Add a few of arch_prctl() handles:
- ARCH_ENABLE_TAGGED_ADDR enabled LAM. The argument is required number
of tag bits. It is rounded up to the nearest LAM mode that can
provide it. For now only LAM_U57 is supported, with 6 tag bits.
- ARCH_GET_UNTAG_MASK returns untag mask. It can indicates where tag
bits located in the address.
- ARCH_GET_MAX_TAG_BITS returns the maximum tag bits user can request.
Zero if LAM is not supported.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/include/asm/mmu.h | 2 ++
arch/x86/include/uapi/asm/prctl.h | 4 +++
arch/x86/kernel/process.c | 3 ++
arch/x86/kernel/process_64.c | 55 ++++++++++++++++++++++++++++++-
4 files changed, 63 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 9cac8c45a647..e80762e998ce 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -12,6 +12,8 @@
#define MM_CONTEXT_UPROBE_IA32 0
/* vsyscall page is accessible on this MM */
#define MM_CONTEXT_HAS_VSYSCALL 1
+/* Do not allow changing LAM mode */
+#define MM_CONTEXT_LOCK_LAM 2
/*
* x86 has arch-specific MMU state beyond what lives in mm_struct.
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index 500b96e71f18..a31e27b95b19 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -20,4 +20,8 @@
#define ARCH_MAP_VDSO_32 0x2002
#define ARCH_MAP_VDSO_64 0x2003
+#define ARCH_GET_UNTAG_MASK 0x4001
+#define ARCH_ENABLE_TAGGED_ADDR 0x4002
+#define ARCH_GET_MAX_TAG_BITS 0x4003
+
#endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ef6bde1d40d8..cc0677f58f42 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -162,6 +162,9 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
savesegment(es, p->thread.es);
savesegment(ds, p->thread.ds);
+
+ if (p->mm && (clone_flags & (CLONE_VM | CLONE_VFORK)) == CLONE_VM)
+ set_bit(MM_CONTEXT_LOCK_LAM, &p->mm->context.flags);
#else
p->thread.sp0 = (unsigned long) (childregs + 1);
savesegment(gs, p->thread.gs);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 8b06034e8c70..88aae519c8f8 100644
--- 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;
--
2.39.1
