[PATCH] x86_64: Convert page fault error codes to symbolic constants.

Much better to deal with these than with the magic numbers.

And remove the comment describing the bits - kernel source
is no replacement for an architecture manual.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 17 insertions, 17 deletions

diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index 2a9c836133a9..26eac194064b 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -35,6 +35,13 @@
 #include <asm-generic/sections.h>
 #include <asm/kdebug.h>
 
+/* Page fault error code bits */
+#define PF_PROT (1<<0)          /* or no page found */
+#define PF_WRITE        (1<<1)
+#define PF_USER (1<<2)
+#define PF_RSVD (1<<3)
+#define PF_INSTR        (1<<4)
+
 void bust_spinlocks(int yes)
 {
         int loglevel_save = console_loglevel;
@@ -68,7 +75,7 @@ static noinline int is_prefetch(struct pt_regs *regs, unsigned long addr,
         unsigned char *max_instr;
 
         /* If it was a exec fault ignore */
-        if (error_code & (1<<4))
+        if (error_code & PF_INSTR)
                 return 0;
         
         instr = (unsigned char *)convert_rip_to_linear(current, regs);
@@ -293,13 +300,6 @@ int exception_trace = 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
  */
 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
                                         unsigned long error_code)
@@ -350,7 +350,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
                  * is always initialized because it's shared with the main
                  * kernel text. Only vmalloc may need PML4 syncups.
                  */
-                if (!(error_code & 0xd) &&
+                if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
                       ((address >= VMALLOC_START && address < VMALLOC_END))) {
                         if (vmalloc_fault(address) < 0)
                                 goto bad_area_nosemaphore;
@@ -363,7 +363,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
                 goto bad_area_nosemaphore;
         }
 
-        if (unlikely(error_code & (1 << 3)))
+        if (unlikely(error_code & PF_RSVD))
                 pgtable_bad(address, regs, error_code);
 
         /*
@@ -390,7 +390,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
          * 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->rip))
                         goto bad_area_nosemaphore;
                 down_read(&mm->mmap_sem);
@@ -417,17 +417,17 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 good_area:
         info.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 */
+                case 0:                 /* read, not present */
                         if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                                 goto bad_area;
         }
@@ -462,7 +462,7 @@ bad_area:
 
 bad_area_nosemaphore:
         /* User mode accesses just cause a SIGSEGV */
-        if (error_code & 4) {
+        if (error_code & PF_USER) {
                 if (is_prefetch(regs, address, error_code))
                         return;
 
@@ -558,7 +558,7 @@ 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;
 
         tsk->thread.cr2 = address;