[PATCH 1/4] NOMMU: Implement /proc/pid/maps for NOMMU

[PATCH 1/4] NOMMU: Implement /proc/pid/maps for NOMMU

[David Howells]

From: David Howells <dhowells@redhat.com>

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>
---

 Documentation/nommu-mmap.txt |    3 ++
 fs/proc/internal.h           |    1 +
 fs/proc/nommu.c              |   20 ++++++++---
 fs/proc/task_nommu.c         |   74 ++++++++++++++++++++++++++++++++++--------
 include/linux/proc_fs.h      |    2 +
 5 files changed, 80 insertions(+), 20 deletions(-)

diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt
index b88ebe4..83f4b08 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 146a434..987c773 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 cff10ab..d7dbdf9 100644
--- a/fs/proc/nommu.c
+++ b/fs/proc/nommu.c
@@ -33,19 +33,15 @@ #include <asm/div64.h>
 #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 se
 	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 4616ed5..091aa8e 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_ma
 
 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_operati
 	.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 17e7578..73beb46 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -269,7 +269,9 @@ static inline struct proc_dir_entry *PDE
 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 */

[PATCH 2/4] NOMMU: Order the per-mm_struct VMA list

[David Howells]

From: David Howells <dhowells@redhat.com>

Order the per-mm_struct VMA list by address so that searching it can be cut
short when the appropriate address has been exceeded.

Signed-Off-By: David Howells <dhowells@redhat.com>
---

 mm/nommu.c |  105 ++++++++++++++++++++++++++++++++++++++++++------------------
 1 files changed, 73 insertions(+), 32 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 9d57c2a..20da741 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -286,6 +286,49 @@ static void show_process_blocks(void)
 }
 #endif /* DEBUG */
 
+/*
+ * add a VMA into a process's mm_struct in the appropriate place in the list
+ * - should be called with mm->mmap_sem held writelocked
+ */
+static void add_vma_to_mm(struct mm_struct *mm, struct vm_list_struct *vml)
+{
+	struct vm_list_struct **ppv;
+
+	for (ppv = &current->mm->context.vmlist; *ppv; ppv = &(*ppv)->next)
+		if ((*ppv)->vma->vm_start > vml->vma->vm_start)
+			break;
+
+	vml->next = *ppv;
+	*ppv = vml;
+}
+
+/*
+ * look up the first VMA in which addr resides, NULL if none
+ * - should be called with mm->mmap_sem at least held readlocked
+ */
+struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
+{
+	struct vm_list_struct *loop, *vml;
+
+	/* search the vm_start ordered list */
+	vml = NULL;
+	for (loop = mm->context.vmlist; loop; loop = loop->next) {
+		if (loop->vma->vm_start > addr)
+			break;
+		vml = loop;
+	}
+
+	if (vml && vml->vma->vm_end > addr)
+		return vml->vma;
+
+	return NULL;
+}
+
+EXPORT_SYMBOL(find_vma);
+
+/*
+ * find a VMA in the global tree
+ */
 static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
 {
 	struct vm_area_struct *vma;
@@ -305,6 +348,9 @@ static inline struct vm_area_struct *fin
 	return NULL;
 }
 
+/*
+ * add a VMA in the global tree
+ */
 static void add_nommu_vma(struct vm_area_struct *vma)
 {
 	struct vm_area_struct *pvma;
@@ -351,6 +397,9 @@ static void add_nommu_vma(struct vm_area
 	rb_insert_color(&vma->vm_rb, &nommu_vma_tree);
 }
 
+/*
+ * delete a VMA from the global list
+ */
 static void delete_nommu_vma(struct vm_area_struct *vma)
 {
 	struct address_space *mapping;
@@ -828,8 +877,7 @@ unsigned long do_mmap_pgoff(struct file 
 	realalloc += kobjsize(vml);
 	askedalloc += sizeof(*vml);
 
-	vml->next = current->mm->context.vmlist;
-	current->mm->context.vmlist = vml;
+	add_vma_to_mm(current->mm, vml);
 
 	up_write(&nommu_vma_sem);
 
@@ -908,6 +956,11 @@ static void put_vma(struct vm_area_struc
 	}
 }
 
+/*
+ * release a mapping
+ * - under NOMMU conditions the parameters must match exactly to the mapping to
+ *   be removed
+ */
 int do_munmap(struct mm_struct *mm, unsigned long addr, size_t len)
 {
 	struct vm_list_struct *vml, **parent;
@@ -917,10 +970,13 @@ #ifdef DEBUG
 	printk("do_munmap:\n");
 #endif
 
-	for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next)
+	for (parent = &mm->context.vmlist; *parent; parent = &(*parent)->next) {
+		if ((*parent)->vma->vm_start > addr)
+			break;
 		if ((*parent)->vma->vm_start == addr &&
 		    ((len == 0) || ((*parent)->vma->vm_end == end)))
 			goto found;
+	}
 
 	printk("munmap of non-mmaped memory by process %d (%s): %p\n",
 	       current->pid, current->comm, (void *) addr);
@@ -946,7 +1002,20 @@ #endif
 	return 0;
 }
 
-/* Release all mmaps. */
+asmlinkage long sys_munmap(unsigned long addr, size_t len)
+{
+	int ret;
+	struct mm_struct *mm = current->mm;
+
+	down_write(&mm->mmap_sem);
+	ret = do_munmap(mm, addr, len);
+	up_write(&mm->mmap_sem);
+	return ret;
+}
+
+/*
+ * Release all mappings
+ */
 void exit_mmap(struct mm_struct * mm)
 {
 	struct vm_list_struct *tmp;
@@ -973,17 +1042,6 @@ #endif
 	}
 }
 
-asmlinkage long sys_munmap(unsigned long addr, size_t len)
-{
-	int ret;
-	struct mm_struct *mm = current->mm;
-
-	down_write(&mm->mmap_sem);
-	ret = do_munmap(mm, addr, len);
-	up_write(&mm->mmap_sem);
-	return ret;
-}
-
 unsigned long do_brk(unsigned long addr, unsigned long len)
 {
 	return -ENOMEM;
@@ -1037,23 +1095,6 @@ unsigned long do_mremap(unsigned long ad
 	return vml->vma->vm_start;
 }
 
-/*
- * Look up the first VMA which satisfies  addr < vm_end,  NULL if none
- * - should be called with mm->mmap_sem at least readlocked
- */
-struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
-{
-	struct vm_list_struct *vml;
-
-	for (vml = mm->context.vmlist; vml; vml = vml->next)
-		if (addr >= vml->vma->vm_start && addr < vml->vma->vm_end)
-			return vml->vma;
-
-	return NULL;
-}
-
-EXPORT_SYMBOL(find_vma);
-
 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 			unsigned int foll_flags)
 {

[PATCH 3/4] NOMMU: Make mremap() partially work for NOMMU kernels

[David Howells]

From: David Howells <dhowells@redhat.com>

Make mremap() partially work for NOMMU kernels.  It may resize a VMA provided
that it doesn't exceed the size of the slab object in which the storage is
allocated that the VMA refers to.  Shareable VMAs may not be resized.

Moving VMAs (as permitted by MREMAP_MAYMOVE) is not currently supported.

This patch also makes use of the fact that the VMA list is now ordered to cut
it short when possible.

Signed-Off-By: David Howells <dhowells@redhat.com>
---

 Documentation/nommu-mmap.txt |   24 ++++++++++++++++
 mm/nommu.c                   |   63 +++++++++++++++++++++++++++++++-----------
 2 files changed, 70 insertions(+), 17 deletions(-)

diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt
index 83f4b08..3ce8906 100644
--- a/Documentation/nommu-mmap.txt
+++ b/Documentation/nommu-mmap.txt
@@ -128,6 +128,30 @@ FURTHER NOTES ON NO-MMU MMAP
      error will result if they don't. This is most likely to be encountered
      with character device files, pipes, fifos and sockets.
 
+
+=============
+NO-MMU MREMAP
+=============
+
+The mremap() function is partially supported.  It may change the size of a
+mapping, and may move it[*] if MREMAP_MAYMOVE is specified and if the new size
+of the mapping exceeds the size of the slab object currently occupied by the
+memory to which the mapping refers, or if a smaller slab object could be used.
+
+MREMAP_FIXED is not supported, though it is ignored if there's no change of
+address and the object does not need to be moved.
+
+Shared mappings may not be moved.  Shareable mappings may not be moved either,
+even if they are not currently shared.
+
+The mremap() function must be given an exact match for base address and size of
+a previously mapped object.  It may not be used to create holes in existing
+mappings, move parts of existing mappings or resize parts of mappings.  It must
+act on a complete mapping.
+
+[*] Not currently supported.
+
+
 ============================================
 PROVIDING SHAREABLE CHARACTER DEVICE SUPPORT
 ============================================
diff --git a/mm/nommu.c b/mm/nommu.c
index 20da741..a0ba6ac 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -327,6 +327,26 @@ struct vm_area_struct *find_vma(struct m
 EXPORT_SYMBOL(find_vma);
 
 /*
+ * look up the first VMA exactly that exactly matches addr
+ * - should be called with mm->mmap_sem at least held readlocked
+ */
+static inline struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
+						    unsigned long addr)
+{
+	struct vm_list_struct *vml;
+
+	/* search the vm_start ordered list */
+	for (vml = mm->context.vmlist; vml; vml = vml->next) {
+		if (vml->vma->vm_start == addr)
+			return vml->vma;
+		if (vml->vma->vm_start > addr)
+			break;
+	}
+
+	return NULL;
+}
+
+/*
  * find a VMA in the global tree
  */
 static inline struct vm_area_struct *find_nommu_vma(unsigned long start)
@@ -1048,20 +1068,20 @@ unsigned long do_brk(unsigned long addr,
 }
 
 /*
- * Expand (or shrink) an existing mapping, potentially moving it at the
- * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
+ * expand (or shrink) an existing mapping, potentially moving it at the same
+ * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
  *
- * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
- * This option implies MREMAP_MAYMOVE.
+ * under NOMMU conditions, we only permit changing a mapping's size, and only
+ * as long as it stays within the hole allocated by the kmalloc() call in
+ * do_mmap_pgoff() and the block is not shareable
  *
- * on uClinux, we only permit changing a mapping's size, and only as long as it stays within the
- * hole allocated by the kmalloc() call in do_mmap_pgoff() and the block is not shareable
+ * MREMAP_FIXED is not supported under NOMMU conditions
  */
 unsigned long do_mremap(unsigned long addr,
 			unsigned long old_len, unsigned long new_len,
 			unsigned long flags, unsigned long new_addr)
 {
-	struct vm_list_struct *vml = NULL;
+	struct vm_area_struct *vma;
 
 	/* insanity checks first */
 	if (new_len == 0)
@@ -1070,29 +1090,38 @@ unsigned long do_mremap(unsigned long ad
 	if (flags & MREMAP_FIXED && new_addr != addr)
 		return (unsigned long) -EINVAL;
 
-	for (vml = current->mm->context.vmlist; vml; vml = vml->next)
-		if (vml->vma->vm_start == addr)
-			goto found;
-
-	return (unsigned long) -EINVAL;
+	vma = find_vma_exact(current->mm, addr);
+	if (!vma)
+		return (unsigned long) -EINVAL;
 
- found:
-	if (vml->vma->vm_end != vml->vma->vm_start + old_len)
+	if (vma->vm_end != vma->vm_start + old_len)
 		return (unsigned long) -EFAULT;
 
-	if (vml->vma->vm_flags & VM_MAYSHARE)
+	if (vma->vm_flags & VM_MAYSHARE)
 		return (unsigned long) -EPERM;
 
 	if (new_len > kobjsize((void *) addr))
 		return (unsigned long) -ENOMEM;
 
 	/* all checks complete - do it */
-	vml->vma->vm_end = vml->vma->vm_start + new_len;
+	vma->vm_end = vma->vm_start + new_len;
 
 	askedalloc -= old_len;
 	askedalloc += new_len;
 
-	return vml->vma->vm_start;
+	return vma->vm_start;
+}
+
+asmlinkage unsigned long sys_mremap(unsigned long addr,
+	unsigned long old_len, unsigned long new_len,
+	unsigned long flags, unsigned long new_addr)
+{
+	unsigned long ret;
+
+	down_write(&current->mm->mmap_sem);
+	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
+	up_write(&current->mm->mmap_sem);
+	return ret;
 }
 
 struct page *follow_page(struct vm_area_struct *vma, unsigned long address,

[PATCH 4/4] NOMMU: Add docs about shared memory

[David Howells]

From: David Howells <dhowells@redhat.com>

Add documentation about using shared memory in NOMMU mode.

Signed-Off-By: David Howells <dhowells@redhat.com>
---

 Documentation/nommu-mmap.txt |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt
index 3ce8906..4db7c18 100644
--- a/Documentation/nommu-mmap.txt
+++ b/Documentation/nommu-mmap.txt
@@ -129,6 +129,15 @@ FURTHER NOTES ON NO-MMU MMAP
      with character device files, pipes, fifos and sockets.
 
 
+==========================
+INTERPROCESS SHARED MEMORY
+==========================
+
+Both SYSV IPC SHM shared memory and POSIX shared memory is supported in NOMMU
+mode.  The former through the usual mechanism, the latter through files created
+on ramfs or tmpfs mounts.
+
+
 =============
 NO-MMU MREMAP
 =============