x86: Fix do_go_exec() - const argv[]

Commit 54841ab50c20d6fa6c9cc3eb826989da3a22d934 made the argv parameter
to do_go_exec() const but did not allow for the fact that argv[-1] is
set to point to the global data structure and relies on argv being non-
const.

With this patch, do_go_exec() creates a new copy of the argv array with
an extra element to store global data pointer rather than simply
clobbering an arbitrary memory location.

diff --git a/arch/i386/lib/board.c b/arch/i386/lib/board.c
index 684cdb84a3340e88dae75ad0064e41da7c6b6520..93f910b4955ff16d4c7974fe4d366b1eb8921e3a 100644 (file)
--- a/arch/i386/lib/board.c
+++ b/arch/i386/lib/board.c
@@ -431,15 +431,30 @@ void hang (void)
        for (;;);
 }
 
-unsigned long do_go_exec (ulong (*entry)(int, char *[]), int argc, char * const argv[])
+unsigned long do_go_exec (ulong (*entry)(int, char * const []), int argc, char * const argv[])
 {
+       unsigned long ret = 0;
+       char **argv_tmp;
+
        /*
-        * x86 does not use a dedicated register to pass the pointer
-        * to the global_data
+        * x86 does not use a dedicated register to pass the pointer to
+        * the global_data, so it is instead passed as argv[-1]. By using
+        * argv[-1], the called 'Application' can use the contents of
+        * argv natively. However, to safely use argv[-1] a new copy of
+        * argv is needed with the extra element
         */
-       argv[-1] = (char *)gd;
+       argv_tmp = malloc(sizeof(char *) * (argc + 1));
+
+       if (argv_tmp) {
+               argv_tmp[0] = (char *)gd;
+
+               memcpy(&argv_tmp[1], argv, (size_t)(sizeof(char *) * argc));
+
+               ret = (entry) (argc, &argv_tmp[1]);
+               free(argv_tmp);
+       }
 
-       return (entry) (argc, argv);
+       return ret;
 }
 
 void setup_pcat_compatibility(void)