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, 6 insertions, 3 deletions

diff --git a/arch/avr32/kernel/process.c b/arch/avr32/kernel/process.c
index e5daddff397d..9c46aaad11ce 100644
--- a/arch/avr32/kernel/process.c
+++ b/arch/avr32/kernel/process.c
@@ -384,8 +384,9 @@ asmlinkage int sys_vfork(struct pt_regs *regs)
 }
 
 asmlinkage int sys_execve(const char __user *ufilename,
-                          char __user *__user *uargv,
-                          char __user *__user *uenvp, struct pt_regs *regs)
+                          const char __user *const __user *uargv,
+                          const char __user *const __user *uenvp,
+                          struct pt_regs *regs)
 {
         int error;
         char *filename;
diff --git a/arch/avr32/kernel/sys_avr32.c b/arch/avr32/kernel/sys_avr32.c
index 459349b5ed5a..62635a09ae3e 100644
--- a/arch/avr32/kernel/sys_avr32.c
+++ b/arch/avr32/kernel/sys_avr32.c
@@ -7,7 +7,9 @@
  */
 #include <linux/unistd.h>
 
-int kernel_execve(const char *file, char **argv, char **envp)
+int kernel_execve(const char *file,
+                  const char *const *argv,
+                  const char *const *envp)
 {
         register long scno asm("r8") = __NR_execve;
         register long sc1 asm("r12") = (long)file;