x86, mm: fault.c cleanup

Impact: cleanup, no code changed

Clean up various small details, which can be correctness checked
automatically:

 - tidy up the include file section
 - eliminate unnecessary includes
 - introduce show_signal_msg() to clean up code flow
 - standardize the code flow
 - standardize comments and other style details
 - more cleanups, pointed out by checkpatch

No code changed on either 32-bit nor 64-bit:

arch/x86/mm/fault.o:

   text	   data	    bss	    dec	    hex	filename
   4632	     32	     24	   4688	   1250	fault.o.before
   4632	     32	     24	   4688	   1250	fault.o.after

the md5 changed due to a change in a single instruction:

   2e8a8241e7f0d69706776a5a26c90bc0  fault.o.before.asm
   c5c3d36e725586eb74f0e10692f0193e  fault.o.after.asm

Because a __LINE__ reference in a WARN_ONCE() has changed.

On 32-bit a few stack offsets changed - no code size difference
nor any functionality difference.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 331 insertions, 215 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e4b9fc5001c6..351d679bf977 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1,56 +1,59 @@
 /*
  *  Copyright (C) 1995  Linus Torvalds
- *  Copyright (C) 2001,2002 Andi Kleen, SuSE Labs.
+ *  Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
  */
-
-#include <linux/signal.h>
-#include <linux/sched.h>
-#include <linux/kernel.h>
-#include <linux/errno.h>
-#include <linux/string.h>
-#include <linux/types.h>
-#include <linux/ptrace.h>
-#include <linux/mmiotrace.h>
-#include <linux/mman.h>
-#include <linux/mm.h>
-#include <linux/smp.h>
 #include <linux/interrupt.h>
-#include <linux/init.h>
-#include <linux/tty.h>
-#include <linux/vt_kern.h>              /* For unblank_screen() */
+#include <linux/mmiotrace.h>
+#include <linux/bootmem.h>
 #include <linux/compiler.h>
 #include <linux/highmem.h>
-#include <linux/bootmem.h>              /* for max_low_pfn */
-#include <linux/vmalloc.h>
-#include <linux/module.h>
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <linux/vt_kern.h>
+#include <linux/signal.h>
+#include <linux/kernel.h>
+#include <linux/ptrace.h>
+#include <linux/string.h>
+#include <linux/module.h>
 #include <linux/kdebug.h>
+#include <linux/errno.h>
 #include <linux/magic.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/mman.h>
+#include <linux/tty.h>
+#include <linux/smp.h>
+#include <linux/mm.h>
+
+#include <asm-generic/sections.h>
 
-#include <asm/system.h>
-#include <asm/desc.h>
-#include <asm/segment.h>
-#include <asm/pgalloc.h>
-#include <asm/smp.h>
 #include <asm/tlbflush.h>
+#include <asm/pgalloc.h>
+#include <asm/segment.h>
+#include <asm/system.h>
 #include <asm/proto.h>
-#include <asm-generic/sections.h>
 #include <asm/traps.h>
+#include <asm/desc.h>
 
 /*
- * 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
+ * Page fault error code bits:
+ *
+ *   bit 0 ==    0: no page found       1: protection fault
+ *   bit 1 ==    0: read access         1: write access
+ *   bit 2 ==    0: kernel-mode access  1: user-mode access
+ *   bit 3 ==                           1: use of reserved bit detected
+ *   bit 4 ==                           1: 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)
+enum x86_pf_error_code {
+
+        PF_PROT         =               1 << 0,
+        PF_WRITE        =               1 << 1,
+        PF_USER         =               1 << 2,
+        PF_RSVD         =               1 << 3,
+        PF_INSTR        =               1 << 4,
+};
 
 static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr)
 {
@@ -82,23 +85,27 @@ static inline int notify_page_fault(struct pt_regs *regs)
 }
 
 /*
- * X86_32
- * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
- * Check that here and ignore it.
+ * Prefetch quirks:
+ *
+ * 32-bit mode:
+ *
+ *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
+ *   Check that here and ignore it.
  *
- * X86_64
- * Sometimes the CPU reports invalid exceptions on prefetch.
- * Check that here and ignore it.
+ * 64-bit mode:
  *
- * Opcode checker based on code by Richard Brunner
+ *   Sometimes the CPU reports invalid exceptions on prefetch.
+ *   Check that here and ignore it.
+ *
+ * Opcode checker based on code by Richard Brunner.
  */
-static int is_prefetch(struct pt_regs *regs, unsigned long error_code,
-                        unsigned long addr)
+static int
+is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
 {
+        unsigned char *max_instr;
         unsigned char *instr;
         int scan_more = 1;
         int prefetch = 0;
-        unsigned char *max_instr;
 
         /*
          * If it was a exec (instruction fetch) fault on NX page, then
@@ -114,9 +121,9 @@ static int is_prefetch(struct pt_regs *regs, unsigned long error_code,
                 return 0;
 
         while (scan_more && instr < max_instr) {
-                unsigned char opcode;
                 unsigned char instr_hi;
                 unsigned char instr_lo;
+                unsigned char opcode;
 
                 if (probe_kernel_address(instr, opcode))
                         break;
@@ -173,15 +180,17 @@ static int is_prefetch(struct pt_regs *regs, unsigned long error_code,
         return prefetch;
 }
 
-static void force_sig_info_fault(int si_signo, int si_code,
-        unsigned long address, struct task_struct *tsk)
+static void
+force_sig_info_fault(int si_signo, int si_code, unsigned long address,
+                     struct task_struct *tsk)
 {
         siginfo_t info;
 
-        info.si_signo = si_signo;
-        info.si_errno = 0;
-        info.si_code = si_code;
-        info.si_addr = (void __user *)address;
+        info.si_signo   = si_signo;
+        info.si_errno   = 0;
+        info.si_code    = si_code;
+        info.si_addr    = (void __user *)address;
+
         force_sig_info(si_signo, &info, tsk);
 }
 
@@ -189,6 +198,7 @@ static void force_sig_info_fault(int si_signo, int si_code,
 static int bad_address(void *p)
 {
         unsigned long dummy;
+
         return probe_kernel_address((unsigned long *)p, dummy);
 }
 #endif
@@ -200,13 +210,14 @@ static void dump_pagetable(unsigned long address)
 
         page = read_cr3();
         page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
+
 #ifdef CONFIG_X86_PAE
         printk("*pdpt = %016Lx ", page);
         if ((page >> PAGE_SHIFT) < max_low_pfn
             && page & _PAGE_PRESENT) {
                 page &= PAGE_MASK;
                 page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
-                                                         & (PTRS_PER_PMD - 1)];
+                                                        & (PTRS_PER_PMD - 1)];
                 printk(KERN_CONT "*pde = %016Lx ", page);
                 page &= ~_PAGE_NX;
         }
@@ -218,14 +229,15 @@ static void dump_pagetable(unsigned long address)
          * We must not directly access the pte in the highpte
          * case if the page table is located in highmem.
          * And let's rather not kmap-atomic the pte, just in case
-         * it's allocated already.
+         * it's allocated already:
          */
         if ((page >> PAGE_SHIFT) < max_low_pfn
             && (page & _PAGE_PRESENT)
             && !(page & _PAGE_PSE)) {
+
                 page &= PAGE_MASK;
                 page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
-                                                         & (PTRS_PER_PTE - 1)];
+                                                        & (PTRS_PER_PTE - 1)];
                 printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
         }
 
@@ -239,26 +251,38 @@ static void dump_pagetable(unsigned long address)
         pgd = (pgd_t *)read_cr3();
 
         pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK);
+
         pgd += pgd_index(address);
-        if (bad_address(pgd)) goto bad;
+        if (bad_address(pgd))
+                goto bad;
+
         printk("PGD %lx ", pgd_val(*pgd));
-        if (!pgd_present(*pgd)) goto ret;
+
+        if (!pgd_present(*pgd))
+                goto out;
 
         pud = pud_offset(pgd, address);
-        if (bad_address(pud)) goto bad;
+        if (bad_address(pud))
+                goto bad;
+
         printk("PUD %lx ", pud_val(*pud));
         if (!pud_present(*pud) || pud_large(*pud))
-                goto ret;
+                goto out;
 
         pmd = pmd_offset(pud, address);
-        if (bad_address(pmd)) goto bad;
+        if (bad_address(pmd))
+                goto bad;
+
         printk("PMD %lx ", pmd_val(*pmd));
-        if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret;
+        if (!pmd_present(*pmd) || pmd_large(*pmd))
+                goto out;
 
         pte = pte_offset_kernel(pmd, address);
-        if (bad_address(pte)) goto bad;
+        if (bad_address(pte))
+                goto bad;
+
         printk("PTE %lx", pte_val(*pte));
-ret:
+out:
         printk("\n");
         return;
 bad:
@@ -285,7 +309,6 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
          * and redundant with the set_pmd() on non-PAE. As would
          * set_pud.
          */
-
         pud = pud_offset(pgd, address);
         pud_k = pud_offset(pgd_k, address);
         if (!pud_present(*pud_k))
@@ -295,11 +318,14 @@ static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
         pmd_k = pmd_offset(pud_k, address);
         if (!pmd_present(*pmd_k))
                 return NULL;
+
         if (!pmd_present(*pmd)) {
                 set_pmd(pmd, *pmd_k);
                 arch_flush_lazy_mmu_mode();
-        } else
+        } else {
                 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
+        }
+
         return pmd_k;
 }
 #endif
@@ -312,29 +338,37 @@ KERN_ERR "******* Please consider a BIOS update.\n"
 KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n";
 #endif
 
-/* Workaround for K8 erratum #93 & buggy BIOS.
-   BIOS SMM functions are required to use a specific workaround
-   to avoid corruption of the 64bit RIP register on C stepping K8.
-   A lot of BIOS that didn't get tested properly miss this.
-   The OS sees this as a page fault with the upper 32bits of RIP cleared.
-   Try to work around it here.
-   Note we only handle faults in kernel here.
-   Does nothing for X86_32
+/*
+ * Workaround for K8 erratum #93 & buggy BIOS.
+ *
+ * BIOS SMM functions are required to use a specific workaround
+ * to avoid corruption of the 64bit RIP register on C stepping K8.
+ *
+ * A lot of BIOS that didn't get tested properly miss this.
+ *
+ * The OS sees this as a page fault with the upper 32bits of RIP cleared.
+ * Try to work around it here.
+ *
+ * Note we only handle faults in kernel here.
+ * Does nothing on 32-bit.
  */
 static int is_errata93(struct pt_regs *regs, unsigned long address)
 {
 #ifdef CONFIG_X86_64
-        static int warned;
+        static int once;
+
         if (address != regs->ip)
                 return 0;
+
         if ((address >> 32) != 0)
                 return 0;
+
         address |= 0xffffffffUL << 32;
         if ((address >= (u64)_stext && address <= (u64)_etext) ||
             (address >= MODULES_VADDR && address <= MODULES_END)) {
-                if (!warned) {
+                if (!once) {
                         printk(errata93_warning);
-                        warned = 1;
+                        once = 1;
                 }
                 regs->ip = address;
                 return 1;
@@ -344,16 +378,17 @@ static int is_errata93(struct pt_regs *regs, unsigned long address)
 }
 
 /*
- * Work around K8 erratum #100 K8 in compat mode occasionally jumps to illegal
- * addresses >4GB.  We catch this in the page fault handler because these
- * addresses are not reachable. Just detect this case and return.  Any code
+ * Work around K8 erratum #100 K8 in compat mode occasionally jumps
+ * to illegal addresses >4GB.
+ *
+ * We catch this in the page fault handler because these addresses
+ * are not reachable. Just detect this case and return.  Any code
  * segment in LDT is compatibility mode.
  */
 static int is_errata100(struct pt_regs *regs, unsigned long address)
 {
 #ifdef CONFIG_X86_64
-        if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) &&
-            (address >> 32))
+        if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
                 return 1;
 #endif
         return 0;
@@ -363,8 +398,9 @@ static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
 {
 #ifdef CONFIG_X86_F00F_BUG
         unsigned long nr;
+
         /*
-         * Pentium F0 0F C7 C8 bug workaround.
+         * Pentium F0 0F C7 C8 bug workaround:
          */
         if (boot_cpu_data.f00f_bug) {
                 nr = (address - idt_descr.address) >> 3;
@@ -378,8 +414,9 @@ static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
         return 0;
 }
 
-static void show_fault_oops(struct pt_regs *regs, unsigned long error_code,
-                            unsigned long address)
+static void
+show_fault_oops(struct pt_regs *regs, unsigned long error_code,
+                unsigned long address)
 {
 #ifdef CONFIG_X86_32
         if (!oops_may_print())
@@ -389,12 +426,14 @@ static void show_fault_oops(struct pt_regs *regs, unsigned long error_code,
 #ifdef CONFIG_X86_PAE
         if (error_code & PF_INSTR) {
                 unsigned int level;
+
                 pte_t *pte = lookup_address(address, &level);
 
-                if (pte && pte_present(*pte) && !pte_exec(*pte))
+                if (pte && pte_present(*pte) && !pte_exec(*pte)) {
                         printk(KERN_CRIT "kernel tried to execute "
                                 "NX-protected page - exploit attempt? "
                                 "(uid: %d)\n", current_uid());
+                }
         }
 #endif
 
@@ -403,34 +442,45 @@ static void show_fault_oops(struct pt_regs *regs, unsigned long error_code,
                 printk(KERN_CONT "NULL pointer dereference");
         else
                 printk(KERN_CONT "paging request");
+
         printk(KERN_CONT " at %p\n", (void *) address);
         printk(KERN_ALERT "IP:");
         printk_address(regs->ip, 1);
+
         dump_pagetable(address);
 }
 
 #ifdef CONFIG_X86_64
-static noinline void pgtable_bad(struct pt_regs *regs,
-                         unsigned long error_code, unsigned long address)
+static noinline void
+pgtable_bad(struct pt_regs *regs, unsigned long error_code,
+            unsigned long address)
 {
-        unsigned long flags = oops_begin();
-        int sig = SIGKILL;
-        struct task_struct *tsk = current;
+        struct task_struct *tsk;
+        unsigned long flags;
+        int sig;
+
+        flags = oops_begin();
+        tsk = current;
+        sig = SIGKILL;
 
         printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
                tsk->comm, address);
         dump_pagetable(address);
-        tsk->thread.cr2 = address;
-        tsk->thread.trap_no = 14;
-        tsk->thread.error_code = error_code;
+
+        tsk->thread.cr2         = address;
+        tsk->thread.trap_no     = 14;
+        tsk->thread.error_code  = error_code;
+
         if (__die("Bad pagetable", regs, error_code))
                 sig = 0;
+
         oops_end(flags, regs, sig);
 }
 #endif
 
-static noinline void no_context(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address)
+static noinline void
+no_context(struct pt_regs *regs, unsigned long error_code,
+           unsigned long address)
 {
         struct task_struct *tsk = current;
         unsigned long *stackend;
@@ -440,18 +490,20 @@ static noinline void no_context(struct pt_regs *regs,
         int sig;
 #endif
 
-        /* Are we prepared to handle this kernel fault?  */
+        /* Are we prepared to handle this kernel fault? */
         if (fixup_exception(regs))
                 return;
 
         /*
-         * X86_32
-         * Valid to do another page fault here, because if this fault
-         * had been triggered by is_prefetch fixup_exception would have
-         * handled it.
+         * 32-bit:
+         *
+         *   Valid to do another page fault here, because if this fault
+         *   had been triggered by is_prefetch fixup_exception would have
+         *   handled it.
+         *
+         * 64-bit:
          *
-         * X86_64
-         * Hall of shame of CPU/BIOS bugs.
+         *   Hall of shame of CPU/BIOS bugs.
          */
         if (is_prefetch(regs, error_code, address))
                 return;
@@ -461,7 +513,7 @@ static noinline void no_context(struct pt_regs *regs,
 
         /*
          * Oops. The kernel tried to access some bad page. We'll have to
-         * terminate things with extreme prejudice.
+         * terminate things with extreme prejudice:
          */
 #ifdef CONFIG_X86_32
         bust_spinlocks(1);
@@ -471,7 +523,7 @@ static noinline void no_context(struct pt_regs *regs,
 
         show_fault_oops(regs, error_code, address);
 
-        stackend = end_of_stack(tsk);
+        stackend = end_of_stack(tsk);
         if (*stackend != STACK_END_MAGIC)
                 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
 
@@ -487,28 +539,54 @@ static noinline void no_context(struct pt_regs *regs,
         sig = SIGKILL;
         if (__die("Oops", regs, error_code))
                 sig = 0;
+
         /* Executive summary in case the body of the oops scrolled away */
         printk(KERN_EMERG "CR2: %016lx\n", address);
+
         oops_end(flags, regs, sig);
 #endif
 }
 
-static void __bad_area_nosemaphore(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address,
-                        int si_code)
+/*
+ * Print out info about fatal segfaults, if the show_unhandled_signals
+ * sysctl is set:
+ */
+static inline void
+show_signal_msg(struct pt_regs *regs, unsigned long error_code,
+                unsigned long address, struct task_struct *tsk)
+{
+        if (!unhandled_signal(tsk, SIGSEGV))
+                return;
+
+        if (!printk_ratelimit())
+                return;
+
+        printk(KERN_CONT "%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
+                task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
+                tsk->comm, task_pid_nr(tsk), address,
+                (void *)regs->ip, (void *)regs->sp, error_code);
+
+        print_vma_addr(KERN_CONT " in ", regs->ip);
+
+        printk(KERN_CONT "\n");
+}
+
+static void
+__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
+                       unsigned long address, int si_code)
 {
         struct task_struct *tsk = current;
 
         /* User mode accesses just cause a SIGSEGV */
         if (error_code & PF_USER) {
                 /*
-                 * It's possible to have interrupts off here.
+                 * It's possible to have interrupts off here:
                  */
                 local_irq_enable();
 
                 /*
                  * Valid to do another page fault here because this one came
-                 * from user space.
+                 * from user space:
                  */
                 if (is_prefetch(regs, error_code, address))
                         return;
@@ -516,22 +594,16 @@ static void __bad_area_nosemaphore(struct pt_regs *regs,
                 if (is_errata100(regs, address))
                         return;
 
-                if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
-                    printk_ratelimit()) {
-                        printk(
-                        "%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
-                        task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
-                        tsk->comm, task_pid_nr(tsk), address,
-                        (void *) regs->ip, (void *) regs->sp, error_code);
-                        print_vma_addr(" in ", regs->ip);
-                        printk("\n");
-                }
+                if (unlikely(show_unhandled_signals))
+                        show_signal_msg(regs, error_code, address, tsk);
+
+                /* Kernel addresses are always protection faults: */
+                tsk->thread.cr2         = address;
+                tsk->thread.error_code  = error_code | (address >= TASK_SIZE);
+                tsk->thread.trap_no     = 14;
 
-                tsk->thread.cr2 = address;
-                /* Kernel addresses are always protection faults */
-                tsk->thread.error_code = error_code | (address >= TASK_SIZE);
-                tsk->thread.trap_no = 14;
                 force_sig_info_fault(SIGSEGV, si_code, address, tsk);
+
                 return;
         }
 
@@ -541,15 +613,16 @@ static void __bad_area_nosemaphore(struct pt_regs *regs,
         no_context(regs, error_code, address);
 }
 
-static noinline void bad_area_nosemaphore(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address)
+static noinline void
+bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
+                     unsigned long address)
 {
         __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
 }
 
-static void __bad_area(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address,
-                        int si_code)
+static void
+__bad_area(struct pt_regs *regs, unsigned long error_code,
+           unsigned long address, int si_code)
 {
         struct mm_struct *mm = current->mm;
 
@@ -562,67 +635,77 @@ static void __bad_area(struct pt_regs *regs,
         __bad_area_nosemaphore(regs, error_code, address, si_code);
 }
 
-static noinline void bad_area(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address)
+static noinline void
+bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 {
         __bad_area(regs, error_code, address, SEGV_MAPERR);
 }
 
-static noinline void bad_area_access_error(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address)
+static noinline void
+bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
+                      unsigned long address)
 {
         __bad_area(regs, error_code, address, SEGV_ACCERR);
 }
 
 /* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
-static void out_of_memory(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address)
+static void
+out_of_memory(struct pt_regs *regs, unsigned long error_code,
+              unsigned long address)
 {
         /*
          * We ran out of memory, call the OOM killer, and return the userspace
-         * (which will retry the fault, or kill us if we got oom-killed).
+         * (which will retry the fault, or kill us if we got oom-killed):
          */
         up_read(&current->mm->mmap_sem);
+
         pagefault_out_of_memory();
 }
 
-static void do_sigbus(struct pt_regs *regs,
-                        unsigned long error_code, unsigned long address)
+static void
+do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
 {
         struct task_struct *tsk = current;
         struct mm_struct *mm = tsk->mm;
 
         up_read(&mm->mmap_sem);
 
-        /* Kernel mode? Handle exceptions or die */
+        /* Kernel mode? Handle exceptions or die: */
         if (!(error_code & PF_USER))
                 no_context(regs, error_code, address);
+
 #ifdef CONFIG_X86_32
-        /* User space => ok to do another page fault */
+        /* User space => ok to do another page fault: */
         if (is_prefetch(regs, error_code, address))
                 return;
 #endif
-        tsk->thread.cr2 = address;
-        tsk->thread.error_code = error_code;
-        tsk->thread.trap_no = 14;
+
+        tsk->thread.cr2         = address;
+        tsk->thread.error_code  = error_code;
+        tsk->thread.trap_no     = 14;
+
         force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
 }
 
-static noinline void mm_fault_error(struct pt_regs *regs,
-                unsigned long error_code, unsigned long address, unsigned int fault)
+static noinline void
+mm_fault_error(struct pt_regs *regs, unsigned long error_code,
+               unsigned long address, unsigned int fault)
 {
-        if (fault & VM_FAULT_OOM)
+        if (fault & VM_FAULT_OOM) {
                 out_of_memory(regs, error_code, address);
-        else if (fault & VM_FAULT_SIGBUS)
-                do_sigbus(regs, error_code, address);
-        else
-                BUG();
+        } else {
+                if (fault & VM_FAULT_SIGBUS)
+                        do_sigbus(regs, error_code, address);
+                else
+                        BUG();
+        }
 }
 
 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
 {
         if ((error_code & PF_WRITE) && !pte_write(*pte))
                 return 0;
+
         if ((error_code & PF_INSTR) && !pte_exec(*pte))
                 return 0;
 
@@ -630,16 +713,19 @@ static int spurious_fault_check(unsigned long error_code, pte_t *pte)
 }
 
 /*
- * Handle a spurious fault caused by a stale TLB entry.  This allows
- * us to lazily refresh the TLB when increasing the permissions of a
- * kernel page (RO -> RW or NX -> X).  Doing it eagerly is very
- * expensive since that implies doing a full cross-processor TLB
- * flush, even if no stale TLB entries exist on other processors.
+ * Handle a spurious fault caused by a stale TLB entry.
+ *
+ * This allows us to lazily refresh the TLB when increasing the
+ * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
+ * eagerly is very expensive since that implies doing a full
+ * cross-processor TLB flush, even if no stale TLB entries exist
+ * on other processors.
+ *
  * There are no security implications to leaving a stale TLB when
  * increasing the permissions on a page.
  */
-static noinline int spurious_fault(unsigned long error_code,
-                                unsigned long address)
+static noinline int
+spurious_fault(unsigned long error_code, unsigned long address)
 {
         pgd_t *pgd;
         pud_t *pud;
@@ -678,20 +764,23 @@ static noinline int spurious_fault(unsigned long error_code,
                 return 0;
 
         /*
-         * Make sure we have permissions in PMD
-         * If not, then there's a bug in the page tables.
+         * Make sure we have permissions in PMD.
+         * If not, then there's a bug in the page tables:
          */
         ret = spurious_fault_check(error_code, (pte_t *) pmd);
         WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
+
         return ret;
 }
 
 /*
- * X86_32
- * Handle a fault on the vmalloc or module mapping area
+ * 32-bit:
+ *
+ *   Handle a fault on the vmalloc or module mapping area
  *
- * X86_64
- * Handle a fault on the vmalloc area
+ * 64-bit:
+ *
+ *   Handle a fault on the vmalloc area
  *
  * This assumes no large pages in there.
  */
@@ -702,7 +791,7 @@ static noinline int vmalloc_fault(unsigned long address)
         pmd_t *pmd_k;
         pte_t *pte_k;
 
-        /* Make sure we are in vmalloc area */
+        /* Make sure we are in vmalloc area: */
         if (!(address >= VMALLOC_START && address < VMALLOC_END))
                 return -1;
 
@@ -717,9 +806,11 @@ static noinline int vmalloc_fault(unsigned long address)
         pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
         if (!pmd_k)
                 return -1;
+
         pte_k = pte_offset_kernel(pmd_k, address);
         if (!pte_present(*pte_k))
                 return -1;
+
         return 0;
 #else
         pgd_t *pgd, *pgd_ref;
@@ -727,69 +818,84 @@ static noinline int vmalloc_fault(unsigned long address)
         pmd_t *pmd, *pmd_ref;
         pte_t *pte, *pte_ref;
 
-        /* Make sure we are in vmalloc area */
+        /* Make sure we are in vmalloc area: */
         if (!(address >= VMALLOC_START && address < VMALLOC_END))
                 return -1;
 
-        /* Copy kernel mappings over when needed. This can also
-           happen within a race in page table update. In the later
-           case just flush. */
-
+        /*
+         * Copy kernel mappings over when needed. This can also
+         * happen within a race in page table update. In the later
+         * case just flush:
+         */
         pgd = pgd_offset(current->active_mm, address);
         pgd_ref = pgd_offset_k(address);
         if (pgd_none(*pgd_ref))
                 return -1;
+
         if (pgd_none(*pgd))
                 set_pgd(pgd, *pgd_ref);
         else
                 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
 
-        /* Below here mismatches are bugs because these lower tables
-           are shared */
+        /*
+         * Below here mismatches are bugs because these lower tables
+         * are shared:
+         */
 
         pud = pud_offset(pgd, address);
         pud_ref = pud_offset(pgd_ref, address);
         if (pud_none(*pud_ref))
                 return -1;
+
         if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
                 BUG();
+
         pmd = pmd_offset(pud, address);
         pmd_ref = pmd_offset(pud_ref, address);
         if (pmd_none(*pmd_ref))
                 return -1;
+
         if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
                 BUG();
+
         pte_ref = pte_offset_kernel(pmd_ref, address);
         if (!pte_present(*pte_ref))
                 return -1;
+
         pte = pte_offset_kernel(pmd, address);
-        /* Don't use pte_page here, because the mappings can point
-           outside mem_map, and the NUMA hash lookup cannot handle
-           that. */
+
+        /*
+         * Don't use pte_page here, because the mappings can point
+         * outside mem_map, and the NUMA hash lookup cannot handle
+         * that:
+         */
         if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
                 BUG();
+
         return 0;
 #endif
 }
 
 int show_unhandled_signals = 1;
 
-static inline int access_error(unsigned long error_code, int write,
-                                struct vm_area_struct *vma)
+static inline int
+access_error(unsigned long error_code, int write, struct vm_area_struct *vma)
 {
         if (write) {
-                /* write, present and write, not present */
+                /* write, present and write, not present: */
                 if (unlikely(!(vma->vm_flags & VM_WRITE)))
                         return 1;
-        } else if (unlikely(error_code & PF_PROT)) {
-                /* read, present */
-                return 1;
-        } else {
-                /* read, not present */
-                if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
-                        return 1;
+                return 0;
         }
 
+        /* read, present: */
+        if (unlikely(error_code & PF_PROT))
+                return 1;
+
+        /* read, not present: */
+        if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
+                return 1;
+
         return 0;
 }
 
@@ -797,9 +903,9 @@ static int fault_in_kernel_space(unsigned long address)
 {
 #ifdef CONFIG_X86_32
         return address >= TASK_SIZE;
-#else /* !CONFIG_X86_32 */
+#else
         return address >= TASK_SIZE64;
-#endif /* CONFIG_X86_32 */
+#endif
 }
 
 /*
@@ -812,18 +918,19 @@ asmlinkage
 #endif
 void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 {
-        unsigned long address;
+        struct vm_area_struct *vma;
         struct task_struct *tsk;
+        unsigned long address;
         struct mm_struct *mm;
-        struct vm_area_struct *vma;
         int write;
         int fault;
 
         tsk = current;
         mm = tsk->mm;
+
         prefetchw(&mm->mmap_sem);
 
-        /* get the address */
+        /* Get the faulting address: */
         address = read_cr2();
 
         if (unlikely(kmmio_fault(regs, address)))
@@ -847,22 +954,23 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
                     vmalloc_fault(address) >= 0)
                         return;
 
-                /* Can handle a stale RO->RW TLB */
+                /* Can handle a stale RO->RW TLB: */
                 if (spurious_fault(error_code, address))
                         return;
 
-                /* kprobes don't want to hook the spurious faults. */
+                /* kprobes don't want to hook the spurious faults: */
                 if (notify_page_fault(regs))
                         return;
                 /*
                  * Don't take the mm semaphore here. If we fixup a prefetch
-                 * fault we could otherwise deadlock.
+                 * fault we could otherwise deadlock:
                  */
                 bad_area_nosemaphore(regs, error_code, address);
+
                 return;
         }
 
-        /* kprobes don't want to hook the spurious faults. */
+        /* kprobes don't want to hook the spurious faults: */
         if (unlikely(notify_page_fault(regs)))
                 return;
         /*
@@ -870,13 +978,15 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
          * vmalloc fault has been handled.
          *
          * User-mode registers count as a user access even for any
-         * potential system fault or CPU buglet.
+         * potential system fault or CPU buglet:
          */
         if (user_mode_vm(regs)) {
                 local_irq_enable();
                 error_code |= PF_USER;
-        } else if (regs->flags & X86_EFLAGS_IF)
-                local_irq_enable();
+        } else {
+                if (regs->flags & X86_EFLAGS_IF)
+                        local_irq_enable();
+        }
 
 #ifdef CONFIG_X86_64
         if (unlikely(error_code & PF_RSVD))
@@ -884,8 +994,8 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 #endif
 
         /*
-         * 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 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)) {
                 bad_area_nosemaphore(regs, error_code, address);
@@ -894,19 +1004,19 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
         /*
          * When running in the kernel we expect faults to occur only to
-         * addresses in user space.  All other faults represent errors in the
-         * kernel and should generate an OOPS.  Unfortunately, in the case of an
-         * erroneous fault occurring in a code path which already holds mmap_sem
-         * we will deadlock attempting to validate the fault against the
-         * address space.  Luckily the kernel only validly references user
-         * space from well defined areas of code, which are listed in the
-         * exceptions table.
+         * addresses in user space.  All other faults represent errors in
+         * the kernel and should generate an OOPS.  Unfortunately, in the
+         * case of an erroneous fault occurring in a code path which already
+         * holds mmap_sem we will deadlock attempting to validate the fault
+         * against the address space.  Luckily the kernel only validly
+         * references user space from well defined areas of code, which are
+         * listed in the exceptions table.
          *
          * As the vast majority of faults will be valid we will only perform
-         * the source reference check when there is a possibility of a deadlock.
-         * Attempt to lock the address space, if we cannot we then validate the
-         * source.  If this is invalid we can skip the address space check,
-         * thus avoiding the deadlock.
+         * the source reference check when there is a possibility of a
+         * deadlock. Attempt to lock the address space, if we cannot we then
+         * validate the source. If this is invalid we can skip the address
+         * space check, thus avoiding the deadlock:
          */
         if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
                 if ((error_code & PF_USER) == 0 &&
@@ -917,8 +1027,9 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
                 down_read(&mm->mmap_sem);
         } else {
                 /*
-                 * The above down_read_trylock() might have succeeded in which
-                 * case we'll have missed the might_sleep() from down_read().
+                 * The above down_read_trylock() might have succeeded in
+                 * which case we'll have missed the might_sleep() from
+                 * down_read():
                  */
                 might_sleep();
         }
@@ -938,7 +1049,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
                 /*
                  * Accessing the stack below %sp is always a bug.
                  * The large cushion allows instructions like enter
-                 * and pusha to work.  ("enter $65535,$31" pushes
+                 * and pusha to work. ("enter $65535, $31" pushes
                  * 32 pointers and then decrements %sp by 65535.)
                  */
                 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
@@ -957,6 +1068,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
          */
 good_area:
         write = error_code & PF_WRITE;
+
         if (unlikely(access_error(error_code, write, vma))) {
                 bad_area_access_error(regs, error_code, address);
                 return;
@@ -965,13 +1077,15 @@ good_area:
         /*
          * If for any reason at all we couldn't handle the fault,
          * make sure we exit gracefully rather than endlessly redo
-         * the fault.
+         * the fault:
          */
         fault = handle_mm_fault(mm, vma, address, write);
+
         if (unlikely(fault & VM_FAULT_ERROR)) {
                 mm_fault_error(regs, error_code, address, fault);
                 return;
         }
+
         if (fault & VM_FAULT_MAJOR)
                 tsk->maj_flt++;
         else
@@ -1004,13 +1118,13 @@ void vmalloc_sync_all(void)
         for (address = VMALLOC_START & PMD_MASK;
              address >= TASK_SIZE && address < FIXADDR_TOP;
              address += PMD_SIZE) {
+
                 unsigned long flags;
                 struct page *page;
 
                 spin_lock_irqsave(&pgd_lock, flags);
                 list_for_each_entry(page, &pgd_list, lru) {
-                        if (!vmalloc_sync_one(page_address(page),
-                                              address))
+                        if (!vmalloc_sync_one(page_address(page), address))
                                 break;
                 }
                 spin_unlock_irqrestore(&pgd_lock, flags);
@@ -1018,12 +1132,14 @@ void vmalloc_sync_all(void)
 #else /* CONFIG_X86_64 */
         for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END;
              address += PGDIR_SIZE) {
+
                 const pgd_t *pgd_ref = pgd_offset_k(address);
                 unsigned long flags;
                 struct page *page;
 
                 if (pgd_none(*pgd_ref))
                         continue;
+
                 spin_lock_irqsave(&pgd_lock, flags);
                 list_for_each_entry(page, &pgd_list, lru) {
                         pgd_t *pgd;