x86: PAT: modify follow_phys to return phys_addr prot and return value

Impact: Changes and globalizes an existing static interface.

Follow_phys does similar things as follow_pfnmap_pte. Make a minor change
to follow_phys so that it can be used in place of follow_pfnmap_pte.
Physical address return value with 0 as error return does not work in
follow_phys as the actual physical address 0 mapping may exist in pte.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 16 insertions, 17 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 35f811b0cd69..2f6e2f886d4b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -804,6 +804,8 @@ int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
                         struct vm_area_struct *vma);
 void unmap_mapping_range(struct address_space *mapping,
                 loff_t const holebegin, loff_t const holelen, int even_cows);
+int follow_phys(struct vm_area_struct *vma, unsigned long address,
+                unsigned int flags, unsigned long *prot, resource_size_t *phys);
 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
                         void *buf, int len, int write);
 
diff --git a/mm/memory.c b/mm/memory.c
index 1e8f0d347c0e..79f28e35d4fc 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2981,9 +2981,9 @@ int in_gate_area_no_task(unsigned long addr)
 #endif  /* __HAVE_ARCH_GATE_AREA */
 
 #ifdef CONFIG_HAVE_IOREMAP_PROT
-static resource_size_t follow_phys(struct vm_area_struct *vma,
-                        unsigned long address, unsigned int flags,
-                        unsigned long *prot)
+int follow_phys(struct vm_area_struct *vma,
+                unsigned long address, unsigned int flags,
+                unsigned long *prot, resource_size_t *phys)
 {
         pgd_t *pgd;
         pud_t *pud;
@@ -2992,24 +2992,26 @@ static resource_size_t follow_phys(struct vm_area_struct *vma,
         spinlock_t *ptl;
         resource_size_t phys_addr = 0;
         struct mm_struct *mm = vma->vm_mm;
+        int ret = -EINVAL;
 
-        VM_BUG_ON(!(vma->vm_flags & (VM_IO | VM_PFNMAP)));
+        if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
+                goto out;
 
         pgd = pgd_offset(mm, address);
         if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
-                goto no_page_table;
+                goto out;
 
         pud = pud_offset(pgd, address);
         if (pud_none(*pud) || unlikely(pud_bad(*pud)))
-                goto no_page_table;
+                goto out;
 
         pmd = pmd_offset(pud, address);
         if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
-                goto no_page_table;
+                goto out;
 
         /* We cannot handle huge page PFN maps. Luckily they don't exist. */
         if (pmd_huge(*pmd))
-                goto no_page_table;
+                goto out;
 
         ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
         if (!ptep)
@@ -3024,13 +3026,13 @@ static resource_size_t follow_phys(struct vm_area_struct *vma,
         phys_addr <<= PAGE_SHIFT; /* Shift here to avoid overflow on PAE */
 
         *prot = pgprot_val(pte_pgprot(pte));
+        *phys = phys_addr;
+        ret = 0;
 
 unlock:
         pte_unmap_unlock(ptep, ptl);
 out:
-        return phys_addr;
-no_page_table:
-        return 0;
+        return ret;
 }
 
 int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
@@ -3041,12 +3043,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
         void *maddr;
         int offset = addr & (PAGE_SIZE-1);
 
-        if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
-                return -EINVAL;
-
-        phys_addr = follow_phys(vma, addr, write, &prot);
-
-        if (!phys_addr)
+        if (follow_phys(vma, addr, write, &prot, &phys_addr))
                 return -EINVAL;
 
         maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);