Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull more arm64 updates from Catalin Marinas:

 - Silence module allocation failures when CONFIG_ARM*_MODULE_PLTS is
   enabled. This requires a check for __GFP_NOWARN in alloc_vmap_area()

 - Improve/sanitise user tagged pointers handling in the kernel

 - Inline asm fixes/cleanups

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: Silence first allocation with CONFIG_ARM64_MODULE_PLTS=y
  ARM: Silence first allocation with CONFIG_ARM_MODULE_PLTS=y
  mm: Silence vmap() allocation failures based on caller gfp_flags
  arm64: uaccess: suppress spurious clang warning
  arm64: atomic_lse: match asm register sizes
  arm64: armv8_deprecated: ensure extension of addr
  arm64: uaccess: ensure extension of access_ok() addr
  arm64: ensure extension of smp_store_release value
  arm64: xchg: hazard against entire exchange variable
  arm64: documentation: document tagged pointer stack constraints
  arm64: entry: improve data abort handling of tagged pointers
  arm64: hw_breakpoint: fix watchpoint matching for tagged pointers
  arm64: traps: fix userspace cache maintenance emulation on a tagged pointer

Author: torvalds

Documentation/arm64/tagged-pointers.txt

@@ -11,24 +11,56 @@ in AArch64 Linux.
 The kernel configures the translation tables so that translations made
 via TTBR0 (i.e. userspace mappings) have the top byte (bits 63:56) of
 the virtual address ignored by the translation hardware. This frees up
-this byte for application use, with the following caveats:
+this byte for application use.
 
-	(1) The kernel requires that all user addresses passed to EL1
-	    are tagged with tag 0x00. This means that any syscall
-	    parameters containing user virtual addresses *must* have
-	    their top byte cleared before trapping to the kernel.
 
-	(2) Non-zero tags are not preserved when delivering signals.
-	    This means that signal handlers in applications making use
-	    of tags cannot rely on the tag information for user virtual
-	    addresses being maintained for fields inside siginfo_t.
-	    One exception to this rule is for signals raised in response
-	    to watchpoint debug exceptions, where the tag information
-	    will be preserved.
+Passing tagged addresses to the kernel
+--------------------------------------
 
-	(3) Special care should be taken when using tagged pointers,
-	    since it is likely that C compilers will not hazard two
-	    virtual addresses differing only in the upper byte.
+All interpretation of userspace memory addresses by the kernel assumes
+an address tag of 0x00.
+
+This includes, but is not limited to, addresses found in:
+
+ - pointer arguments to system calls, including pointers in structures
+   passed to system calls,
+
+ - the stack pointer (sp), e.g. when interpreting it to deliver a
+   signal,
+
+ - the frame pointer (x29) and frame records, e.g. when interpreting
+   them to generate a backtrace or call graph.
+
+Using non-zero address tags in any of these locations may result in an
+error code being returned, a (fatal) signal being raised, or other modes
+of failure.
+
+For these reasons, passing non-zero address tags to the kernel via
+system calls is forbidden, and using a non-zero address tag for sp is
+strongly discouraged.
+
+Programs maintaining a frame pointer and frame records that use non-zero
+address tags may suffer impaired or inaccurate debug and profiling
+visibility.
+
+
+Preserving tags
+---------------
+
+Non-zero tags are not preserved when delivering signals. This means that
+signal handlers in applications making use of tags cannot rely on the
+tag information for user virtual addresses being maintained for fields
+inside siginfo_t. One exception to this rule is for signals raised in
+response to watchpoint debug exceptions, where the tag information will
+be preserved.
 
 The architecture prevents the use of a tagged PC, so the upper byte will
 be set to a sign-extension of bit 55 on exception return.
+
+
+Other considerations
+--------------------
+
+Special care should be taken when using tagged pointers, since it is
+likely that C compilers will not hazard two virtual addresses differing
+only in the upper byte.

arch/arm/kernel/module.c

@@ -40,8 +40,15 @@
 #ifdef CONFIG_MMU
 void *module_alloc(unsigned long size)
 {
-	void *p = __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
-				GFP_KERNEL, PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
+	gfp_t gfp_mask = GFP_KERNEL;
+	void *p;
+
+	/* Silence the initial allocation */
+	if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS))
+		gfp_mask |= __GFP_NOWARN;
+
+	p = __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
+				gfp_mask, PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
 				__builtin_return_address(0));
 	if (!IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || p)
 		return p;

arch/arm64/include/asm/asm-uaccess.h

@@ -62,4 +62,13 @@ alternative_if ARM64_ALT_PAN_NOT_UAO
 alternative_else_nop_endif
 	.endm
 
+/*
+ * Remove the address tag from a virtual address, if present.
+ */
+	.macro	clear_address_tag, dst, addr
+	tst	\addr, #(1 << 55)
+	bic	\dst, \addr, #(0xff << 56)
+	csel	\dst, \dst, \addr, eq
+	.endm
+
 #endif

arch/arm64/include/asm/atomic_lse.h

@@ -322,7 +322,7 @@ static inline void atomic64_and(long i, atomic64_t *v)
 #define ATOMIC64_FETCH_OP_AND(name, mb, cl...)				\
 static inline long atomic64_fetch_and##name(long i, atomic64_t *v)	\
 {									\
-	register long x0 asm ("w0") = i;				\
+	register long x0 asm ("x0") = i;				\
 	register atomic64_t *x1 asm ("x1") = v;				\
 									\
 	asm volatile(ARM64_LSE_ATOMIC_INSN(				\
@@ -394,7 +394,7 @@ ATOMIC64_OP_SUB_RETURN(        , al, "memory")
 #define ATOMIC64_FETCH_OP_SUB(name, mb, cl...)				\
 static inline long atomic64_fetch_sub##name(long i, atomic64_t *v)	\
 {									\
-	register long x0 asm ("w0") = i;				\
+	register long x0 asm ("x0") = i;				\
 	register atomic64_t *x1 asm ("x1") = v;				\
 									\
 	asm volatile(ARM64_LSE_ATOMIC_INSN(				\

arch/arm64/include/asm/barrier.h

@@ -42,25 +42,35 @@
 #define __smp_rmb()	dmb(ishld)
 #define __smp_wmb()	dmb(ishst)
 
-#define __smp_store_release(p, v)						\
+#define __smp_store_release(p, v)					\
 do {									\
+	union { typeof(*p) __val; char __c[1]; } __u =			\
+		{ .__val = (__force typeof(*p)) (v) }; 			\
 	compiletime_assert_atomic_type(*p);				\
 	switch (sizeof(*p)) {						\
 	case 1:								\
 		asm volatile ("stlrb %w1, %0"				\
-				: "=Q" (*p) : "r" (v) : "memory");	\
+				: "=Q" (*p)				\
+				: "r" (*(__u8 *)__u.__c)		\
+				: "memory");				\
 		break;							\
 	case 2:								\
 		asm volatile ("stlrh %w1, %0"				\
-				: "=Q" (*p) : "r" (v) : "memory");	\
+				: "=Q" (*p)				\
+				: "r" (*(__u16 *)__u.__c)		\
+				: "memory");				\
 		break;							\
 	case 4:								\
 		asm volatile ("stlr %w1, %0"				\
-				: "=Q" (*p) : "r" (v) : "memory");	\
+				: "=Q" (*p)				\
+				: "r" (*(__u32 *)__u.__c)		\
+				: "memory");				\
 		break;							\
 	case 8:								\
 		asm volatile ("stlr %1, %0"				\
-				: "=Q" (*p) : "r" (v) : "memory");	\
+				: "=Q" (*p)				\
+				: "r" (*(__u64 *)__u.__c)		\
+				: "memory");				\
 		break;							\
 	}								\
 } while (0)

arch/arm64/include/asm/cmpxchg.h

@@ -46,7 +46,7 @@ static inline unsigned long __xchg_case_##name(unsigned long x,		\
 	"	swp" #acq_lse #rel #sz "\t%" #w "3, %" #w "0, %2\n"	\
 		__nops(3)						\
 	"	" #nop_lse)						\
-	: "=&r" (ret), "=&r" (tmp), "+Q" (*(u8 *)ptr)			\
+	: "=&r" (ret), "=&r" (tmp), "+Q" (*(unsigned long *)ptr)	\
 	: "r" (x)							\
 	: cl);								\
 									\

arch/arm64/include/asm/uaccess.h

@@ -69,20 +69,21 @@ static inline void set_fs(mm_segment_t fs)
  */
 #define __range_ok(addr, size)						\
 ({									\
+	unsigned long __addr = (unsigned long __force)(addr);		\
 	unsigned long flag, roksum;					\
 	__chk_user_ptr(addr);						\
 	asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"		\
 		: "=&r" (flag), "=&r" (roksum)				\
-		: "1" (addr), "Ir" (size),				\
+		: "1" (__addr), "Ir" (size),				\
 		  "r" (current_thread_info()->addr_limit)		\
 		: "cc");						\
 	flag;								\
 })
 
 /*
- * When dealing with data aborts or instruction traps we may end up with
- * a tagged userland pointer. Clear the tag to get a sane pointer to pass
- * on to access_ok(), for instance.
+ * When dealing with data aborts, watchpoints, or instruction traps we may end
+ * up with a tagged userland pointer. Clear the tag to get a sane pointer to
+ * pass on to access_ok(), for instance.
  */
 #define untagged_addr(addr)		sign_extend64(addr, 55)
 
@@ -230,7 +231,7 @@ do {									\
 			       (err), ARM64_HAS_UAO);			\
 		break;							\
 	case 8:								\
-		__get_user_asm("ldr", "ldtr", "%",  __gu_val, (ptr),	\
+		__get_user_asm("ldr", "ldtr", "%x",  __gu_val, (ptr),	\
 			       (err), ARM64_HAS_UAO);			\
 		break;							\
 	default:							\
@@ -297,7 +298,7 @@ do {									\
 			       (err), ARM64_HAS_UAO);			\
 		break;							\
 	case 8:								\
-		__put_user_asm("str", "sttr", "%", __pu_val, (ptr),	\
+		__put_user_asm("str", "sttr", "%x", __pu_val, (ptr),	\
 			       (err), ARM64_HAS_UAO);			\
 		break;							\
 	default:							\

arch/arm64/kernel/armv8_deprecated.c

@@ -306,7 +306,8 @@ do {								\
 	_ASM_EXTABLE(0b, 4b)					\
 	_ASM_EXTABLE(1b, 4b)					\
 	: "=&r" (res), "+r" (data), "=&r" (temp), "=&r" (temp2)	\
-	: "r" (addr), "i" (-EAGAIN), "i" (-EFAULT),		\
+	: "r" ((unsigned long)addr), "i" (-EAGAIN),		\
+	  "i" (-EFAULT),					\
 	  "i" (__SWP_LL_SC_LOOPS)				\
 	: "memory");						\
 	uaccess_disable();					\

arch/arm64/kernel/entry.S

@@ -428,12 +428,13 @@ el1_da:
 	/*
 	 * Data abort handling
 	 */
-	mrs	x0, far_el1
+	mrs	x3, far_el1
 	enable_dbg
 	// re-enable interrupts if they were enabled in the aborted context
 	tbnz	x23, #7, 1f			// PSR_I_BIT
 	enable_irq
 1:
+	clear_address_tag x0, x3
 	mov	x2, sp				// struct pt_regs
 	bl	do_mem_abort
 
@@ -594,7 +595,7 @@ el0_da:
 	// enable interrupts before calling the main handler
 	enable_dbg_and_irq
 	ct_user_exit
-	bic	x0, x26, #(0xff << 56)
+	clear_address_tag x0, x26
 	mov	x1, x25
 	mov	x2, sp
 	bl	do_mem_abort

arch/arm64/kernel/hw_breakpoint.c

@@ -36,6 +36,7 @@
 #include <asm/traps.h>
 #include <asm/cputype.h>
 #include <asm/system_misc.h>
+#include <asm/uaccess.h>
 
 /* Breakpoint currently in use for each BRP. */
 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
@@ -721,6 +722,8 @@ static u64 get_distance_from_watchpoint(unsigned long addr, u64 val,
 	u64 wp_low, wp_high;
 	u32 lens, lene;
 
+	addr = untagged_addr(addr);
+
 	lens = __ffs(ctrl->len);
 	lene = __fls(ctrl->len);