A recent optimization change in LLVM [1] aims to transform certain loop idioms into calls to strlen() or wcslen(). This change transforms the first while loop in UniStrcat() into a call to wcslen(), breaking the build when UniStrcat() gets inlined into alloc_path_with_tree_prefix():
ld.lld: error: undefined symbol: wcslen
referenced by nls_ucs2_utils.h:54 (fs/smb/client/../../nls/nls_ucs2_utils.h:54) vmlinux.o:(alloc_path_with_tree_prefix) referenced by nls_ucs2_utils.h:54 (fs/smb/client/../../nls/nls_ucs2_utils.h:54) vmlinux.o:(alloc_path_with_tree_prefix)
The kernel does not build with '-ffreestanding' (which would avoid this transformation) because it does want libcall optimizations in general and turning on '-ffreestanding' disables the majority of them. While '-fno-builtin-wcslen' would be more targeted at the problem, it does not work with LTO.
Add a basic wcslen() to avoid this linkage failure. While no architecture or FORTIFY_SOURCE overrides this, add it to string.c instead of string_helpers.c so that it is built with '-ffreestanding', otherwise the compiler might transform it into a call to itself.
Cc: stable@vger.kernel.org Link: https://github.com/llvm/llvm-project/commit/9694844d7e36fd5e01011ab56b64f27b... [1] Signed-off-by: Nathan Chancellor nathan@kernel.org --- include/linux/string.h | 2 ++ lib/string.c | 11 +++++++++++ 2 files changed, 13 insertions(+)
diff --git a/include/linux/string.h b/include/linux/string.h index 0403a4ca4c11..b000f445a2c7 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -10,6 +10,7 @@ #include <linux/stddef.h> /* for NULL */ #include <linux/err.h> /* for ERR_PTR() */ #include <linux/errno.h> /* for E2BIG */ +#include <linux/nls_types.h> /* for wchar_t */ #include <linux/overflow.h> /* for check_mul_overflow() */ #include <linux/stdarg.h> #include <uapi/linux/string.h> @@ -203,6 +204,7 @@ extern __kernel_size_t strlen(const char *); #ifndef __HAVE_ARCH_STRNLEN extern __kernel_size_t strnlen(const char *,__kernel_size_t); #endif +__kernel_size_t wcslen(const wchar_t *s); #ifndef __HAVE_ARCH_STRPBRK extern char * strpbrk(const char *,const char *); #endif diff --git a/lib/string.c b/lib/string.c index eb4486ed40d2..2c6f8c8f4159 100644 --- a/lib/string.c +++ b/lib/string.c @@ -21,6 +21,7 @@ #include <linux/errno.h> #include <linux/limits.h> #include <linux/linkage.h> +#include <linux/nls_types.h> #include <linux/stddef.h> #include <linux/string.h> #include <linux/types.h> @@ -429,6 +430,16 @@ size_t strnlen(const char *s, size_t count) EXPORT_SYMBOL(strnlen); #endif
+size_t wcslen(const wchar_t *s) +{ + const wchar_t *sc; + + for (sc = s; *sc != '\0'; ++sc) + /* nothing */; + return sc - s; +} +EXPORT_SYMBOL(wcslen); + #ifndef __HAVE_ARCH_STRSPN /** * strspn - Calculate the length of the initial substring of @s which only contain letters in @accept