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2019-07-31lib/vdso/32: Provide legacy syscall fallbacksThomas Gleixner1-1/+11
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
2019-07-31lib/vdso: Move fallback invocation to the callersThomas Gleixner1-17/+36
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
2019-07-31lib/vdso/32: Remove inconsistent NULL pointer checksThomas Gleixner1-16/+2
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
2019-06-26lib/vdso: Make delta calculation work correctlyThomas Gleixner1-4/+15
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
2019-06-22lib/vdso: Add compat supportVincenzo Frascino1-0/+4
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
2019-06-22lib/vdso: Provide generic VDSO implementationVincenzo Frascino3-0/+282
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