Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR
Signed-off-by: Prasanna Karthik <mkarthi3@visteon.com>
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Since 906c55579a ("timekeeping: Copy the shadow-timekeeper over the
real timekeeper last") it has become possible on ARM to:
- Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
via syscall.
- Subsequently obtain a timestamp for the same clock ID via VDSO which
predates the first timestamp (by one jiffy).
This is because ARM's update_vsyscall is deriving the coarse time
using the __current_kernel_time interface, when it should really be
using the timekeeper object provided to it by the timekeeping core.
It happened to work before only because __current_kernel_time would
access the same timekeeper object which had been passed to
update_vsyscall. This is no longer the case.
Cc: stable@vger.kernel.org
Fixes: 906c55579a ("timekeeping: Copy the shadow-timekeeper over the real timekeeper last")
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Pull ARM updates from Russell King:
"Included in this update are both some long term fixes and some new
features.
Fixes:
- An integer overflow in the calculation of ELF_ET_DYN_BASE.
- Avoiding OOMs for high-order IOMMU allocations
- SMP requires the data cache to be enabled for synchronisation
primitives to work, so prevent the CPU_DCACHE_DISABLE option being
visible on SMP builds.
- A bug going back 10+ years in the noMMU ARM94* CPU support code,
where it corrupts registers. Found by folk getting Linux running
on their cameras.
- Versatile Express needs an errata workaround enabled for CPU
hot-unplug to work.
Features:
- Clean up module linker by handling out of range relocations
separately from relocation cases we don't handle.
- Fix a long term bug in the pci_mmap_page_range() code, which we
hope won't impact userspace (we hope there's no users of the
existing broken interface.)
- Don't map DMA coherent allocations when we don't have a MMU.
- Drop experimental status for SMP_ON_UP.
- Warn when DT doesn't specify ePAPR mandatory cache properties.
- Add documentation concerning how we find the start of physical
memory for AUTO_ZRELADDR kernels, detailing why we have chosen the
mask and the implications of changing it.
- Updates from Ard Biesheuvel to address some issues with large
kernels (such as allyesconfig) failing to link.
- Allow hibernation to work on modern (ARMv7) CPUs - this appears to
have never worked in the past on these CPUs.
- Enable IRQ_SHOW_LEVEL, which changes the /proc/interrupts output
format (hopefully without userspace breaking... let's hope that if
it causes someone a problem, they tell us.)
- Fix tegra-ahb DT offsets.
- Rework ARM errata 643719 code (and ARMv7 flush_cache_louis()/
flush_dcache_all()) code to be more efficient, and enable this
errata workaround by default for ARMv7+SMP CPUs. This complements
the Versatile Express fix above.
- Rework ARMv7 context code for errata 430973, so that only Cortex A8
CPUs are impacted by the branch target buffer flush when this
errata is enabled. Also update the help text to indicate that all
r1p* A8 CPUs are impacted.
- Switch ARM to the generic show_mem() implementation, it conveys all
the information which we were already reporting.
- Prevent slow timer sources being used for udelay() - timers running
at less than 1MHz are not useful for this, and can cause udelay()
to return immediately, without any wait. Using such a slow timer
is silly.
- VDSO support for 32-bit ARM, mainly for gettimeofday() using the
ARM architected timer.
- Perf support for Scorpion performance monitoring units"
vdso semantic conflict fixed up as per linux-next.
* 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm: (52 commits)
ARM: update errata 430973 documentation to cover Cortex A8 r1p*
ARM: ensure delay timer has sufficient accuracy for delays
ARM: switch to use the generic show_mem() implementation
ARM: proc-v7: avoid errata 430973 workaround for non-Cortex A8 CPUs
ARM: enable ARM errata 643719 workaround by default
ARM: cache-v7: optimise test for Cortex A9 r0pX devices
ARM: cache-v7: optimise branches in v7_flush_cache_louis
ARM: cache-v7: consolidate initialisation of cache level index
ARM: cache-v7: shift CLIDR to extract appropriate field before masking
ARM: cache-v7: use movw/movt instructions
ARM: allow 16-bit instructions in ALT_UP()
ARM: proc-arm94*.S: fix setup function
ARM: vexpress: fix CPU hotplug with CT9x4 tile.
ARM: 8276/1: Make CPU_DCACHE_DISABLE depend on !SMP
ARM: 8335/1: Documentation: DT bindings: Tegra AHB: document the legacy base address
ARM: 8334/1: amba: tegra-ahb: detect and correct bogus base address
ARM: 8333/1: amba: tegra-ahb: fix register offsets in the macros
ARM: 8339/1: Enable CONFIG_GENERIC_IRQ_SHOW_LEVEL
ARM: 8338/1: kexec: Relax SMP validation to improve DT compatibility
ARM: 8337/1: mm: Do not invoke OOM for higher order IOMMU DMA allocations
...
Initialize the VDSO page list at boot, install the VDSO mapping at
exec time, and update the data page during timer ticks. This code is
not built if CONFIG_VDSO is not enabled.
Account for the VDSO length when randomizing the offset from the
stack. The [vdso] and [vvar] pages are placed immediately following
the sigpage with separate _install_special_mapping calls.
We want to "penalize" systems lacking the arch timer as little
as possible. Previous versions of this code installed the VDSO
unconditionally and unmodified, making it a measurably slower way for
glibc to invoke the real syscalls on such systems. E.g. calling
gettimeofday via glibc goes from ~560ns to ~630ns on i.MX6Q.
If we can indicate to glibc that the time-related APIs in the VDSO are
not accelerated, glibc can continue to invoke the syscalls directly
instead of dispatching through the VDSO only to fall back to the slow
path.
Thus, if the architected timer is unusable for whatever reason, patch
the VDSO at boot time so that symbol lookups for gettimeofday and
clock_gettime return NULL. (This is similar to what powerpc does and
borrows code from there.) This allows glibc to perform the syscall
directly instead of passing control to the VDSO, which minimizes the
penalty. In my measurements the time taken for a gettimeofday call
via glibc goes from ~560ns to ~580ns (again on i.MX6Q), and this is
solely due to adding a test and branch to glibc's gettimeofday syscall
wrapper.
An alternative to patching the VDSO at boot would be to not install
the VDSO at all when the arch timer isn't usable. Another alternative
is to include a separate "dummy" vdso.so without gettimeofday and
clock_gettime, which would be selected at boot time. Either of these
would get cumbersome if the VDSO were to gain support for an API such
as getcpu which is unrelated to arch timer support.
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
