x86/vdso: Fake 32bit VDSO build on 64bit compile for vgetcpu

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The 64bit register constrains in __arch_hweight64() cannot be
fulfilled in a 32-bit build. The function is only declared but not used
within vclock_gettime.c and gcc does not care. LLVM complains and
aborts. Reportedly because it validates extended asm even if latter
would get compiled out, see

  https://lore.kernel.org/r/Y%2BJ%2BUQ1vAKr6RHuH@dev-arch.thelio-3990X

i.e., a long standing design difference between gcc and LLVM.

Move the "fake a 32 bit kernel configuration" bits from vclock_gettime.c
into a common header file. Use this from vclock_gettime.c and vgetcpu.c.

  [ bp: Add background info from Nathan. ]

Fixes: 92d33063c0 ("x86/vdso: Provide getcpu for x86-32.")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/Y+IsCWQdXEr8d9Vy@linutronix.de

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This commit is contained in:

Sebastian Andrzej Siewior 2023-02-07 11:46:33 +01:00 • committed by Borislav Petkov (AMD)

parent 5646bbd668

commit 877cff5296

3 changed files with 27 additions and 26 deletions

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25

arch/x86/entry/vdso/vdso32/fake_32bit_build.h

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27

arch/x86/entry/vdso/vdso32/vclock_gettime.c

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1

arch/x86/entry/vdso/vdso32/vgetcpu.c

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