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/um/kernel/exec.c b/arch/um/kernel/exec.c
index 59b20d93b6d4..cd145eda3579 100644
--- a/arch/um/kernel/exec.c
+++ b/arch/um/kernel/exec.c
@@ -44,8 +44,9 @@ void start_thread(struct pt_regs *regs, unsigned long eip, unsigned long esp)
         PT_REGS_SP(regs) = esp;
 }
 
-static long execve1(const char *file, char __user * __user *argv,
-                    char __user *__user *env)
+static long execve1(const char *file,
+                    const char __user *const __user *argv,
+                    const char __user *const __user *env)
 {
         long error;
 
diff --git a/arch/um/kernel/syscall.c b/arch/um/kernel/syscall.c
index 7427c0b1930c..5ddb246626db 100644
--- a/arch/um/kernel/syscall.c
+++ b/arch/um/kernel/syscall.c
@@ -51,7 +51,9 @@ long old_mmap(unsigned long addr, unsigned long len,
         return err;
 }
 
-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[])
 {
         mm_segment_t fs;
         int ret;