[PATCH] x86: Fix build of UML with KASAN

[Vincent Whitchurch]

Building UML with KASAN fails since commit 69d4c0d32186 ("entry, kasan,
x86: Disallow overriding mem*() functions") with the following errors:

 $ tools/testing/kunit/kunit.py run --kconfig_add CONFIG_KASAN=y
 ...
 ld: mm/kasan/shadow.o: in function `memset':
 shadow.c:(.text+0x40): multiple definition of `memset';
 arch/x86/lib/memset_64.o:(.noinstr.text+0x0): first defined here
 ld: mm/kasan/shadow.o: in function `memmove':
 shadow.c:(.text+0x90): multiple definition of `memmove';
 arch/x86/lib/memmove_64.o:(.noinstr.text+0x0): first defined here
 ld: mm/kasan/shadow.o: in function `memcpy':
 shadow.c:(.text+0x110): multiple definition of `memcpy';
 arch/x86/lib/memcpy_64.o:(.noinstr.text+0x0): first defined here

If I'm reading that commit right, the !GENERIC_ENTRY case is still
supposed to be allowed to override the mem*() functions, so use weak
aliases in that case.

Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
---
 arch/x86/lib/memcpy_64.S  | 4 ++++
 arch/x86/lib/memmove_64.S | 4 ++++
 arch/x86/lib/memset_64.S  | 4 ++++
 3 files changed, 12 insertions(+)

diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 8f95fb267caa7..5dc265b36ef0b 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -40,7 +40,11 @@ SYM_TYPED_FUNC_START(__memcpy)
 SYM_FUNC_END(__memcpy)
 EXPORT_SYMBOL(__memcpy)
 
+#ifdef CONFIG_GENERIC_ENTRY
 SYM_FUNC_ALIAS(memcpy, __memcpy)
+#else
+SYM_FUNC_ALIAS_WEAK(memcpy, __memcpy)
+#endif
 EXPORT_SYMBOL(memcpy)
 
 SYM_FUNC_START_LOCAL(memcpy_orig)
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index 02661861e5dd9..3b1a02357fb29 100644
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -215,5 +215,9 @@ SYM_FUNC_START(__memmove)
 SYM_FUNC_END(__memmove)
 EXPORT_SYMBOL(__memmove)
 
+#ifdef CONFIG_GENERIC_ENTRY
 SYM_FUNC_ALIAS(memmove, __memmove)
+#else
+SYM_FUNC_ALIAS_WEAK(memmove, __memmove)
+#endif
 EXPORT_SYMBOL(memmove)
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 7c59a704c4584..fe27538a355db 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -40,7 +40,11 @@ SYM_FUNC_START(__memset)
 SYM_FUNC_END(__memset)
 EXPORT_SYMBOL(__memset)
 
+#ifdef CONFIG_GENERIC_ENTRY
 SYM_FUNC_ALIAS(memset, __memset)
+#else
+SYM_FUNC_ALIAS_WEAK(memset, __memset)
+#endif
 EXPORT_SYMBOL(memset)
 
 SYM_FUNC_START_LOCAL(memset_orig)

---
base-commit: 9561de3a55bed6bdd44a12820ba81ec416e705a7
change-id: 20230609-uml-kasan-2392dd4c3858

Best regards,
-- 
Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>