[RFC simple allocator v2 1/2] Create Simple Allocator module
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Tue Feb 14 19:30:56 UTC 2017
Hi Benjamin,
Thank you for the patch. I've CC'ed the linux-api mailing list.
On Monday 13 Feb 2017 15:45:05 Benjamin Gaignard wrote:
> This is the core of simple allocator module.
> It aim to offert one common ioctl to allocate specific memory.
>
> version 2:
> - rebased on 4.10-rc7
>
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard at linaro.org>
> ---
> Documentation/simple-allocator.txt | 81 +++++++++++
> drivers/Kconfig | 2 +
> drivers/Makefile | 1 +
> drivers/simpleallocator/Kconfig | 10 ++
> drivers/simpleallocator/Makefile | 1 +
> drivers/simpleallocator/simple-allocator-priv.h | 33 +++++
> drivers/simpleallocator/simple-allocator.c | 180 +++++++++++++++++++++
> include/uapi/linux/simple-allocator.h | 35 +++++
> 8 files changed, 343 insertions(+)
> create mode 100644 Documentation/simple-allocator.txt
> create mode 100644 drivers/simpleallocator/Kconfig
> create mode 100644 drivers/simpleallocator/Makefile
> create mode 100644 drivers/simpleallocator/simple-allocator-priv.h
> create mode 100644 drivers/simpleallocator/simple-allocator.c
> create mode 100644 include/uapi/linux/simple-allocator.h
>
> diff --git a/Documentation/simple-allocator.txt
> b/Documentation/simple-allocator.txt new file mode 100644
> index 0000000..89ba883
> --- /dev/null
> +++ b/Documentation/simple-allocator.txt
> @@ -0,0 +1,81 @@
> +Simple Allocator Framework
There's nothing simple in buffer allocation, otherwise we would have solved
the problem a long time ago. Let's not use a misleading name.
> +Simple Allocator offer a single ioctl SA_IOC_ALLOC to allocate buffers
> +on dedicated memory regions and export them as a dmabuf file descriptor.
> +Using dmabuf file descriptor allow to share this memory between processes
> +and/or import it into other frameworks like v4l2 or drm/kms (prime).
> +When userland wants to free the memory only a call to close() in needed
> +so it could done even without knowing that buffer has been allocated by
> +simple allocator ioctl.
> +
> +Each memory regions will be seen as a filein /dev/.
> +For example CMA regions will exposed has /dev/cmaX.
Why do you need multiple devices ? Furthermore, given how central this API
will become, I believe it needs very strict review, and would be a candidate
for a syscall.
Without diving into details yet, there are a few particular points I'm
concerned about.
- What is the scope of this API ? What problems do you want to solve, plan to
solve in the future, and consider as out of scope ?
- How should we handle permissions and resource limits ? Is file-based
permission on a device node a good model ? How do we prevent or at least
mitigate memory-related DoS ?
- How should such a central allocator API interact with containers and
virtualization in general ?
- What model do we want to expose to applications to select a memory type ?
You still haven't convinced me that we should expose memory pools explicitly
to application (à la ION), and I believe a usage/constraint model would be
better.
> +Implementing a simple allocator
> +-------------------------------
> +
> +Simple Allocator provide helpers functions to register/unregister an
> +allocator:
> +- simple_allocator_register(struct sa_device *sadev)
> + Register simple_allocator_device using sa_device structure where name,
> + owner and allocate fields must be set.
> +
> +- simple_allocator_unregister(struct sa_device *sadev)
> + Unregister a simple allocator device.
> +
> +Using Simple Allocator /dev interface example
> +---------------------------------------------
> +
> +This example of code allocate a buffer on the first CMA region (/dev/cma0)
> +before mmap and close it.
> +
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <sys/ioctl.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +
> +#include "simple-allocator.h"
> +
> +#define LENGTH 1024*16
> +
> +void main (void)
> +{
> + struct simple_allocate_data data;
> + int fd = open("/dev/cma0", O_RDWR, 0);
> + int ret;
> + void *mem;
> +
> + if (fd < 0) {
> + printf("Can't open /dev/cma0\n");
> + return;
> + }
> +
> + memset(&data, 0, sizeof(data));
> +
> + data.length = LENGTH;
> + data.flags = O_RDWR | O_CLOEXEC;
> +
> + ret = ioctl(fd, SA_IOC_ALLOC, &data);
> + if (ret) {
> + printf("Buffer allocation failed\n");
> + goto end;
> + }
> +
> + mem = mmap(0, LENGTH, PROT_READ | PROT_WRITE, MAP_SHARED, data.fd, 0);
> + if (mem == MAP_FAILED) {
> + printf("mmap failed\n");
> + }
> +
> + memset(mem, 0xFF, LENGTH);
> + munmap(mem, LENGTH);
> +
> + printf("test simple allocator CMA OK\n");
> +end:
> + close(fd);
> +}
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index e1e2066..a6d8828 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -202,4 +202,6 @@ source "drivers/hwtracing/intel_th/Kconfig"
>
> source "drivers/fpga/Kconfig"
>
> +source "drivers/simpleallocator/Kconfig"
> +
> endmenu
> diff --git a/drivers/Makefile b/drivers/Makefile
> index 060026a..5081eb8 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -173,3 +173,4 @@ obj-$(CONFIG_STM) += hwtracing/stm/
> obj-$(CONFIG_ANDROID) += android/
> obj-$(CONFIG_NVMEM) += nvmem/
> obj-$(CONFIG_FPGA) += fpga/
> +obj-$(CONFIG_SIMPLE_ALLOCATOR) += simpleallocator/
> diff --git a/drivers/simpleallocator/Kconfig
> b/drivers/simpleallocator/Kconfig new file mode 100644
> index 0000000..c6fc2e3
> --- /dev/null
> +++ b/drivers/simpleallocator/Kconfig
> @@ -0,0 +1,10 @@
> +menu "Simple Allocator"
> +
> +config SIMPLE_ALLOCATOR
> + tristate "Simple Alllocator Framework"
> + select DMA_SHARED_BUFFER
> + ---help---
> + The Simple Allocator Framework adds an API to allocate and share
> + memory in userland.
> +
> +endmenu
> diff --git a/drivers/simpleallocator/Makefile
> b/drivers/simpleallocator/Makefile new file mode 100644
> index 0000000..e27c6ad
> --- /dev/null
> +++ b/drivers/simpleallocator/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_SIMPLE_ALLOCATOR) += simple-allocator.o
> diff --git a/drivers/simpleallocator/simple-allocator-priv.h
> b/drivers/simpleallocator/simple-allocator-priv.h new file mode 100644
> index 0000000..33f5a33
> --- /dev/null
> +++ b/drivers/simpleallocator/simple-allocator-priv.h
> @@ -0,0 +1,33 @@
> +/*
> + * Copyright (C) Linaro 2016
> + *
> + * Author: Benjamin Gaignard <benjamin.gaignard at linaro.org>
> + *
> + * License terms: GNU General Public License (GPL)
> + */
> +
> +#ifndef _SIMPLE_ALLOCATOR_PRIV_H_
> +#define _SIMPLE_ALLOCATOR_PRIV_H_
> +
> +#include <linux/cdev.h>
> +#include <linux/device.h>
> +#include <linux/dma-buf.h>
> +
> +/**
> + * struct sa_device - simple allocator device
> + * @owner: module owner, must be set to THIS_MODULE
> + * @name: name of the allocator
> + * @allocate: callabck for memory allocation
> + */
> +struct sa_device {
> + struct device dev;
> + struct cdev chrdev;
> + struct module *owner;
> + const char *name;
> + struct dma_buf *(*allocate)(struct sa_device *, u64 length, u32
flags);
> +};
> +
> +int simple_allocator_register(struct sa_device *sadev);
> +void simple_allocator_unregister(struct sa_device *sadev);
> +
> +#endif
> diff --git a/drivers/simpleallocator/simple-allocator.c
> b/drivers/simpleallocator/simple-allocator.c new file mode 100644
> index 0000000..d89ccbf
> --- /dev/null
> +++ b/drivers/simpleallocator/simple-allocator.c
> @@ -0,0 +1,180 @@
> +/*
> + * Copyright (C) Linaro 2016
> + *
> + * Author: Benjamin Gaignard <benjamin.gaignard at linaro.org>
> + *
> + * License terms: GNU General Public License (GPL)
> + */
> +
> +#include <linux/module.h>
> +#include <linux/simple-allocator.h>
> +#include <linux/uaccess.h>
> +
> +#include "simple-allocator-priv.h"
> +
> +#define SA_MAJOR 222
> +#define SA_NUM_DEVICES 256
> +#define SA_NAME "simple_allocator"
> +
> +static int sa_minor;
> +
> +static struct class sa_class = {
> + .name = SA_NAME,
> +};
> +
> +static long sa_ioctl(struct file *filp, unsigned int cmd, unsigned long
> arg) +{
> + struct sa_device *sadev = filp->private_data;
> + int ret = -ENODEV;
> +
> + switch (cmd) {
> + case SA_IOC_ALLOC:
> + {
> + struct simple_allocate_data data;
> + struct dma_buf *dmabuf;
> +
> + if (copy_from_user(&data, (void __user *)arg, _IOC_SIZE(cmd)))
> + return -EFAULT;
> +
> + if (data.version != 0)
> + return -EINVAL;
> +
> + dmabuf = sadev->allocate(sadev, data.length, data.flags);
> + if (!dmabuf)
> + return -EINVAL;
> +
> + data.fd = dma_buf_fd(dmabuf, data.flags);
> + if (data.fd < 0) {
> + dma_buf_put(dmabuf);
> + return -EINVAL;
> + }
> +
> + data.length = dmabuf->size;
> +
> + if (copy_to_user((void __user *)arg, &data, _IOC_SIZE(cmd))) {
> + dma_buf_put(dmabuf);
> + return -EFAULT;
> + }
> +
> + return 0;
> + }
> + }
> + return ret;
> +}
> +
> +static int sa_open(struct inode *inode, struct file *filp)
> +{
> + struct sa_device *sadev = container_of(inode->i_cdev,
> + struct sa_device, chrdev);
> +
> + if (!sadev)
> + return -ENODEV;
> +
> + get_device(&sadev->dev);
> + filp->private_data = sadev;
> + return 0;
> +}
> +
> +static int sa_release(struct inode *inode, struct file *filp)
> +{
> + struct sa_device *sadev = container_of(inode->i_cdev,
> + struct sa_device, chrdev);
> +
> + if (!sadev)
> + return -ENODEV;
> +
> + put_device(&sadev->dev);
> + return 0;
> +}
> +
> +static const struct file_operations sa_fops = {
> + .owner = THIS_MODULE,
> + .open = sa_open,
> + .release = sa_release,
> + .unlocked_ioctl = sa_ioctl,
> +};
> +
> +/**
> + * simple_allocator_register - register a simple allocator
> + * @sadev: simple allocator structure to be registered
> + *
> + * Return 0 if allocator has been regsitered, either a negative value.
> + */
> +int simple_allocator_register(struct sa_device *sadev)
> +{
> + int ret;
> +
> + if (!sadev->name || !sadev->allocate)
> + return -EINVAL;
> +
> + cdev_init(&sadev->chrdev, &sa_fops);
> + sadev->chrdev.owner = sadev->owner;
> +
> + ret = cdev_add(&sadev->chrdev, MKDEV(SA_MAJOR, sa_minor), 1);
> + if (ret < 0)
> + return ret;
> +
> + sadev->dev.class = &sa_class;
> + sadev->dev.devt = MKDEV(SA_MAJOR, sa_minor);
> + dev_set_name(&sadev->dev, "%s%d", sadev->name, sa_minor);
> + ret = device_register(&sadev->dev);
> + if (ret < 0)
> + goto cleanup;
> +
> + sa_minor++;
> + return 0;
> +
> +cleanup:
> + cdev_del(&sadev->chrdev);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(simple_allocator_register);
> +
> +/**
> + * simple_allocator_unregister - unregister a simple allocator
> + * @sadev: simple allocator device to be unregistered
> + */
> +void simple_allocator_unregister(struct sa_device *sadev)
> +{
> + if (!sadev)
> + return;
> +
> + cdev_del(&sadev->chrdev);
> + device_del(&sadev->dev);
> + put_device(&sadev->dev);
> +}
> +EXPORT_SYMBOL_GPL(simple_allocator_unregister);
> +
> +static int __init sa_init(void)
> +{
> + dev_t dev = MKDEV(SA_MAJOR, 0);
> + int ret;
> +
> + ret = register_chrdev_region(dev, SA_NUM_DEVICES, SA_NAME);
> + if (ret < 0)
> + return ret;
> +
> + ret = class_register(&sa_class);
> + if (ret < 0) {
> + unregister_chrdev_region(dev, SA_NUM_DEVICES);
> + return -EIO;
> + }
> +
> + return 0;
> +}
> +
> +static void __exit sa_exit(void)
> +{
> + dev_t dev = MKDEV(SA_MAJOR, 0);
> +
> + class_unregister(&sa_class);
> + unregister_chrdev_region(dev, SA_NUM_DEVICES);
> +}
> +
> +subsys_initcall(sa_init);
> +module_exit(sa_exit);
> +
> +MODULE_AUTHOR("Benjamin Gaignard <benjamin.gaignard at linaro.org>");
> +MODULE_DESCRIPTION("Simple allocator");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS_CHARDEV_MAJOR(SA_MAJOR);
> diff --git a/include/uapi/linux/simple-allocator.h
> b/include/uapi/linux/simple-allocator.h new file mode 100644
> index 0000000..5520a85
> --- /dev/null
> +++ b/include/uapi/linux/simple-allocator.h
> @@ -0,0 +1,35 @@
> +/*
> + * Copyright (C) Linaro 2016
> + *
> + * Author: Benjamin Gaignard <benjamin.gaignard at linaro.org>
> + *
> + * License terms: GNU General Public License (GPL), version 2
> + */
> +
> +#ifndef _SIMPLE_ALLOCATOR_H_
> +#define _SIMPLE_ALLOCATOR_H_
> +
> +#include <linux/ioctl.h>
> +#include <linux/types.h>
> +
> +/**
> + * struct simple_allocate_data - allocation parameters
> + * @version: structure version (must be set to 0)
> + * @length: size of the requested buffer
> + * @flags: mode flags for the file like O_RDWR or O_CLOEXEC
> + * @fd: returned file descriptor
> + */
> +struct simple_allocate_data {
> + __u64 version;
> + __u64 length;
> + __u32 flags;
> + __u32 reserved1;
> + __s32 fd;
> + __u32 reserved2;
> +};
> +
> +#define SA_IOC_MAGIC 'S'
> +
> +#define SA_IOC_ALLOC _IOWR(SA_IOC_MAGIC, 0, struct simple_allocate_data)
> +
> +#endif
--
Regards,
Laurent Pinchart
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