A driver to let userspace turn memfd regions into dma-bufs.
Use case: Allows qemu create dmabufs for the vga framebuffer or
virtio-gpu ressources. Then they can be passed around to display
those guest things on the host. To spice client for classic full
framebuffer display, and hopefully some day to wayland server for
seamless guest window display.
Note: Initial revision which supports a single region only so it
can't handle virtio-gpu ressources yet.
qemu test branch:
https://git.kraxel.org/cgit/qemu/log/?h=sirius/udmabuf
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
---
include/uapi/linux/udmabuf.h | 19 ++
drivers/dma-buf/udmabuf.c | 240 ++++++++++++++++++++++
tools/testing/selftests/drivers/dma-buf/udmabuf.c | 95 +++++++++
drivers/dma-buf/Kconfig | 7 +
drivers/dma-buf/Makefile | 1 +
tools/testing/selftests/drivers/dma-buf/Makefile | 5 +
6 files changed, 367 insertions(+)
create mode 100644 include/uapi/linux/udmabuf.h
create mode 100644 drivers/dma-buf/udmabuf.c
create mode 100644 tools/testing/selftests/drivers/dma-buf/udmabuf.c
create mode 100644 tools/testing/selftests/drivers/dma-buf/Makefile
diff --git a/include/uapi/linux/udmabuf.h b/include/uapi/linux/udmabuf.h
new file mode 100644
index 0000000000..2fbe69cf05
--- /dev/null
+++ b/include/uapi/linux/udmabuf.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_LINUX_UDMABUF_H
+#define _UAPI_LINUX_UDMABUF_H
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+#define UDMABUF_FLAGS_CLOEXEC 0x01
+
+struct udmabuf_create {
+ __u32 memfd;
+ __u32 flags;
+ __u64 offset;
+ __u64 size;
+};
+
+#define UDMABUF_CREATE _IOW(0x42, 0x23, struct udmabuf_create)
+
+#endif /* _UAPI_LINUX_UDMABUF_H */
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
new file mode 100644
index 0000000000..f9600dc985
--- /dev/null
+++ b/drivers/dma-buf/udmabuf.c
@@ -0,0 +1,240 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/miscdevice.h>
+#include <linux/dma-buf.h>
+#include <linux/highmem.h>
+#include <linux/cred.h>
+#include <linux/shmem_fs.h>
+
+#include <uapi/linux/udmabuf.h>
+
+struct udmabuf {
+ struct file *filp;
+ u32 pagecount;
+ struct page **pages;
+};
+
+static int udmabuf_vm_fault(struct vm_fault *vmf)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct udmabuf *ubuf = vma->vm_private_data;
+
+ if (WARN_ON(vmf->pgoff >= ubuf->pagecount))
+ return VM_FAULT_SIGBUS;
+
+ vmf->page = ubuf->pages[vmf->pgoff];
+ get_page(vmf->page);
+ return 0;
+}
+
+static const struct vm_operations_struct udmabuf_vm_ops = {
+ .fault = udmabuf_vm_fault,
+};
+
+static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
+{
+ struct udmabuf *ubuf = buf->priv;
+
+ if ((vma->vm_flags & VM_SHARED) == 0)
+ return -EINVAL;
+
+ vma->vm_ops = &udmabuf_vm_ops;
+ vma->vm_private_data = ubuf;
+ return 0;
+}
+
+static struct sg_table *map_udmabuf(struct dma_buf_attachment *at,
+ enum dma_data_direction direction)
+{
+ struct udmabuf *ubuf = at->dmabuf->priv;
+ struct sg_table *sg;
+
+ sg = kzalloc(sizeof(*sg), GFP_KERNEL);
+ if (!sg)
+ goto err1;
+ if (sg_alloc_table_from_pages(sg, ubuf->pages, ubuf->pagecount,
+ 0, ubuf->pagecount << PAGE_SHIFT,
+ GFP_KERNEL) < 0)
+ goto err2;
+ if (!dma_map_sg(at->dev, sg->sgl, sg->nents, direction))
+ goto err3;
+
+ return sg;
+
+err3:
+ sg_free_table(sg);
+err2:
+ kfree(sg);
+err1:
+ return ERR_PTR(-ENOMEM);
+}
+
+static void unmap_udmabuf(struct dma_buf_attachment *at,
+ struct sg_table *sg,
+ enum dma_data_direction direction)
+{
+ sg_free_table(sg);
+ kfree(sg);
+}
+
+static void release_udmabuf(struct dma_buf *buf)
+{
+ struct udmabuf *ubuf = buf->priv;
+ pgoff_t pg;
+
+ for (pg = 0; pg < ubuf->pagecount; pg++)
+ put_page(ubuf->pages[pg]);
+ fput(ubuf->filp);
+ kfree(ubuf->pages);
+ kfree(ubuf);
+}
+
+static void *kmap_atomic_udmabuf(struct dma_buf *buf, unsigned long page_num)
+{
+ struct udmabuf *ubuf = buf->priv;
+ struct page *page = ubuf->pages[page_num];
+
+ return kmap_atomic(page);
+}
+
+static void *kmap_udmabuf(struct dma_buf *buf, unsigned long page_num)
+{
+ struct udmabuf *ubuf = buf->priv;
+ struct page *page = ubuf->pages[page_num];
+
+ return kmap(page);
+}
+
+static struct dma_buf_ops udmabuf_ops = {
+ .map_dma_buf = map_udmabuf,
+ .unmap_dma_buf = unmap_udmabuf,
+ .release = release_udmabuf,
+ .map_atomic = kmap_atomic_udmabuf,
+ .map = kmap_udmabuf,
+ .mmap = mmap_udmabuf,
+};
+
+static long udmabuf_ioctl_create(struct file *filp, unsigned long arg)
+{
+ DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
+ struct udmabuf_create create;
+ struct udmabuf *ubuf;
+ struct dma_buf *buf;
+ pgoff_t pgoff, pgidx;
+ struct page *page;
+ int ret = -EINVAL;
+ u32 flags;
+
+ if (copy_from_user(&create, (void __user *)arg,
+ sizeof(struct udmabuf_create)))
+ return -EFAULT;
+
+ if (!IS_ALIGNED(create.offset, PAGE_SIZE))
+ return -EINVAL;
+ if (!IS_ALIGNED(create.size, PAGE_SIZE))
+ return -EINVAL;
+
+ ubuf = kzalloc(sizeof(struct udmabuf), GFP_KERNEL);
+ if (!ubuf)
+ return -ENOMEM;
+
+ ubuf->filp = fget(create.memfd);
+ if (!ubuf->filp)
+ goto err_free_ubuf;
+ if (!shmem_mapping(file_inode(ubuf->filp)->i_mapping))
+ goto err_free_ubuf;
+
+ ubuf->pagecount = create.size >> PAGE_SHIFT;
+ ubuf->pages = kmalloc_array(ubuf->pagecount, sizeof(struct page*),
+ GFP_KERNEL);
+ if (!ubuf->pages) {
+ ret = -ENOMEM;
+ goto err_free_ubuf;
+ }
+
+ pgoff = create.offset >> PAGE_SHIFT;
+ for (pgidx = 0; pgidx < ubuf->pagecount; pgidx++) {
+ page = shmem_read_mapping_page(
+ file_inode(ubuf->filp)->i_mapping, pgoff + pgidx);
+ if (IS_ERR(page)) {
+ ret = PTR_ERR(buf);
+ goto err_put_pages;
+ }
+ ubuf->pages[pgidx] = page;
+ }
+
+ exp_info.ops = &udmabuf_ops;
+ exp_info.size = ubuf->pagecount << PAGE_SHIFT;
+ exp_info.priv = ubuf;
+
+ buf = dma_buf_export(&exp_info);
+ if (IS_ERR(buf)) {
+ ret = PTR_ERR(buf);
+ goto err_put_pages;
+ }
+
+ flags = 0;
+ if (create.flags & UDMABUF_FLAGS_CLOEXEC)
+ flags |= O_CLOEXEC;
+ return dma_buf_fd(buf, flags);
+
+err_put_pages:
+ while (pgidx > 0)
+ put_page(ubuf->pages[--pgidx]);
+err_free_ubuf:
+ fput(ubuf->filp);
+ kfree(ubuf->pages);
+ kfree(ubuf);
+ return ret;
+}
+
+static long udmabuf_ioctl(struct file *filp, unsigned int ioctl,
+ unsigned long arg)
+{
+ long ret;
+
+ switch (ioctl) {
+ case UDMABUF_CREATE:
+ ret = udmabuf_ioctl_create(filp, arg);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+ return ret;
+}
+
+static const struct file_operations udmabuf_fops = {
+ .owner = THIS_MODULE,
+ .unlocked_ioctl = udmabuf_ioctl,
+};
+
+static struct miscdevice udmabuf_misc = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "udmabuf",
+ .fops = &udmabuf_fops,
+};
+
+static int __init udmabuf_dev_init(void)
+{
+ return misc_register(&udmabuf_misc);
+}
+
+static void __exit udmabuf_dev_exit(void)
+{
+ misc_deregister(&udmabuf_misc);
+}
+
+module_init(udmabuf_dev_init)
+module_exit(udmabuf_dev_exit)
+
+MODULE_AUTHOR("Gerd Hoffmann <kraxel@xxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
diff --git a/tools/testing/selftests/drivers/dma-buf/udmabuf.c b/tools/testing/selftests/drivers/dma-buf/udmabuf.c
new file mode 100644
index 0000000000..d46c58b0dd
--- /dev/null
+++ b/tools/testing/selftests/drivers/dma-buf/udmabuf.c
@@ -0,0 +1,95 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <malloc.h>
+
+#include <sys/ioctl.h>
+#include <sys/syscall.h>
+#include <linux/memfd.h>
+#include <linux/udmabuf.h>
+
+#define TEST_PREFIX "drivers/dma-buf/udmabuf"
+#define NUM_PAGES 4
+
+static int memfd_create(const char *name, unsigned int flags)
+{
+ return syscall(__NR_memfd_create, name, flags);
+}
+
+int main(int argc, char *argv[])
+{
+ struct udmabuf_create create;
+ int devfd, memfd, buf, ret;
+ off_t size;
+ void *mem;
+
+ devfd = open("/dev/udmabuf", O_RDWR);
+ if (devfd < 0) {
+ printf("%s: [skip,no-udmabuf]\n", TEST_PREFIX);
+ exit(77);
+ }
+
+ memfd = memfd_create("udmabuf-test", MFD_CLOEXEC);
+ if (memfd < 0) {
+ printf("%s: [skip,no-memfd]\n", TEST_PREFIX);
+ exit(77);
+ }
+
+ size = getpagesize() * NUM_PAGES;
+ ret = ftruncate(memfd, size);
+ if (ret == -1) {
+ printf("%s: [FAIL,memfd-truncate]\n", TEST_PREFIX);
+ exit(1);
+ }
+
+ memset(&create, 0, sizeof(create));
+
+ /* should fail (offset not page aligned) */
+ create.memfd = memfd;
+ create.offset = getpagesize()/2;
+ create.size = getpagesize();
+ buf = ioctl(devfd, UDMABUF_CREATE, &create);
+ if (buf >= 0) {
+ printf("%s: [FAIL,test-1]\n", TEST_PREFIX);
+ exit(1);
+ }
+
+ /* should fail (size not multiple of page) */
+ create.memfd = memfd;
+ create.offset = 0;
+ create.size = getpagesize()/2;
+ buf = ioctl(devfd, UDMABUF_CREATE, &create);
+ if (buf >= 0) {
+ printf("%s: [FAIL,test-2]\n", TEST_PREFIX);
+ exit(1);
+ }
+
+ /* should fail (not memfd) */
+ create.memfd = 0; /* stdin */
+ create.offset = 0;
+ create.size = size;
+ buf = ioctl(devfd, UDMABUF_CREATE, &create);
+ if (buf >= 0) {
+ printf("%s: [FAIL,test-3]\n", TEST_PREFIX);
+ exit(1);
+ }
+
+ /* should work */
+ create.memfd = memfd;
+ create.offset = 0;
+ create.size = size;
+ buf = ioctl(devfd, UDMABUF_CREATE, &create);
+ if (buf < 0) {
+ printf("%s: [FAIL,test-4]\n", TEST_PREFIX);
+ exit(1);
+ }
+
+ fprintf(stderr, "%s: ok\n", TEST_PREFIX);
+ close(buf);
+ close(memfd);
+ close(devfd);
+ return 0;
+}
diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
index ed3b785bae..19be3ec62d 100644
--- a/drivers/dma-buf/Kconfig
+++ b/drivers/dma-buf/Kconfig
@@ -30,4 +30,11 @@ config SW_SYNC
WARNING: improper use of this can result in deadlocking kernel
drivers from userspace. Intended for test and debug only.
+config UDMABUF
+ bool "userspace dmabuf misc driver"
+ default n
+ depends on DMA_SHARED_BUFFER
