From 61df817d1d1bfe54c751e0f135aa1cdf817de4ad Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Fri, 28 Mar 2025 12:26:32 -0700 Subject: lib/string.c: Add wcslen() 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/9694844d7e36fd5e01011ab56b64f27b867aa72d [1] Signed-off-by: Nathan Chancellor Link: https://lore.kernel.org/r/20250328-string-add-wcslen-for-llvm-opt-v3-2-a180b4c0c1c4@kernel.org Signed-off-by: Kees Cook --- 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 0403a4ca4c116a..b000f445a2c716 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -10,6 +10,7 @@ #include /* for NULL */ #include /* for ERR_PTR() */ #include /* for E2BIG */ +#include /* for wchar_t */ #include /* for check_mul_overflow() */ #include #include @@ -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 eb4486ed40d259..2c6f8c8f415913 100644 --- a/lib/string.c +++ b/lib/string.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include @@ -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 -- cgit 1.2.3-korg