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

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

Posted by Sebastian Andrzej Siewior 2 years, 7 months ago

The 64bit register constrains in __arch_hweight64() can not be
fulfilled in a 32bit build. The function is only declared, not used
within vclock_gettime.c and gcc does not care. LLVM complains and
aborts.

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.

Fixes: 92d33063c081a ("x86/vdso: Provide getcpu for x86-32.")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 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 0000000000000..db1b15f686e32
--- /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 283ed9d004267..86981decfea83 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 b777f84ffae9b..3a9791f5e9989 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"
-- 
2.39.1

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

Posted by Nathan Chancellor 2 years, 7 months ago

On Tue, Feb 07, 2023 at 11:46:33AM +0100, Sebastian Andrzej Siewior wrote:
> The 64bit register constrains in __arch_hweight64() can not be
> fulfilled in a 32bit build. The function is only declared, not used
> within vclock_gettime.c and gcc does not care. LLVM complains and
> aborts.
> 
> 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.
> 
> Fixes: 92d33063c081a ("x86/vdso: Provide getcpu for x86-32.")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Thank you so much for the fix! Boris inquired why this happens with
clang and I wrote a little blurb here if that is helpful at all:

https://lore.kernel.org/Y+J+UQ1vAKr6RHuH@dev-arch.thelio-3990X/

Regardless, this works for me.

Tested-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  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 0000000000000..db1b15f686e32
> --- /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 283ed9d004267..86981decfea83 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 b777f84ffae9b..3a9791f5e9989 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"
> -- 
> 2.39.1
>

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

Posted by Damian Tometzki 2 years, 7 months ago

Hello Sebastian,
Linux Kernel build 6.2.0rc7 was successfully with clang-17.

Many Thanks
Damian Tometzki


On Tue, 07. Feb 11:46, Sebastian Andrzej Siewior wrote:
> The 64bit register constrains in __arch_hweight64() can not be
> fulfilled in a 32bit build. The function is only declared, not used
> within vclock_gettime.c and gcc does not care. LLVM complains and
> aborts.
> 
> 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.
> 
> Fixes: 92d33063c081a ("x86/vdso: Provide getcpu for x86-32.")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  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 0000000000000..db1b15f686e32
> --- /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 283ed9d004267..86981decfea83 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 b777f84ffae9b..3a9791f5e9989 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"
> -- 
> 2.39.1
>

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

Posted by tip-bot2 for Sebastian Andrzej Siewior 2 years, 7 months ago

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@linutronix.de>
AuthorDate:    Tue, 07 Feb 2023 11:46:33 +01:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
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@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
---
 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"