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

[tip-bot2 for Sebastian Andrzej Siewior]

The following commit has been merged into the x86/vdso branch of tip:

Commit-ID:     877cff5296faa6ef312f8002216bbf73bea006c7
Gitweb:        https://git.kernel.org/tip/877cff5296faa6ef312f8002216bbf73bea006c7
Author:        Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate:    Tue, 07 Feb 2023 11:46:33 +01:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 07 Feb 2023 18:20:41 +01:00

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: 92d33063c081a ("x86/vdso: Provide getcpu for x86-32.")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/Y+IsCWQdXEr8d9Vy@xxxxxxxxxxxxx
---
 arch/x86/entry/vdso/vdso32/fake_32bit_build.h | 25 +++++++++++++++++-
 arch/x86/entry/vdso/vdso32/vclock_gettime.c   | 27 +------------------
 arch/x86/entry/vdso/vdso32/vgetcpu.c          |  1 +-
 3 files changed, 27 insertions(+), 26 deletions(-)
 create mode 100644 arch/x86/entry/vdso/vdso32/fake_32bit_build.h

diff --git a/arch/x86/entry/vdso/vdso32/fake_32bit_build.h b/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
new file mode 100644
index 0000000..db1b15f
--- /dev/null
+++ b/arch/x86/entry/vdso/vdso32/fake_32bit_build.h
@@ -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
diff --git a/arch/x86/entry/vdso/vdso32/vclock_gettime.c b/arch/x86/entry/vdso/vdso32/vclock_gettime.c
index 283ed9d..86981de 100644
--- a/arch/x86/entry/vdso/vdso32/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vdso32/vclock_gettime.c
@@ -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"
diff --git a/arch/x86/entry/vdso/vdso32/vgetcpu.c b/arch/x86/entry/vdso/vdso32/vgetcpu.c
index b777f84..3a9791f 100644
--- a/arch/x86/entry/vdso/vdso32/vgetcpu.c
+++ b/arch/x86/entry/vdso/vdso32/vgetcpu.c
@@ -1,2 +1,3 @@
 // SPDX-License-Identifier: GPL-2.0
+#include "fake_32bit_build.h"
 #include "../vgetcpu.c"