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powerpc/time: Fix mftb()/get_tb() for use with the compat VDSO

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When we're building the compat VDSO we are building 32-bit code but in
the context of a 64-bit kernel configuration.

To make this work we need to be careful in some places when using
ifdefs to differentiate between CONFIG_PPC64 and __powerpc64__.

CONFIG_PPC64 indicates the kernel we're building is 64-bit, but it
doesn't tell us that we're currently building 64-bit code - we could
be building 32-bit code for the compat VDSO.

On the other hand __powerpc64__ tells us that we are currently
building 64-bit code (and therefore we must also be building a 64-bit
kernel).

In the case of get_tb() we want to use the 32-bit code sequence
regardless of whether the kernel we're building for is 64-bit or
32-bit, what matters is the word size of the current object. So we
need to check __powerpc64__ to decide if we use mftb() or the
mftbu()/mftb() sequence.

For mftb() the logic for CPU_FTR_CELL_TB_BUG only makes sense if we're
building 64-bit code, so guard that with a __powerpc64__ check.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201126131006.2431205-4-mpe@ellerman.id.au
This commit is contained in:
Michael Ellerman 2020-11-27 00:10:01 +11:00
parent d26b3817d9
commit 5c189c523e
1 changed files with 10 additions and 2 deletions
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12
arch/powerpc/include/asm/vdso/timebase.h
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@ -8,7 +8,11 @@
#include <asm/reg.h>
#if defined(CONFIG_PPC_CELL) || defined(CONFIG_E500)
/*
* We use __powerpc64__ here because we want the compat VDSO to use the 32-bit
* version below in the else case of the ifdef.
*/
#if defined(__powerpc64__) && (defined(CONFIG_PPC_CELL) || defined(CONFIG_E500))
#define mftb() ({unsigned long rval; \
asm volatile( \
"90: mfspr %0, %2;\n" \
@ -49,7 +53,11 @@ static inline u64 get_tb(void)
{
unsigned int tbhi, tblo, tbhi2;
if (IS_ENABLED(CONFIG_PPC64))
/*
* We use __powerpc64__ here not CONFIG_PPC64 because we want the compat
* VDSO to use the 32-bit compatible version in the while loop below.
*/
if (__is_defined(__powerpc64__))
return mftb();
do {