- Compat register fault reporting fix

- Documentation clarification on tagged pointers
 - hwcap widened to 64-bit (user space already reading it as 64-bit)
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Merge tag 'arm64-stable' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64

Pull ARM64 fixes from Catalin Marinas:
 - Compat register fault reporting fix
 - Documentation clarification on tagged pointers
 - hwcap widened to 64-bit (user space already reading it as 64-bit)

* tag 'arm64-stable' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64:
  arm64: Widen hwcap to be 64 bit
  arm64: Correctly report LR and SP for compat tasks
  arm64: documentation: tighten up tagged pointer documentation
  arm64: Make do_bad_area() function static

Documentation/arm64/tagged-pointers.txt

@@ -18,17 +18,17 @@ this byte for application use, with the following caveats:
 	    parameters containing user virtual addresses *must* have
 	    their top byte cleared before trapping to the kernel.
 
-	(2) Tags are not guaranteed to be 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 debug exceptions, where the tag information
+	(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.
 
 	(3) Special care should be taken when using tagged pointers,
 	    since it is likely that C compilers will not hazard two
-	    addresses differing only in the upper bits.
+	    virtual addresses differing only in the upper byte.
 
 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.

arch/arm64/include/asm/hwcap.h

@@ -43,6 +43,6 @@
 				 COMPAT_HWCAP_VFPv3|COMPAT_HWCAP_VFPv4|\
 				 COMPAT_HWCAP_NEON|COMPAT_HWCAP_IDIV)
 
-extern unsigned int elf_hwcap;
+extern unsigned long elf_hwcap;
 #endif
 #endif

arch/arm64/kernel/process.c

@@ -143,15 +143,26 @@ void machine_restart(char *cmd)
 
 void __show_regs(struct pt_regs *regs)
 {
-	int i;
+	int i, top_reg;
+	u64 lr, sp;
+
+	if (compat_user_mode(regs)) {
+		lr = regs->compat_lr;
+		sp = regs->compat_sp;
+		top_reg = 12;
+	} else {
+		lr = regs->regs[30];
+		sp = regs->sp;
+		top_reg = 29;
+	}
 
 	show_regs_print_info(KERN_DEFAULT);
 	print_symbol("PC is at %s\n", instruction_pointer(regs));
-	print_symbol("LR is at %s\n", regs->regs[30]);
+	print_symbol("LR is at %s\n", lr);
 	printk("pc : [<%016llx>] lr : [<%016llx>] pstate: %08llx\n",
-	       regs->pc, regs->regs[30], regs->pstate);
-	printk("sp : %016llx\n", regs->sp);
-	for (i = 29; i >= 0; i--) {
+	       regs->pc, lr, regs->pstate);
+	printk("sp : %016llx\n", sp);
+	for (i = top_reg; i >= 0; i--) {
 		printk("x%-2d: %016llx ", i, regs->regs[i]);
 		if (i % 2 == 0)
 			printk("\n");

arch/arm64/kernel/setup.c

@@ -57,7 +57,7 @@
 unsigned int processor_id;
 EXPORT_SYMBOL(processor_id);
 
-unsigned int elf_hwcap __read_mostly;
+unsigned long elf_hwcap __read_mostly;
 EXPORT_SYMBOL_GPL(elf_hwcap);
 
 static const char *cpu_name;

arch/arm64/mm/fault.c

@@ -130,7 +130,7 @@ static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 	force_sig_info(sig, &si, tsk);
 }
 
-void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs)
 {
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->active_mm;