x86: cosmetic fixes fault_{32|64}.c

First step towards unifying these files.
- Checkpatch trailing whitespace fixes
- Checkpatch indentation of switch statement fixes
- Checkpatch single statement ifs need no braces fixes
- Checkpatch consistent spacing after comma fixes
- Introduce defines for pagefault error bits from X86_64 and add useful
  comment from X86_32.  Use these defines in X86_32 where obvious.
- Unify comments between 32|64 bit
- Small ifdef movement for CONFIG_KPROBES in notify_page_fault()
- Introduce X86_64 only case statement

No Functional Changes.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/mm/fault_32.c

 /*
- *  linux/arch/i386/mm/fault.c
- *
  *  Copyright (C) 1995  Linus Torvalds
  */
 
@@ -30,11 +28,25 @@
 #include <asm/desc.h>
 #include <asm/segment.h>
 
-extern void die(const char *,struct pt_regs *,long);
+/*
+ * Page fault error code bits
+ *	bit 0 == 0 means no page found, 1 means protection fault
+ *	bit 1 == 0 means read, 1 means write
+ *	bit 2 == 0 means kernel, 1 means user-mode
+ *	bit 3 == 1 means use of reserved bit detected
+ *	bit 4 == 1 means fault was an instruction fetch
+ */
+#define PF_PROT	(1<<0)
+#define PF_WRITE	(1<<1)
+#define PF_USER	(1<<2)
+#define PF_RSVD	(1<<3)
+#define PF_INSTR	(1<<4)
+
+extern void die(const char *, struct pt_regs *, long);
 
-#ifdef CONFIG_KPROBES
 static inline int notify_page_fault(struct pt_regs *regs)
 {
+#ifdef CONFIG_KPROBES
 	int ret = 0;
 
 	/* kprobe_running() needs smp_processor_id() */
@@ -46,13 +58,10 @@ static inline int notify_page_fault(struct pt_regs *regs)
 	}
 
 	return ret;
-}
 #else
-static inline int notify_page_fault(struct pt_regs *regs)
-{
 	return 0;
-}
 #endif
+}
 
 /*
  * Return EIP plus the CS segment base.  The segment limit is also
@@ -116,9 +125,9 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
 	/* Decode the code segment base from the descriptor */
 	base = get_desc_base((struct desc_struct *)desc);
 
-	if (seg & (1<<2)) { 
+	if (seg & (1<<2))
 		mutex_unlock(&current->mm->context.lock);
-	} else
+	else
 		put_cpu();
 
 	/* Adjust EIP and segment limit, and clamp at the kernel limit.
@@ -136,7 +145,7 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
 static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
 {
 	unsigned long limit;
-	unsigned char *instr = (unsigned char *)get_segment_eip (regs, &limit);
+	unsigned char *instr = (unsigned char *)get_segment_eip(regs, &limit);
 	int scan_more = 1;
 	int prefetch = 0;
 	int i;
@@ -158,16 +167,32 @@ static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
 		switch (instr_hi) {
 		case 0x20:
 		case 0x30:
-			/* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
+			/*
+			 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
+			 * In X86_64 long mode, the CPU will signal invalid
+			 * opcode if some of these prefixes are present so
+			 * X86_64 will never get here anyway
+			 */
 			scan_more = ((instr_lo & 7) == 0x6);
 			break;
-			
+#ifdef CONFIG_X86_64
+		case 0x40:
+			/*
+			 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
+			 * Need to figure out under what instruction mode the
+			 * instruction was issued. Could check the LDT for lm,
+			 * but for now it's good enough to assume that long
+			 * mode only uses well known segments or kernel.
+			 */
+			scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS);
+			break;
+#endif
 		case 0x60:
 			/* 0x64 thru 0x67 are valid prefixes in all modes. */
 			scan_more = (instr_lo & 0xC) == 0x4;
 			break;
 		case 0xF0:
-			/* 0xF0, 0xF2, and 0xF3 are valid prefixes */
+			/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
 			scan_more = !instr_lo || (instr_lo>>1) == 1;
 			break;
 		case 0x00:
@@ -284,19 +309,12 @@ int show_unhandled_signals = 1;
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
  * routines.
- *
- * error_code:
- *	bit 0 == 0 means no page found, 1 means protection fault
- *	bit 1 == 0 means read, 1 means write
- *	bit 2 == 0 means kernel, 1 means user-mode
- *	bit 3 == 1 means use of reserved bit detected
- *	bit 4 == 1 means fault was an instruction fetch
  */
 void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
 	struct task_struct *tsk;
 	struct mm_struct *mm;
-	struct vm_area_struct * vma;
+	struct vm_area_struct *vma;
 	unsigned long address;
 	int write, si_code;
 	int fault;
@@ -350,7 +368,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
 	/*
 	 * If we're in an interrupt, have no user context or are running in an
-	 * atomic region then we must not take the fault..
+	 * atomic region then we must not take the fault.
 	 */
 	if (in_atomic() || !mm)
 		goto bad_area_nosemaphore;
@@ -371,7 +389,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	 * thus avoiding the deadlock.
 	 */
 	if (!down_read_trylock(&mm->mmap_sem)) {
-		if ((error_code & 4) == 0 &&
+		if ((error_code & PF_USER) == 0 &&
 		    !search_exception_tables(regs->ip))
 			goto bad_area_nosemaphore;
 		down_read(&mm->mmap_sem);
@@ -384,7 +402,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 		goto good_area;
 	if (!(vma->vm_flags & VM_GROWSDOWN))
 		goto bad_area;
-	if (error_code & 4) {
+	if (error_code & PF_USER) {
 		/*
 		 * Accessing the stack below %sp is always a bug.
 		 * The large cushion allows instructions like enter
@@ -403,15 +421,15 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 good_area:
 	si_code = SEGV_ACCERR;
 	write = 0;
-	switch (error_code & 3) {
+	switch (error_code & (PF_PROT|PF_WRITE)) {
 	default:	/* 3: write, present */
 		/* fall through */
-		case 2:		/* write, not present */
+	case PF_WRITE:		/* write, not present */
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
 		write++;
 		break;
-		case 1:		/* read, present */
+	case PF_PROT:		/* read, present */
 		goto bad_area;
 	case 0:			/* read, not present */
 		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
@@ -457,7 +475,7 @@ bad_area:
 
 bad_area_nosemaphore:
 	/* User mode accesses just cause a SIGSEGV */
-	if (error_code & 4) {
+	if (error_code & PF_USER) {
 		/*
 		 * It's possible to have interrupts off here.
 		 */
@@ -541,7 +559,7 @@ no_context:
 		else
 			printk(KERN_ALERT "BUG: unable to handle kernel paging"
 					" request");
-		printk(" at virtual address %08lx\n",address);
+		printk(" at virtual address %08lx\n", address);
 		printk(KERN_ALERT "printing ip: %08lx ", regs->ip);
 
 		page = read_cr3();
@@ -605,7 +623,7 @@ do_sigbus:
 	up_read(&mm->mmap_sem);
 
 	/* Kernel mode? Handle exceptions or die */
-	if (!(error_code & 4))
+	if (!(error_code & PF_USER))
 		goto no_context;
 
 	/* User space => ok to do another page fault */

arch/x86/mm/fault_64.c

 /*
- *  linux/arch/x86-64/mm/fault.c
- *
  *  Copyright (C) 1995  Linus Torvalds
  *  Copyright (C) 2001,2002 Andi Kleen, SuSE Labs.
  */
@@ -33,16 +31,23 @@
 #include <asm/proto.h>
 #include <asm-generic/sections.h>
 
-/* Page fault error code bits */
-#define PF_PROT	(1<<0)		/* or no page found */
+/*
+ * Page fault error code bits
+ *	bit 0 == 0 means no page found, 1 means protection fault
+ *	bit 1 == 0 means read, 1 means write
+ *	bit 2 == 0 means kernel, 1 means user-mode
+ *	bit 3 == 1 means use of reserved bit detected
+ *	bit 4 == 1 means fault was an instruction fetch
+ */
+#define PF_PROT	(1<<0)
 #define PF_WRITE	(1<<1)
 #define PF_USER	(1<<2)
 #define PF_RSVD	(1<<3)
 #define PF_INSTR	(1<<4)
 
-#ifdef CONFIG_KPROBES
 static inline int notify_page_fault(struct pt_regs *regs)
 {
+#ifdef CONFIG_KPROBES
 	int ret = 0;
 
 	/* kprobe_running() needs smp_processor_id() */
@@ -54,13 +59,10 @@ static inline int notify_page_fault(struct pt_regs *regs)
 	}
 
 	return ret;
-}
 #else
-static inline int notify_page_fault(struct pt_regs *regs)
-{
 	return 0;
-}
 #endif
+}
 
 /* Sometimes the CPU reports invalid exceptions on prefetch.
    Check that here and ignore.
@@ -98,23 +100,26 @@ static noinline int is_prefetch(struct pt_regs *regs, unsigned long addr,
 		switch (instr_hi) {
 		case 0x20:
 		case 0x30:
-			/* Values 0x26,0x2E,0x36,0x3E are valid x86
-			   prefixes.  In long mode, the CPU will signal
-			   invalid opcode if some of these prefixes are
-			   present so we will never get here anyway */
+			/*
+			 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
+			 * In X86_64 long mode, the CPU will signal invalid
+			 * opcode if some of these prefixes are present so
+			 * X86_64 will never get here anyway
+			 */
 			scan_more = ((instr_lo & 7) == 0x6);
 			break;
-			
+#ifdef CONFIG_X86_64
 		case 0x40:
-			/* In AMD64 long mode, 0x40 to 0x4F are valid REX prefixes
-			   Need to figure out under what instruction mode the
-			   instruction was issued ... */
-			/* Could check the LDT for lm, but for now it's good
-			   enough to assume that long mode only uses well known
-			   segments or kernel. */
+			/*
+			 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
+			 * Need to figure out under what instruction mode the
+			 * instruction was issued. Could check the LDT for lm,
+			 * but for now it's good enough to assume that long
+			 * mode only uses well known segments or kernel.
+			 */
 			scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS);
 			break;
-			
+#endif
 		case 0x60:
 			/* 0x64 thru 0x67 are valid prefixes in all modes. */
 			scan_more = (instr_lo & 0xC) == 0x4;
@@ -296,7 +301,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 {
 	struct task_struct *tsk;
 	struct mm_struct *mm;
-	struct vm_area_struct * vma;
+	struct vm_area_struct *vma;
 	unsigned long address;
 	int write, fault;
 	unsigned long flags;
@@ -360,8 +365,8 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 		pgtable_bad(address, regs, error_code);
 
 	/*
-	 * If we're in an interrupt or have no user
-	 * context, we must not take the fault..
+	 * If we're in an interrupt, have no user context or are running in an
+	 * atomic region then we must not take the fault.
 	 */
 	if (unlikely(in_atomic() || !mm))
 		goto bad_area_nosemaphore;
@@ -403,7 +408,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 		goto good_area;
 	if (!(vma->vm_flags & VM_GROWSDOWN))
 		goto bad_area;
-	if (error_code & 4) {
+	if (error_code & PF_USER) {
 		/* Allow userspace just enough access below the stack pointer
 		 * to let the 'enter' instruction work.
 		 */
@@ -505,11 +510,9 @@ bad_area_nosemaphore:
 	}
 
 no_context:
-	
 	/* Are we prepared to handle this kernel fault?  */
-	if (fixup_exception(regs)) {
+	if (fixup_exception(regs))
 		return;
-	}
 
 	/*
 	 * Hall of shame of CPU/BIOS bugs.
@@ -532,7 +535,7 @@ no_context:
 		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
 	else
 		printk(KERN_ALERT "Unable to handle kernel paging request");
-	printk(" at %016lx RIP: \n" KERN_ALERT,address);
+	printk(" at %016lx RIP: \n" KERN_ALERT, address);
 	printk_address(regs->ip);
 	dump_pagetable(address);
 	tsk->thread.cr2 = address;