From: Khalid Aziz <khalid@kernel.org>
Reserve a range of ioctls for msharefs and add the first two ioctls
to get and set the start address and size of an mshare region.
Signed-off-by: Khalid Aziz <khalid@kernel.org>
Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
---
.../userspace-api/ioctl/ioctl-number.rst | 1 +
include/uapi/linux/msharefs.h | 29 ++++++++
mm/mshare.c | 72 +++++++++++++++++++
3 files changed, 102 insertions(+)
create mode 100644 include/uapi/linux/msharefs.h
diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index e91c0376ee59..d2fa6b117f66 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -301,6 +301,7 @@ Code Seq# Include File Comments
'v' 20-27 arch/powerpc/include/uapi/asm/vas-api.h VAS API
'v' C0-FF linux/meye.h conflict!
'w' all CERN SCI driver
+'x' 00-1F linux/msharefs.h msharefs filesystem
'y' 00-1F packet based user level communications
<mailto:zapman@interlan.net>
'z' 00-3F CAN bus card conflict!
diff --git a/include/uapi/linux/msharefs.h b/include/uapi/linux/msharefs.h
new file mode 100644
index 000000000000..c7b509c7e093
--- /dev/null
+++ b/include/uapi/linux/msharefs.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * msharefs defines a memory region that is shared across processes.
+ * ioctl is used on files created under msharefs to set various
+ * attributes on these shared memory regions
+ *
+ *
+ * Copyright (C) 2024 Oracle Corp. All rights reserved.
+ * Author: Khalid Aziz <khalid@kernel.org>
+ */
+
+#ifndef _UAPI_LINUX_MSHAREFS_H
+#define _UAPI_LINUX_MSHAREFS_H
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+/*
+ * msharefs specific ioctl commands
+ */
+#define MSHAREFS_GET_SIZE _IOR('x', 0, struct mshare_info)
+#define MSHAREFS_SET_SIZE _IOW('x', 1, struct mshare_info)
+
+struct mshare_info {
+ __u64 start;
+ __u64 size;
+};
+
+#endif
diff --git a/mm/mshare.c b/mm/mshare.c
index a37849e724e1..af46eb76d2bc 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -10,15 +10,20 @@
*
* Copyright (C) 2024 Oracle Corp. All rights reserved.
* Author: Khalid Aziz <khalid@kernel.org>
+ * Author: Matthew Wilcox <willy@infradead.org>
*
*/
#include <linux/fs.h>
#include <linux/fs_context.h>
+#include <linux/spinlock_types.h>
#include <uapi/linux/magic.h>
+#include <uapi/linux/msharefs.h>
struct mshare_data {
struct mm_struct *mm;
+ spinlock_t m_lock;
+ struct mshare_info minfo;
};
struct msharefs_info {
@@ -28,8 +33,74 @@ struct msharefs_info {
static const struct inode_operations msharefs_dir_inode_ops;
static const struct inode_operations msharefs_file_inode_ops;
+static long
+msharefs_set_size(struct mm_struct *mm, struct mshare_data *m_data,
+ struct mshare_info *minfo)
+{
+ unsigned long end = minfo->start + minfo->size;
+
+ /*
+ * Validate alignment for start address, and size
+ */
+ if ((minfo->start | end) & (PGDIR_SIZE - 1)) {
+ spin_unlock(&m_data->m_lock);
+ return -EINVAL;
+ }
+
+ mm->mmap_base = minfo->start;
+ mm->task_size = minfo->size;
+ if (!mm->task_size)
+ mm->task_size--;
+
+ m_data->minfo.start = mm->mmap_base;
+ m_data->minfo.size = mm->task_size;
+ spin_unlock(&m_data->m_lock);
+
+ return 0;
+}
+
+static long
+msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+ struct mshare_data *m_data = filp->private_data;
+ struct mm_struct *mm = m_data->mm;
+ struct mshare_info minfo;
+
+ switch (cmd) {
+ case MSHAREFS_GET_SIZE:
+ spin_lock(&m_data->m_lock);
+ minfo = m_data->minfo;
+ spin_unlock(&m_data->m_lock);
+
+ if (copy_to_user((void __user *)arg, &minfo, sizeof(minfo)))
+ return -EFAULT;
+
+ return 0;
+
+ case MSHAREFS_SET_SIZE:
+ if (copy_from_user(&minfo, (struct mshare_info __user *)arg,
+ sizeof(minfo)))
+ return -EFAULT;
+
+ /*
+ * If this mshare region has been set up once already, bail out
+ */
+ spin_lock(&m_data->m_lock);
+ if (m_data->minfo.start != 0) {
+ spin_unlock(&m_data->m_lock);
+ return -EINVAL;
+ }
+
+ return msharefs_set_size(mm, m_data, &minfo);
+
+ default:
+ return -ENOTTY;
+ }
+}
+
static const struct file_operations msharefs_file_operations = {
.open = simple_open,
+ .unlocked_ioctl = msharefs_ioctl,
.llseek = no_llseek,
};
@@ -54,6 +125,7 @@ msharefs_fill_mm(struct inode *inode)
goto err_free;
}
m_data->mm = mm;
+ spin_lock_init(&m_data->m_lock);
inode->i_private = m_data;
return 0;
--
2.43.5On Wed, Sep 4, 2024 at 1:22 AM Anthony Yznaga <anthony.yznaga@oracle.com> wrote:
> Reserve a range of ioctls for msharefs and add the first two ioctls
> to get and set the start address and size of an mshare region.
[...]
> +static long
> +msharefs_set_size(struct mm_struct *mm, struct mshare_data *m_data,
> + struct mshare_info *minfo)
> +{
> + unsigned long end = minfo->start + minfo->size;
> +
> + /*
> + * Validate alignment for start address, and size
> + */
> + if ((minfo->start | end) & (PGDIR_SIZE - 1)) {
> + spin_unlock(&m_data->m_lock);
> + return -EINVAL;
> + }
> +
> + mm->mmap_base = minfo->start;
> + mm->task_size = minfo->size;
> + if (!mm->task_size)
> + mm->task_size--;
> +
> + m_data->minfo.start = mm->mmap_base;
> + m_data->minfo.size = mm->task_size;
> + spin_unlock(&m_data->m_lock);
> +
> + return 0;
> +}
> +
> +static long
> +msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> +{
> + struct mshare_data *m_data = filp->private_data;
> + struct mm_struct *mm = m_data->mm;
> + struct mshare_info minfo;
> +
> + switch (cmd) {
> + case MSHAREFS_GET_SIZE:
> + spin_lock(&m_data->m_lock);
> + minfo = m_data->minfo;
> + spin_unlock(&m_data->m_lock);
> +
> + if (copy_to_user((void __user *)arg, &minfo, sizeof(minfo)))
> + return -EFAULT;
> +
> + return 0;
> +
> + case MSHAREFS_SET_SIZE:
> + if (copy_from_user(&minfo, (struct mshare_info __user *)arg,
> + sizeof(minfo)))
> + return -EFAULT;
> +
> + /*
> + * If this mshare region has been set up once already, bail out
> + */
> + spin_lock(&m_data->m_lock);
> + if (m_data->minfo.start != 0) {
Is there actually anything that prevents msharefs_set_size() from
setting up m_data with ->minfo.start==0, so that a second
MSHAREFS_SET_SIZE invocation will succeed? It would probably be more
reliable to have a separate flag for "has this thing been set up yet".
> + spin_unlock(&m_data->m_lock);
> + return -EINVAL;
> + }
> +
> + return msharefs_set_size(mm, m_data, &minfo);
> +
> + default:
> + return -ENOTTY;
> + }
> +}
On 10/14/24 1:08 PM, Jann Horn wrote:
> On Wed, Sep 4, 2024 at 1:22 AM Anthony Yznaga <anthony.yznaga@oracle.com> wrote:
>> Reserve a range of ioctls for msharefs and add the first two ioctls
>> to get and set the start address and size of an mshare region.
> [...]
>> +static long
>> +msharefs_set_size(struct mm_struct *mm, struct mshare_data *m_data,
>> + struct mshare_info *minfo)
>> +{
>> + unsigned long end = minfo->start + minfo->size;
>> +
>> + /*
>> + * Validate alignment for start address, and size
>> + */
>> + if ((minfo->start | end) & (PGDIR_SIZE - 1)) {
>> + spin_unlock(&m_data->m_lock);
>> + return -EINVAL;
>> + }
>> +
>> + mm->mmap_base = minfo->start;
>> + mm->task_size = minfo->size;
>> + if (!mm->task_size)
>> + mm->task_size--;
>> +
>> + m_data->minfo.start = mm->mmap_base;
>> + m_data->minfo.size = mm->task_size;
>> + spin_unlock(&m_data->m_lock);
>> +
>> + return 0;
>> +}
>> +
>> +static long
>> +msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>> +{
>> + struct mshare_data *m_data = filp->private_data;
>> + struct mm_struct *mm = m_data->mm;
>> + struct mshare_info minfo;
>> +
>> + switch (cmd) {
>> + case MSHAREFS_GET_SIZE:
>> + spin_lock(&m_data->m_lock);
>> + minfo = m_data->minfo;
>> + spin_unlock(&m_data->m_lock);
>> +
>> + if (copy_to_user((void __user *)arg, &minfo, sizeof(minfo)))
>> + return -EFAULT;
>> +
>> + return 0;
>> +
>> + case MSHAREFS_SET_SIZE:
>> + if (copy_from_user(&minfo, (struct mshare_info __user *)arg,
>> + sizeof(minfo)))
>> + return -EFAULT;
>> +
>> + /*
>> + * If this mshare region has been set up once already, bail out
>> + */
>> + spin_lock(&m_data->m_lock);
>> + if (m_data->minfo.start != 0) {
> Is there actually anything that prevents msharefs_set_size() from
> setting up m_data with ->minfo.start==0, so that a second
> MSHAREFS_SET_SIZE invocation will succeed? It would probably be more
> reliable to have a separate flag for "has this thing been set up yet".
Thanks for pointing this out. Yes, this is problematic. A start address
of 0 generally won't work because mmap() will fail unless there are
sufficient privileges (cap_map_addr will return -EPERM). I already have
changes to use the size to indicate initialization, but it may make
sense to have flags.
Anthony
>
>
>> + spin_unlock(&m_data->m_lock);
>> + return -EINVAL;
>> + }
>> +
>> + return msharefs_set_size(mm, m_data, &minfo);
>> +
>> + default:
>> + return -ENOTTY;
>> + }
>> +}
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