Adjust TLS in wasip3 with threads

CMakeLists.txt

@@ -204,17 +204,6 @@ add_link_options(
   -resource-dir ${tmp_resource_dir}
 )
 
-if (HAVE_WASM_LIBCALL_THREAD_CONTEXT)
-  # TODO: shouldn't have to pass these as it means it's required by all end
-  # users as well. Ideally this would be part of the driver in rustc/clang, but
-  # that's left for a future change.
-  add_link_options(
-    -Wl,--export-if-defined=__wasm_init_tls
-    -Wl,--export-if-defined=__tls_size
-    -Wl,--export-if-defined=__tls_align
-  )
-endif()
-
 # Expose the public headers to the implementation. We use `-isystem` for
 # purpose for two reasons:
 #

libc-bottom-half/crt/wasip3_symbol_references.h

@@ -5,6 +5,7 @@
 #ifdef __wasm_libcall_thread_context__
 
 #include <wasi/version.h>
+#include <wasi/wasip3_tls.h>
 
 // Force some symbols to be linked in for wasip3
 extern void __wasm_init_task(void);
@@ -15,6 +16,30 @@ __attribute__((used)) static void *__wasm_init_async_task_ref =
     __wasm_init_async_task;
 __attribute__((used)) static void *cabi_realloc_ref = cabi_realloc;
 
+// Export a symbol from this object which describes the TLS information
+// required for this object. This encapsulates the size/align information as
+// well as an initialization function.
+//
+// Note that being part of `crt1-*.o` this is exported from all libraries,
+// which is what we want because each library has a unique return value from
+// `__builtin_wasm_tls_*` intrinsics and a separate `__wasm_init_tls` function.
+//
+// For more information on this see
+// https://github.com/WebAssembly/wasi-libc/issues/857 which has since been
+// adjusted with this scheme.
+static size_t tls_size_and_align(size_t *align) {
+  *align = __builtin_wasm_tls_align();
+  return __builtin_wasm_tls_size();
+}
+
+void __wasm_init_tls(void *base);
+
+__attribute__((visibility("default")))
+struct __wasilibc_library_tls_info __wasm_library_tls_info = {
+  .tls_size_and_align = tls_size_and_align,
+  .init_tls = __wasm_init_tls,
+};
+
 // Force `__wasm_{g,s}et_{stack_pointer,tls_base}` to exist as defined symbols.
 // These end up as imported functions which `wit-component` recognizes, and what
 // exactly they're hooked up to will depend on `wit-component` when this is

libc-top-half/headers/private/wasi/wasip3_tls.h

@@ -13,14 +13,18 @@
 #ifdef __wasm_libcall_thread_context__
 
 struct __wasilibc_library_tls_info {
-  size_t tls_size;
-  size_t tls_align;
+  // Stores this library's TLS alignment in `*align` and returns its TLS size.
+  //
+  // Note that a library with no thread-local storage at all reports a size of
+  // zero, but `*align` is always at least 1 so that callers can use it as a
+  // divisor/mask without special-casing.
+  size_t (*tls_size_and_align)(size_t *align);
   void (*init_tls)(void *);
 };
 
 struct __wasilibc_program_tls_info {
   size_t num_libraries;
-  const struct __wasilibc_library_tls_info *library_info;
+  const struct __wasilibc_library_tls_info **library_info;
   void **main_thread_tls_base;
 };
 

libc-top-half/musl/src/thread/coop-threads/pthread_create.c

@@ -164,10 +164,14 @@ static size_t thread_tls_size(size_t *align) {
   size_t result_align = _Alignof(void *);
 
   for (size_t i = 0; i < info->num_libraries; i++) {
-    const struct __wasilibc_library_tls_info *library = &info->library_info[i];
-    size = align_up(size, library->tls_align) + library->tls_size;
-    if (library->tls_align > result_align)
-      result_align = library->tls_align;
+    const struct __wasilibc_library_tls_info *library = info->library_info[i];
+    size_t library_align;
+    size_t library_size = library->tls_size_and_align(&library_align);
+    if (library_size == 0)
+      continue;
+    size = align_up(size, library_align) + library_size;
+    if (library_align > result_align)
+      result_align = library_align;
   }
 
   *align = result_align;
@@ -190,10 +194,14 @@ static void *layout_thread_tls(void *block) {
   void **bases = block;
   uintptr_t next = (uintptr_t)block + info->num_libraries * sizeof(void *);
   for (size_t i = 0; i < info->num_libraries; i++) {
-    const struct __wasilibc_library_tls_info *library = &info->library_info[i];
-    next = align_up(next, library->tls_align);
+    const struct __wasilibc_library_tls_info *library = info->library_info[i];
+    size_t library_align;
+    size_t library_size = library->tls_size_and_align(&library_align);
+    if (library_size == 0)
+      continue;
+    next = align_up(next, library_align);
     bases[i] = (void *)next;
-    next += library->tls_size;
+    next += library_size;
   }
   return bases;
 }
@@ -258,7 +266,7 @@ hidden void __wasi_coop_thread_start_C(struct start_args *args) {
     void **bases = args->tls_layout;
     size_t num_libraries = info->num_libraries;
     for (size_t i = 0; i < num_libraries; i++)
-      info->library_info[i].init_tls(bases[i]);
+      info->library_info[i]->init_tls(bases[i]);
   }
   *__pthread_self() = self_copy;
 

test/CMakeLists.txt

@@ -811,7 +811,6 @@ function(add_posix_test test_file)
   string(REPLACE "/" "_" test_name ${test_name})
   set(test_name "open_posix_test_${test_name}")
   set(test_file "${CMAKE_CURRENT_SOURCE_DIR}/open-posix-test-suite/${test_file}")
-  set_source_files_properties(${test_file} PROPERTIES GENERATED TRUE)
 
   add_test_pair(${test_name} ${test_file}
     CFLAGS -Wno-unused-parameter -Wno-unused-variable -Wno-sign-compare -Wno-unused-but-set-global