of 32-bit
ARM hardware will provide fast user-space implementations of the
following system calls:
- gettimeofday
- clock_gettime
The kernel implementation depends on the ARMv7 Generic Timers
Extension to accelerate these system calls. So CPUs such as
Cortex-A15 and -A7 benefit, while Cortex-A9, -A8, and pre-v7 CPUs do
not. On systems where the VDSO does not provide any speedup, the
kernel prevents the relevant symbol lookups from succeeding.
On OMAP5 (Cortex-A15) gettimeofday latency decreases from ~350ns to
~120ns. On BeagleBone Black (Cortex-A8) it goes from ~650ns to
~660ns, which to my mind is an acceptable cost.
Verified that no new test failures are introduced on kernels with and
without the VDSO.
* sysdeps/unix/sysv/linux/arm/Makefile: (sysdep_routines):
Include dl-vdso.
* sysdeps/unix/sysv/linux/arm/init-first.c: New file:
Use VDSO routines for gettimeofday, clock_gettime if
available.
* sysdeps/unix/sysv/linux/arm/libc-vdso.h: New file:
Declare VDSO symbols.
* sysdeps/unix/sysv/linux/arm/sysdep.h:
[HAVE_GETTIMEOFDAY_VSYSCALL]: Define.
[HAVE_CLOCK_GETTIME_VSYSCALL]: Define.
* sysdeps/unix/sysv/linux/arm/Versions: Add
__vdso_clock_gettime.
This patch removes ARM __ASSUME_SIGFRAME_V2 now that the
2.6.18-and-later signal frame layout can be assumed, renaming the
affected functions accordingly now only one version of them is needed
in glibc. (sigrestorer.S did not in fact include <kernel-features.h>
and it appears that, unlike other such cases, it didn't get the header
indirectly, so the v1 functions would have been compiled in even when
sigaction.c didn't reference them.)
(alpha and hppa also have architecture-specific __ASSUME_* macros that
should now be removed: __ASSUME_FDATASYNC and __ASSUME_LWS_CAS
respectively. I don't have any plans to do anything on that myself.)
Tested on ARM.
* sysdeps/unix/sysv/linux/arm/kernel-features.h
(__ASSUME_SIGFRAME_V2): Remove macro.
* sysdeps/unix/sysv/linux/arm/sigrestorer.S: Update comment.
[!__ASSUME_SIGFRAME_V2]: Remove conditional code.
(__default_sa_restorer_v2): Rename to __default_sa_restorer.
(__default_rt_sa_restorer_v2): Rename to __default_rt_sa_restorer.
* sysdeps/unix/sysv/linux/arm/sigaction.c (__default_sa_restorer):
Declare as function. Remove conditional macro definitions.
(__default_rt_sa_restorer): Likewise.
(__default_sa_restorer_v1): Remove declaration.
(__default_sa_restorer_v2): Likewise.
(__default_rt_sa_restorer_v1): Likewise.
(__default_rt_sa_restorer_v2): Likewise.
* sysdeps/unix/sysv/linux/arm/Versions (GLIBC_PRIVATE): Remove
__default_sa_restorer_v1, __default_rt_sa_restorer_v1,
__default_sa_restorer_v2 and __default_rt_sa_restorer_v2.
This patch cleans up some symbol versioning code in the ARM port that
exists only as relics of the old-ABI port, which was removed some time
ago.
The minimum symbol version in the ARM port is GLIBC_2.4 (the version
where the EABI port was introduced). Thus, any SHLIB_COMPAT
conditionals where the later version is 2.4 or later are obsolete and
can be removed. In addition, there is no need to set symbol versions
before 2.4 explicitly if the symbols would have a version of 2.4 by
default anyway. This includes most of the entries in
sysdeps/unix/sysv/linux/arm/Versions: those for GLIBC_2.0 are for
libgcc unwind functions that aren't actually in ARM EABI glibc at all,
while those for GLIBC_2.2 and GLIBC_2.3.3 are for functions which for
the old-ABI port may have had versions different from the
architecture-independent default, but where for EABI the default
suffices (both the default and the version in that file map to 2.4, so
the entries in that file do nothing). The GLIBC_2.1 entries are
needed (architecture-specific functions), but it seems less confusing
for those to say GLIBC_2.4, as the actual version those symbols in
fact have.
Various cases in the <fenv.h> functions where a function is defined as
__fe* with an fe* versioned alias are cleaned up just to define fe*
directly, as done e.g. on AArch64. If in future we actually need an
__fe* name for use from C90 functions in libm as discussed recently,
of course we can add one on all architectures and make the fe* name
into a weak alias for that particular function, but for now the __fe*
names aren't needed.
In the case of posix_fadvise64, the __posix_fadvise64_l64 name and
posix_fadvise64 alias are kept as __posix_fadvise64_l64 is used in
posix_fadvise. (For that to be a namespace-clean use, posix_fadvise64
needs to be a *weak* alias not a strong one as at present, but that's
an independent preexisting bug.)
(There remain references to GLIBC_2_2 in
sysdeps/unix/sysv/linux/arm/{msgctl.c,semctl.c,shmctl.c}. As those
files are used by alpha which has a genuine 2.2 version for those
functions, I think those references need to stay as-is.)
Tested that the disassembly of installed shared libraries is unchanged
by this patch (though function names shown in disassembly change to no
longer have @@GLIBC_2.4, now those functions get versioned only by the
version map and not redundantly at assembler time) and that the ABI
tests pass.
* sysdeps/arm/fclrexcpt.c (__feclearexcept): Rename to
feclearexcept. Remove symbol versioning code.
* sysdeps/arm/fegetenv.c (__fegetenv): Rename to fegetenv. Remove
symbol versioning code.
* sysdeps/arm/fesetenv.c (__fesetenv): Rename to fesetenv. Remove
symbol versioning code.
* sysdeps/arm/feupdateenv.c (__feupdateenv): Rename to
feupdateenv. Remove symbol versioning code.
* sysdeps/arm/fgetexcptflg.c (__fegetexceptflag): Rename to
fegetexceptflag. Remove symbol versioning code.
* sysdeps/arm/fsetexcptflg.c (__fesetexceptflag): Rename to
fesetexceptflag. Remove symbol versioning code.
* sysdeps/unix/sysv/linux/arm/Versions (libc): Remove GLIBC_2.0,
GLIBC_2.2 and GLIBC_2.3.3 entries. Change GLIBC_2.1 to GLIBC_2.4.
* sysdeps/unix/sysv/linux/arm/posix_fadvise64.c
(__posix_fadvise64_l32): Remove prototype.
[SHLIB_COMPAT(libc, GLIBC_2_2, GLIBC_2_3_3)]: Remove conditional
code.
I've moved the ARM port from ports to the main sysdeps hierarchy.
Beyond the README update, the move of the files was simply
git mv ports/sysdeps/arm sysdeps/arm
git mv ports/sysdeps/unix/arm sysdeps/unix/arm
git mv ports/sysdeps/unix/sysv/linux/arm sysdeps/unix/sysv/linux/arm
and in addition to the ChangeLog entries here, I put a note at the top
of ports/ChangeLog.arm similar to that at the top of
ChangeLog.powerpc. There is deliberately no NEWS change, as I think
it makes the most sense to put in a general note above all ports
having moved if we can achieve that for 2.20.
Tested that disassembly of installed shared libraries for arm is the
same before and after this patch, except for data (not instructions)
in ld.so (there are assertions in sysdeps/arm/dl-machine.h, and the
path by which that file is found, and so by which it appears in the
assertion message, changes as a result of the move).
* sysdeps/arm: Move directory from ports/sysdeps/arm.
* sysdeps/unix/arm: Move directory from ports/sysdeps/unix/arm.
* sysdeps/unix/sysv/linux/arm: Move directory from
ports/sysdeps/unix/sysv/linux/arm.
* README: Update listing for arm-*-linux-gnueabi.
ports/ChangeLog.arm:
* sysdeps/arm: Move directory to ../sysdeps/arm.
* sysdeps/unix/arm: Move directory to ../sysdeps.arm.
* sysdeps/unix/sysv/linux/arm: Move directory to
../sysdeps/unix/sysv/linux/arm.
1998-12-20 Philip Blundell <philb@gnu.org>
* sysdeps/unix/sysv/linux/arm/sysdep.h (INLINE_SYSCALL): Add
implementation.
* sysdeps/unix/sysv/linux/arm/syscalls.list: Remove wrappers for
now-inlined calls.
1998-12-22 Philip Blundell <pb@nexus.co.uk>
* sysdeps/unix/sysv/linux/arm/ioperm.c: New file.
Implementation of inb, outb etc for ARM systems.
* sysdeps/unix/sysv/linux/arm/sys/io.h: Likewise.
* sysdeps/unix/sysv/linux/arm/Versions: Add appropriate
entries for the above.
