Make do_execve() take a const filename pointer

Make do_execve() take a const filename pointer so that kernel_execve() compiles
correctly on ARM:

arch/arm/kernel/sys_arm.c:88: warning: passing argument 1 of 'do_execve' discards qualifiers from pointer target type

This also requires the argv and envp arguments to be consted twice, once for
the pointer array and once for the strings the array points to.  This is
because do_execve() passes a pointer to the filename (now const) to
copy_strings_kernel().  A simpler alternative would be to cast the filename
pointer in do_execve() when it's passed to copy_strings_kernel().

do_execve() may not change any of the strings it is passed as part of the argv
or envp lists as they are some of them in .rodata, so marking these strings as
const should be fine.

Further kernel_execve() and sys_execve() need to be changed to match.

This has been test built on x86_64, frv, arm and mips.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 7 insertions, 6 deletions

diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index 2b108538d0d9..3098a38f3ae1 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -24,10 +24,11 @@ static int __init no_initrd(char *str)
 
 __setup("noinitrd", no_initrd);
 
-static int __init do_linuxrc(void * shell)
+static int __init do_linuxrc(void *_shell)
 {
-        static char *argv[] = { "linuxrc", NULL, };
-        extern char * envp_init[];
+        static const char *argv[] = { "linuxrc", NULL, };
+        extern const char *envp_init[];
+        const char *shell = _shell;
 
         sys_close(old_fd);sys_close(root_fd);
         sys_setsid();
diff --git a/init/main.c b/init/main.c
index 22d61cb06f98..94ab488039aa 100644
--- a/init/main.c
+++ b/init/main.c
@@ -197,8 +197,8 @@ static int __init set_reset_devices(char *str)
 
 __setup("reset_devices", set_reset_devices);
 
-static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
-char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
+static const char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
+const char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
 static const char *panic_later, *panic_param;
 
 extern const struct obs_kernel_param __setup_start[], __setup_end[];
@@ -809,7 +809,7 @@ static void __init do_pre_smp_initcalls(void)
                 do_one_initcall(*fn);
 }
 
-static void run_init_process(char *init_filename)
+static void run_init_process(const char *init_filename)
 {
         argv_init[0] = init_filename;
         kernel_execve(init_filename, argv_init, envp_init);