tools/nolibc: pass argc, argv and envp to constructors

Since 2005 glibc has passed argc, argv, and envp to all constructors.
As it is cheap and easy to do so, mirror that behaviour in nolibc.
This makes it easier to migrate applications to nolibc.

Link: https://lore.kernel.org/r/20240728-nolibc-constructor-args-v1-1-36d0bf5cd4c0@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Author: t-8ch

tools/include/nolibc/crt.h

@@ -13,11 +13,11 @@ const unsigned long *_auxv __attribute__((weak));
 static void __stack_chk_init(void);
 static void exit(int);
 
-extern void (*const __preinit_array_start[])(void) __attribute__((weak));
-extern void (*const __preinit_array_end[])(void) __attribute__((weak));
+extern void (*const __preinit_array_start[])(int, char **, char**) __attribute__((weak));
+extern void (*const __preinit_array_end[])(int, char **, char**) __attribute__((weak));
 
-extern void (*const __init_array_start[])(void) __attribute__((weak));
-extern void (*const __init_array_end[])(void) __attribute__((weak));
+extern void (*const __init_array_start[])(int, char **, char**) __attribute__((weak));
+extern void (*const __init_array_end[])(int, char **, char**) __attribute__((weak));
 
 extern void (*const __fini_array_start[])(void) __attribute__((weak));
 extern void (*const __fini_array_end[])(void) __attribute__((weak));
@@ -29,7 +29,8 @@ void _start_c(long *sp)
 	char **argv;
 	char **envp;
 	int exitcode;
-	void (* const *func)(void);
+	void (* const *ctor_func)(int, char **, char **);
+	void (* const *dtor_func)(void);
 	const unsigned long *auxv;
 	/* silence potential warning: conflicting types for 'main' */
 	int _nolibc_main(int, char **, char **) __asm__ ("main");
@@ -66,16 +67,16 @@ void _start_c(long *sp)
 		;
 	_auxv = auxv;
 
-	for (func = __preinit_array_start; func < __preinit_array_end; func++)
-		(*func)();
-	for (func = __init_array_start; func < __init_array_end; func++)
-		(*func)();
+	for (ctor_func = __preinit_array_start; ctor_func < __preinit_array_end; ctor_func++)
+		(*ctor_func)(argc, argv, envp);
+	for (ctor_func = __init_array_start; ctor_func < __init_array_end; ctor_func++)
+		(*ctor_func)(argc, argv, envp);
 
 	/* go to application */
 	exitcode = _nolibc_main(argc, argv, envp);
 
-	for (func = __fini_array_end; func > __fini_array_start;)
-		(*--func)();
+	for (dtor_func = __fini_array_end; dtor_func > __fini_array_start;)
+		(*--dtor_func)();
 
 	exit(exitcode);
 }

tools/testing/selftests/nolibc/nolibc-test.c

@@ -686,9 +686,10 @@ static void constructor1(void)
 }
 
 __attribute__((constructor))
-static void constructor2(void)
+static void constructor2(int argc, char **argv, char **envp)
 {
-	constructor_test_value *= 2;
+	if (argc && argv && envp)
+		constructor_test_value *= 2;
 }
 
 int run_startup(int min, int max)