linux-stable.git/lib/vdso, branch v5.7.4

lib/vdso: Provide sanity check for cycles (again)

2020-06-18T12:31:08+00:00

commit 72ce778007e57e8996b4bebdec738fc5e1145fd2 upstream.

The original x86 VDSO implementation checked for the validity of the clock
source read by testing whether the returned signed cycles value is less
than zero. This check was also used by the vdso read function to signal
that the current selected clocksource is not VDSO capable.

During the rework of the VDSO code the check was removed and replaced with
a check for the clocksource mode being != NONE.

This turned out to be a mistake because the check is necessary for paravirt
and hyperv clock sources. The reason is that these clock sources have their
own internal sequence counter to validate the clocksource at the point of
reading it. This is necessary because the hypervisor can invalidate the
clocksource asynchronously so a check during the VDSO data update is not
sufficient. Having a separate indicator for the validity is slower than
just validating the cycles value. The check for it being negative turned
out to be the fastest implementation and safe as it would require an uptime
of ~73 years with a 4GHz counter frequency to result in a false positive.

Add an optional function to validate the cycles with a default
implementation which allows the compiler to optimize it out for
architectures which do not require it.

Fixes: 5d51bee725cc ("clocksource: Add common vdso clock mode storage")
Reported-by: Miklos Szeredi 
Signed-off-by: Thomas Gleixner 
Tested-by: Miklos Szeredi 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200606221531.963970768@linutronix.de
Signed-off-by: Greg Kroah-Hartman

lib/vdso: Enable common headers

2020-03-21T14:24:03+00:00

The vDSO library should only include the necessary headers required for
a userspace library (UAPI and a minimal set of kernel headers). To make
this possible it is necessary to isolate from the kernel headers the
common parts that are strictly necessary to build the library.

Refactor the unified vdso code to use the common headers.

Signed-off-by: Vincenzo Frascino 
Signed-off-by: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20200320145351.32292-26-vincenzo.frascino@arm.com

lib/vdso: Allow architectures to provide the vdso data pointer

2020-02-17T19:12:18+00:00

On powerpc, __arch_get_vdso_data() clobbers the link register, requiring
the caller to save it.

As the parent function already has to set a stack frame and saves the link
register before calling the C vdso function, retrieving the vdso data
pointer there is less overhead.

Split out the functional code from the __cvdso.*() interfaces into new
static functions which can either be called from the existing interfaces
with the vdso data pointer supplied via __arch_get_vdso_data() or directly
from ASM code.

Signed-off-by: Christophe Leroy 
Signed-off-by: Thomas Gleixner 
Tested-by: Vincenzo Frascino 
Reviewed-by: Vincenzo Frascino 
Link: https://lore.kernel.org/r/abf97996602ef07223fec30c005df78e5ed41b2e.1580399657.git.christophe.leroy@c-s.fr
Link: https://lkml.kernel.org/r/20200207124403.965789141@linutronix.de

lib/vdso: Allow architectures to override the ns shift operation

2020-02-17T19:12:18+00:00

On powerpc/32, GCC (8.1) generates pretty bad code for the ns >>= vd->shift
operation taking into account that the shift is always <= 32 and the upper
part of the result is likely to be zero. GCC makes reversed assumptions
considering the shift to be likely >= 32 and the upper part to be like not
zero.

unsigned long long shift(unsigned long long x, unsigned char s)
{
	return x >> s;
}

results in:

00000018 :
  18:	35 25 ff e0 	addic.  r9,r5,-32
  1c:	41 80 00 10 	blt     2c 
  20:	7c 64 4c 30 	srw     r4,r3,r9
  24:	38 60 00 00 	li      r3,0
  28:	4e 80 00 20 	blr
  2c:	54 69 08 3c 	rlwinm  r9,r3,1,0,30
  30:	21 45 00 1f 	subfic  r10,r5,31
  34:	7c 84 2c 30 	srw     r4,r4,r5
  38:	7d 29 50 30 	slw     r9,r9,r10
  3c:	7c 63 2c 30 	srw     r3,r3,r5
  40:	7d 24 23 78 	or      r4,r9,r4
  44:	4e 80 00 20 	blr

Even when forcing the shift to be smaller than 32 with an &= 31, it still
considers the shift as likely >= 32.

Move the default shift implementation into an inline which can be redefined
in architecture code via a macro.

[ tglx: Made the shift argument u32 and removed the __arch prefix ]

Signed-off-by: Christophe Leroy 
Signed-off-by: Thomas Gleixner 
Tested-by: Vincenzo Frascino 
Reviewed-by: Vincenzo Frascino 
Link: https://lore.kernel.org/r/b3d449de856982ed060a71e6ace8eeca4654e685.1580399657.git.christophe.leroy@c-s.fr
Link: https://lkml.kernel.org/r/20200207124403.857649978@linutronix.de

lib/vdso: Allow fixed clock mode

2020-02-17T19:12:18+00:00

Some architectures have a fixed clocksource which is known at compile time
and cannot be replaced or disabled at runtime, e.g. timebase on
PowerPC. For such cases the clock mode check in the VDSO code is pointless.

Move the check for a VDSO capable clocksource into an inline function and
allow architectures to redefine it via a macro.

[ tglx: Removed the #ifdef mess ]

Signed-off-by: Christophe Leroy 
Signed-off-by: Thomas Gleixner 
Tested-by: Vincenzo Frascino 
Reviewed-by: Vincenzo Frascino 
Link: https://lkml.kernel.org/r/20200207124403.748756829@linutronix.de

lib/vdso: Move VCLOCK_TIMENS to vdso_clock_modes

2020-02-17T19:12:17+00:00

Move the time namespace indicator clock mode to the other ones for
consistency sake.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Vincenzo Frascino 
Link: https://lkml.kernel.org/r/20200207124403.656097274@linutronix.de

lib/vdso: Cleanup clock mode storage leftovers

2020-02-17T19:12:17+00:00

Now that all architectures are converted to use the generic storage the
helpers and conditionals can be removed.

Signed-off-by: Thomas Gleixner 
Tested-by: Vincenzo Frascino 
Reviewed-by: Vincenzo Frascino 
Link: https://lkml.kernel.org/r/20200207124403.470699892@linutronix.de

clocksource: Add common vdso clock mode storage

2020-02-17T13:40:23+00:00

All architectures which use the generic VDSO code have their own storage
for the VDSO clock mode. That's pointless and just requires duplicate code.

Provide generic storage for it. The new Kconfig symbol is intermediate and
will be removed once all architectures are converted over.

Signed-off-by: Thomas Gleixner 
Tested-by: Vincenzo Frascino 
Reviewed-by: Vincenzo Frascino 
Link: https://lkml.kernel.org/r/20200207124403.028046322@linutronix.de

lib/vdso: Allow the high resolution parts to be compiled out

2020-02-17T13:40:20+00:00

If the architecture knows at compile time that there is no VDSO capable
clocksource supported it makes sense to optimize the guts of the high
resolution parts of the VDSO out at build time. Add a helper function to
check whether the VDSO should be high resolution capable and provide a stub
which can be overridden by an architecture.

Signed-off-by: Thomas Gleixner 
Tested-by: Vincenzo Frascino 
Reviewed-by: Vincenzo Frascino 
Link: https://lkml.kernel.org/r/20200207124402.530143168@linutronix.de

lib/vdso: Only read hrtimer_res when needed in __cvdso_clock_getres()

2020-01-16T20:24:46+00:00

Only perform READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res) for
HRES and RAW clocks.

Signed-off-by: Christophe Leroy 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/7ac2f0d21652f95e2bbdfa6bd514ae6c7caf53ab.1579196675.git.christophe.leroy@c-s.fr