Add an ioctl for mapping objects within an mshare region. The
arguments are the same as mmap() although only shared anonymous
memory with some restrictions is supported initially.
Signed-off-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>
---
include/uapi/linux/msharefs.h | 9 +++++
mm/mshare.c | 71 +++++++++++++++++++++++++++++++++++
2 files changed, 80 insertions(+)
diff --git a/include/uapi/linux/msharefs.h b/include/uapi/linux/msharefs.h
index c7b509c7e093..fea0afdf000d 100644
--- a/include/uapi/linux/msharefs.h
+++ b/include/uapi/linux/msharefs.h
@@ -20,10 +20,19 @@
*/
#define MSHAREFS_GET_SIZE _IOR('x', 0, struct mshare_info)
#define MSHAREFS_SET_SIZE _IOW('x', 1, struct mshare_info)
+#define MSHAREFS_CREATE_MAPPING _IOW('x', 2, struct mshare_create)
struct mshare_info {
__u64 start;
__u64 size;
};
+struct mshare_create {
+ __u64 addr;
+ __u64 size;
+ __u64 offset;
+ __u32 prot;
+ __u32 flags;
+ __u32 fd;
+};
#endif
diff --git a/mm/mshare.c b/mm/mshare.c
index 8f47c8d6e6a4..7b89bf7f5ffc 100644
--- a/mm/mshare.c
+++ b/mm/mshare.c
@@ -16,6 +16,7 @@
#include <linux/fs.h>
#include <linux/fs_context.h>
+#include <linux/mman.h>
#include <linux/spinlock_types.h>
#include <uapi/linux/magic.h>
#include <uapi/linux/msharefs.h>
@@ -154,12 +155,65 @@ msharefs_set_size(struct mm_struct *mm, struct mshare_data *m_data,
return 0;
}
+static long
+msharefs_create_mapping(struct mm_struct *mm, struct mshare_data *m_data,
+ struct mshare_create *mcreate)
+{
+ unsigned long mshare_start, mshare_end;
+ unsigned long mapped_addr;
+ unsigned long populate = 0;
+ unsigned long addr = mcreate->addr;
+ unsigned long size = mcreate->size;
+ unsigned int fd = mcreate->fd;
+ int prot = mcreate->prot;
+ int flags = mcreate->flags;
+ vm_flags_t vm_flags;
+ int err = -EINVAL;
+
+ mshare_start = m_data->minfo.start;
+ mshare_end = mshare_start + m_data->minfo.size;
+
+ if ((addr < mshare_start) || (addr >= mshare_end) ||
+ (addr + size > mshare_end))
+ goto out;
+
+ /*
+ * XXX Keep things simple initially and only allow the mapping of
+ * anonymous shared memory at fixed addresses without unmapping.
+ */
+ if ((flags & (MAP_SHARED | MAP_FIXED)) != (MAP_SHARED | MAP_FIXED))
+ goto out;
+
+ if (fd != -1)
+ goto out;
+
+ flags |= MAP_FIXED_NOREPLACE;
+ vm_flags = VM_NOHUGEPAGE;
+
+ if (mmap_write_lock_killable(mm)) {
+ err = -EINTR;
+ goto out;
+ }
+
+ err = 0;
+ mapped_addr = __do_mmap(NULL, addr, size, prot, flags, vm_flags,
+ 0, &populate, NULL, mm);
+
+ if (IS_ERR_VALUE(mapped_addr))
+ err = (long)mapped_addr;
+
+ mmap_write_unlock(mm);
+out:
+ return err;
+}
+
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;
+ struct mshare_create mcreate;
switch (cmd) {
case MSHAREFS_GET_SIZE:
@@ -188,6 +242,23 @@ msharefs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return msharefs_set_size(mm, m_data, &minfo);
+ case MSHAREFS_CREATE_MAPPING:
+ if (copy_from_user(&mcreate, (struct mshare_create __user *)arg,
+ sizeof(mcreate)))
+ return -EFAULT;
+
+ /*
+ * validate mshare region
+ */
+ spin_lock(&m_data->m_lock);
+ if (m_data->minfo.start == 0) {
+ spin_unlock(&m_data->m_lock);
+ return -EINVAL;
+ }
+ spin_unlock(&m_data->m_lock);
+
+ return msharefs_create_mapping(mm, m_data, &mcreate);
+
default:
return -ENOTTY;
}
--
2.43.5
