In prepare_namespace(), do_mount() can be used instead of ksys_mount() as the first and third argument are const strings in the kernel, the second and fourth argument are passed through anyway, and the fifth argument is NULL. In do_mount_root(), ksys_mount() is called with the first and third argument being already kernelspace strings, which do not need to be copied over from userspace to kernelspace (again). The second and fourth arguments are passed through to do_mount() anyway. The fifth argument, while already residing in kernelspace, needs to be put into a page of its own. Then, do_mount() can be used instead of ksys_mount(). Once this is done, there are no in-kernel users to ksys_mount() left, which can therefore be removed.
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| @@ -1231,8 +1231,6 @@ asmlinkage long sys_ni_syscall(void); · 1230 unmodified lines | |||
| 1231 | * the ksys_xyzyyz() functions prototyped below. | 1231 | * the ksys_xyzyyz() functions prototyped below. |
| 1232 | */ | 1232 | */ |
| 1233 | 1233 | ||
| 1234 | int ksys_mount(const char __user *dev_name, const char __user *dir_name, | ||
| 1235 | const char __user *type, unsigned long flags, void __user *data); | ||
| 1236 | int ksys_umount(char __user *name, int flags); | 1234 | int ksys_umount(char __user *name, int flags); |
| 1237 | int ksys_dup(unsigned int fildes); | 1235 | int ksys_dup(unsigned int fildes); |
| 1238 | int ksys_chroot(const char __user *filename); | 1236 | int ksys_chroot(const char __user *filename); |