x86/mm: Provide arch_prctl() interface for LAM

[sfrench/cifs-2.6.git] / arch / x86 / kernel / process_64.c

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index cd34bcf7f860e43cd1977ba4088c5dc8cfe2971f..186f34add8658451662c717ed0bae0c8efc09a5d 100644 (file)
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -743,6 +743,48 @@ static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr)
 }
 #endif
 
+#ifdef CONFIG_ADDRESS_MASKING
+
+#define LAM_U57_BITS 6
+
+static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
+{
+       if (!cpu_feature_enabled(X86_FEATURE_LAM))
+               return -ENODEV;
+
+       /* PTRACE_ARCH_PRCTL */
+       if (current->mm != mm)
+               return -EINVAL;
+
+       if (mmap_write_lock_killable(mm))
+               return -EINTR;
+
+       if (test_bit(MM_CONTEXT_LOCK_LAM, &mm->context.flags)) {
+               mmap_write_unlock(mm);
+               return -EBUSY;
+       }
+
+       if (!nr_bits) {
+               mmap_write_unlock(mm);
+               return -EINVAL;
+       } else if (nr_bits <= LAM_U57_BITS) {
+               mm->context.lam_cr3_mask = X86_CR3_LAM_U57;
+               mm->context.untag_mask =  ~GENMASK(62, 57);
+       } else {
+               mmap_write_unlock(mm);
+               return -EINVAL;
+       }
+
+       write_cr3(__read_cr3() | mm->context.lam_cr3_mask);
+       set_tlbstate_lam_mode(mm);
+       set_bit(MM_CONTEXT_LOCK_LAM, &mm->context.flags);
+
+       mmap_write_unlock(mm);
+
+       return 0;
+}
+#endif
+
 long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
 {
        int ret = 0;
@@ -830,7 +872,18 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
        case ARCH_MAP_VDSO_64:
                return prctl_map_vdso(&vdso_image_64, arg2);
 #endif
-
+#ifdef CONFIG_ADDRESS_MASKING
+       case ARCH_GET_UNTAG_MASK:
+               return put_user(task->mm->context.untag_mask,
+                               (unsigned long __user *)arg2);
+       case ARCH_ENABLE_TAGGED_ADDR:
+               return prctl_enable_tagged_addr(task->mm, arg2);
+       case ARCH_GET_MAX_TAG_BITS:
+               if (!cpu_feature_enabled(X86_FEATURE_LAM))
+                       return put_user(0, (unsigned long __user *)arg2);
+               else
+                       return put_user(LAM_U57_BITS, (unsigned long __user *)arg2);
+#endif
        default:
                ret = -EINVAL;
                break;