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

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
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
arch/x86/entry/vdso/vdso32/fake_32bit_build.h Normal file
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@ -0,0 +1,25 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifdef CONFIG_X86_64
/*
* in case of a 32 bit VDSO for a 64 bit kernel fake a 32 bit kernel
* configuration
*/
#undef CONFIG_64BIT
#undef CONFIG_X86_64
#undef CONFIG_COMPAT
#undef CONFIG_PGTABLE_LEVELS
#undef CONFIG_ILLEGAL_POINTER_VALUE
#undef CONFIG_SPARSEMEM_VMEMMAP
#undef CONFIG_NR_CPUS
#undef CONFIG_PARAVIRT_XXL
#define CONFIG_X86_32 1
#define CONFIG_PGTABLE_LEVELS 2
#define CONFIG_PAGE_OFFSET 0
#define CONFIG_ILLEGAL_POINTER_VALUE 0
#define CONFIG_NR_CPUS 1
#define BUILD_VDSO32_64
#endif

27
arch/x86/entry/vdso/vdso32/vclock_gettime.c
View File

@ -1,29 +1,4 @@
// SPDX-License-Identifier: GPL-2.0
#define BUILD_VDSO32
#ifdef CONFIG_X86_64
/*
* in case of a 32 bit VDSO for a 64 bit kernel fake a 32 bit kernel
* configuration
*/
#undef CONFIG_64BIT
#undef CONFIG_X86_64
#undef CONFIG_COMPAT
#undef CONFIG_PGTABLE_LEVELS
#undef CONFIG_ILLEGAL_POINTER_VALUE
#undef CONFIG_SPARSEMEM_VMEMMAP
#undef CONFIG_NR_CPUS
#undef CONFIG_PARAVIRT_XXL
#define CONFIG_X86_32 1
#define CONFIG_PGTABLE_LEVELS 2
#define CONFIG_PAGE_OFFSET 0
#define CONFIG_ILLEGAL_POINTER_VALUE 0
#define CONFIG_NR_CPUS 1
#define BUILD_VDSO32_64
#endif
#include "fake_32bit_build.h"
#include "../vclock_gettime.c"

1
arch/x86/entry/vdso/vdso32/vgetcpu.c
View File

@ -1,2 +1,3 @@
// SPDX-License-Identifier: GPL-2.0
#include "fake_32bit_build.h"
#include "../vgetcpu.c"