Add support for pthread_getattr_np (#470)

Author: Milek7

Makefile

@@ -258,6 +258,7 @@ LIBC_TOP_HALF_MUSL_SOURCES += \
         thread/pthread_create.c \
         thread/pthread_detach.c \
         thread/pthread_equal.c \
+        thread/pthread_getattr_np.c \
         thread/pthread_getspecific.c \
         thread/pthread_join.c \
         thread/pthread_key_create.c \

expected/wasm32-wasip1-threads/defined-symbols.txt

@@ -1010,6 +1010,7 @@ pthread_condattr_setpshared
 pthread_create
 pthread_detach
 pthread_equal
+pthread_getattr_np
 pthread_getspecific
 pthread_join
 pthread_key_create

libc-top-half/musl/src/env/__init_tls.c

@@ -31,25 +31,35 @@ extern unsigned char __global_base;
 extern weak unsigned char __stack_high;
 extern weak unsigned char __stack_low;
 
-static inline void setup_default_stack_size()
+struct stack_bounds {
+	void *base;
+	size_t size;
+};
+
+static inline struct stack_bounds get_stack_bounds()
 {
-	ptrdiff_t stack_size;
+	struct stack_bounds bounds;
 
-	if (&__stack_high)
-		stack_size = &__stack_high - &__stack_low;
-	else {
+	if (&__stack_high) {
+		bounds.base = &__stack_high;
+		bounds.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 (sp > &__global_base) {
+			bounds.base = &__heap_base;
+			bounds.size = &__heap_base - &__data_end;
+		} else {
+			bounds.base = &__global_base;
+			bounds.size = (size_t)&__global_base;
+		}
 	}
 
-	__default_stacksize =
-		stack_size < DEFAULT_STACK_MAX ?
-		stack_size : DEFAULT_STACK_MAX;
+	return bounds;
 }
 
 void __wasi_init_tp() {
@@ -68,8 +78,14 @@ int __init_tp(void *p)
 	td->detach_state = DT_JOINABLE;
 	td->tid = __syscall(SYS_set_tid_address, &__thread_list_lock);
 #else
-	setup_default_stack_size();
+	struct stack_bounds bounds = get_stack_bounds();
+	__default_stacksize =
+		bounds.size < DEFAULT_STACK_MAX ?
+		bounds.size : DEFAULT_STACK_MAX;
 	td->detach_state = DT_JOINABLE;
+	td->stack = bounds.base;
+	td->stack_size = bounds.size;
+	td->guard_size = 0;
 	/*
 	 * Initialize the TID to a value which doesn't conflict with
 	 * host-allocated TIDs, so that TID-based locks can work.

libc-top-half/musl/src/thread/pthread_getattr_np.c

@@ -1,7 +1,9 @@
 #define _GNU_SOURCE
 #include "pthread_impl.h"
 #include "libc.h"
+#ifdef __wasilibc_unmodified_upstream
 #include <sys/mman.h>
+#endif
 
 int pthread_getattr_np(pthread_t t, pthread_attr_t *a)
 {
@@ -12,13 +14,17 @@ int pthread_getattr_np(pthread_t t, pthread_attr_t *a)
 		a->_a_stackaddr = (uintptr_t)t->stack;
 		a->_a_stacksize = t->stack_size;
 	} else {
+#ifdef __wasilibc_unmodified_upstream
 		char *p = (void *)libc.auxv;
 		size_t l = PAGE_SIZE;
 		p += -(uintptr_t)p & PAGE_SIZE-1;
 		a->_a_stackaddr = (uintptr_t)p;
 		while (mremap(p-l-PAGE_SIZE, PAGE_SIZE, 2*PAGE_SIZE, 0)==MAP_FAILED && errno==ENOMEM)
 			l += PAGE_SIZE;
 		a->_a_stacksize = l;
+#else
+		return ENOSYS;
+#endif
 	}
 	return 0;
 }