arch: riscv + xtensa + x86: workaround needed for LLVM linker

Due to slight differences in the way that LLVM and GNU linkers work, the call to `z_stack_space_get()` is not dead-stripped when linking with `lld` but it is dead-stripped when linking with GNU `ld`. The `z_stack_space_get()` function is only available when `CONFIG_INIT_STACKS` and `CONFIG_THREAD_STACK_INFO` are defined. The issue is reproducible (although requires building LLVM and setting up some environment variables) and goes away with the proposed workaround. Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

Author: cfriedt

arch/riscv/core/thread.c

@@ -207,6 +207,15 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 int arch_thread_priv_stack_space_get(const struct k_thread *thread, size_t *stack_size,
  size_t *unused_ptr)
 {
+if (!IS_ENABLED(CONFIG_INIT_STACKS) || !IS_ENABLED(CONFIG_THREAD_STACK_INFO)) {
+/*
+ * This is needed to ensure that the call to z_stack_space_get() below is properly
+ * dead-stripped when linking using LLVM / lld. For more info, please see issue
+ * #98491.
+ */
+return -EINVAL;
+}
+
 if ((thread->base.user_options & K_USER) != K_USER) {
 return -EINVAL;
 }

arch/x86/core/userspace.c

@@ -189,6 +189,15 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 int arch_thread_priv_stack_space_get(const struct k_thread *thread, size_t *stack_size,
  size_t *unused_ptr)
 {
+if (!IS_ENABLED(CONFIG_INIT_STACKS) || !IS_ENABLED(CONFIG_THREAD_STACK_INFO)) {
+/*
+ * This is needed to ensure that the call to z_stack_space_get() below is properly
+ * dead-stripped when linking using LLVM / lld. For more info, please see issue
+ * #98491.
+ */
+return -EINVAL;
+}
+
 struct z_x86_thread_stack_header *hdr_stack_obj;
 
 if ((thread->base.user_options & K_USER) != K_USER) {

arch/xtensa/core/thread.c

@@ -240,6 +240,15 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 int arch_thread_priv_stack_space_get(const struct k_thread *thread, size_t *stack_size,
  size_t *unused_ptr)
 {
+if (!IS_ENABLED(CONFIG_INIT_STACKS) || !IS_ENABLED(CONFIG_THREAD_STACK_INFO)) {
+/*
+ * This is needed to ensure that the call to z_stack_space_get() below is properly
+ * dead-stripped when linking using LLVM / lld. For more info, please see issue
+ * #98491.
+ */
+return -EINVAL;
+}
+
 struct xtensa_thread_stack_header *hdr_stack_obj;
 
 if ((thread->base.user_options & K_USER) != K_USER) {