[PATCH] um: Use asm-generic/timex.h over the host architecture one

The removal of the architecture-specific asm/timex.h was meant to fall
back to asm-generic/timex.h. However on UML, the host architecture
headers are earlier on the include path and therefore asm/timex.h from
the host architecture is used.
On x86 that header in turn requires the generation of cpufeaturemasks.h,
which is not set up for UML and the build fails.

In file included from ../arch/x86/include/asm/tsc.h:9,
                 from ../arch/x86/include/asm/timex.h:6,
                 from ../include/linux/timex.h:67,
                 from ../include/linux/time32.h:13,
                 from ../include/linux/time.h:60,
                 from ../include/linux/jiffies.h:10,
                 from ../include/linux/ktime.h:25,
                 from ../include/linux/timer.h:6,
                 from ../include/linux/uprobes.h:18,
                 from ../include/linux/mm_types.h:16,
                 from ../include/linux/mmzone.h:22,
                 from ../include/linux/gfp.h:7,
                 from ../include/linux/slab.h:17,
                 from ../include/linux/crypto.h:18,
                 from ../arch/um/kernel/asm-offsets.c:6:
arch/x86/include/asm/tsc.h: In function ‘get_cycles’:
arch/um/include/asm/cpufeature.h:52:39: error: implicit declaration of function ‘DISABLED_MASK_BIT_SET’ [-Wimplicit-function-declaration]
   52 |         (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : _static_cpu_has(bit))
      |                                       ^~~~~~~~~~~~~~~~~~~~~
arch/x86/include/asm/tsc.h:79:14: note: in expansion of macro ‘cpu_feature_enabled’
   79 |         if (!cpu_feature_enabled(X86_FEATURE_TSC))
      |              ^~~~~~~~~~~~~~~~~~~
arch/um/include/asm/cpufeature.h:115:17: error: implicit declaration of function ‘_static_cpu_has’ [-Wimplicit-function-declaration]
  115 |                 _static_cpu_has(bit)                            \
      |                 ^~~~~~~~~~~~~~~
arch/um/include/asm/cpufeature.h:52:72: note: in expansion of macro ‘_static_cpu_has’
   52 |         (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : _static_cpu_has(bit))
      |                                                                        ^~~~~~~~~~~~~~~
arch/x86/include/asm/tsc.h:79:14: note: in expansion of macro ‘cpu_feature_enabled’
   79 |         if (!cpu_feature_enabled(X86_FEATURE_TSC))
      |              ^~~~~~~~~~~~~~~~~~~
arch/um/include/asm/cpufeature.h:115:17: note: ‘_static_cpu_has’ is a function-like macro and might be used incorrectly
arch/um/include/asm/cpufeature.h:52:72: note: in expansion of macro ‘_static_cpu_has’
   52 |         (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : _static_cpu_has(bit))
      |                                                                        ^~~~~~~~~~~~~~~
arch/x86/include/asm/tsc.h:79:14: note: in expansion of macro ‘cpu_feature_enabled’
   79 |         if (!cpu_feature_enabled(X86_FEATURE_TSC))
      |              ^~~~~~~~~~~~~~~~~~~

The x86-specific timex.h also doesn't make sense on UML in general.

Reintroduce the UML-specific asm/timex.h and add a comment to document
its necessity.

Fixes: 3ed403bbc967 ("treewide: Remove CLOCK_TICK_RATE")
Signed-off-by: Thomas Weißschuh <[email protected]>
---
 arch/um/include/asm/timex.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/um/include/asm/timex.h b/arch/um/include/asm/timex.h
new file mode 100644
index 000000000000..dfb4f460fb87
--- /dev/null
+++ b/arch/um/include/asm/timex.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_TIMEX_H
+#define __UM_TIMEX_H
+
+/* Do not fall back to the host architecture header. */
+#include <asm-generic/timex.h>
+
+#endif

---
base-commit: bd5f485f3f026225b86573e559af0b7254ef4184
change-id: 20260819-uml-timex-fix-fccb27f9ca51

Best regards,
--  
Thomas Weißschuh <[email protected]>