threads: Retrieve default stack size from __heap_base/__data_end (#350)

[wasi-libc.git] / libc-top-half / musl / src / env / __init_tls.c

diff --git a/libc-top-half/musl/src/env/__init_tls.c b/libc-top-half/musl/src/env/__init_tls.c
index ee785bc11e4c517d93c10b1e3a750366724497f3..5e32f5446ec7e53fa70dd12388fd25470a9cac96 100644 (file)
--- a/libc-top-half/musl/src/env/__init_tls.c
+++ b/libc-top-half/musl/src/env/__init_tls.c
@@ -16,6 +16,43 @@
 volatile int __thread_list_lock;
 
 #ifndef __wasilibc_unmodified_upstream
+
+/* These symbols are generated by wasm-ld. __stack_high/__stack_low
+ * symbols are only available in LLVM v16 and higher, therefore they're
+ * defined as weak symbols and if not available, __heap_base/__data_end
+ * is used instead.
+ *
+ * TODO: remove usage of __heap_base/__data_end for stack size calculation
+ * once we drop support for LLVM v15 and older.
+ */
+extern unsigned char __heap_base;
+extern unsigned char __data_end;
+extern unsigned char __global_base;
+extern weak unsigned char __stack_high;
+extern weak unsigned char __stack_low;
+
+static inline void setup_default_stack_size()
+{
+       ptrdiff_t stack_size;
+
+       if (&__stack_high)
+               stack_size = &__stack_high - &__stack_low;
+       else {
+               unsigned char *sp;
+               __asm__(
+                       ".globaltype __stack_pointer, i32\n"
+                       "global.get __stack_pointer\n"
+                       "local.set %0\n"
+                       : "=r"(sp));
+               stack_size = sp > &__global_base ? &__heap_base - &__data_end : (ptrdiff_t)&__global_base;
+       }
+
+       if (stack_size > __default_stacksize)
+               __default_stacksize =
+                       stack_size < DEFAULT_STACK_MAX ?
+                       stack_size : DEFAULT_STACK_MAX;
+}
+
 void __wasi_init_tp() {
        __init_tp((void *)__get_tp());
 }
@@ -31,6 +68,8 @@ int __init_tp(void *p)
        if (!r) libc.can_do_threads = 1;
        td->detach_state = DT_JOINABLE;
        td->tid = __syscall(SYS_set_tid_address, &__thread_list_lock);
+#else
+       setup_default_stack_size();
 #endif
        td->locale = &libc.global_locale;
        td->robust_list.head = &td->robust_list.head;