On Wed, Mar 26, 2025 at 7:19 PM Nathan Chancellor <[email protected]> wrote: > > 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.
... > --- a/include/linux/string.h > +++ b/include/linux/string.h > @@ -7,6 +7,7 @@ > #include <linux/cleanup.h> /* for DEFINE_FREE() */ > #include <linux/compiler.h> /* for inline */ > #include <linux/types.h> /* for size_t */ > +#include <linux/nls_types.h> /* for wchar_t */ I know it's not ordered, but can we at least not make it worse, i.e. squeeze this to be after the compiler.h? Or even somewhere after below the err*.h? Whatever gives a better (sparsely) ordered overall result... > #include <linux/stddef.h> /* for NULL */ > #include <linux/err.h> /* for ERR_PTR() */ ... > #ifndef __HAVE_ARCH_STRNLEN > extern __kernel_size_t strnlen(const char *,__kernel_size_t); > #endif > +extern __kernel_size_t wcslen(const wchar_t *s); I'm wondering why we still continue putting this 'extern' keyword. Yes, I see that the rest is like this, but for new code do we really need it? > #ifndef __HAVE_ARCH_STRPBRK > extern char * strpbrk(const char *,const char *); > #endif -- With Best Regards, Andy Shevchenko
