[PATCH] uml: fault handler micro-cleanups

Avoid chomping low bits of address for functions doing it by themselves,
fix whitespace, add a correctness checking.

I did this for remap-file-pages protection support, it was useful on its
own too.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 13 insertions, 15 deletions

diff --git a/arch/um/kernel/trap_kern.c b/arch/um/kernel/trap_kern.c
index bef8abd5ea9e..b5fc89fe9eab 100644
--- a/arch/um/kernel/trap_kern.c
+++ b/arch/um/kernel/trap_kern.c
@@ -26,6 +26,7 @@
 #include "mem.h"
 #include "mem_kern.h"
 
+/* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
 int handle_page_fault(unsigned long address, unsigned long ip, 
                       int is_write, int is_user, int *code_out)
 {
@@ -35,7 +36,6 @@ int handle_page_fault(unsigned long address, unsigned long ip,
         pud_t *pud;
         pmd_t *pmd;
         pte_t *pte;
-        unsigned long page;
         int err = -EFAULT;
 
         *code_out = SEGV_MAPERR;
@@ -52,7 +52,7 @@ int handle_page_fault(unsigned long address, unsigned long ip,
         else if(expand_stack(vma, address)) 
                 goto out;
 
- good_area:
+good_area:
         *code_out = SEGV_ACCERR;
         if(is_write && !(vma->vm_flags & VM_WRITE)) 
                 goto out;
@@ -60,9 +60,8 @@ int handle_page_fault(unsigned long address, unsigned long ip,
         if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
                 goto out;
 
-        page = address & PAGE_MASK;
         do {
- survive:
+survive:
                 switch (handle_mm_fault(mm, vma, address, is_write)){
                 case VM_FAULT_MINOR:
                         current->min_flt++;
@@ -79,16 +78,16 @@ int handle_page_fault(unsigned long address, unsigned long ip,
                 default:
                         BUG();
                 }
-                pgd = pgd_offset(mm, page);
-                pud = pud_offset(pgd, page);
-                pmd = pmd_offset(pud, page);
-                pte = pte_offset_kernel(pmd, page);
+                pgd = pgd_offset(mm, address);
+                pud = pud_offset(pgd, address);
+                pmd = pmd_offset(pud, address);
+                pte = pte_offset_kernel(pmd, address);
         } while(!pte_present(*pte));
         err = 0;
         *pte = pte_mkyoung(*pte);
         if(pte_write(*pte)) *pte = pte_mkdirty(*pte);
-        flush_tlb_page(vma, page);
- out:
+        flush_tlb_page(vma, address);
+out:
         up_read(&mm->mmap_sem);
         return(err);
 
@@ -144,19 +143,18 @@ unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 
                       address, ip);
 
-        if(err == -EACCES){
+        if (err == -EACCES) {
                 si.si_signo = SIGBUS;
                 si.si_errno = 0;
                 si.si_code = BUS_ADRERR;
                 si.si_addr = (void *)address;
                 current->thread.arch.faultinfo = fi;
                 force_sig_info(SIGBUS, &si, current);
-        }
-        else if(err == -ENOMEM){
+        } else if (err == -ENOMEM) {
                 printk("VM: killing process %s\n", current->comm);
                 do_exit(SIGKILL);
-        }
-        else {
+        } else {
+                BUG_ON(err != -EFAULT);
                 si.si_signo = SIGSEGV;
                 si.si_addr = (void *) address;
                 current->thread.arch.faultinfo = fi;