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To address the regression which causes seccomp to deny applications the
access to clock_gettime64() and clock_getres64() syscalls because they
are not enabled in the existing filters.
That trips over the fact that 32bit VDSOs use the new clock_gettime64() and
clock_getres64() syscalls in the fallback path.
Add a conditional to invoke the 32bit legacy fallback syscalls instead of
the new 64bit variants. The conditional can go away once all architectures
are converted.
Fixes: 00b26474c2f1 ("lib/vdso: Provide generic VDSO implementation")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1907301134470.1738@nanos.tec.linutronix.de
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To allow syscall fallbacks using the legacy 32bit syscall for 32bit VDSO
builds, move the fallback invocation out into the callers.
Split the common code out of __cvdso_clock_gettime/getres() and invoke the
syscall fallback in the 64bit and 32bit variants.
Preparatory work for using legacy syscalls in 32bit VDSO. No functional
change.
Fixes: 00b26474c2f1 ("lib/vdso: Provide generic VDSO implementation")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/20190728131648.695579736@linutronix.de
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The 32bit variants of vdso_clock_gettime()/getres() have a NULL pointer
check for the timespec pointer. That's inconsistent vs. 64bit.
But the vdso implementation will never be consistent versus the syscall
because the only case which it can handle is NULL. Any other invalid
pointer will cause a segfault. So special casing NULL is not really useful.
Remove it along with the superflouos syscall fallback invocation as that
will return -EFAULT anyway. That also gets rid of the dubious typecast
which only works because the pointer is NULL.
Fixes: 00b26474c2f1 ("lib/vdso: Provide generic VDSO implementation")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20190728131648.587523358@linutronix.de
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The x86 vdso implementation on which the generic vdso library is based on
has subtle (unfortunately undocumented) twists:
1) The code assumes that the clocksource mask is U64_MAX which means that
no bits are masked. Which is true for any valid x86 VDSO clocksource.
Stupidly it still did the mask operation for no reason and at the wrong
place right after reading the clocksource.
2) It contains a sanity check to catch the case where slightly
unsynchronized TSC values can be observed which would cause the delta
calculation to make a huge jump. It therefore checks whether the
current TSC value is larger than the value on which the current
conversion is based on. If it's not larger the base value is used to
prevent time jumps.
#1 Is not only stupid for the X86 case because it does the masking for no
reason it is also completely wrong for clocksources with a smaller mask
which can legitimately wrap around during a conversion period. The core
timekeeping code does it correct by applying the mask after the delta
calculation:
(now - base) & mask
#2 is equally broken for clocksources which have smaller masks and can wrap
around during a conversion period because there the now > base check is
just wrong and causes stale time stamps and time going backwards issues.
Unbreak it by:
1) Removing the mask operation from the clocksource read which makes the
fallback detection work for all clocksources
2) Replacing the conditional delta calculation with a overrideable inline
function.
#2 could reuse clocksource_delta() from the timekeeping code but that
results in a significant performance hit for the x86 VSDO. The timekeeping
core code must have the non optimized version as it has to operate
correctly with clocksources which have smaller masks as well to handle the
case where TSC is discarded as timekeeper clocksource and replaced by HPET
or pmtimer. For the VDSO there is no replacement clocksource. If TSC is
unusable the syscall is enforced which does the right thing.
To accommodate to the needs of various architectures provide an
override-able inline function which defaults to the regular delta
calculation with masking:
(now - base) & mask
Override it for x86 with the non-masking and checking version.
This unbreaks the ARM64 syscall fallback operation, allows to use
clocksources with arbitrary width and preserves the performance
optimization for x86.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: LAK <linux-arm-kernel@lists.infradead.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: catalin.marinas@arm.com
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux@armlinux.org.uk
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: paul.burton@mips.com
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: salyzyn@android.com
Cc: pcc@google.com
Cc: shuah@kernel.org
Cc: 0x7f454c46@gmail.com
Cc: linux@rasmusvillemoes.dk
Cc: huw@codeweavers.com
Cc: sthotton@marvell.com
Cc: andre.przywara@arm.com
Cc: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1906261159230.32342@nanos.tec.linutronix.de
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Some 64 bit architectures have support for 32 bit applications that
require a separate version of the vDSOs.
Add support to the generic code for compat fallback functions.
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shijith Thotton <sthotton@marvell.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Huw Davies <huw@codeweavers.com>
Link: https://lkml.kernel.org/r/20190621095252.32307-10-vincenzo.frascino@arm.com
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In the last few years the kernel gained quite some architecture specific
vdso implementations which contain very similar code.
Introduce a generic VDSO implementation of gettimeofday() which will be
shareable between architectures once they are converted over.
The implementation is based on the current x86 VDSO code.
[ tglx: Massaged changelog and made the kernel doc tabular ]
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Shijith Thotton <sthotton@marvell.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Salyzyn <salyzyn@android.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Huw Davies <huw@codeweavers.com>
Link: https://lkml.kernel.org/r/20190621095252.32307-3-vincenzo.frascino@arm.com
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