Add command-line argument and environment syscalls

Author: acfoltzer

basics/libc/crt1.c

@@ -1,14 +1,76 @@
+#include <stdlib.h>
+#include <sysexits.h>
+#include <wasi/core.h>
+
+extern char **environ;
 extern void __wasm_call_ctors(void);
 extern int main(int, char *[]);
 extern void __prepare_for_exit(void);
 void _Exit(int) __attribute__((noreturn));
 
+static __wasi_errno_t populate_args(size_t *argc, char **argv) {
+    __wasi_errno_t err;
+
+    /* Get the sizes of the arrays we'll have to create to copy in the args. */
+    size_t argv_size;
+    err = __wasi_arg_sizes_get(argc, &argv_size);
+    if (err != __WASI_ESUCCESS) {
+        return err;
+    }
+
+    /* Allocate memory for the array of pointers. */
+    argv = malloc(sizeof(char *) * *argc);
+    /* Allocate memory for storing the argument chars. */
+    char *argv_buf = malloc(sizeof(char) * argv_size);
+    if (argv == NULL || argv_buf == NULL) {
+        return __WASI_ENOMEM;
+    }
+
+    /* Fill the argument chars, and the argv array with pointers into those chars. */
+    return __wasi_argv_get(argv, argv_buf);
+}
+
+static __wasi_errno_t populate_environ() {
+    __wasi_errno_t err;
+
+    /* Get the sizes of the arrays we'll have to create to copy in the environment. */
+    size_t environ_count;
+    size_t environ_size;
+    err = __wasi_environ_sizes_get(&environ_count, &environ_size);
+    if (err != __WASI_ESUCCESS) {
+        return err;
+    }
+
+    /* Allocate memory for the array of pointers. */
+    environ = malloc(sizeof(char *) * environ_count);
+    /* Allocate memory for storing the environment chars. */
+    char *environ_buf = malloc(sizeof(char) * environ_size);
+    if (environ == NULL || environ_buf == NULL) {
+        return __WASI_ENOMEM;
+    }
+
+    /* Fill the environment chars, and the __environ array with pointers into those chars. */
+    return __wasi_environ_get(environ, environ_buf);
+}
+
 void _start(void) {
     /* The linker synthesizes this to call constructors. */
     __wasm_call_ctors();
 
-    /* For now, just call main with no arguments. */
-    int r = main(0, 0);
+    /* Fill in the environment from WASI syscalls. */
+    if (populate_environ() != __WASI_ESUCCESS) {
+        _Exit(EX_OSERR);
+    }
+
+    /* Fill in the arguments from WASI syscalls. */
+    size_t argc;
+    char **argv;
+    if (populate_args(&argc, argv) != __WASI_ESUCCESS) {
+        _Exit(EX_OSERR);
+    }
+
+    /* Call main with the arguments. */
+    int r = main(argc, argv);
 
     /* Call atexit functions, destructors, stdio cleanup, etc. */
     __prepare_for_exit();

expected/wasm32-wasi/undefined-symbols.txt

@@ -23,8 +23,12 @@ __subtf3
 __trunctfdf2
 __trunctfsf2
 __unordtf2
+__wasi_arg_sizes_get
+__wasi_argv_get
 __wasi_clock_res_get
 __wasi_clock_time_get
+__wasi_environ_get
+__wasi_environ_sizes_get
 __wasi_fd_advise
 __wasi_fd_allocate
 __wasi_fd_close

libc-bottom-half/headers/public/wasi/core.h

@@ -426,6 +426,16 @@ _Static_assert(_Alignof(__wasi_subscription_t) == 8, "non-wasi data layout");
 #define __WASI_SYSCALL_NAME(name) \
     __attribute__((__import_module__("wasi_unstable"), __import_name__(#name)))
 
+__wasi_errno_t __wasi_arg_sizes_get(
+    size_t *argc,
+    size_t *argv_size
+) __WASI_SYSCALL_NAME(arg_sizes_get) __attribute__((__warn_unused_result__));
+
+__wasi_errno_t __wasi_argv_get(
+    char **argv,
+    char *argv_buf
+) __WASI_SYSCALL_NAME(argv_get) __attribute__((__warn_unused_result__));
+
 __wasi_errno_t __wasi_clock_res_get(
     __wasi_clockid_t clock_id,
     __wasi_timestamp_t *resolution
@@ -437,6 +447,16 @@ __wasi_errno_t __wasi_clock_time_get(
     __wasi_timestamp_t *time
 ) __WASI_SYSCALL_NAME(clock_time_get) __attribute__((__warn_unused_result__));
 
+__wasi_errno_t __wasi_environ_get(
+    char **environ,
+    char *environ_buf
+) __WASI_SYSCALL_NAME(environ_get) __attribute__((__warn_unused_result__));
+
+__wasi_errno_t __wasi_environ_sizes_get(
+    size_t *environ_count,
+    size_t *environ_size
+) __WASI_SYSCALL_NAME(environ_sizes_get) __attribute__((__warn_unused_result__));
+
 __wasi_errno_t __wasi_fd_close(
     __wasi_fd_t fd
 ) __WASI_SYSCALL_NAME(fd_close) __attribute__((__warn_unused_result__));