android-mainline/Revert-staging-remove-ashmem.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@google.com>
Date: Wed, 13 Apr 2022 13:43:59 +0200
Subject: Revert "staging: remove ashmem"

This reverts commit 721412ed3d819e767cac2b06646bf03aa158aaec.

Android just isn't ready yet to give it up :(

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ie0a443d55e6e72df97c3d3eabb7358ae3a12548a
Signed-off-by: Lee Jones <joneslee@google.com>
---
 drivers/staging/Kconfig               |   2 +
 drivers/staging/Makefile              |   1 +
 drivers/staging/android/Kconfig       |  15 +
 drivers/staging/android/Makefile      |   4 +
 drivers/staging/android/TODO          |   8 +
 drivers/staging/android/ashmem.c      | 973 ++++++++++++++++++++++++++
 drivers/staging/android/ashmem.h      |  24 +
 drivers/staging/android/uapi/ashmem.h |  43 ++
 8 files changed, 1070 insertions(+)
 create mode 100644 drivers/staging/android/Kconfig
 create mode 100644 drivers/staging/android/Makefile
 create mode 100644 drivers/staging/android/TODO
 create mode 100644 drivers/staging/android/ashmem.c
 create mode 100644 drivers/staging/android/ashmem.h
 create mode 100644 drivers/staging/android/uapi/ashmem.h

diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -56,6 +56,8 @@ source "drivers/staging/nvec/Kconfig"
 
 source "drivers/staging/media/Kconfig"
 
+source "drivers/staging/android/Kconfig"
+
 source "drivers/staging/board/Kconfig"
 
 source "drivers/staging/gdm724x/Kconfig"
diff --git a/drivers/staging/Makefile b/drivers/staging/Makefile
--- a/drivers/staging/Makefile
+++ b/drivers/staging/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_IIO)		+= iio/
 obj-$(CONFIG_FB_SM750)		+= sm750fb/
 obj-$(CONFIG_USB_EMXX)		+= emxx_udc/
 obj-$(CONFIG_MFD_NVEC)		+= nvec/
+obj-$(CONFIG_ASHMEM)		+= android/
 obj-$(CONFIG_STAGING_BOARD)	+= board/
 obj-$(CONFIG_LTE_GDM724X)	+= gdm724x/
 obj-$(CONFIG_FB_TFT)		+= fbtft/
diff --git a/drivers/staging/android/Kconfig b/drivers/staging/android/Kconfig
new file mode 100644
--- /dev/null
+++ b/drivers/staging/android/Kconfig
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+menu "Android"
+
+config ASHMEM
+	bool "Enable the Anonymous Shared Memory Subsystem"
+	depends on SHMEM
+	help
+	  The ashmem subsystem is a new shared memory allocator, similar to
+	  POSIX SHM but with different behavior and sporting a simpler
+	  file-based API.
+
+	  It is, in theory, a good memory allocator for low-memory devices,
+	  because it can discard shared memory units when under memory pressure.
+
+endmenu
diff --git a/drivers/staging/android/Makefile b/drivers/staging/android/Makefile
new file mode 100644
--- /dev/null
+++ b/drivers/staging/android/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+ccflags-y += -I$(src)			# needed for trace events
+
+obj-$(CONFIG_ASHMEM)			+= ashmem.o
diff --git a/drivers/staging/android/TODO b/drivers/staging/android/TODO
new file mode 100644
--- /dev/null
+++ b/drivers/staging/android/TODO
@@ -0,0 +1,8 @@
+TODO:
+	- sparse fixes
+	- rename files to be not so "generic"
+	- add proper arch dependencies as needed
+	- audit userspace interfaces to make sure they are sane
+
+Please send patches to Greg Kroah-Hartman <greg@kroah.com> and Cc:
+Arve Hjønnevåg <arve@android.com> and Riley Andrews <riandrews@android.com>
diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
new file mode 100644
--- /dev/null
+++ b/drivers/staging/android/ashmem.c
@@ -0,0 +1,973 @@
+// SPDX-License-Identifier: GPL-2.0
+/* mm/ashmem.c
+ *
+ * Anonymous Shared Memory Subsystem, ashmem
+ *
+ * Copyright (C) 2008 Google, Inc.
+ *
+ * Robert Love <rlove@google.com>
+ */
+
+#define pr_fmt(fmt) "ashmem: " fmt
+
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/falloc.h>
+#include <linux/miscdevice.h>
+#include <linux/security.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/uaccess.h>
+#include <linux/personality.h>
+#include <linux/bitops.h>
+#include <linux/mutex.h>
+#include <linux/shmem_fs.h>
+#include "ashmem.h"
+
+#define ASHMEM_NAME_PREFIX "dev/ashmem/"
+#define ASHMEM_NAME_PREFIX_LEN (sizeof(ASHMEM_NAME_PREFIX) - 1)
+#define ASHMEM_FULL_NAME_LEN (ASHMEM_NAME_LEN + ASHMEM_NAME_PREFIX_LEN)
+
+/**
+ * struct ashmem_area - The anonymous shared memory area
+ * @name:		The optional name in /proc/pid/maps
+ * @unpinned_list:	The list of all ashmem areas
+ * @file:		The shmem-based backing file
+ * @size:		The size of the mapping, in bytes
+ * @prot_mask:		The allowed protection bits, as vm_flags
+ *
+ * The lifecycle of this structure is from our parent file's open() until
+ * its release(). It is also protected by 'ashmem_mutex'
+ *
+ * Warning: Mappings do NOT pin this structure; It dies on close()
+ */
+struct ashmem_area {
+	char name[ASHMEM_FULL_NAME_LEN];
+	struct list_head unpinned_list;
+	struct file *file;
+	size_t size;
+	unsigned long prot_mask;
+};
+
+/**
+ * struct ashmem_range - A range of unpinned/evictable pages
+ * @lru:	         The entry in the LRU list
+ * @unpinned:	         The entry in its area's unpinned list
+ * @asma:	         The associated anonymous shared memory area.
+ * @pgstart:	         The starting page (inclusive)
+ * @pgend:	         The ending page (inclusive)
+ * @purged:	         The purge status (ASHMEM_NOT or ASHMEM_WAS_PURGED)
+ *
+ * The lifecycle of this structure is from unpin to pin.
+ * It is protected by 'ashmem_mutex'
+ */
+struct ashmem_range {
+	struct list_head lru;
+	struct list_head unpinned;
+	struct ashmem_area *asma;
+	size_t pgstart;
+	size_t pgend;
+	unsigned int purged;
+};
+
+/* LRU list of unpinned pages, protected by ashmem_mutex */
+static LIST_HEAD(ashmem_lru_list);
+
+static atomic_t ashmem_shrink_inflight = ATOMIC_INIT(0);
+static DECLARE_WAIT_QUEUE_HEAD(ashmem_shrink_wait);
+
+/*
+ * long lru_count - The count of pages on our LRU list.
+ *
+ * This is protected by ashmem_mutex.
+ */
+static unsigned long lru_count;
+
+/*
+ * ashmem_mutex - protects the list of and each individual ashmem_area
+ *
+ * Lock Ordering: ashmex_mutex -> i_mutex -> i_alloc_sem
+ */
+static DEFINE_MUTEX(ashmem_mutex);
+
+static struct kmem_cache *ashmem_area_cachep __read_mostly;
+static struct kmem_cache *ashmem_range_cachep __read_mostly;
+
+/*
+ * A separate lockdep class for the backing shmem inodes to resolve the lockdep
+ * warning about the race between kswapd taking fs_reclaim before inode_lock
+ * and write syscall taking inode_lock and then fs_reclaim.
+ * Note that such race is impossible because ashmem does not support write
+ * syscalls operating on the backing shmem.
+ */
+static struct lock_class_key backing_shmem_inode_class;
+
+static inline unsigned long range_size(struct ashmem_range *range)
+{
+	return range->pgend - range->pgstart + 1;
+}
+
+static inline bool range_on_lru(struct ashmem_range *range)
+{
+	return range->purged == ASHMEM_NOT_PURGED;
+}
+
+static inline bool page_range_subsumes_range(struct ashmem_range *range,
+					     size_t start, size_t end)
+{
+	return (range->pgstart >= start) && (range->pgend <= end);
+}
+
+static inline bool page_range_subsumed_by_range(struct ashmem_range *range,
+						size_t start, size_t end)
+{
+	return (range->pgstart <= start) && (range->pgend >= end);
+}
+
+static inline bool page_in_range(struct ashmem_range *range, size_t page)
+{
+	return (range->pgstart <= page) && (range->pgend >= page);
+}
+
+static inline bool page_range_in_range(struct ashmem_range *range,
+				       size_t start, size_t end)
+{
+	return page_in_range(range, start) || page_in_range(range, end) ||
+		page_range_subsumes_range(range, start, end);
+}
+
+static inline bool range_before_page(struct ashmem_range *range,
+				     size_t page)
+{
+	return range->pgend < page;
+}
+
+#define PROT_MASK		(PROT_EXEC | PROT_READ | PROT_WRITE)
+
+/**
+ * lru_add() - Adds a range of memory to the LRU list
+ * @range:     The memory range being added.
+ *
+ * The range is first added to the end (tail) of the LRU list.
+ * After this, the size of the range is added to @lru_count
+ */
+static inline void lru_add(struct ashmem_range *range)
+{
+	list_add_tail(&range->lru, &ashmem_lru_list);
+	lru_count += range_size(range);
+}
+
+/**
+ * lru_del() - Removes a range of memory from the LRU list
+ * @range:     The memory range being removed
+ *
+ * The range is first deleted from the LRU list.
+ * After this, the size of the range is removed from @lru_count
+ */
+static inline void lru_del(struct ashmem_range *range)
+{
+	list_del(&range->lru);
+	lru_count -= range_size(range);
+}
+
+/**
+ * range_alloc() - Allocates and initializes a new ashmem_range structure
+ * @asma:	   The associated ashmem_area
+ * @prev_range:	   The previous ashmem_range in the sorted asma->unpinned list
+ * @purged:	   Initial purge status (ASMEM_NOT_PURGED or ASHMEM_WAS_PURGED)
+ * @start:	   The starting page (inclusive)
+ * @end:	   The ending page (inclusive)
+ * @new_range:	   The placeholder for the new range
+ *
+ * This function is protected by ashmem_mutex.
+ */
+static void range_alloc(struct ashmem_area *asma,
+			struct ashmem_range *prev_range, unsigned int purged,
+			size_t start, size_t end,
+			struct ashmem_range **new_range)
+{
+	struct ashmem_range *range = *new_range;
+
+	*new_range = NULL;
+	range->asma = asma;
+	range->pgstart = start;
+	range->pgend = end;
+	range->purged = purged;
+
+	list_add_tail(&range->unpinned, &prev_range->unpinned);
+
+	if (range_on_lru(range))
+		lru_add(range);
+}
+
+/**
+ * range_del() - Deletes and deallocates an ashmem_range structure
+ * @range:	 The associated ashmem_range that has previously been allocated
+ */
+static void range_del(struct ashmem_range *range)
+{
+	list_del(&range->unpinned);
+	if (range_on_lru(range))
+		lru_del(range);
+	kmem_cache_free(ashmem_range_cachep, range);
+}
+
+/**
+ * range_shrink() - Shrinks an ashmem_range
+ * @range:	    The associated ashmem_range being shrunk
+ * @start:	    The starting byte of the new range
+ * @end:	    The ending byte of the new range
+ *
+ * This does not modify the data inside the existing range in any way - It
+ * simply shrinks the boundaries of the range.
+ *
+ * Theoretically, with a little tweaking, this could eventually be changed
+ * to range_resize, and expand the lru_count if the new range is larger.
+ */
+static inline void range_shrink(struct ashmem_range *range,
+				size_t start, size_t end)
+{
+	size_t pre = range_size(range);
+
+	range->pgstart = start;
+	range->pgend = end;
+
+	if (range_on_lru(range))
+		lru_count -= pre - range_size(range);
+}
+
+/**
+ * ashmem_open() - Opens an Anonymous Shared Memory structure
+ * @inode:	   The backing file's index node(?)
+ * @file:	   The backing file
+ *
+ * Please note that the ashmem_area is not returned by this function - It is
+ * instead written to "file->private_data".
+ *
+ * Return: 0 if successful, or another code if unsuccessful.
+ */
+static int ashmem_open(struct inode *inode, struct file *file)
+{
+	struct ashmem_area *asma;
+	int ret;
+
+	ret = generic_file_open(inode, file);
+	if (ret)
+		return ret;
+
+	asma = kmem_cache_zalloc(ashmem_area_cachep, GFP_KERNEL);
+	if (!asma)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&asma->unpinned_list);
+	memcpy(asma->name, ASHMEM_NAME_PREFIX, ASHMEM_NAME_PREFIX_LEN);
+	asma->prot_mask = PROT_MASK;
+	file->private_data = asma;
+
+	return 0;
+}
+
+/**
+ * ashmem_release() - Releases an Anonymous Shared Memory structure
+ * @ignored:	      The backing file's Index Node(?) - It is ignored here.
+ * @file:	      The backing file
+ *
+ * Return: 0 if successful. If it is anything else, go have a coffee and
+ * try again.
+ */
+static int ashmem_release(struct inode *ignored, struct file *file)
+{
+	struct ashmem_area *asma = file->private_data;
+	struct ashmem_range *range, *next;
+
+	mutex_lock(&ashmem_mutex);
+	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned)
+		range_del(range);
+	mutex_unlock(&ashmem_mutex);
+
+	if (asma->file)
+		fput(asma->file);
+	kmem_cache_free(ashmem_area_cachep, asma);
+
+	return 0;
+}
+
+static ssize_t ashmem_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct ashmem_area *asma = iocb->ki_filp->private_data;
+	int ret = 0;
+
+	mutex_lock(&ashmem_mutex);
+
+	/* If size is not set, or set to 0, always return EOF. */
+	if (asma->size == 0)
+		goto out_unlock;
+
+	if (!asma->file) {
+		ret = -EBADF;
+		goto out_unlock;
+	}
+
+	/*
+	 * asma and asma->file are used outside the lock here.  We assume
+	 * once asma->file is set it will never be changed, and will not
+	 * be destroyed until all references to the file are dropped and
+	 * ashmem_release is called.
+	 */
+	mutex_unlock(&ashmem_mutex);
+	ret = vfs_iter_read(asma->file, iter, &iocb->ki_pos, 0);
+	mutex_lock(&ashmem_mutex);
+	if (ret > 0)
+		asma->file->f_pos = iocb->ki_pos;
+out_unlock:
+	mutex_unlock(&ashmem_mutex);
+	return ret;
+}
+
+static loff_t ashmem_llseek(struct file *file, loff_t offset, int origin)
+{
+	struct ashmem_area *asma = file->private_data;
+	loff_t ret;
+
+	mutex_lock(&ashmem_mutex);
+
+	if (asma->size == 0) {
+		mutex_unlock(&ashmem_mutex);
+		return -EINVAL;
+	}
+
+	if (!asma->file) {
+		mutex_unlock(&ashmem_mutex);
+		return -EBADF;
+	}
+
+	mutex_unlock(&ashmem_mutex);
+
+	ret = vfs_llseek(asma->file, offset, origin);
+	if (ret < 0)
+		return ret;
+
+	/** Copy f_pos from backing file, since f_ops->llseek() sets it */
+	file->f_pos = asma->file->f_pos;
+	return ret;
+}
+
+static inline vm_flags_t calc_vm_may_flags(unsigned long prot)
+{
+	return _calc_vm_trans(prot, PROT_READ,  VM_MAYREAD) |
+	       _calc_vm_trans(prot, PROT_WRITE, VM_MAYWRITE) |
+	       _calc_vm_trans(prot, PROT_EXEC,  VM_MAYEXEC);
+}
+
+static int ashmem_vmfile_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	/* do not allow to mmap ashmem backing shmem file directly */
+	return -EPERM;
+}
+
+static unsigned long
+ashmem_vmfile_get_unmapped_area(struct file *file, unsigned long addr,
+				unsigned long len, unsigned long pgoff,
+				unsigned long flags)
+{
+	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
+}
+
+static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	static struct file_operations vmfile_fops;
+	struct ashmem_area *asma = file->private_data;
+	int ret = 0;
+
+	mutex_lock(&ashmem_mutex);
+
+	/* user needs to SET_SIZE before mapping */
+	if (!asma->size) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* requested mapping size larger than object size */
+	if (vma->vm_end - vma->vm_start > PAGE_ALIGN(asma->size)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* requested protection bits must match our allowed protection mask */
+	if ((vma->vm_flags & ~calc_vm_prot_bits(asma->prot_mask, 0)) &
+	    calc_vm_prot_bits(PROT_MASK, 0)) {
+		ret = -EPERM;
+		goto out;
+	}
+	vma->vm_flags &= ~calc_vm_may_flags(~asma->prot_mask);
+
+	if (!asma->file) {
+		char *name = ASHMEM_NAME_DEF;
+		struct file *vmfile;
+		struct inode *inode;
+
+		if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
+			name = asma->name;
+
+		/* ... and allocate the backing shmem file */
+		vmfile = shmem_file_setup(name, asma->size, vma->vm_flags);
+		if (IS_ERR(vmfile)) {
+			ret = PTR_ERR(vmfile);
+			goto out;
+		}
+		vmfile->f_mode |= FMODE_LSEEK;
+		inode = file_inode(vmfile);
+		lockdep_set_class(&inode->i_rwsem, &backing_shmem_inode_class);
+		asma->file = vmfile;
+		/*
+		 * override mmap operation of the vmfile so that it can't be
+		 * remapped which would lead to creation of a new vma with no
+		 * asma permission checks. Have to override get_unmapped_area
+		 * as well to prevent VM_BUG_ON check for f_ops modification.
+		 */
+		if (!vmfile_fops.mmap) {
+			vmfile_fops = *vmfile->f_op;
+			vmfile_fops.mmap = ashmem_vmfile_mmap;
+			vmfile_fops.get_unmapped_area =
+					ashmem_vmfile_get_unmapped_area;
+		}
+		vmfile->f_op = &vmfile_fops;
+	}
+	get_file(asma->file);
+
+	/*
+	 * XXX - Reworked to use shmem_zero_setup() instead of
+	 * shmem_set_file while we're in staging. -jstultz
+	 */
+	if (vma->vm_flags & VM_SHARED) {
+		ret = shmem_zero_setup(vma);
+		if (ret) {
+			fput(asma->file);
+			goto out;
+		}
+	} else {
+		vma_set_anonymous(vma);
+	}
+
+	vma_set_file(vma, asma->file);
+	/* XXX: merge this with the get_file() above if possible */
+	fput(asma->file);
+
+out:
+	mutex_unlock(&ashmem_mutex);
+	return ret;
+}
+
+/*
+ * ashmem_shrink - our cache shrinker, called from mm/vmscan.c
+ *
+ * 'nr_to_scan' is the number of objects to scan for freeing.
+ *
+ * 'gfp_mask' is the mask of the allocation that got us into this mess.
+ *
+ * Return value is the number of objects freed or -1 if we cannot
+ * proceed without risk of deadlock (due to gfp_mask).
+ *
+ * We approximate LRU via least-recently-unpinned, jettisoning unpinned partial
+ * chunks of ashmem regions LRU-wise one-at-a-time until we hit 'nr_to_scan'
+ * pages freed.
+ */
+static unsigned long
+ashmem_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
+{
+	unsigned long freed = 0;
+
+	/* We might recurse into filesystem code, so bail out if necessary */
+	if (!(sc->gfp_mask & __GFP_FS))
+		return SHRINK_STOP;
+
+	if (!mutex_trylock(&ashmem_mutex))
+		return -1;
+
+	while (!list_empty(&ashmem_lru_list)) {
+		struct ashmem_range *range =
+			list_first_entry(&ashmem_lru_list, typeof(*range), lru);
+		loff_t start = range->pgstart * PAGE_SIZE;
+		loff_t end = (range->pgend + 1) * PAGE_SIZE;
+		struct file *f = range->asma->file;
+
+		get_file(f);
+		atomic_inc(&ashmem_shrink_inflight);
+		range->purged = ASHMEM_WAS_PURGED;
+		lru_del(range);
+
+		freed += range_size(range);
+		mutex_unlock(&ashmem_mutex);
+		f->f_op->fallocate(f,
+				   FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+				   start, end - start);
+		fput(f);
+		if (atomic_dec_and_test(&ashmem_shrink_inflight))
+			wake_up_all(&ashmem_shrink_wait);
+		if (!mutex_trylock(&ashmem_mutex))
+			goto out;
+		if (--sc->nr_to_scan <= 0)
+			break;
+	}
+	mutex_unlock(&ashmem_mutex);
+out:
+	return freed;
+}
+
+static unsigned long
+ashmem_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	/*
+	 * note that lru_count is count of pages on the lru, not a count of
+	 * objects on the list. This means the scan function needs to return the
+	 * number of pages freed, not the number of objects scanned.
+	 */
+	return lru_count;
+}
+
+static struct shrinker ashmem_shrinker = {
+	.count_objects = ashmem_shrink_count,
+	.scan_objects = ashmem_shrink_scan,
+	/*
+	 * XXX (dchinner): I wish people would comment on why they need on
+	 * significant changes to the default value here
+	 */
+	.seeks = DEFAULT_SEEKS * 4,
+};
+
+static int set_prot_mask(struct ashmem_area *asma, unsigned long prot)
+{
+	int ret = 0;
+
+	mutex_lock(&ashmem_mutex);
+
+	/* the user can only remove, not add, protection bits */
+	if ((asma->prot_mask & prot) != prot) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* does the application expect PROT_READ to imply PROT_EXEC? */
+	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
+		prot |= PROT_EXEC;
+
+	asma->prot_mask = prot;
+
+out:
+	mutex_unlock(&ashmem_mutex);
+	return ret;
+}
+
+static int set_name(struct ashmem_area *asma, void __user *name)
+{
+	int len;
+	int ret = 0;
+	char local_name[ASHMEM_NAME_LEN];
+
+	/*
+	 * Holding the ashmem_mutex while doing a copy_from_user might cause
+	 * an data abort which would try to access mmap_lock. If another
+	 * thread has invoked ashmem_mmap then it will be holding the
+	 * semaphore and will be waiting for ashmem_mutex, there by leading to
+	 * deadlock. We'll release the mutex and take the name to a local
+	 * variable that does not need protection and later copy the local
+	 * variable to the structure member with lock held.
+	 */
+	len = strncpy_from_user(local_name, name, ASHMEM_NAME_LEN);
+	if (len < 0)
+		return len;
+
+	mutex_lock(&ashmem_mutex);
+	/* cannot change an existing mapping's name */
+	if (asma->file)
+		ret = -EINVAL;
+	else
+		strscpy(asma->name + ASHMEM_NAME_PREFIX_LEN, local_name,
+			ASHMEM_NAME_LEN);
+
+	mutex_unlock(&ashmem_mutex);
+	return ret;
+}
+
+static int get_name(struct ashmem_area *asma, void __user *name)
+{
+	int ret = 0;
+	size_t len;
+	/*
+	 * Have a local variable to which we'll copy the content
+	 * from asma with the lock held. Later we can copy this to the user
+	 * space safely without holding any locks. So even if we proceed to
+	 * wait for mmap_lock, it won't lead to deadlock.
+	 */
+	char local_name[ASHMEM_NAME_LEN];
+
+	mutex_lock(&ashmem_mutex);
+	if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0') {
+		/*
+		 * Copying only `len', instead of ASHMEM_NAME_LEN, bytes
+		 * prevents us from revealing one user's stack to another.
+		 */
+		len = strlen(asma->name + ASHMEM_NAME_PREFIX_LEN) + 1;
+		memcpy(local_name, asma->name + ASHMEM_NAME_PREFIX_LEN, len);
+	} else {
+		len = sizeof(ASHMEM_NAME_DEF);
+		memcpy(local_name, ASHMEM_NAME_DEF, len);
+	}
+	mutex_unlock(&ashmem_mutex);
+
+	/*
+	 * Now we are just copying from the stack variable to userland
+	 * No lock held
+	 */
+	if (copy_to_user(name, local_name, len))
+		ret = -EFAULT;
+	return ret;
+}
+
+/*
+ * ashmem_pin - pin the given ashmem region, returning whether it was
+ * previously purged (ASHMEM_WAS_PURGED) or not (ASHMEM_NOT_PURGED).
+ *
+ * Caller must hold ashmem_mutex.
+ */
+static int ashmem_pin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
+		      struct ashmem_range **new_range)
+{
+	struct ashmem_range *range, *next;
+	int ret = ASHMEM_NOT_PURGED;
+
+	list_for_each_entry_safe(range, next, &asma->unpinned_list, unpinned) {
+		/* moved past last applicable page; we can short circuit */
+		if (range_before_page(range, pgstart))
+			break;
+
+		/*
+		 * The user can ask us to pin pages that span multiple ranges,
+		 * or to pin pages that aren't even unpinned, so this is messy.
+		 *
+		 * Four cases:
+		 * 1. The requested range subsumes an existing range, so we
+		 *    just remove the entire matching range.
+		 * 2. The requested range overlaps the start of an existing
+		 *    range, so we just update that range.
+		 * 3. The requested range overlaps the end of an existing
+		 *    range, so we just update that range.
+		 * 4. The requested range punches a hole in an existing range,
+		 *    so we have to update one side of the range and then
+		 *    create a new range for the other side.
+		 */
+		if (page_range_in_range(range, pgstart, pgend)) {
+			ret |= range->purged;
+
+			/* Case #1: Easy. Just nuke the whole thing. */
+			if (page_range_subsumes_range(range, pgstart, pgend)) {
+				range_del(range);
+				continue;
+			}
+
+			/* Case #2: We overlap from the start, so adjust it */
+			if (range->pgstart >= pgstart) {
+				range_shrink(range, pgend + 1, range->pgend);
+				continue;
+			}
+
+			/* Case #3: We overlap from the rear, so adjust it */
+			if (range->pgend <= pgend) {
+				range_shrink(range, range->pgstart,
+					     pgstart - 1);
+				continue;
+			}
+
+			/*
+			 * Case #4: We eat a chunk out of the middle. A bit
+			 * more complicated, we allocate a new range for the
+			 * second half and adjust the first chunk's endpoint.
+			 */
+			range_alloc(asma, range, range->purged,
+				    pgend + 1, range->pgend, new_range);
+			range_shrink(range, range->pgstart, pgstart - 1);
+			break;
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * ashmem_unpin - unpin the given range of pages. Returns zero on success.
+ *
+ * Caller must hold ashmem_mutex.
+ */
+static int ashmem_unpin(struct ashmem_area *asma, size_t pgstart, size_t pgend,
+			struct ashmem_range **new_range)
+{
+	struct ashmem_range *range = NULL, *iter, *next;
+	unsigned int purged = ASHMEM_NOT_PURGED;
+
+restart:
+	list_for_each_entry_safe(iter, next, &asma->unpinned_list, unpinned) {
+		/* short circuit: this is our insertion point */
+		if (range_before_page(iter, pgstart)) {
+			range = iter;
+			break;
+		}
+
+		/*
+		 * The user can ask us to unpin pages that are already entirely
+		 * or partially pinned. We handle those two cases here.
+		 */
+		if (page_range_subsumed_by_range(iter, pgstart, pgend))
+			return 0;
+		if (page_range_in_range(iter, pgstart, pgend)) {
+			pgstart = min(iter->pgstart, pgstart);
+			pgend = max(iter->pgend, pgend);
+			purged |= iter->purged;
+			range_del(iter);
+			goto restart;
+		}
+	}
+
+	range = list_prepare_entry(range, &asma->unpinned_list, unpinned);
+	range_alloc(asma, range, purged, pgstart, pgend, new_range);
+	return 0;
+}
+
+/*
+ * ashmem_get_pin_status - Returns ASHMEM_IS_UNPINNED if _any_ pages in the
+ * given interval are unpinned and ASHMEM_IS_PINNED otherwise.
+ *
+ * Caller must hold ashmem_mutex.
+ */
+static int ashmem_get_pin_status(struct ashmem_area *asma, size_t pgstart,
+				 size_t pgend)
+{
+	struct ashmem_range *range;
+	int ret = ASHMEM_IS_PINNED;
+
+	list_for_each_entry(range, &asma->unpinned_list, unpinned) {
+		if (range_before_page(range, pgstart))
+			break;
+		if (page_range_in_range(range, pgstart, pgend)) {
+			ret = ASHMEM_IS_UNPINNED;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static int ashmem_pin_unpin(struct ashmem_area *asma, unsigned long cmd,
+			    void __user *p)
+{
+	struct ashmem_pin pin;
+	size_t pgstart, pgend;
+	int ret = -EINVAL;
+	struct ashmem_range *range = NULL;
+
+	if (copy_from_user(&pin, p, sizeof(pin)))
+		return -EFAULT;
+
+	if (cmd == ASHMEM_PIN || cmd == ASHMEM_UNPIN) {
+		range = kmem_cache_zalloc(ashmem_range_cachep, GFP_KERNEL);
+		if (!range)
+			return -ENOMEM;
+	}
+
+	mutex_lock(&ashmem_mutex);
+	wait_event(ashmem_shrink_wait, !atomic_read(&ashmem_shrink_inflight));
+
+	if (!asma->file)
+		goto out_unlock;
+
+	/* per custom, you can pass zero for len to mean "everything onward" */
+	if (!pin.len)
+		pin.len = PAGE_ALIGN(asma->size) - pin.offset;
+
+	if ((pin.offset | pin.len) & ~PAGE_MASK)
+		goto out_unlock;
+
+	if (((__u32)-1) - pin.offset < pin.len)
+		goto out_unlock;
+
+	if (PAGE_ALIGN(asma->size) < pin.offset + pin.len)
+		goto out_unlock;
+
+	pgstart = pin.offset / PAGE_SIZE;
+	pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
+
+	switch (cmd) {
+	case ASHMEM_PIN:
+		ret = ashmem_pin(asma, pgstart, pgend, &range);
+		break;
+	case ASHMEM_UNPIN:
+		ret = ashmem_unpin(asma, pgstart, pgend, &range);
+		break;
+	case ASHMEM_GET_PIN_STATUS:
+		ret = ashmem_get_pin_status(asma, pgstart, pgend);
+		break;
+	}
+
+out_unlock:
+	mutex_unlock(&ashmem_mutex);
+	if (range)
+		kmem_cache_free(ashmem_range_cachep, range);
+
+	return ret;
+}
+
+static long ashmem_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct ashmem_area *asma = file->private_data;
+	long ret = -ENOTTY;
+
+	switch (cmd) {
+	case ASHMEM_SET_NAME:
+		ret = set_name(asma, (void __user *)arg);
+		break;
+	case ASHMEM_GET_NAME:
+		ret = get_name(asma, (void __user *)arg);
+		break;
+	case ASHMEM_SET_SIZE:
+		ret = -EINVAL;
+		mutex_lock(&ashmem_mutex);
+		if (!asma->file) {
+			ret = 0;
+			asma->size = (size_t)arg;
+		}
+		mutex_unlock(&ashmem_mutex);
+		break;
+	case ASHMEM_GET_SIZE:
+		ret = asma->size;
+		break;
+	case ASHMEM_SET_PROT_MASK:
+		ret = set_prot_mask(asma, arg);
+		break;
+	case ASHMEM_GET_PROT_MASK:
+		ret = asma->prot_mask;
+		break;
+	case ASHMEM_PIN:
+	case ASHMEM_UNPIN:
+	case ASHMEM_GET_PIN_STATUS:
+		ret = ashmem_pin_unpin(asma, cmd, (void __user *)arg);
+		break;
+	case ASHMEM_PURGE_ALL_CACHES:
+		ret = -EPERM;
+		if (capable(CAP_SYS_ADMIN)) {
+			struct shrink_control sc = {
+				.gfp_mask = GFP_KERNEL,
+				.nr_to_scan = LONG_MAX,
+			};
+			ret = ashmem_shrink_count(&ashmem_shrinker, &sc);
+			ashmem_shrink_scan(&ashmem_shrinker, &sc);
+		}
+		break;
+	}
+
+	return ret;
+}
+
+/* support of 32bit userspace on 64bit platforms */
+#ifdef CONFIG_COMPAT
+static long compat_ashmem_ioctl(struct file *file, unsigned int cmd,
+				unsigned long arg)
+{
+	switch (cmd) {
+	case COMPAT_ASHMEM_SET_SIZE:
+		cmd = ASHMEM_SET_SIZE;
+		break;
+	case COMPAT_ASHMEM_SET_PROT_MASK:
+		cmd = ASHMEM_SET_PROT_MASK;
+		break;
+	}
+	return ashmem_ioctl(file, cmd, arg);
+}
+#endif
+#ifdef CONFIG_PROC_FS
+static void ashmem_show_fdinfo(struct seq_file *m, struct file *file)
+{
+	struct ashmem_area *asma = file->private_data;
+
+	mutex_lock(&ashmem_mutex);
+
+	if (asma->file)
+		seq_printf(m, "inode:\t%ld\n", file_inode(asma->file)->i_ino);
+
+	if (asma->name[ASHMEM_NAME_PREFIX_LEN] != '\0')
+		seq_printf(m, "name:\t%s\n",
+			   asma->name + ASHMEM_NAME_PREFIX_LEN);
+
+	seq_printf(m, "size:\t%zu\n", asma->size);
+
+	mutex_unlock(&ashmem_mutex);
+}
+#endif
+static const struct file_operations ashmem_fops = {
+	.owner = THIS_MODULE,
+	.open = ashmem_open,
+	.release = ashmem_release,
+	.read_iter = ashmem_read_iter,
+	.llseek = ashmem_llseek,
+	.mmap = ashmem_mmap,
+	.unlocked_ioctl = ashmem_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = compat_ashmem_ioctl,
+#endif
+#ifdef CONFIG_PROC_FS
+	.show_fdinfo = ashmem_show_fdinfo,
+#endif
+};
+
+static struct miscdevice ashmem_misc = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "ashmem",
+	.fops = &ashmem_fops,
+};
+
+static int __init ashmem_init(void)
+{
+	int ret = -ENOMEM;
+
+	ashmem_area_cachep = kmem_cache_create("ashmem_area_cache",
+					       sizeof(struct ashmem_area),
+					       0, 0, NULL);
+	if (!ashmem_area_cachep) {
+		pr_err("failed to create slab cache\n");
+		goto out;
+	}
+
+	ashmem_range_cachep = kmem_cache_create("ashmem_range_cache",
+						sizeof(struct ashmem_range),
+						0, SLAB_RECLAIM_ACCOUNT, NULL);
+	if (!ashmem_range_cachep) {
+		pr_err("failed to create slab cache\n");
+		goto out_free1;
+	}
+
+	ret = misc_register(&ashmem_misc);
+	if (ret) {
+		pr_err("failed to register misc device!\n");
+		goto out_free2;
+	}
+
+	ret = register_shrinker(&ashmem_shrinker, "android-ashmem");
+	if (ret) {
+		pr_err("failed to register shrinker!\n");
+		goto out_demisc;
+	}
+
+	pr_info("initialized\n");
+
+	return 0;
+
+out_demisc:
+	misc_deregister(&ashmem_misc);
+out_free2:
+	kmem_cache_destroy(ashmem_range_cachep);
+out_free1:
+	kmem_cache_destroy(ashmem_area_cachep);
+out:
+	return ret;
+}
+device_initcall(ashmem_init);
diff --git a/drivers/staging/android/ashmem.h b/drivers/staging/android/ashmem.h
new file mode 100644
--- /dev/null
+++ b/drivers/staging/android/ashmem.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Apache-2.0 */
+/*
+ * include/linux/ashmem.h
+ *
+ * Copyright 2008 Google Inc.
+ * Author: Robert Love
+ */
+
+#ifndef _LINUX_ASHMEM_H
+#define _LINUX_ASHMEM_H
+
+#include <linux/limits.h>
+#include <linux/ioctl.h>
+#include <linux/compat.h>
+
+#include "uapi/ashmem.h"
+
+/* support of 32bit userspace on 64bit platforms */
+#ifdef CONFIG_COMPAT
+#define COMPAT_ASHMEM_SET_SIZE		_IOW(__ASHMEMIOC, 3, compat_size_t)
+#define COMPAT_ASHMEM_SET_PROT_MASK	_IOW(__ASHMEMIOC, 5, unsigned int)
+#endif
+
+#endif	/* _LINUX_ASHMEM_H */
diff --git a/drivers/staging/android/uapi/ashmem.h b/drivers/staging/android/uapi/ashmem.h
new file mode 100644
--- /dev/null
+++ b/drivers/staging/android/uapi/ashmem.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Apache-2.0 */
+/*
+ * Copyright 2008 Google Inc.
+ * Author: Robert Love
+ */
+
+#ifndef _UAPI_LINUX_ASHMEM_H
+#define _UAPI_LINUX_ASHMEM_H
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+#define ASHMEM_NAME_LEN		256
+
+#define ASHMEM_NAME_DEF		"dev/ashmem"
+
+/* Return values from ASHMEM_PIN: Was the mapping purged while unpinned? */
+#define ASHMEM_NOT_PURGED	0
+#define ASHMEM_WAS_PURGED	1
+
+/* Return values from ASHMEM_GET_PIN_STATUS: Is the mapping pinned? */
+#define ASHMEM_IS_UNPINNED	0
+#define ASHMEM_IS_PINNED	1
+
+struct ashmem_pin {
+	__u32 offset;	/* offset into region, in bytes, page-aligned */
+	__u32 len;	/* length forward from offset, in bytes, page-aligned */
+};
+
+#define __ASHMEMIOC		0x77
+
+#define ASHMEM_SET_NAME		_IOW(__ASHMEMIOC, 1, char[ASHMEM_NAME_LEN])
+#define ASHMEM_GET_NAME		_IOR(__ASHMEMIOC, 2, char[ASHMEM_NAME_LEN])
+#define ASHMEM_SET_SIZE		_IOW(__ASHMEMIOC, 3, size_t)
+#define ASHMEM_GET_SIZE		_IO(__ASHMEMIOC, 4)
+#define ASHMEM_SET_PROT_MASK	_IOW(__ASHMEMIOC, 5, unsigned long)
+#define ASHMEM_GET_PROT_MASK	_IO(__ASHMEMIOC, 6)
+#define ASHMEM_PIN		_IOW(__ASHMEMIOC, 7, struct ashmem_pin)
+#define ASHMEM_UNPIN		_IOW(__ASHMEMIOC, 8, struct ashmem_pin)
+#define ASHMEM_GET_PIN_STATUS	_IO(__ASHMEMIOC, 9)
+#define ASHMEM_PURGE_ALL_CACHES	_IO(__ASHMEMIOC, 10)
+
+#endif	/* _UAPI_LINUX_ASHMEM_H */