[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>

diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index 2a9c836133a9aa581f7c8aca998a49c39e7afbf2..26eac194064b8a2851705db6cfa3bd1bd5bc5e8a 100644 (file)
--- 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;