8 files changed, 144 insertions, 18 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 8b22d7d8b991..680fb566b928 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -510,6 +510,7 @@ prototypes:
         void (*close)(struct vm_area_struct*);
         int (*fault)(struct vm_area_struct*, struct vm_fault *);
         int (*page_mkwrite)(struct vm_area_struct *, struct page *);
+        int (*access)(struct vm_area_struct *, unsigned long, void*, int, int);
 
 locking rules:
                 BKL     mmap_sem        PageLocked(page)
@@ -517,6 +518,7 @@ open:		no	yes
 close:          no      yes
 fault:          no      yes
 page_mkwrite:   no      yes             no
+access:         no      yes
 
         ->page_mkwrite() is called when a previously read-only page is
 about to become writeable. The file system is responsible for
@@ -525,6 +527,11 @@ taking to lock out truncate, the page range should be verified to be
 within i_size. The page mapping should also be checked that it is not
 NULL.
 
+        ->access() is called when get_user_pages() fails in
+acces_process_vm(), typically used to debug a process through
+/proc/pid/mem or ptrace.  This function is needed only for
+VM_IO | VM_PFNMAP VMAs.
+
 ================================================================================
                         Dubious stuff
 
diff --git a/arch/Kconfig b/arch/Kconfig
index 4d5ebbc1e72b..6093c0be58b0 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -31,6 +31,9 @@ config KRETPROBES
         def_bool y
         depends on KPROBES && HAVE_KRETPROBES
 
+config HAVE_IOREMAP_PROT
+        def_bool n
+
 config HAVE_KPROBES
         def_bool n
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 03980cb04291..b2ddfcf01728 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -21,6 +21,7 @@ config X86
         select HAVE_UNSTABLE_SCHED_CLOCK
         select HAVE_IDE
         select HAVE_OPROFILE
+        select HAVE_IOREMAP_PROT
         select HAVE_KPROBES
         select HAVE_KRETPROBES
         select HAVE_DYNAMIC_FTRACE
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 24c1d3c30186..016f335bbeea 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -330,6 +330,14 @@ static void __iomem *ioremap_default(resource_size_t phys_addr,
         return (void __iomem *)ret;
 }
 
+void __iomem *ioremap_prot(resource_size_t phys_addr, unsigned long size,
+                                unsigned long prot_val)
+{
+        return __ioremap_caller(phys_addr, size, (prot_val & _PAGE_CACHE_MASK),
+                                __builtin_return_address(0));
+}
+EXPORT_SYMBOL(ioremap_prot);
+
 /**
  * iounmap - Free a IO remapping
  * @addr: virtual address from ioremap_*
diff --git a/include/asm-x86/io_32.h b/include/asm-x86/io_32.h
index 4df44ed54077..e876d89ac156 100644
--- a/include/asm-x86/io_32.h
+++ b/include/asm-x86/io_32.h
@@ -110,6 +110,8 @@ static inline void *phys_to_virt(unsigned long address)
  */
 extern void __iomem *ioremap_nocache(resource_size_t offset, unsigned long size);
 extern void __iomem *ioremap_cache(resource_size_t offset, unsigned long size);
+extern void __iomem *ioremap_prot(resource_size_t offset, unsigned long size,
+                                unsigned long prot_val);
 
 /*
  * The default ioremap() behavior is non-cached:
diff --git a/include/asm-x86/io_64.h b/include/asm-x86/io_64.h
index ddd8058a5026..22995c5c5adc 100644
--- a/include/asm-x86/io_64.h
+++ b/include/asm-x86/io_64.h
@@ -175,6 +175,8 @@ extern void early_iounmap(void *addr, unsigned long size);
  */
 extern void __iomem *ioremap_nocache(resource_size_t offset, unsigned long size);
 extern void __iomem *ioremap_cache(resource_size_t offset, unsigned long size);
+extern void __iomem *ioremap_prot(resource_size_t offset, unsigned long size,
+                                unsigned long prot_val);
 
 /*
  * The default ioremap() behavior is non-cached:
diff --git a/include/linux/mm.h b/include/linux/mm.h
index eb815cfc1b35..5c7f8f64f70e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -170,6 +170,12 @@ struct vm_operations_struct {
         /* notification that a previously read-only page is about to become
          * writable, if an error is returned it will cause a SIGBUS */
         int (*page_mkwrite)(struct vm_area_struct *vma, struct page *page);
+
+        /* called by access_process_vm when get_user_pages() fails, typically
+         * for use by special VMAs that can switch between memory and hardware
+         */
+        int (*access)(struct vm_area_struct *vma, unsigned long addr,
+                      void *buf, int len, int write);
 #ifdef CONFIG_NUMA
         /*
          * set_policy() op must add a reference to any non-NULL @new mempolicy
@@ -771,6 +777,8 @@ 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 generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
+                        void *buf, int len, int write);
 
 static inline void unmap_shared_mapping_range(struct address_space *mapping,
                 loff_t const holebegin, loff_t const holelen)
diff --git a/mm/memory.c b/mm/memory.c
index 46dbed4b7446..87350321e66f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2751,6 +2751,86 @@ 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)
+{
+        pgd_t *pgd;
+        pud_t *pud;
+        pmd_t *pmd;
+        pte_t *ptep, pte;
+        spinlock_t *ptl;
+        resource_size_t phys_addr = 0;
+        struct mm_struct *mm = vma->vm_mm;
+
+        VM_BUG_ON(!(vma->vm_flags & (VM_IO | VM_PFNMAP)));
+
+        pgd = pgd_offset(mm, address);
+        if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
+                goto no_page_table;
+
+        pud = pud_offset(pgd, address);
+        if (pud_none(*pud) || unlikely(pud_bad(*pud)))
+                goto no_page_table;
+
+        pmd = pmd_offset(pud, address);
+        if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
+                goto no_page_table;
+
+        /* We cannot handle huge page PFN maps. Luckily they don't exist. */
+        if (pmd_huge(*pmd))
+                goto no_page_table;
+
+        ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+        if (!ptep)
+                goto out;
+
+        pte = *ptep;
+        if (!pte_present(pte))
+                goto unlock;
+        if ((flags & FOLL_WRITE) && !pte_write(pte))
+                goto unlock;
+        phys_addr = pte_pfn(pte);
+        phys_addr <<= PAGE_SHIFT; /* Shift here to avoid overflow on PAE */
+
+        *prot = pgprot_val(pte_pgprot(pte));
+
+unlock:
+        pte_unmap_unlock(ptep, ptl);
+out:
+        return phys_addr;
+no_page_table:
+        return 0;
+}
+
+int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
+                        void *buf, int len, int write)
+{
+        resource_size_t phys_addr;
+        unsigned long prot = 0;
+        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)
+                return -EINVAL;
+
+        maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
+        if (write)
+                memcpy_toio(maddr + offset, buf, len);
+        else
+                memcpy_fromio(buf, maddr + offset, len);
+        iounmap(maddr);
+
+        return len;
+}
+#endif
+
 /*
  * Access another process' address space.
  * Source/target buffer must be kernel space,
@@ -2760,7 +2840,6 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
 {
         struct mm_struct *mm;
         struct vm_area_struct *vma;
-        struct page *page;
         void *old_buf = buf;
 
         mm = get_task_mm(tsk);
@@ -2772,28 +2851,44 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
         while (len) {
                 int bytes, ret, offset;
                 void *maddr;
+                struct page *page = NULL;
 
                 ret = get_user_pages(tsk, mm, addr, 1,
                                 write, 1, &page, &vma);
-                if (ret <= 0)
-                        break;
-
-                bytes = len;
-                offset = addr & (PAGE_SIZE-1);
-                if (bytes > PAGE_SIZE-offset)
-                        bytes = PAGE_SIZE-offset;
-
-                maddr = kmap(page);
-                if (write) {
-                        copy_to_user_page(vma, page, addr,
-                                          maddr + offset, buf, bytes);
-                        set_page_dirty_lock(page);
+                if (ret <= 0) {
+                        /*
+                         * Check if this is a VM_IO | VM_PFNMAP VMA, which
+                         * we can access using slightly different code.
+                         */
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+                        vma = find_vma(mm, addr);
+                        if (!vma)
+                                break;
+                        if (vma->vm_ops && vma->vm_ops->access)
+                                ret = vma->vm_ops->access(vma, addr, buf,
+                                                          len, write);
+                        if (ret <= 0)
+#endif
+                                break;
+                        bytes = ret;
                 } else {
-                        copy_from_user_page(vma, page, addr,
-                                            buf, maddr + offset, bytes);
+                        bytes = len;
+                        offset = addr & (PAGE_SIZE-1);
+                        if (bytes > PAGE_SIZE-offset)
+                                bytes = PAGE_SIZE-offset;
+
+                        maddr = kmap(page);
+                        if (write) {
+                                copy_to_user_page(vma, page, addr,
+                                                  maddr + offset, buf, bytes);
+                                set_page_dirty_lock(page);
+                        } else {
+                                copy_from_user_page(vma, page, addr,
+                                                    buf, maddr + offset, bytes);
+                        }
+                        kunmap(page);
+                        page_cache_release(page);
                 }
-                kunmap(page);
-                page_cache_release(page);
                 len -= bytes;
                 buf += bytes;
                 addr += bytes;