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>

4 files changed, 12 insertions, 6 deletions

diff --git a/arch/sparc/kernel/process_32.c b/arch/sparc/kernel/process_32.c
index 40e29fc..1752929 100644
--- a/arch/sparc/kernel/process_32.c
+++ b/arch/sparc/kernel/process_32.c
@@ -633,8 +633,10 @@ asmlinkage int sparc_execve(struct pt_regs *regs)
 	if(IS_ERR(filename))
 		goto out;
 	error = do_execve(filename,
-			  (char __user * __user *)regs->u_regs[base + UREG_I1],
-			  (char __user * __user *)regs->u_regs[base + UREG_I2],
+			  (const char __user *const  __user *)
+			  regs->u_regs[base + UREG_I1],
+			  (const char __user *const  __user *)
+			  regs->u_regs[base + UREG_I2],
 			  regs);
 	putname(filename);
 out:
diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
index dbe81a3..485f547 100644
--- a/arch/sparc/kernel/process_64.c
+++ b/arch/sparc/kernel/process_64.c
@@ -739,9 +739,9 @@ asmlinkage int sparc_execve(struct pt_regs *regs)
 	if (IS_ERR(filename))
 		goto out;
 	error = do_execve(filename,
-			  (char __user * __user *)
+			  (const char __user *const __user *)
 			  regs->u_regs[base + UREG_I1],
-			  (char __user * __user *)
+			  (const char __user *const __user *)
 			  regs->u_regs[base + UREG_I2], regs);
 	putname(filename);
 	if (!error) {
diff --git a/arch/sparc/kernel/sys_sparc_32.c b/arch/sparc/kernel/sys_sparc_32.c
index ee995b7..5079413 100644
--- a/arch/sparc/kernel/sys_sparc_32.c
+++ b/arch/sparc/kernel/sys_sparc_32.c
@@ -282,7 +282,9 @@ out:
  * Do a system call from kernel instead of calling sys_execve so we
  * end up with proper pt_regs.
  */
-int kernel_execve(const char *filename, char *const argv[], char *const envp[])
+int kernel_execve(const char *filename,
+		  const char *const argv[],
+		  const char *const envp[])
 {
 	long __res;
 	register long __g1 __asm__ ("g1") = __NR_execve;
diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
index 3d435c4..f836f4e 100644
--- a/arch/sparc/kernel/sys_sparc_64.c
+++ b/arch/sparc/kernel/sys_sparc_64.c
@@ -758,7 +758,9 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
  * Do a system call from kernel instead of calling sys_execve so we
  * end up with proper pt_regs.
  */
-int kernel_execve(const char *filename, char *const argv[], char *const envp[])
+int kernel_execve(const char *filename,
+		  const char *const argv[],
+		  const char *const envp[])
 {
 	long __res;
 	register long __g1 __asm__ ("g1") = __NR_execve;