[PATCH] NOMMU: Implement /proc/pid/maps for NOMMU

Implement /proc/pid/maps for NOMMU by reading the vm_area_list attached to
current->mm->context.vmlist.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 80 insertions, 20 deletions

diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt
index b88ebe4d808c..83f4b083d57e 100644
--- a/Documentation/nommu-mmap.txt
+++ b/Documentation/nommu-mmap.txt
@@ -116,6 +116,9 @@ FURTHER NOTES ON NO-MMU MMAP
  (*) A list of all the mappings on the system is visible through /proc/maps in
      no-MMU mode.
 
+ (*) A list of all the mappings in use by a process is visible through
+     /proc/<pid>/maps in no-MMU mode.
+
  (*) Supplying MAP_FIXED or a requesting a particular mapping address will
      result in an error.
 
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 146a434ba944..987c773dbb20 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -28,6 +28,7 @@ do {						\
         (vmi)->largest_chunk = 0;               \
 } while(0)
 
+extern int nommu_vma_show(struct seq_file *, struct vm_area_struct *);
 #endif
 
 extern void create_seq_entry(char *name, mode_t mode, const struct file_operations *f);
diff --git a/fs/proc/nommu.c b/fs/proc/nommu.c
index cff10ab1af63..d7dbdf9e0f49 100644
--- a/fs/proc/nommu.c
+++ b/fs/proc/nommu.c
@@ -33,19 +33,15 @@
 #include "internal.h"
 
 /*
- * display a list of all the VMAs the kernel knows about
- * - nommu kernals have a single flat list
+ * display a single VMA to a sequenced file
  */
-static int nommu_vma_list_show(struct seq_file *m, void *v)
+int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma)
 {
-        struct vm_area_struct *vma;
         unsigned long ino = 0;
         struct file *file;
         dev_t dev = 0;
         int flags, len;
 
-        vma = rb_entry((struct rb_node *) v, struct vm_area_struct, vm_rb);
-
         flags = vma->vm_flags;
         file = vma->vm_file;
 
@@ -78,6 +74,18 @@ static int nommu_vma_list_show(struct seq_file *m, void *v)
         return 0;
 }
 
+/*
+ * display a list of all the VMAs the kernel knows about
+ * - nommu kernals have a single flat list
+ */
+static int nommu_vma_list_show(struct seq_file *m, void *v)
+{
+        struct vm_area_struct *vma;
+
+        vma = rb_entry((struct rb_node *) v, struct vm_area_struct, vm_rb);
+        return nommu_vma_show(m, vma);
+}
+
 static void *nommu_vma_list_start(struct seq_file *m, loff_t *_pos)
 {
         struct rb_node *_rb;
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 4616ed50ffcd..091aa8e48e02 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -138,25 +138,63 @@ out:
 }
 
 /*
- * Albert D. Cahalan suggested to fake entries for the traditional
- * sections here.  This might be worth investigating.
+ * display mapping lines for a particular process's /proc/pid/maps
  */
-static int show_map(struct seq_file *m, void *v)
+static int show_map(struct seq_file *m, void *_vml)
 {
-        return 0;
+        struct vm_list_struct *vml = _vml;
+        return nommu_vma_show(m, vml->vma);
 }
+
 static void *m_start(struct seq_file *m, loff_t *pos)
 {
+        struct proc_maps_private *priv = m->private;
+        struct vm_list_struct *vml;
+        struct mm_struct *mm;
+        loff_t n = *pos;
+
+        /* pin the task and mm whilst we play with them */
+        priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
+        if (!priv->task)
+                return NULL;
+
+        mm = get_task_mm(priv->task);
+        if (!mm) {
+                put_task_struct(priv->task);
+                priv->task = NULL;
+                return NULL;
+        }
+
+        down_read(&mm->mmap_sem);
+
+        /* start from the Nth VMA */
+        for (vml = mm->context.vmlist; vml; vml = vml->next)
+                if (n-- == 0)
+                        return vml;
         return NULL;
 }
-static void m_stop(struct seq_file *m, void *v)
+
+static void m_stop(struct seq_file *m, void *_vml)
 {
+        struct proc_maps_private *priv = m->private;
+
+        if (priv->task) {
+                struct mm_struct *mm = priv->task->mm;
+                up_read(&mm->mmap_sem);
+                mmput(mm);
+                put_task_struct(priv->task);
+        }
 }
-static void *m_next(struct seq_file *m, void *v, loff_t *pos)
+
+static void *m_next(struct seq_file *m, void *_vml, loff_t *pos)
 {
-        return NULL;
+        struct vm_list_struct *vml = _vml;
+
+        (*pos)++;
+        return vml ? vml->next : NULL;
 }
-static struct seq_operations proc_pid_maps_op = {
+
+static struct seq_operations proc_pid_maps_ops = {
         .start  = m_start,
         .next   = m_next,
         .stop   = m_stop,
@@ -165,11 +203,19 @@ static struct seq_operations proc_pid_maps_op = {
 
 static int maps_open(struct inode *inode, struct file *file)
 {
-        int ret;
-        ret = seq_open(file, &proc_pid_maps_op);
-        if (!ret) {
-                struct seq_file *m = file->private_data;
-                m->private = NULL;
+        struct proc_maps_private *priv;
+        int ret = -ENOMEM;
+
+        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+        if (priv) {
+                priv->pid = proc_pid(inode);
+                ret = seq_open(file, &proc_pid_maps_ops);
+                if (!ret) {
+                        struct seq_file *m = file->private_data;
+                        m->private = priv;
+                } else {
+                        kfree(priv);
+                }
         }
         return ret;
 }
@@ -178,6 +224,6 @@ struct file_operations proc_maps_operations = {
         .open           = maps_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
-        .release        = seq_release,
+        .release        = seq_release_private,
 };
 
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 3435ca38dd14..57f70bc8b24b 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -268,7 +268,9 @@ static inline struct proc_dir_entry *PDE(const struct inode *inode)
 struct proc_maps_private {
         struct pid *pid;
         struct task_struct *task;
+#ifdef CONFIG_MMU
         struct vm_area_struct *tail_vma;
+#endif
 };
 
 #endif /* _LINUX_PROC_FS_H */