[PATCHv4 0/8] Linear Address Masking enabling

[PATCHv4 0/8] Linear Address Masking enabling

[Kirill A. Shutemov]

Linear Address Masking[1] (LAM) modifies the checking that is applied to
64-bit linear addresses, allowing software to use of the untranslated
address bits for metadata.

The patchset brings support for LAM for userspace addresses.

LAM_U48 enabling is controversial since it competes for bits with
5-level paging. Its enabling isolated into an optional last patch that
can be applied at maintainer's discretion.

Please review and consider applying.

v4:
  - Fix untagged_addr() for LAM_U48;
  - Remove no-threads restriction on LAM enabling;
  - Fix mm_struct access from /proc/$PID/arch_status
  - Fix LAM handling in initialize_tlbstate_and_flush()
  - Pack tlb_state better;
  - Comments and commit messages;
v3:
  - Rebased onto v5.19-rc1
  - Per-process enabling;
  - API overhaul (again);
  - Avoid branches and costly computations in the fast path;
  - LAM_U48 is in optional patch.
v2:
  - Rebased onto v5.18-rc1
  - New arch_prctl(2)-based API
  - Expose status of LAM (or other thread features) in
    /proc/$PID/arch_status

[1] ISE, Chapter 14.
https://software.intel.com/content/dam/develop/external/us/en/documents-tps/architecture-instruction-set-extensions-programming-reference.pdf

Kirill A. Shutemov (8):
  x86/mm: Fix CR3_ADDR_MASK
  x86: CPUID and CR3/CR4 flags for Linear Address Masking
  mm: Pass down mm_struct to untagged_addr()
  x86/mm: Handle LAM on context switch
  x86/uaccess: Provide untagged_addr() and remove tags before address
    check
  x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR
  x86: Expose untagging mask in /proc/$PID/arch_status
  x86/mm: Extend LAM to support to LAM_U48

 arch/arm64/include/asm/memory.h               |  4 +-
 arch/arm64/include/asm/signal.h               |  2 +-
 arch/arm64/include/asm/uaccess.h              |  4 +-
 arch/arm64/kernel/hw_breakpoint.c             |  2 +-
 arch/arm64/kernel/traps.c                     |  4 +-
 arch/arm64/mm/fault.c                         | 10 +--
 arch/sparc/include/asm/pgtable_64.h           |  2 +-
 arch/sparc/include/asm/uaccess_64.h           |  2 +
 arch/x86/include/asm/cpufeatures.h            |  1 +
 arch/x86/include/asm/elf.h                    |  3 +-
 arch/x86/include/asm/mmu.h                    |  2 +
 arch/x86/include/asm/mmu_context.h            | 58 ++++++++++++++
 arch/x86/include/asm/processor-flags.h        |  2 +-
 arch/x86/include/asm/tlbflush.h               |  4 +
 arch/x86/include/asm/uaccess.h                | 42 +++++++++-
 arch/x86/include/uapi/asm/prctl.h             |  3 +
 arch/x86/include/uapi/asm/processor-flags.h   |  6 ++
 arch/x86/kernel/Makefile                      |  2 +
 arch/x86/kernel/fpu/xstate.c                  | 47 -----------
 arch/x86/kernel/proc.c                        | 60 ++++++++++++++
 arch/x86/kernel/process.c                     |  3 +
 arch/x86/kernel/process_64.c                  | 78 ++++++++++++++++++-
 arch/x86/kernel/sys_x86_64.c                  |  5 +-
 arch/x86/mm/hugetlbpage.c                     |  6 +-
 arch/x86/mm/mmap.c                            |  9 ++-
 arch/x86/mm/tlb.c                             | 68 ++++++++++++----
 .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c       |  2 +-
 drivers/gpu/drm/radeon/radeon_gem.c           |  2 +-
 drivers/infiniband/hw/mlx4/mr.c               |  2 +-
 drivers/media/common/videobuf2/frame_vector.c |  2 +-
 drivers/media/v4l2-core/videobuf-dma-contig.c |  2 +-
 .../staging/media/atomisp/pci/hmm/hmm_bo.c    |  2 +-
 drivers/tee/tee_shm.c                         |  2 +-
 drivers/vfio/vfio_iommu_type1.c               |  2 +-
 fs/proc/task_mmu.c                            |  2 +-
 include/linux/mm.h                            | 11 ---
 include/linux/uaccess.h                       | 15 ++++
 lib/strncpy_from_user.c                       |  2 +-
 lib/strnlen_user.c                            |  2 +-
 mm/gup.c                                      |  6 +-
 mm/madvise.c                                  |  2 +-
 mm/mempolicy.c                                |  6 +-
 mm/migrate.c                                  |  2 +-
 mm/mincore.c                                  |  2 +-
 mm/mlock.c                                    |  4 +-
 mm/mmap.c                                     |  2 +-
 mm/mprotect.c                                 |  2 +-
 mm/mremap.c                                   |  2 +-
 mm/msync.c                                    |  2 +-
 virt/kvm/kvm_main.c                           |  2 +-
 51 files changed, 385 insertions(+), 126 deletions(-)
 create mode 100644 arch/x86/kernel/proc.c

-- 
2.35.1

[PATCHv4 1/8] x86/mm: Fix CR3_ADDR_MASK

[Kirill A. Shutemov]

The mask must not include bits above physical address mask. These bits
are reserved and can be used for other things. Bits 61 and 62 are used
for Linear Address Masking.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
 arch/x86/include/asm/processor-flags.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/processor-flags.h b/arch/x86/include/asm/processor-flags.h
index 02c2cbda4a74..a7f3d9100adb 100644
--- a/arch/x86/include/asm/processor-flags.h
+++ b/arch/x86/include/asm/processor-flags.h
@@ -35,7 +35,7 @@
  */
 #ifdef CONFIG_X86_64
 /* Mask off the address space ID and SME encryption bits. */
-#define CR3_ADDR_MASK	__sme_clr(0x7FFFFFFFFFFFF000ull)
+#define CR3_ADDR_MASK	__sme_clr(PHYSICAL_PAGE_MASK)
 #define CR3_PCID_MASK	0xFFFull
 #define CR3_NOFLUSH	BIT_ULL(63)
 
-- 
2.35.1

[PATCHv4 2/8] x86: CPUID and CR3/CR4 flags for Linear Address Masking

[Kirill A. Shutemov]

Enumerate Linear Address Masking and provide defines for CR3 and CR4
flags.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/cpufeatures.h          | 1 +
 arch/x86/include/uapi/asm/processor-flags.h | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 03acc823838a..6ad5841e087f 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -300,6 +300,7 @@
 /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
 #define X86_FEATURE_AVX_VNNI		(12*32+ 4) /* AVX VNNI instructions */
 #define X86_FEATURE_AVX512_BF16		(12*32+ 5) /* AVX512 BFLOAT16 instructions */
+#define X86_FEATURE_LAM			(12*32+26) /* Linear Address Masking */
 
 /* AMD-defined CPU features, CPUID level 0x80000008 (EBX), word 13 */
 #define X86_FEATURE_CLZERO		(13*32+ 0) /* CLZERO instruction */
diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index c47cc7f2feeb..d898432947ff 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -82,6 +82,10 @@
 #define X86_CR3_PCID_BITS	12
 #define X86_CR3_PCID_MASK	(_AC((1UL << X86_CR3_PCID_BITS) - 1, UL))
 
+#define X86_CR3_LAM_U57_BIT	61 /* Activate LAM for userspace, 62:57 bits masked */
+#define X86_CR3_LAM_U57		_BITULL(X86_CR3_LAM_U57_BIT)
+#define X86_CR3_LAM_U48_BIT	62 /* Activate LAM for userspace, 62:48 bits masked */
+#define X86_CR3_LAM_U48		_BITULL(X86_CR3_LAM_U48_BIT)
 #define X86_CR3_PCID_NOFLUSH_BIT 63 /* Preserve old PCID */
 #define X86_CR3_PCID_NOFLUSH    _BITULL(X86_CR3_PCID_NOFLUSH_BIT)
 
@@ -132,6 +136,8 @@
 #define X86_CR4_PKE		_BITUL(X86_CR4_PKE_BIT)
 #define X86_CR4_CET_BIT		23 /* enable Control-flow Enforcement Technology */
 #define X86_CR4_CET		_BITUL(X86_CR4_CET_BIT)
+#define X86_CR4_LAM_SUP_BIT	28 /* LAM for supervisor pointers */
+#define X86_CR4_LAM_SUP		_BITUL(X86_CR4_LAM_SUP_BIT)
 
 /*
  * x86-64 Task Priority Register, CR8
-- 
2.35.1

[PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr()

[Kirill A. Shutemov]

Intel Linear Address Masking (LAM) brings per-mm untagging rules. Pass
down mm_struct to the untagging helper. It will help to apply untagging
policy correctly.

In most cases, current->mm is the one to use, but there are some
exceptions, such as get_user_page_remote().

Move dummy implementation of untagged_addr() from <linux/mm.h> to
<linux/uaccess.h>. <asm/uaccess.h> can override the implementation.
Moving the dummy header outside <linux/mm.h> helps to avoid header hell
if you need to defer mm_struct within the helper.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
 arch/arm64/include/asm/memory.h                  |  4 ++--
 arch/arm64/include/asm/signal.h                  |  2 +-
 arch/arm64/include/asm/uaccess.h                 |  4 ++--
 arch/arm64/kernel/hw_breakpoint.c                |  2 +-
 arch/arm64/kernel/traps.c                        |  4 ++--
 arch/arm64/mm/fault.c                            | 10 +++++-----
 arch/sparc/include/asm/pgtable_64.h              |  2 +-
 arch/sparc/include/asm/uaccess_64.h              |  2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c          |  2 +-
 drivers/gpu/drm/radeon/radeon_gem.c              |  2 +-
 drivers/infiniband/hw/mlx4/mr.c                  |  2 +-
 drivers/media/common/videobuf2/frame_vector.c    |  2 +-
 drivers/media/v4l2-core/videobuf-dma-contig.c    |  2 +-
 drivers/staging/media/atomisp/pci/hmm/hmm_bo.c   |  2 +-
 drivers/tee/tee_shm.c                            |  2 +-
 drivers/vfio/vfio_iommu_type1.c                  |  2 +-
 fs/proc/task_mmu.c                               |  2 +-
 include/linux/mm.h                               | 11 -----------
 include/linux/uaccess.h                          | 15 +++++++++++++++
 lib/strncpy_from_user.c                          |  2 +-
 lib/strnlen_user.c                               |  2 +-
 mm/gup.c                                         |  6 +++---
 mm/madvise.c                                     |  2 +-
 mm/mempolicy.c                                   |  6 +++---
 mm/migrate.c                                     |  2 +-
 mm/mincore.c                                     |  2 +-
 mm/mlock.c                                       |  4 ++--
 mm/mmap.c                                        |  2 +-
 mm/mprotect.c                                    |  2 +-
 mm/mremap.c                                      |  2 +-
 mm/msync.c                                       |  2 +-
 virt/kvm/kvm_main.c                              |  2 +-
 33 files changed, 59 insertions(+), 53 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 0af70d9abede..88bee513b74c 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -215,8 +215,8 @@ static inline unsigned long kaslr_offset(void)
 #define __untagged_addr(addr)	\
 	((__force __typeof__(addr))sign_extend64((__force u64)(addr), 55))
 
-#define untagged_addr(addr)	({					\
-	u64 __addr = (__force u64)(addr);					\
+#define untagged_addr(mm, addr)	({					\
+	u64 __addr = (__force u64)(addr);				\
 	__addr &= __untagged_addr(__addr);				\
 	(__force __typeof__(addr))__addr;				\
 })
diff --git a/arch/arm64/include/asm/signal.h b/arch/arm64/include/asm/signal.h
index ef449f5f4ba8..0899c355c398 100644
--- a/arch/arm64/include/asm/signal.h
+++ b/arch/arm64/include/asm/signal.h
@@ -18,7 +18,7 @@ static inline void __user *arch_untagged_si_addr(void __user *addr,
 	if (sig == SIGTRAP && si_code == TRAP_BRKPT)
 		return addr;
 
-	return untagged_addr(addr);
+	return untagged_addr(current->mm, addr);
 }
 #define arch_untagged_si_addr arch_untagged_si_addr
 
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 63f9c828f1a7..bdcc014bd297 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -44,7 +44,7 @@ static inline int access_ok(const void __user *addr, unsigned long size)
 	 */
 	if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
 	    (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
-		addr = untagged_addr(addr);
+		addr = untagged_addr(current->mm, addr);
 
 	return likely(__access_ok(addr, size));
 }
@@ -217,7 +217,7 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
 	"	csel	%0, %1, xzr, eq\n"
 	: "=&r" (safe_ptr)
 	: "r" (ptr), "r" (TASK_SIZE_MAX - 1),
-	  "r" (untagged_addr(ptr))
+	  "r" (untagged_addr(current->mm, ptr))
 	: "cc");
 
 	csdb();
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index b29a311bb055..d637cee7b771 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -715,7 +715,7 @@ static u64 get_distance_from_watchpoint(unsigned long addr, u64 val,
 	u64 wp_low, wp_high;
 	u32 lens, lene;
 
-	addr = untagged_addr(addr);
+	addr = untagged_addr(current->mm, addr);
 
 	lens = __ffs(ctrl->len);
 	lene = __fls(ctrl->len);
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 9ac7a81b79be..385612d9890b 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -476,7 +476,7 @@ void arm64_notify_segfault(unsigned long addr)
 	int code;
 
 	mmap_read_lock(current->mm);
-	if (find_vma(current->mm, untagged_addr(addr)) == NULL)
+	if (find_vma(current->mm, untagged_addr(current->mm, addr)) == NULL)
 		code = SEGV_MAPERR;
 	else
 		code = SEGV_ACCERR;
@@ -540,7 +540,7 @@ static void user_cache_maint_handler(unsigned long esr, struct pt_regs *regs)
 	int ret = 0;
 
 	tagged_address = pt_regs_read_reg(regs, rt);
-	address = untagged_addr(tagged_address);
+	address = untagged_addr(current->mm, tagged_address);
 
 	switch (crm) {
 	case ESR_ELx_SYS64_ISS_CRM_DC_CVAU:	/* DC CVAU, gets promoted */
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index c5e11768e5c1..9577d7e37f36 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -454,7 +454,7 @@ static void set_thread_esr(unsigned long address, unsigned long esr)
 static void do_bad_area(unsigned long far, unsigned long esr,
 			struct pt_regs *regs)
 {
-	unsigned long addr = untagged_addr(far);
+	unsigned long addr = untagged_addr(current->mm, far);
 
 	/*
 	 * If we are in kernel mode at this point, we have no context to
@@ -524,7 +524,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 	vm_fault_t fault;
 	unsigned long vm_flags;
 	unsigned int mm_flags = FAULT_FLAG_DEFAULT;
-	unsigned long addr = untagged_addr(far);
+	unsigned long addr = untagged_addr(mm, far);
 
 	if (kprobe_page_fault(regs, esr))
 		return 0;
@@ -675,7 +675,7 @@ static int __kprobes do_translation_fault(unsigned long far,
 					  unsigned long esr,
 					  struct pt_regs *regs)
 {
-	unsigned long addr = untagged_addr(far);
+	unsigned long addr = untagged_addr(current->mm, far);
 
 	if (is_ttbr0_addr(addr))
 		return do_page_fault(far, esr, regs);
@@ -719,7 +719,7 @@ static int do_sea(unsigned long far, unsigned long esr, struct pt_regs *regs)
 		 * UNKNOWN for synchronous external aborts. Mask them out now
 		 * so that userspace doesn't see them.
 		 */
-		siaddr  = untagged_addr(far);
+		siaddr  = untagged_addr(current->mm, far);
 	}
 	arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr);
 
@@ -809,7 +809,7 @@ static const struct fault_info fault_info[] = {
 void do_mem_abort(unsigned long far, unsigned long esr, struct pt_regs *regs)
 {
 	const struct fault_info *inf = esr_to_fault_info(esr);
-	unsigned long addr = untagged_addr(far);
+	unsigned long addr = untagged_addr(current->mm, far);
 
 	if (!inf->fn(far, esr, regs))
 		return;
diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 4679e45c8348..1336d7bfaab9 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -1071,7 +1071,7 @@ static inline unsigned long __untagged_addr(unsigned long start)
 
 	return start;
 }
-#define untagged_addr(addr) \
+#define untagged_addr(mm, addr) \
 	((__typeof__(addr))(__untagged_addr((unsigned long)(addr))))
 
 static inline bool pte_access_permitted(pte_t pte, bool write)
diff --git a/arch/sparc/include/asm/uaccess_64.h b/arch/sparc/include/asm/uaccess_64.h
index 94266a5c5b04..b825a5dd0210 100644
--- a/arch/sparc/include/asm/uaccess_64.h
+++ b/arch/sparc/include/asm/uaccess_64.h
@@ -8,8 +8,10 @@
 
 #include <linux/compiler.h>
 #include <linux/string.h>
+#include <linux/mm_types.h>
 #include <asm/asi.h>
 #include <asm/spitfire.h>
+#include <asm/pgtable.h>
 
 #include <asm/processor.h>
 #include <asm-generic/access_ok.h>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 6b6d46e29e6e..b37199b16643 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -1491,7 +1491,7 @@ int amdgpu_amdkfd_gpuvm_alloc_memory_of_gpu(
 		if (flags & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) {
 			if (!offset || !*offset)
 				return -EINVAL;
-			user_addr = untagged_addr(*offset);
+			user_addr = untagged_addr(current->mm, *offset);
 		} else if (flags & (KFD_IOC_ALLOC_MEM_FLAGS_DOORBELL |
 				    KFD_IOC_ALLOC_MEM_FLAGS_MMIO_REMAP)) {
 			bo_type = ttm_bo_type_sg;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index 8ef31d687ef3..691dfb3f2c0e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -382,7 +382,7 @@ int amdgpu_gem_userptr_ioctl(struct drm_device *dev, void *data,
 	uint32_t handle;
 	int r;
 
-	args->addr = untagged_addr(args->addr);
+	args->addr = untagged_addr(current->mm, args->addr);
 
 	if (offset_in_page(args->addr | args->size))
 		return -EINVAL;
diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
index 8c01a7f0e027..2c3980677f64 100644
--- a/drivers/gpu/drm/radeon/radeon_gem.c
+++ b/drivers/gpu/drm/radeon/radeon_gem.c
@@ -371,7 +371,7 @@ int radeon_gem_userptr_ioctl(struct drm_device *dev, void *data,
 	uint32_t handle;
 	int r;
 
-	args->addr = untagged_addr(args->addr);
+	args->addr = untagged_addr(current->mm, args->addr);
 
 	if (offset_in_page(args->addr | args->size))
 		return -EINVAL;
diff --git a/drivers/infiniband/hw/mlx4/mr.c b/drivers/infiniband/hw/mlx4/mr.c
index 04a67b481608..b2860feeae3c 100644
--- a/drivers/infiniband/hw/mlx4/mr.c
+++ b/drivers/infiniband/hw/mlx4/mr.c
@@ -379,7 +379,7 @@ static struct ib_umem *mlx4_get_umem_mr(struct ib_device *device, u64 start,
 	 * again
 	 */
 	if (!ib_access_writable(access_flags)) {
-		unsigned long untagged_start = untagged_addr(start);
+		unsigned long untagged_start = untagged_addr(current->mm, start);
 		struct vm_area_struct *vma;
 
 		mmap_read_lock(current->mm);
diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c
index 542dde9d2609..7e62f7a2555d 100644
--- a/drivers/media/common/videobuf2/frame_vector.c
+++ b/drivers/media/common/videobuf2/frame_vector.c
@@ -47,7 +47,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 	if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
 		nr_frames = vec->nr_allocated;
 
-	start = untagged_addr(start);
+	start = untagged_addr(mm, start);
 
 	ret = pin_user_pages_fast(start, nr_frames,
 				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
diff --git a/drivers/media/v4l2-core/videobuf-dma-contig.c b/drivers/media/v4l2-core/videobuf-dma-contig.c
index 52312ce2ba05..a1444f8afa05 100644
--- a/drivers/media/v4l2-core/videobuf-dma-contig.c
+++ b/drivers/media/v4l2-core/videobuf-dma-contig.c
@@ -157,8 +157,8 @@ static void videobuf_dma_contig_user_put(struct videobuf_dma_contig_memory *mem)
 static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
 					struct videobuf_buffer *vb)
 {
-	unsigned long untagged_baddr = untagged_addr(vb->baddr);
 	struct mm_struct *mm = current->mm;
+	unsigned long untagged_baddr = untagged_addr(mm, vb->baddr);
 	struct vm_area_struct *vma;
 	unsigned long prev_pfn, this_pfn;
 	unsigned long pages_done, user_address;
diff --git a/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c b/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c
index 0168f9839c90..863d30a7ad23 100644
--- a/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c
+++ b/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c
@@ -913,7 +913,7 @@ static int alloc_user_pages(struct hmm_buffer_object *bo,
 	 * and map to user space
 	 */
 
-	userptr = untagged_addr(userptr);
+	userptr = untagged_addr(current->mm, userptr);
 
 	bo->pages = pages;
 
diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index f2b1bcefcadd..386be09cb2cd 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -261,7 +261,7 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
 	shm->flags = flags;
 	shm->ctx = ctx;
 	shm->id = id;
-	addr = untagged_addr(addr);
+	addr = untagged_addr(current->mm, addr);
 	start = rounddown(addr, PAGE_SIZE);
 	shm->offset = addr - start;
 	shm->size = length;
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index c13b9290e357..5ac6c61d7caa 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -561,7 +561,7 @@ static int vaddr_get_pfns(struct mm_struct *mm, unsigned long vaddr,
 		goto done;
 	}
 
-	vaddr = untagged_addr(vaddr);
+	vaddr = untagged_addr(mm, vaddr);
 
 retry:
 	vma = vma_lookup(mm, vaddr);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 2d04e3470d4c..c7d262bd6d6b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1659,7 +1659,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 	/* watch out for wraparound */
 	start_vaddr = end_vaddr;
 	if (svpfn <= (ULONG_MAX >> PAGE_SHIFT))
-		start_vaddr = untagged_addr(svpfn << PAGE_SHIFT);
+		start_vaddr = untagged_addr(mm, svpfn << PAGE_SHIFT);
 
 	/* Ensure the address is inside the task */
 	if (start_vaddr > mm->task_size)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bc8f326be0ce..f0cb92ff1391 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -94,17 +94,6 @@ extern int mmap_rnd_compat_bits __read_mostly;
 #include <asm/page.h>
 #include <asm/processor.h>
 
-/*
- * Architectures that support memory tagging (assigning tags to memory regions,
- * embedding these tags into addresses that point to these memory regions, and
- * checking that the memory and the pointer tags match on memory accesses)
- * redefine this macro to strip tags from pointers.
- * It's defined as noop for architectures that don't support memory tagging.
- */
-#ifndef untagged_addr
-#define untagged_addr(addr) (addr)
-#endif
-
 #ifndef __pa_symbol
 #define __pa_symbol(x)  __pa(RELOC_HIDE((unsigned long)(x), 0))
 #endif
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 5a328cf02b75..46fd816179d7 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -10,6 +10,21 @@
 
 #include <asm/uaccess.h>
 
+/*
+ * Architectures that support memory tagging (assigning tags to memory regions,
+ * embedding these tags into addresses that point to these memory regions, and
+ * checking that the memory and the pointer tags match on memory accesses)
+ * redefine this macro to strip tags from pointers.
+ *
+ * Passing down mm_struct allows to define untagging rules on per-process
+ * basis.
+ *
+ * It's defined as noop for architectures that don't support memory tagging.
+ */
+#ifndef untagged_addr
+#define untagged_addr(mm, addr) (addr)
+#endif
+
 /*
  * Architectures should provide two primitives (raw_copy_{to,from}_user())
  * and get rid of their private instances of copy_{to,from}_user() and
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 6432b8c3e431..6e1e2aa0c994 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -121,7 +121,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
 		return 0;
 
 	max_addr = TASK_SIZE_MAX;
-	src_addr = (unsigned long)untagged_addr(src);
+	src_addr = (unsigned long)untagged_addr(current->mm, src);
 	if (likely(src_addr < max_addr)) {
 		unsigned long max = max_addr - src_addr;
 		long retval;
diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
index feeb935a2299..abc096a68f05 100644
--- a/lib/strnlen_user.c
+++ b/lib/strnlen_user.c
@@ -97,7 +97,7 @@ long strnlen_user(const char __user *str, long count)
 		return 0;
 
 	max_addr = TASK_SIZE_MAX;
-	src_addr = (unsigned long)untagged_addr(str);
+	src_addr = (unsigned long)untagged_addr(current->mm, str);
 	if (likely(src_addr < max_addr)) {
 		unsigned long max = max_addr - src_addr;
 		long retval;
diff --git a/mm/gup.c b/mm/gup.c
index 551264407624..dbe825faf842 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1104,7 +1104,7 @@ static long __get_user_pages(struct mm_struct *mm,
 	if (!nr_pages)
 		return 0;
 
-	start = untagged_addr(start);
+	start = untagged_addr(mm, start);
 
 	VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
 
@@ -1285,7 +1285,7 @@ int fixup_user_fault(struct mm_struct *mm,
 	struct vm_area_struct *vma;
 	vm_fault_t ret;
 
-	address = untagged_addr(address);
+	address = untagged_addr(mm, address);
 
 	if (unlocked)
 		fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
@@ -2865,7 +2865,7 @@ static int internal_get_user_pages_fast(unsigned long start,
 	if (!(gup_flags & FOLL_FAST_ONLY))
 		might_lock_read(&current->mm->mmap_lock);
 
-	start = untagged_addr(start) & PAGE_MASK;
+	start = untagged_addr(current->mm, start) & PAGE_MASK;
 	len = nr_pages << PAGE_SHIFT;
 	if (check_add_overflow(start, len, &end))
 		return 0;
diff --git a/mm/madvise.c b/mm/madvise.c
index d7b4f2602949..e3c668ddb099 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1373,7 +1373,7 @@ int do_madvise(struct mm_struct *mm, unsigned long start, size_t len_in, int beh
 	size_t len;
 	struct blk_plug plug;
 
-	start = untagged_addr(start);
+	start = untagged_addr(mm, start);
 
 	if (!madvise_behavior_valid(behavior))
 		return -EINVAL;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d39b01fd52fe..a03b4d2bc26a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1458,7 +1458,7 @@ static long kernel_mbind(unsigned long start, unsigned long len,
 	int lmode = mode;
 	int err;
 
-	start = untagged_addr(start);
+	start = untagged_addr(current->mm, start);
 	err = sanitize_mpol_flags(&lmode, &mode_flags);
 	if (err)
 		return err;
@@ -1481,7 +1481,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le
 	unsigned long end;
 	int err = -ENOENT;
 
-	start = untagged_addr(start);
+	start = untagged_addr(mm, start);
 	if (start & ~PAGE_MASK)
 		return -EINVAL;
 	/*
@@ -1684,7 +1684,7 @@ static int kernel_get_mempolicy(int __user *policy,
 	if (nmask != NULL && maxnode < nr_node_ids)
 		return -EINVAL;
 
-	addr = untagged_addr(addr);
+	addr = untagged_addr(current->mm, addr);
 
 	err = do_get_mempolicy(&pval, &nodes, addr, flags);
 
diff --git a/mm/migrate.c b/mm/migrate.c
index e51588e95f57..af05049b055b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1714,7 +1714,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
 			goto out_flush;
 		if (get_user(node, nodes + i))
 			goto out_flush;
-		addr = (unsigned long)untagged_addr(p);
+		addr = (unsigned long)untagged_addr(mm, p);
 
 		err = -ENODEV;
 		if (node < 0 || node >= MAX_NUMNODES)
diff --git a/mm/mincore.c b/mm/mincore.c
index fa200c14185f..72c55bd9d184 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -236,7 +236,7 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
 	unsigned long pages;
 	unsigned char *tmp;
 
-	start = untagged_addr(start);
+	start = untagged_addr(current->mm, start);
 
 	/* Check the start address: needs to be page-aligned.. */
 	if (start & ~PAGE_MASK)
diff --git a/mm/mlock.c b/mm/mlock.c
index 716caf851043..054168d3e648 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -571,7 +571,7 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
 	unsigned long lock_limit;
 	int error = -ENOMEM;
 
-	start = untagged_addr(start);
+	start = untagged_addr(current->mm, start);
 
 	if (!can_do_mlock())
 		return -EPERM;
@@ -634,7 +634,7 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 {
 	int ret;
 
-	start = untagged_addr(start);
+	start = untagged_addr(current->mm, start);
 
 	len = PAGE_ALIGN(len + (offset_in_page(start)));
 	start &= PAGE_MASK;
diff --git a/mm/mmap.c b/mm/mmap.c
index 61e6135c54ef..1a7baf6b6b8e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2926,7 +2926,7 @@ EXPORT_SYMBOL(vm_munmap);
 
 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
 {
-	addr = untagged_addr(addr);
+	addr = untagged_addr(current->mm, addr);
 	return __vm_munmap(addr, len, true);
 }
 
diff --git a/mm/mprotect.c b/mm/mprotect.c
index ba5592655ee3..871e954f6155 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -622,7 +622,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 				(prot & PROT_READ);
 	struct mmu_gather tlb;
 
-	start = untagged_addr(start);
+	start = untagged_addr(current->mm, start);
 
 	prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
 	if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
diff --git a/mm/mremap.c b/mm/mremap.c
index b522cd0259a0..f76648bc4f67 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -906,7 +906,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 	 *
 	 * See Documentation/arm64/tagged-address-abi.rst for more information.
 	 */
-	addr = untagged_addr(addr);
+	addr = untagged_addr(mm, addr);
 
 	if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
 		return ret;
diff --git a/mm/msync.c b/mm/msync.c
index 137d1c104f3e..5fe989bd3c4b 100644
--- a/mm/msync.c
+++ b/mm/msync.c
@@ -37,7 +37,7 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
 	int unmapped_error = 0;
 	int error = -EINVAL;
 
-	start = untagged_addr(start);
+	start = untagged_addr(mm, start);
 
 	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
 		goto out;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a49df8988cd6..03f7ad0ebc8a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1876,7 +1876,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		return -EINVAL;
 	/* We can read the guest memory with __xxx_user() later on. */
 	if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
-	    (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
+	    (mem->userspace_addr != untagged_addr(kvm->mm, mem->userspace_addr)) ||
 	     !access_ok((void __user *)(unsigned long)mem->userspace_addr,
 			mem->memory_size))
 		return -EINVAL;
-- 
2.35.1

[PATCHv4 4/8] x86/mm: Handle LAM on context switch

[Kirill A. Shutemov]

Linear Address Masking mode for userspace pointers encoded in CR3 bits.
The mode is selected per-thread. Add new thread features indicate that the
thread has Linear Address Masking enabled.

switch_mm_irqs_off() now respects these flags and constructs CR3
accordingly.

The active LAM mode gets recorded in the tlb_state.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/mmu.h         |  1 +
 arch/x86/include/asm/mmu_context.h | 24 +++++++++++
 arch/x86/include/asm/tlbflush.h    |  4 ++
 arch/x86/mm/tlb.c                  | 68 +++++++++++++++++++++++-------
 4 files changed, 82 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 5d7494631ea9..d150e92163b6 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -40,6 +40,7 @@ typedef struct {
 
 #ifdef CONFIG_X86_64
 	unsigned short flags;
+	u64 lam_cr3_mask;
 #endif
 
 	struct mutex lock;
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index b8d40ddeab00..e6eac047c728 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -91,6 +91,29 @@ static inline void switch_ldt(struct mm_struct *prev, struct mm_struct *next)
 }
 #endif
 
+#ifdef CONFIG_X86_64
+static inline u64 mm_cr3_lam_mask(struct mm_struct *mm)
+{
+	return mm->context.lam_cr3_mask;
+}
+
+static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
+{
+	mm->context.lam_cr3_mask = oldmm->context.lam_cr3_mask;
+}
+
+#else
+
+static inline u64 mm_cr3_lam_mask(struct mm_struct *mm)
+{
+	return 0;
+}
+
+static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
+{
+}
+#endif
+
 #define enter_lazy_tlb enter_lazy_tlb
 extern void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk);
 
@@ -168,6 +191,7 @@ static inline int arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
 {
 	arch_dup_pkeys(oldmm, mm);
 	paravirt_arch_dup_mmap(oldmm, mm);
+	dup_lam(oldmm, mm);
 	return ldt_dup_context(oldmm, mm);
 }
 
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 4af5579c7ef7..2d70d75e207f 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -100,6 +100,10 @@ struct tlb_state {
 	 */
 	bool invalidate_other;
 
+#ifdef CONFIG_X86_64
+	u8 lam;
+#endif
+
 	/*
 	 * Mask that contains TLB_NR_DYN_ASIDS+1 bits to indicate
 	 * the corresponding user PCID needs a flush next time we
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index d400b6d9d246..c5c4f76329c2 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -154,17 +154,17 @@ static inline u16 user_pcid(u16 asid)
 	return ret;
 }
 
-static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
+static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, u64 lam)
 {
 	if (static_cpu_has(X86_FEATURE_PCID)) {
-		return __sme_pa(pgd) | kern_pcid(asid);
+		return __sme_pa(pgd) | kern_pcid(asid) | lam;
 	} else {
 		VM_WARN_ON_ONCE(asid != 0);
-		return __sme_pa(pgd);
+		return __sme_pa(pgd) | lam;
 	}
 }
 
-static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
+static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid, u64 lam)
 {
 	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
 	/*
@@ -173,7 +173,7 @@ static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
 	 * boot because all CPU's the have same capabilities:
 	 */
 	VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
-	return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
+	return __sme_pa(pgd) | kern_pcid(asid) | lam | CR3_NOFLUSH;
 }
 
 /*
@@ -274,15 +274,15 @@ static inline void invalidate_user_asid(u16 asid)
 		  (unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask));
 }
 
-static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, bool need_flush)
+static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, u64 lam, bool need_flush)
 {
 	unsigned long new_mm_cr3;
 
 	if (need_flush) {
 		invalidate_user_asid(new_asid);
-		new_mm_cr3 = build_cr3(pgdir, new_asid);
+		new_mm_cr3 = build_cr3(pgdir, new_asid, lam);
 	} else {
-		new_mm_cr3 = build_cr3_noflush(pgdir, new_asid);
+		new_mm_cr3 = build_cr3_noflush(pgdir, new_asid, lam);
 	}
 
 	/*
@@ -486,11 +486,38 @@ void cr4_update_pce(void *ignored)
 static inline void cr4_update_pce_mm(struct mm_struct *mm) { }
 #endif
 
+#ifdef CONFIG_X86_64
+static inline u64 tlbstate_lam_cr3_mask(void)
+{
+	u64 lam = this_cpu_read(cpu_tlbstate.lam);
+
+	return lam << X86_CR3_LAM_U57_BIT;
+}
+
+static inline void set_tlbstate_lam_cr3_mask(u64 mask)
+{
+	this_cpu_write(cpu_tlbstate.lam, mask >> X86_CR3_LAM_U57_BIT);
+}
+
+#else
+
+static inline u64 tlbstate_lam_cr3_mask(void)
+{
+	return 0;
+}
+
+static inline void set_tlbstate_lam_cr3_mask(u64 mask)
+{
+}
+#endif
+
 void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 			struct task_struct *tsk)
 {
 	struct mm_struct *real_prev = this_cpu_read(cpu_tlbstate.loaded_mm);
 	u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	u64 prev_lam = tlbstate_lam_cr3_mask();
+	u64 new_lam = mm_cr3_lam_mask(next);
 	bool was_lazy = this_cpu_read(cpu_tlbstate_shared.is_lazy);
 	unsigned cpu = smp_processor_id();
 	u64 next_tlb_gen;
@@ -504,6 +531,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	 * cpu_tlbstate.loaded_mm) matches next.
 	 *
 	 * NB: leave_mm() calls us with prev == NULL and tsk == NULL.
+	 *
+	 * NB: Initial LAM enabling calls us with prev == next. We must update
+	 * CR3 if prev_lam doesn't match the new one.
 	 */
 
 	/* We don't want flush_tlb_func() to run concurrently with us. */
@@ -520,7 +550,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	 * isn't free.
 	 */
 #ifdef CONFIG_DEBUG_VM
-	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid))) {
+	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid, prev_lam))) {
 		/*
 		 * If we were to BUG here, we'd be very likely to kill
 		 * the system so hard that we don't see the call trace.
@@ -551,7 +581,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 	 * provides that full memory barrier and core serializing
 	 * instruction.
 	 */
-	if (real_prev == next) {
+	if (real_prev == next && prev_lam == new_lam) {
 		VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=
 			   next->context.ctx_id);
 
@@ -622,15 +652,16 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 		barrier();
 	}
 
+	set_tlbstate_lam_cr3_mask(new_lam);
 	if (need_flush) {
 		this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
 		this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
-		load_new_mm_cr3(next->pgd, new_asid, true);
+		load_new_mm_cr3(next->pgd, new_asid, new_lam, true);
 
 		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
 	} else {
 		/* The new ASID is already up to date. */
-		load_new_mm_cr3(next->pgd, new_asid, false);
+		load_new_mm_cr3(next->pgd, new_asid, new_lam, false);
 
 		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
 	}
@@ -691,6 +722,10 @@ void initialize_tlbstate_and_flush(void)
 	/* Assert that CR3 already references the right mm. */
 	WARN_ON((cr3 & CR3_ADDR_MASK) != __pa(mm->pgd));
 
+	/* LAM expected to be disabled in CR3 and init_mm */
+	WARN_ON(cr3 & (X86_CR3_LAM_U48 | X86_CR3_LAM_U57));
+	WARN_ON(mm_cr3_lam_mask(&init_mm));
+
 	/*
 	 * Assert that CR4.PCIDE is set if needed.  (CR4.PCIDE initialization
 	 * doesn't work like other CR4 bits because it can only be set from
@@ -700,7 +735,7 @@ void initialize_tlbstate_and_flush(void)
 		!(cr4_read_shadow() & X86_CR4_PCIDE));
 
 	/* Force ASID 0 and force a TLB flush. */
-	write_cr3(build_cr3(mm->pgd, 0));
+	write_cr3(build_cr3(mm->pgd, 0, 0));
 
 	/* Reinitialize tlbstate. */
 	this_cpu_write(cpu_tlbstate.last_user_mm_spec, LAST_USER_MM_INIT);
@@ -708,6 +743,7 @@ void initialize_tlbstate_and_flush(void)
 	this_cpu_write(cpu_tlbstate.next_asid, 1);
 	this_cpu_write(cpu_tlbstate.ctxs[0].ctx_id, mm->context.ctx_id);
 	this_cpu_write(cpu_tlbstate.ctxs[0].tlb_gen, tlb_gen);
+	set_tlbstate_lam_cr3_mask(0);
 
 	for (i = 1; i < TLB_NR_DYN_ASIDS; i++)
 		this_cpu_write(cpu_tlbstate.ctxs[i].ctx_id, 0);
@@ -1047,8 +1083,10 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
  */
 unsigned long __get_current_cr3_fast(void)
 {
-	unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
-		this_cpu_read(cpu_tlbstate.loaded_mm_asid));
+	unsigned long cr3 =
+		build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
+		this_cpu_read(cpu_tlbstate.loaded_mm_asid),
+		tlbstate_lam_cr3_mask());
 
 	/* For now, be very restrictive about when this can be called. */
 	VM_WARN_ON(in_nmi() || preemptible());
-- 
2.35.1

[PATCHv4 5/8] x86/uaccess: Provide untagged_addr() and remove tags before address check

[Kirill A. Shutemov]

untagged_addr() is a helper used by the core-mm to strip tag bits and
get the address to the canonical shape. In only handles userspace
addresses. The untagging mask is stored in mmu_context and will be set
on enabling LAM for the process.

The tags must not be included into check whether it's okay to access the
userspace address.

Strip tags in access_ok().

get_user() and put_user() don't use access_ok(), but check access
against TASK_SIZE directly in assembly. Strip tags, before calling into
the assembly helper.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/mmu.h         |  1 +
 arch/x86/include/asm/mmu_context.h | 11 ++++++++
 arch/x86/include/asm/uaccess.h     | 42 +++++++++++++++++++++++++++---
 arch/x86/kernel/process.c          |  3 +++
 4 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index d150e92163b6..59c617fc7c6f 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -41,6 +41,7 @@ typedef struct {
 #ifdef CONFIG_X86_64
 	unsigned short flags;
 	u64 lam_cr3_mask;
+	u64 untag_mask;
 #endif
 
 	struct mutex lock;
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index e6eac047c728..05821534aadc 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -100,6 +100,12 @@ static inline u64 mm_cr3_lam_mask(struct mm_struct *mm)
 static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
 {
 	mm->context.lam_cr3_mask = oldmm->context.lam_cr3_mask;
+	mm->context.untag_mask = oldmm->context.untag_mask;
+}
+
+static inline void mm_reset_untag_mask(struct mm_struct *mm)
+{
+	mm->context.untag_mask = -1UL;
 }
 
 #else
@@ -112,6 +118,10 @@ static inline u64 mm_cr3_lam_mask(struct mm_struct *mm)
 static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
 {
 }
+
+static inline void mm_reset_untag_mask(struct mm_struct *mm)
+{
+}
 #endif
 
 #define enter_lazy_tlb enter_lazy_tlb
@@ -138,6 +148,7 @@ static inline int init_new_context(struct task_struct *tsk,
 		mm->context.execute_only_pkey = -1;
 	}
 #endif
+	mm_reset_untag_mask(mm);
 	init_new_context_ldt(mm);
 	return 0;
 }
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 913e593a3b45..803241dfc473 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -6,6 +6,7 @@
  */
 #include <linux/compiler.h>
 #include <linux/kasan-checks.h>
+#include <linux/mm_types.h>
 #include <linux/string.h>
 #include <asm/asm.h>
 #include <asm/page.h>
@@ -20,6 +21,30 @@ static inline bool pagefault_disabled(void);
 # define WARN_ON_IN_IRQ()
 #endif
 
+#ifdef CONFIG_X86_64
+/*
+ * Mask out tag bits from the address.
+ *
+ * Magic with the 'sign' allows to untag userspace pointer without any branches
+ * while leaving kernel addresses intact.
+ */
+#define untagged_addr(mm, addr)	({					\
+	u64 __addr = (__force u64)(addr);				\
+	s64 sign = (s64)__addr >> 63;					\
+	__addr &= (mm)->context.untag_mask | sign;			\
+	(__force __typeof__(addr))__addr;				\
+})
+
+#define untagged_ptr(mm, ptr)	({					\
+	u64 __ptrval = (__force u64)(ptr);				\
+	__ptrval = untagged_addr(mm, __ptrval);				\
+	(__force __typeof__(*(ptr)) *)__ptrval;				\
+})
+#else
+#define untagged_addr(mm, addr)	(addr)
+#define untagged_ptr(mm, ptr)	(ptr)
+#endif
+
 /**
  * access_ok - Checks if a user space pointer is valid
  * @addr: User space pointer to start of block to check
@@ -40,7 +65,7 @@ static inline bool pagefault_disabled(void);
 #define access_ok(addr, size)					\
 ({									\
 	WARN_ON_IN_IRQ();						\
-	likely(__access_ok(addr, size));				\
+	likely(__access_ok(untagged_addr(current->mm, addr), size));	\
 })
 
 #include <asm-generic/access_ok.h>
@@ -125,7 +150,13 @@ extern int __get_user_bad(void);
  * Return: zero on success, or -EFAULT on error.
  * On error, the variable @x is set to zero.
  */
-#define get_user(x,ptr) ({ might_fault(); do_get_user_call(get_user,x,ptr); })
+#define get_user(x,ptr)							\
+({									\
+	__typeof__(*(ptr)) __user *__ptr_clean;				\
+	__ptr_clean = untagged_ptr(current->mm, ptr);			\
+	might_fault();							\
+	do_get_user_call(get_user,x,__ptr_clean);			\
+})
 
 /**
  * __get_user - Get a simple variable from user space, with less checking.
@@ -222,7 +253,12 @@ extern void __put_user_nocheck_8(void);
  *
  * Return: zero on success, or -EFAULT on error.
  */
-#define put_user(x, ptr) ({ might_fault(); do_put_user_call(put_user,x,ptr); })
+#define put_user(x, ptr) ({						\
+	__typeof__(*(ptr)) __user *__ptr_clean;				\
+	__ptr_clean = untagged_ptr(current->mm, ptr);			\
+	might_fault();							\
+	do_put_user_call(put_user,x,__ptr_clean);			\
+})
 
 /**
  * __put_user - Write a simple value into user space, with less checking.
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 9b2772b7e1f3..18b2bfdf7b9b 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -47,6 +47,7 @@
 #include <asm/frame.h>
 #include <asm/unwind.h>
 #include <asm/tdx.h>
+#include <asm/mmu_context.h>
 
 #include "process.h"
 
@@ -367,6 +368,8 @@ void arch_setup_new_exec(void)
 		task_clear_spec_ssb_noexec(current);
 		speculation_ctrl_update(read_thread_flags());
 	}
+
+	mm_reset_untag_mask(current->mm);
 }
 
 #ifdef CONFIG_X86_IOPL_IOPERM
-- 
2.35.1

[PATCHv4 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR

[Kirill A. Shutemov]

Add a couple 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.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/uapi/asm/prctl.h |  3 ++
 arch/x86/kernel/process_64.c      | 55 ++++++++++++++++++++++++++++++-
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h
index 500b96e71f18..38164a05c23c 100644
--- a/arch/x86/include/uapi/asm/prctl.h
+++ b/arch/x86/include/uapi/asm/prctl.h
@@ -20,4 +20,7 @@
 #define ARCH_MAP_VDSO_32		0x2002
 #define ARCH_MAP_VDSO_64		0x2003
 
+#define ARCH_GET_UNTAG_MASK		0x4001
+#define ARCH_ENABLE_TAGGED_ADDR		0x4002
+
 #endif /* _ASM_X86_PRCTL_H */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 1962008fe743..e328b91d1492 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -742,6 +742,55 @@ static long prctl_map_vdso(const struct vdso_image *image, unsigned long addr)
 }
 #endif
 
+static void enable_lam_func(void *mm)
+{
+	struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
+
+	if (loaded_mm != mm)
+		return;
+
+	/* Counterpart of smp_wmb() in prctl_enable_tagged_addr() */
+	smp_rmb();
+
+	/* Update CR3 to get LAM active on the CPU */
+	switch_mm(loaded_mm, loaded_mm, current);
+}
+
+static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
+{
+	int ret = 0;
+
+	if (!cpu_feature_enabled(X86_FEATURE_LAM))
+		return -ENODEV;
+
+	mutex_lock(&mm->context.lock);
+
+	/* Already enabled? */
+	if (mm->context.lam_cr3_mask) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (!nr_bits) {
+		ret = -EINVAL;
+		goto out;
+	} else if (nr_bits <= 6) {
+		mm->context.lam_cr3_mask = X86_CR3_LAM_U57;
+		mm->context.untag_mask =  ~GENMASK(62, 57);
+	} else {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Make lam_cr3_mask and untag_mask visible on other CPUs */
+	smp_wmb();
+
+	on_each_cpu_mask(mm_cpumask(mm), enable_lam_func, mm, true);
+out:
+	mutex_unlock(&mm->context.lock);
+	return ret;
+}
+
 long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
 {
 	int ret = 0;
@@ -829,7 +878,11 @@ 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
-
+	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);
 	default:
 		ret = -EINVAL;
 		break;
-- 
2.35.1

[PATCHv4 7/8] x86: Expose untagging mask in /proc/$PID/arch_status

[Kirill A. Shutemov]

Add a line in /proc/$PID/arch_status to report untag_mask. It can be
used to find out LAM status of the process from the outside. It is
useful for debuggers.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/mmu_context.h | 10 +++++
 arch/x86/kernel/Makefile           |  2 +
 arch/x86/kernel/fpu/xstate.c       | 47 -----------------------
 arch/x86/kernel/proc.c             | 60 ++++++++++++++++++++++++++++++
 4 files changed, 72 insertions(+), 47 deletions(-)
 create mode 100644 arch/x86/kernel/proc.c

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 05821534aadc..a6cded0f5e64 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -103,6 +103,11 @@ static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
 	mm->context.untag_mask = oldmm->context.untag_mask;
 }
 
+static inline unsigned long mm_untag_mask(struct mm_struct *mm)
+{
+	return mm->context.untag_mask;
+}
+
 static inline void mm_reset_untag_mask(struct mm_struct *mm)
 {
 	mm->context.untag_mask = -1UL;
@@ -119,6 +124,11 @@ static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
 {
 }
 
+static inline unsigned long mm_untag_mask(struct mm_struct *mm)
+{
+	return -1UL;
+}
+
 static inline void mm_reset_untag_mask(struct mm_struct *mm)
 {
 }
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 4c8b6ae802ac..313f1d8e7783 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -141,6 +141,8 @@ obj-$(CONFIG_UNWINDER_GUESS)		+= unwind_guess.o
 
 obj-$(CONFIG_AMD_MEM_ENCRYPT)		+= sev.o
 
+obj-$(CONFIG_PROC_FS)			+= proc.o
+
 ###
 # 64 bit specific files
 ifeq ($(CONFIG_X86_64),y)
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index c8340156bfd2..838a6f0627fd 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -10,8 +10,6 @@
 #include <linux/mman.h>
 #include <linux/nospec.h>
 #include <linux/pkeys.h>
-#include <linux/seq_file.h>
-#include <linux/proc_fs.h>
 #include <linux/vmalloc.h>
 
 #include <asm/fpu/api.h>
@@ -1745,48 +1743,3 @@ long fpu_xstate_prctl(int option, unsigned long arg2)
 		return -EINVAL;
 	}
 }
-
-#ifdef CONFIG_PROC_PID_ARCH_STATUS
-/*
- * Report the amount of time elapsed in millisecond since last AVX512
- * use in the task.
- */
-static void avx512_status(struct seq_file *m, struct task_struct *task)
-{
-	unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp);
-	long delta;
-
-	if (!timestamp) {
-		/*
-		 * Report -1 if no AVX512 usage
-		 */
-		delta = -1;
-	} else {
-		delta = (long)(jiffies - timestamp);
-		/*
-		 * Cap to LONG_MAX if time difference > LONG_MAX
-		 */
-		if (delta < 0)
-			delta = LONG_MAX;
-		delta = jiffies_to_msecs(delta);
-	}
-
-	seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta);
-	seq_putc(m, '\n');
-}
-
-/*
- * Report architecture specific information
- */
-int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
-			struct pid *pid, struct task_struct *task)
-{
-	/*
-	 * Report AVX512 state if the processor and build option supported.
-	 */
-	if (cpu_feature_enabled(X86_FEATURE_AVX512F))
-		avx512_status(m, task);
-
-	return 0;
-}
-#endif /* CONFIG_PROC_PID_ARCH_STATUS */
diff --git a/arch/x86/kernel/proc.c b/arch/x86/kernel/proc.c
new file mode 100644
index 000000000000..9765b4d05ce4
--- /dev/null
+++ b/arch/x86/kernel/proc.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/proc_fs.h>
+#include <linux/sched/mm.h>
+#include <linux/seq_file.h>
+#include <uapi/asm/prctl.h>
+#include <asm/mmu_context.h>
+
+/*
+ * Report the amount of time elapsed in millisecond since last AVX512
+ * use in the task.
+ */
+static void avx512_status(struct seq_file *m, struct task_struct *task)
+{
+	unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp);
+	long delta;
+
+	if (!timestamp) {
+		/*
+		 * Report -1 if no AVX512 usage
+		 */
+		delta = -1;
+	} else {
+		delta = (long)(jiffies - timestamp);
+		/*
+		 * Cap to LONG_MAX if time difference > LONG_MAX
+		 */
+		if (delta < 0)
+			delta = LONG_MAX;
+		delta = jiffies_to_msecs(delta);
+	}
+
+	seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta);
+	seq_putc(m, '\n');
+}
+
+/*
+ * Report architecture specific information
+ */
+int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
+			struct pid *pid, struct task_struct *task)
+{
+	struct mm_struct *mm;
+	unsigned long untag_mask = -1UL;
+
+	/*
+	 * Report AVX512 state if the processor and build option supported.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_AVX512F))
+		avx512_status(m, task);
+
+	mm = get_task_mm(task);
+	if (mm) {
+		untag_mask = mm_untag_mask(task->mm);
+		mmput(mm);
+	}
+
+	seq_printf(m, "untag_mask:\t%#lx\n", untag_mask);
+
+	return 0;
+}
-- 
2.35.1

[PATCHv4 OPTIONAL 8/8] x86/mm: Extend LAM to support to LAM_U48

[Kirill A. Shutemov]

LAM_U48 allows to encode 15 bits of tags into address.

LAM_U48 steals bits above 47-bit for tags and makes it impossible for
userspace to use full address space on 5-level paging machine.

Make these features mutually exclusive: whichever gets enabled first
blocks the other one.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/elf.h         |  3 ++-
 arch/x86/include/asm/mmu_context.h | 13 +++++++++++++
 arch/x86/kernel/process_64.c       | 23 +++++++++++++++++++++++
 arch/x86/kernel/sys_x86_64.c       |  5 +++--
 arch/x86/mm/hugetlbpage.c          |  6 ++++--
 arch/x86/mm/mmap.c                 |  9 ++++++++-
 6 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index cb0ff1055ab1..4df13497a770 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -317,7 +317,8 @@ static inline int mmap_is_ia32(void)
 extern unsigned long task_size_32bit(void);
 extern unsigned long task_size_64bit(int full_addr_space);
 extern unsigned long get_mmap_base(int is_legacy);
-extern bool mmap_address_hint_valid(unsigned long addr, unsigned long len);
+extern bool mmap_address_hint_valid(struct mm_struct *mm,
+				    unsigned long addr, unsigned long len);
 extern unsigned long get_sigframe_size(void);
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index a6cded0f5e64..17d31988edd6 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -263,6 +263,19 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 
 unsigned long __get_current_cr3_fast(void);
 
+#ifdef CONFIG_X86_5LEVEL
+static inline bool full_va_allowed(struct mm_struct *mm)
+{
+	/* LAM_U48 steals VA bits above 47-bit for tags */
+	return mm->context.lam_cr3_mask != X86_CR3_LAM_U48;
+}
+#else
+static inline bool full_va_allowed(struct mm_struct *mm)
+{
+	return false;
+}
+#endif
+
 #include <asm-generic/mmu_context.h>
 
 #endif /* _ASM_X86_MMU_CONTEXT_H */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index e328b91d1492..427ebef3f64b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -756,6 +756,16 @@ static void enable_lam_func(void *mm)
 	switch_mm(loaded_mm, loaded_mm, current);
 }
 
+static bool lam_u48_allowed(void)
+{
+	struct mm_struct *mm = current->mm;
+
+	if (!full_va_allowed(mm))
+		return true;
+
+	return find_vma(mm, DEFAULT_MAP_WINDOW) == NULL;
+}
+
 static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
 {
 	int ret = 0;
@@ -763,6 +773,10 @@ static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
 	if (!cpu_feature_enabled(X86_FEATURE_LAM))
 		return -ENODEV;
 
+	/* lam_u48_allowed() requires mmap_lock */
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
 	mutex_lock(&mm->context.lock);
 
 	/* Already enabled? */
@@ -777,6 +791,14 @@ static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
 	} else if (nr_bits <= 6) {
 		mm->context.lam_cr3_mask = X86_CR3_LAM_U57;
 		mm->context.untag_mask =  ~GENMASK(62, 57);
+	} else if (nr_bits <= 15) {
+		if (!lam_u48_allowed()) {
+			ret = -EBUSY;
+			goto out;
+		}
+
+		mm->context.lam_cr3_mask = X86_CR3_LAM_U48;
+		mm->context.untag_mask =  ~GENMASK(62, 48);
 	} else {
 		ret = -EINVAL;
 		goto out;
@@ -788,6 +810,7 @@ static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
 	on_each_cpu_mask(mm_cpumask(mm), enable_lam_func, mm, true);
 out:
 	mutex_unlock(&mm->context.lock);
+	mmap_write_unlock(mm);
 	return ret;
 }
 
diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index 8cc653ffdccd..5ea6aaed89ba 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -21,6 +21,7 @@
 
 #include <asm/elf.h>
 #include <asm/ia32.h>
+#include <asm/mmu_context.h>
 
 /*
  * Align a virtual address to avoid aliasing in the I$ on AMD F15h.
@@ -182,7 +183,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	/* requesting a specific address */
 	if (addr) {
 		addr &= PAGE_MASK;
-		if (!mmap_address_hint_valid(addr, len))
+		if (!mmap_address_hint_valid(mm, addr, len))
 			goto get_unmapped_area;
 
 		vma = find_vma(mm, addr);
@@ -203,7 +204,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	 * !in_32bit_syscall() check to avoid high addresses for x32
 	 * (and make it no op on native i386).
 	 */
-	if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall())
+	if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall() && full_va_allowed(mm))
 		info.high_limit += TASK_SIZE_MAX - DEFAULT_MAP_WINDOW;
 
 	info.align_mask = 0;
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index a0d023cb4292..9fdc8db42365 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -18,6 +18,7 @@
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/elf.h>
+#include <asm/mmu_context.h>
 
 #if 0	/* This is just for testing */
 struct page *
@@ -103,6 +104,7 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 		unsigned long pgoff, unsigned long flags)
 {
 	struct hstate *h = hstate_file(file);
+	struct mm_struct *mm = current->mm;
 	struct vm_unmapped_area_info info;
 
 	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
@@ -114,7 +116,7 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
 	 * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area
 	 * in the full address space.
 	 */
-	if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall())
+	if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall() && full_va_allowed(mm))
 		info.high_limit += TASK_SIZE_MAX - DEFAULT_MAP_WINDOW;
 
 	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
@@ -161,7 +163,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 
 	if (addr) {
 		addr &= huge_page_mask(h);
-		if (!mmap_address_hint_valid(addr, len))
+		if (!mmap_address_hint_valid(mm, addr, len))
 			goto get_unmapped_area;
 
 		vma = find_vma(mm, addr);
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index c90c20904a60..f9ca824729de 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -21,6 +21,7 @@
 #include <linux/elf-randomize.h>
 #include <asm/elf.h>
 #include <asm/io.h>
+#include <asm/mmu_context.h>
 
 #include "physaddr.h"
 
@@ -35,6 +36,8 @@ unsigned long task_size_32bit(void)
 
 unsigned long task_size_64bit(int full_addr_space)
 {
+	if (!full_va_allowed(current->mm))
+		return DEFAULT_MAP_WINDOW;
 	return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
 }
 
@@ -206,11 +209,15 @@ const char *arch_vma_name(struct vm_area_struct *vma)
  * the failure of such a fixed mapping request, so the restriction is not
  * applied.
  */
-bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
+bool mmap_address_hint_valid(struct mm_struct *mm,
+			     unsigned long addr, unsigned long len)
 {
 	if (TASK_SIZE - len < addr)
 		return false;
 
+	if (addr + len > DEFAULT_MAP_WINDOW && !full_va_allowed(mm))
+		return false;
+
 	return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW);
 }
 
-- 
2.35.1

Re: [PATCHv4 4/8] x86/mm: Handle LAM on context switch

[Alexander Potapenko]

On Wed, Jun 22, 2022 at 6:22 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> Linear Address Masking mode for userspace pointers encoded in CR3 bits.
> The mode is selected per-thread. Add new thread features indicate that the
> thread has Linear Address Masking enabled.
>
> switch_mm_irqs_off() now respects these flags and constructs CR3
> accordingly.
>
> The active LAM mode gets recorded in the tlb_state.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
>  arch/x86/include/asm/mmu.h         |  1 +
>  arch/x86/include/asm/mmu_context.h | 24 +++++++++++
>  arch/x86/include/asm/tlbflush.h    |  4 ++
>  arch/x86/mm/tlb.c                  | 68 +++++++++++++++++++++++-------
>  4 files changed, 82 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
> index 5d7494631ea9..d150e92163b6 100644
> --- a/arch/x86/include/asm/mmu.h
> +++ b/arch/x86/include/asm/mmu.h
> @@ -40,6 +40,7 @@ typedef struct {
>
>  #ifdef CONFIG_X86_64
>         unsigned short flags;
> +       u64 lam_cr3_mask;
>  #endif

Can you please add a comment for this field?

>
>         struct mutex lock;
> diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
> index b8d40ddeab00..e6eac047c728 100644
> --- a/arch/x86/include/asm/mmu_context.h
> +++ b/arch/x86/include/asm/mmu_context.h
> @@ -91,6 +91,29 @@ static inline void switch_ldt(struct mm_struct *prev, struct mm_struct *next)
>  }
>  #endif
>
> +#ifdef CONFIG_X86_64
> +static inline u64 mm_cr3_lam_mask(struct mm_struct *mm)
> +{
> +       return mm->context.lam_cr3_mask;
> +}

For the sake of uniformity, can it be either lam_cr3_mask or
cr3_lam_mask everywhere?

>
> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> index 4af5579c7ef7..2d70d75e207f 100644
> --- a/arch/x86/include/asm/tlbflush.h
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -100,6 +100,10 @@ struct tlb_state {
>          */
>         bool invalidate_other;
>
> +#ifdef CONFIG_X86_64
> +       u8 lam;
> +#endif
> +

Comment here as well, please.

>         /*
>          * Mask that contains TLB_NR_DYN_ASIDS+1 bits to indicate
>          * the corresponding user PCID needs a flush next time we
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index d400b6d9d246..c5c4f76329c2 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -154,17 +154,17 @@ static inline u16 user_pcid(u16 asid)
>         return ret;
>  }
>
> -static inline unsigned long build_cr3(pgd_t *pgd, u16 asid)
> +static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, u64 lam)

I think it's more natural to make `lam` an unsigned long, because cr3
is treated as unsigned long everywhere.

>  {
>         if (static_cpu_has(X86_FEATURE_PCID)) {
> -               return __sme_pa(pgd) | kern_pcid(asid);
> +               return __sme_pa(pgd) | kern_pcid(asid) | lam;
>         } else {
>                 VM_WARN_ON_ONCE(asid != 0);
> -               return __sme_pa(pgd);
> +               return __sme_pa(pgd) | lam;
>         }
>  }
>
> -static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
> +static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid, u64 lam)
ditto

>  {
>         VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
>         /*
> @@ -173,7 +173,7 @@ static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid)
>          * boot because all CPU's the have same capabilities:
>          */
>         VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
> -       return __sme_pa(pgd) | kern_pcid(asid) | CR3_NOFLUSH;
> +       return __sme_pa(pgd) | kern_pcid(asid) | lam | CR3_NOFLUSH;
>  }
>
>  /*
> @@ -274,15 +274,15 @@ static inline void invalidate_user_asid(u16 asid)
>                   (unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask));
>  }
>
> -static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, bool need_flush)
> +static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, u64 lam, bool need_flush)
>  {
>         unsigned long new_mm_cr3;
>
>         if (need_flush) {
>                 invalidate_user_asid(new_asid);
> -               new_mm_cr3 = build_cr3(pgdir, new_asid);
> +               new_mm_cr3 = build_cr3(pgdir, new_asid, lam);
>         } else {
> -               new_mm_cr3 = build_cr3_noflush(pgdir, new_asid);
> +               new_mm_cr3 = build_cr3_noflush(pgdir, new_asid, lam);
>         }
>
>         /*
> @@ -486,11 +486,38 @@ void cr4_update_pce(void *ignored)
>  static inline void cr4_update_pce_mm(struct mm_struct *mm) { }
>  #endif
>
> +#ifdef CONFIG_X86_64
> +static inline u64 tlbstate_lam_cr3_mask(void)
Please add comments for these methods.
> +{
> +       u64 lam = this_cpu_read(cpu_tlbstate.lam);
> +
> +       return lam << X86_CR3_LAM_U57_BIT;
> +}
> +
> +static inline void set_tlbstate_lam_cr3_mask(u64 mask)
> +{
> +       this_cpu_write(cpu_tlbstate.lam, mask >> X86_CR3_LAM_U57_BIT);
> +}
> +
> +#else
> +
> +static inline u64 tlbstate_lam_cr3_mask(void)
> +{
> +       return 0;
> +}
> +
> +static inline void set_tlbstate_lam_cr3_mask(u64 mask)
> +{
> +}
> +#endif
> +
>  void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
>                         struct task_struct *tsk)
>  {
>         struct mm_struct *real_prev = this_cpu_read(cpu_tlbstate.loaded_mm);
>         u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
> +       u64 prev_lam = tlbstate_lam_cr3_mask();
> +       u64 new_lam = mm_cr3_lam_mask(next);

Ditto.

>         bool was_lazy = this_cpu_read(cpu_tlbstate_shared.is_lazy);
>         unsigned cpu = smp_processor_id();
>         u64 next_tlb_gen;
> @@ -504,6 +531,9 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
>          * cpu_tlbstate.loaded_mm) matches next.
>          *
>          * NB: leave_mm() calls us with prev == NULL and tsk == NULL.
> +        *
> +        * NB: Initial LAM enabling calls us with prev == next. We must update
> +        * CR3 if prev_lam doesn't match the new one.
>          */
>
>         /* We don't want flush_tlb_func() to run concurrently with us. */
> @@ -520,7 +550,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
>          * isn't free.
>          */
>  #ifdef CONFIG_DEBUG_VM
> -       if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid))) {
> +       if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid, prev_lam))) {
>                 /*
>                  * If we were to BUG here, we'd be very likely to kill
>                  * the system so hard that we don't see the call trace.
> @@ -551,7 +581,7 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
>          * provides that full memory barrier and core serializing
>          * instruction.
>          */
> -       if (real_prev == next) {
> +       if (real_prev == next && prev_lam == new_lam) {

Do we want the warning checks below to only happen if prev_lam==new_lam?

>                 VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=
>                            next->context.ctx_id);
>
> @@ -622,15 +652,16 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
>                 barrier();
>         }
>
> +       set_tlbstate_lam_cr3_mask(new_lam);
>         if (need_flush) {
>                 this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
>                 this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
> -               load_new_mm_cr3(next->pgd, new_asid, true);
> +               load_new_mm_cr3(next->pgd, new_asid, new_lam, true);
>
>                 trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
>         } else {
>                 /* The new ASID is already up to date. */
> -               load_new_mm_cr3(next->pgd, new_asid, false);
> +               load_new_mm_cr3(next->pgd, new_asid, new_lam, false);
>
>                 trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
>         }
> @@ -691,6 +722,10 @@ void initialize_tlbstate_and_flush(void)
>         /* Assert that CR3 already references the right mm. */
>         WARN_ON((cr3 & CR3_ADDR_MASK) != __pa(mm->pgd));
>
> +       /* LAM expected to be disabled in CR3 and init_mm */
> +       WARN_ON(cr3 & (X86_CR3_LAM_U48 | X86_CR3_LAM_U57));
> +       WARN_ON(mm_cr3_lam_mask(&init_mm));
> +
>         /*
>          * Assert that CR4.PCIDE is set if needed.  (CR4.PCIDE initialization
>          * doesn't work like other CR4 bits because it can only be set from
> @@ -700,7 +735,7 @@ void initialize_tlbstate_and_flush(void)
>                 !(cr4_read_shadow() & X86_CR4_PCIDE));
>
>         /* Force ASID 0 and force a TLB flush. */
Please update this comment.

> -       write_cr3(build_cr3(mm->pgd, 0));
> +       write_cr3(build_cr3(mm->pgd, 0, 0));
>
>         /* Reinitialize tlbstate. */
>         this_cpu_write(cpu_tlbstate.last_user_mm_spec, LAST_USER_MM_INIT);
> @@ -708,6 +743,7 @@ void initialize_tlbstate_and_flush(void)
>         this_cpu_write(cpu_tlbstate.next_asid, 1);
>         this_cpu_write(cpu_tlbstate.ctxs[0].ctx_id, mm->context.ctx_id);
>         this_cpu_write(cpu_tlbstate.ctxs[0].tlb_gen, tlb_gen);
> +       set_tlbstate_lam_cr3_mask(0);
>
>         for (i = 1; i < TLB_NR_DYN_ASIDS; i++)
>                 this_cpu_write(cpu_tlbstate.ctxs[i].ctx_id, 0);
> @@ -1047,8 +1083,10 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
>   */
>  unsigned long __get_current_cr3_fast(void)
>  {
> -       unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
> -               this_cpu_read(cpu_tlbstate.loaded_mm_asid));
> +       unsigned long cr3 =
> +               build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
> +               this_cpu_read(cpu_tlbstate.loaded_mm_asid),
> +               tlbstate_lam_cr3_mask());
>
>         /* For now, be very restrictive about when this can be called. */
>         VM_WARN_ON(in_nmi() || preemptible());
> --
> 2.35.1
>


-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

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Re: [PATCHv4 OPTIONAL 8/8] x86/mm: Extend LAM to support to LAM_U48

[Alexander Potapenko]

On Wed, Jun 22, 2022 at 6:23 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> LAM_U48 allows to encode 15 bits of tags into address.
>
> LAM_U48 steals bits above 47-bit for tags and makes it impossible for
> userspace to use full address space on 5-level paging machine.
>
> Make these features mutually exclusive: whichever gets enabled first
> blocks the other one.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>


> @@ -206,11 +209,15 @@ const char *arch_vma_name(struct vm_area_struct *vma)
>   * the failure of such a fixed mapping request, so the restriction is not
>   * applied.
>   */
> -bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
> +bool mmap_address_hint_valid(struct mm_struct *mm,
> +                            unsigned long addr, unsigned long len)
Please make sure to reflect the newly added parameter in the doc comment.
This may also apply to other patches in the series.


-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Diese E-Mail ist vertraulich. Falls Sie diese fälschlicherweise
erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes
weiter, löschen Sie alle Kopien und Anhänge davon und lassen Sie mich
bitte wissen, dass die E-Mail an die falsche Person gesendet wurde.


This e-mail is confidential. If you received this communication by
mistake, please don't forward it to anyone else, please erase all
copies and attachments, and please let me know that it has gone to the
wrong person.

Re: [PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr()

[Alexander Potapenko]

Kirill,


> diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
> index feeb935a2299..abc096a68f05 100644
> --- a/lib/strnlen_user.c
> +++ b/lib/strnlen_user.c
> @@ -97,7 +97,7 @@ long strnlen_user(const char __user *str, long count)
>                 return 0;
>
>         max_addr = TASK_SIZE_MAX;
> -       src_addr = (unsigned long)untagged_addr(str);
> +       src_addr = (unsigned long)untagged_addr(current->mm, str);

In a downstream kernel with LAM disabled I'm seeing current->mm being
NULL at this point, because strnlen_user() is being called by
kdevtmpfs.
IIUC current->mm is only guaranteed to be non-NULL in the userspace
process context, whereas untagged_addr() may get called in random
places.

Am I missing something?



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Re: [PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr()

[Kirill A. Shutemov]

On Tue, Jul 05, 2022 at 05:42:21PM +0200, Alexander Potapenko wrote:
> Kirill,
> 
> 
> > diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
> > index feeb935a2299..abc096a68f05 100644
> > --- a/lib/strnlen_user.c
> > +++ b/lib/strnlen_user.c
> > @@ -97,7 +97,7 @@ long strnlen_user(const char __user *str, long count)
> >                 return 0;
> >
> >         max_addr = TASK_SIZE_MAX;
> > -       src_addr = (unsigned long)untagged_addr(str);
> > +       src_addr = (unsigned long)untagged_addr(current->mm, str);
> 
> In a downstream kernel with LAM disabled I'm seeing current->mm being
> NULL at this point, because strnlen_user() is being called by
> kdevtmpfs.
> IIUC current->mm is only guaranteed to be non-NULL in the userspace
> process context, whereas untagged_addr() may get called in random
> places.
> 
> Am I missing something?

Hm. Could you show a traceback?

As strnlen_user() intended to be used on an user string I expected it to
be called from a process context. I guess I'm wrong, but I don't yet
understand why.

-- 
 Kirill A. Shutemov

Re: [PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr()

[Alexander Potapenko]

On Thu, Jul 7, 2022 at 1:14 AM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Tue, Jul 05, 2022 at 05:42:21PM +0200, Alexander Potapenko wrote:
> > Kirill,
> >
> >
> > > diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
> > > index feeb935a2299..abc096a68f05 100644
> > > --- a/lib/strnlen_user.c
> > > +++ b/lib/strnlen_user.c
> > > @@ -97,7 +97,7 @@ long strnlen_user(const char __user *str, long count)
> > >                 return 0;
> > >
> > >         max_addr = TASK_SIZE_MAX;
> > > -       src_addr = (unsigned long)untagged_addr(str);
> > > +       src_addr = (unsigned long)untagged_addr(current->mm, str);
> >
> > In a downstream kernel with LAM disabled I'm seeing current->mm being
> > NULL at this point, because strnlen_user() is being called by
> > kdevtmpfs.
> > IIUC current->mm is only guaranteed to be non-NULL in the userspace
> > process context, whereas untagged_addr() may get called in random
> > places.
> >
> > Am I missing something?
>
> Hm. Could you show a traceback?
>
> As strnlen_user() intended to be used on an user string I expected it to
> be called from a process context. I guess I'm wrong, but I don't yet
> understand why.

Oh, I see now. The old implementation of devtmpfsd()
(https://elixir.bootlin.com/linux/v5.4/source/drivers/base/devtmpfs.c#L397)
uses ksys_mount(), which assumes that the strings must be copied from
the userspace, whereas they are actually constants in kernel .rodata

Wonder if the validity of mm->current for userspace accesses is
actually enforced anyhow in newer kernels.

> --
>  Kirill A. Shutemov



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg

Re: [PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr()

[Kirill A. Shutemov]

On Thu, Jul 07, 2022 at 10:56:53AM +0200, Alexander Potapenko wrote:
> On Thu, Jul 7, 2022 at 1:14 AM Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> >
> > On Tue, Jul 05, 2022 at 05:42:21PM +0200, Alexander Potapenko wrote:
> > > Kirill,
> > >
> > >
> > > > diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
> > > > index feeb935a2299..abc096a68f05 100644
> > > > --- a/lib/strnlen_user.c
> > > > +++ b/lib/strnlen_user.c
> > > > @@ -97,7 +97,7 @@ long strnlen_user(const char __user *str, long count)
> > > >                 return 0;
> > > >
> > > >         max_addr = TASK_SIZE_MAX;
> > > > -       src_addr = (unsigned long)untagged_addr(str);
> > > > +       src_addr = (unsigned long)untagged_addr(current->mm, str);
> > >
> > > In a downstream kernel with LAM disabled I'm seeing current->mm being
> > > NULL at this point, because strnlen_user() is being called by
> > > kdevtmpfs.
> > > IIUC current->mm is only guaranteed to be non-NULL in the userspace
> > > process context, whereas untagged_addr() may get called in random
> > > places.
> > >
> > > Am I missing something?
> >
> > Hm. Could you show a traceback?
> >
> > As strnlen_user() intended to be used on an user string I expected it to
> > be called from a process context. I guess I'm wrong, but I don't yet
> > understand why.
> 
> Oh, I see now. The old implementation of devtmpfsd()
> (https://elixir.bootlin.com/linux/v5.4/source/drivers/base/devtmpfs.c#L397)
> uses ksys_mount(), which assumes that the strings must be copied from
> the userspace, whereas they are actually constants in kernel .rodata
> 
> Wonder if the validity of mm->current for userspace accesses is
> actually enforced anyhow in newer kernels.

I think it is.

See 967747bbc084 and how it changes strnlen_user(). With max_addr equal to
TASK_SIZE_MAX, strnlen_user() will always fail on a kernel string.

-- 
 Kirill A. Shutemov

Re: [PATCHv4 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR

[Alexander Potapenko]

On Wed, Jun 22, 2022 at 6:22 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> Add a couple 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.
>
Am I right that the desired way to detect the presence of LAM without
enabling it is to check that arch_prctl(ARCH_GET_UNTAG_MASK, ...)
returns zero?

Overall, I think these new arch_prctls should be documented following
the spirit of PR_SET_TAGGED_ADDR_CTRL/PR_GET_TAGGED_ADDR_CTRL
somewhere.

> +
> +static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
> +{
> +       int ret = 0;
> +
> +       if (!cpu_feature_enabled(X86_FEATURE_LAM))
> +               return -ENODEV;
> +
> +       mutex_lock(&mm->context.lock);
> +
> +       /* Already enabled? */
> +       if (mm->context.lam_cr3_mask) {
> +               ret = -EBUSY;
> +               goto out;
> +       }
> +
> +       if (!nr_bits) {
> +               ret = -EINVAL;

One would expect that `arch_prctl(ARCH_ENABLE_TAGGED_ADDR, 0)`
disables tagging for the current process.
Shouldn't this workflow be supported as well?

Re: [PATCHv4 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR

[Kirill A. Shutemov]

On Tue, Jul 12, 2022 at 03:12:01PM +0200, Alexander Potapenko wrote:
> On Wed, Jun 22, 2022 at 6:22 PM Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> >
> > Add a couple 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.
> >
> Am I right that the desired way to detect the presence of LAM without
> enabling it is to check that arch_prctl(ARCH_GET_UNTAG_MASK, ...)
> returns zero?

Returns -1UL, but yes.

> Overall, I think these new arch_prctls should be documented following
> the spirit of PR_SET_TAGGED_ADDR_CTRL/PR_GET_TAGGED_ADDR_CTRL
> somewhere.

The plan is to update man page for the syscall once the interface is
upstream.

> > +
> > +static int prctl_enable_tagged_addr(struct mm_struct *mm, unsigned long nr_bits)
> > +{
> > +       int ret = 0;
> > +
> > +       if (!cpu_feature_enabled(X86_FEATURE_LAM))
> > +               return -ENODEV;
> > +
> > +       mutex_lock(&mm->context.lock);
> > +
> > +       /* Already enabled? */
> > +       if (mm->context.lam_cr3_mask) {
> > +               ret = -EBUSY;
> > +               goto out;
> > +       }
> > +
> > +       if (!nr_bits) {
> > +               ret = -EINVAL;
> 
> One would expect that `arch_prctl(ARCH_ENABLE_TAGGED_ADDR, 0)`
> disables tagging for the current process.
> Shouldn't this workflow be supported as well?

Is there an use-case for it?

I would rather keep the interface minimal. We can always add this in the
future if an use-case comes.

-- 
 Kirill A. Shutemov

Re: [PATCHv4 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR

[Alexander Potapenko]

On Tue, Jul 12, 2022 at 7:14 PM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Tue, Jul 12, 2022 at 03:12:01PM +0200, Alexander Potapenko wrote:
> > On Wed, Jun 22, 2022 at 6:22 PM Kirill A. Shutemov
> > <kirill.shutemov@linux.intel.com> wrote:
> > >
> > > Add a couple 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.
> > >
> > Am I right that the desired way to detect the presence of LAM without
> > enabling it is to check that arch_prctl(ARCH_GET_UNTAG_MASK, ...)
> > returns zero?
>
> Returns -1UL, but yes.

No, I meant the return value of arch_prctl(), but in fact neither
seems to be true.

Right now e.g. for the 5.17 kernel arch_prctl(ARCH_GET_UNTAG_MASK,
&bits) returns -EINVAL regardless of the underlying hardware.
A new kernel with your patches will return 0 and set bits=-1UL on both
non-LAM and LAM-enabled machines. How can we distinguish those?

> >
> > One would expect that `arch_prctl(ARCH_ENABLE_TAGGED_ADDR, 0)`
> > disables tagging for the current process.
> > Shouldn't this workflow be supported as well?
>
> Is there an use-case for it?
>
> I would rather keep the interface minimal. We can always add this in the
> future if an use-case comes.

As discussed offline, we don't have a use-case for this yet, so I don't insist.

> --
>  Kirill A. Shutemov



-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

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Re: [PATCHv4 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR

[Kirill A. Shutemov]

On Thu, Jul 14, 2022 at 04:28:36PM +0200, Alexander Potapenko wrote:
> On Tue, Jul 12, 2022 at 7:14 PM Kirill A. Shutemov
> <kirill.shutemov@linux.intel.com> wrote:
> >
> > On Tue, Jul 12, 2022 at 03:12:01PM +0200, Alexander Potapenko wrote:
> > > On Wed, Jun 22, 2022 at 6:22 PM Kirill A. Shutemov
> > > <kirill.shutemov@linux.intel.com> wrote:
> > > >
> > > > Add a couple 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.
> > > >
> > > Am I right that the desired way to detect the presence of LAM without
> > > enabling it is to check that arch_prctl(ARCH_GET_UNTAG_MASK, ...)
> > > returns zero?
> >
> > Returns -1UL, but yes.
> 
> No, I meant the return value of arch_prctl(), but in fact neither
> seems to be true.
> 
> Right now e.g. for the 5.17 kernel arch_prctl(ARCH_GET_UNTAG_MASK,
> &bits) returns -EINVAL regardless of the underlying hardware.
> A new kernel with your patches will return 0 and set bits=-1UL on both
> non-LAM and LAM-enabled machines. How can we distinguish those?

With CPUID?

-- 
 Kirill A. Shutemov