elf_fdpic_transfer_args_to_stack(): make it generic

This copying of arguments and environment is common to both NOMMU
binary formats we support. Let's make the elf_fdpic version available
to the flat format as well.

While at it, improve the code a bit not to copy below the actual
data area.
Signed-off-by: NNicolas Pitre <nico@linaro.org>
Reviewed-by: NGreg Ungerer <gerg@linux-m68k.org>
Signed-off-by: NGreg Ungerer <gerg@linux-m68k.org>

fs/binfmt_elf_fdpic.c

@@ -67,8 +67,6 @@ static int create_elf_fdpic_tables(struct linux_binprm *, struct mm_struct *,
 				   struct elf_fdpic_params *);
 
 #ifndef CONFIG_MMU
-static int elf_fdpic_transfer_args_to_stack(struct linux_binprm *,
-					    unsigned long *);
 static int elf_fdpic_map_file_constdisp_on_uclinux(struct elf_fdpic_params *,
 						   struct file *,
 						   struct mm_struct *);
@@ -515,8 +513,9 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 	sp = mm->start_stack;
 
 	/* stack the program arguments and environment */
-	if (elf_fdpic_transfer_args_to_stack(bprm, &sp) < 0)
+	if (transfer_args_to_stack(bprm, &sp) < 0)
 		return -EFAULT;
+	sp &= ~15;
 #endif
 
 	/*
@@ -709,39 +708,6 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 	return 0;
 }
 
-/*****************************************************************************/
-/*
- * transfer the program arguments and environment from the holding pages onto
- * the stack
- */
-#ifndef CONFIG_MMU
-static int elf_fdpic_transfer_args_to_stack(struct linux_binprm *bprm,
-					    unsigned long *_sp)
-{
-	unsigned long index, stop, sp;
-	char *src;
-	int ret = 0;
-
-	stop = bprm->p >> PAGE_SHIFT;
-	sp = *_sp;
-
-	for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
-		src = kmap(bprm->page[index]);
-		sp -= PAGE_SIZE;
-		if (copy_to_user((void *) sp, src, PAGE_SIZE) != 0)
-			ret = -EFAULT;
-		kunmap(bprm->page[index]);
-		if (ret < 0)
-			goto out;
-	}
-
-	*_sp = (*_sp - (MAX_ARG_PAGES * PAGE_SIZE - bprm->p)) & ~15;
-
-out:
-	return ret;
-}
-#endif
-
 /*****************************************************************************/
 /*
  * load the appropriate binary image (executable or interpreter) into memory

fs/exec.c

@@ -762,6 +762,39 @@ int setup_arg_pages(struct linux_binprm *bprm,
 }
 EXPORT_SYMBOL(setup_arg_pages);
 
+#else
+
+/*
+ * Transfer the program arguments and environment from the holding pages
+ * onto the stack. The provided stack pointer is adjusted accordingly.
+ */
+int transfer_args_to_stack(struct linux_binprm *bprm,
+			   unsigned long *sp_location)
+{
+	unsigned long index, stop, sp;
+	int ret = 0;
+
+	stop = bprm->p >> PAGE_SHIFT;
+	sp = *sp_location;
+
+	for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
+		unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
+		char *src = kmap(bprm->page[index]) + offset;
+		sp -= PAGE_SIZE - offset;
+		if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
+			ret = -EFAULT;
+		kunmap(bprm->page[index]);
+		if (ret)
+			goto out;
+	}
+
+	*sp_location = sp;
+
+out:
+	return ret;
+}
+EXPORT_SYMBOL(transfer_args_to_stack);
+
 #endif /* CONFIG_MMU */
 
 static struct file *do_open_execat(int fd, struct filename *name, int flags)

include/linux/binfmts.h

@@ -113,6 +113,8 @@ extern int suid_dumpable;
 extern int setup_arg_pages(struct linux_binprm * bprm,
 			   unsigned long stack_top,
 			   int executable_stack);
+extern int transfer_args_to_stack(struct linux_binprm *bprm,
+				  unsigned long *sp_location);
 extern int bprm_change_interp(char *interp, struct linux_binprm *bprm);
 extern int copy_strings_kernel(int argc, const char *const *argv,
 			       struct linux_binprm *bprm);