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/x86/kernel/process.c b/arch/x86/kernel/process.c
index 64ecaf0af9af..57d1868a86aa 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -301,8 +301,9 @@ EXPORT_SYMBOL(kernel_thread);
 /*
  * sys_execve() executes a new program.
  */
-long sys_execve(const char __user *name, char __user * __user *argv,
-                char __user * __user *envp, struct pt_regs *regs)
+long sys_execve(const char __user *name,
+                const char __user *const __user *argv,
+                const char __user *const __user *envp, struct pt_regs *regs)
 {
         long error;
         char *filename;
diff --git a/arch/x86/kernel/sys_i386_32.c b/arch/x86/kernel/sys_i386_32.c
index 196552bb412c..d5e06624e34a 100644
--- a/arch/x86/kernel/sys_i386_32.c
+++ b/arch/x86/kernel/sys_i386_32.c
@@ -28,7 +28,9 @@
  * 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;
         asm volatile ("push %%ebx ; movl %2,%%ebx ; int $0x80 ; pop %%ebx"