RE: [PATCH v10 1/1] efi: a misc char interface for user to update efi firmware

[Kweh, Hock Leong]

> -----Original Message-----
> From: Matt Fleming [mailto:matt@xxxxxxxxxxxxxxxxx]
> Sent: Thursday, January 21, 2016 7:52 PM
> 
> On Fri, 18 Dec, at 08:13:01PM, Kweh Hock Leong wrote:
> > From: "Kweh, Hock Leong" <hock.leong.kweh@xxxxxxxxx>
> >
> > Introducing a kernel module to expose capsule loader interface
> > (misc char device file note) for user to upload capsule binaries.
> >
> > Example method to load the capsule binary:
> > cat firmware.bin > /dev/efi_capsule_loader
> >
> > This patch also export efi_capsule_supported() function symbol for
> > verifying the submitted capsule header in this kernel module.
> >
> > Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@xxxxxxxxx>
> > ---
> >  drivers/firmware/efi/Kconfig          |   10
> >  drivers/firmware/efi/Makefile         |    1
> >  drivers/firmware/efi/capsule-loader.c |  355
> +++++++++++++++++++++++++++++++++
> >  drivers/firmware/efi/capsule.c        |    1
> >  4 files changed, 367 insertions(+)
> >  create mode 100644 drivers/firmware/efi/capsule-loader.c
> 
> [...]
> 
> > +#define pr_fmt(fmt) "EFI: " fmt
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/miscdevice.h>
> > +#include <linux/highmem.h>
> > +#include <linux/slab.h>
> > +#include <linux/mutex.h>
> > +#include <linux/efi.h>
> > +
> > +#define NO_FURTHER_WRITE_ACTION -1
> > +
> > +struct capsule_info {
> > +	bool		header_obtained;
> > +	int		reset_type;
> > +	long		index;
> > +	size_t		count;
> > +	size_t		total_size;
> > +	struct page	**pages;
> > +	size_t		page_bytes_remain;
> > +};
> > +
> > +static DEFINE_MUTEX(capsule_loader_lock);
> 
> This mutex is not needed. It doesn't protect anything in your code.

This is to synchronize/serializes one of the instant is calling efi_capsule_supported()
and the other one is calling efi_capsule_update() which they are exported symbol
from capsule.c.

> 
> > +/**
> > + * efi_free_all_buff_pages - free all previous allocated buffer pages
> > + * @cap_info: pointer to current instance of capsule_info structure
> > + *
> > + *	Besides freeing the buffer pages, it also flagged an
> > + *	NO_FURTHER_WRITE_ACTION flag for indicating to the next write
> entries
> > + *	that there is a flaw happened and any subsequence actions are not
> > + *	valid unless close(2).
> > + **/
> > +static void efi_free_all_buff_pages(struct capsule_info *cap_info)
> > +{
> > +	while (cap_info->index > 0)
> > +		__free_page(cap_info->pages[--cap_info->index]);
> > +
> > +	kfree(cap_info->pages);
> > +
> > +	cap_info->index = NO_FURTHER_WRITE_ACTION;
> > +}
> > +
> > +/**
> > + * efi_capsule_setup_info - to obtain the efi capsule header in the binary
> and
> > + *			    setup capsule_info structure
> > + * @cap_info: pointer to current instance of capsule_info structure
> > + * @kbuff: a mapped 1st page buffer pointer
> > + * @hdr_bytes: the total bytes of received efi header
> > + **/
> > +static ssize_t efi_capsule_setup_info(struct capsule_info *cap_info,
> > +				      void *kbuff, size_t hdr_bytes)
> > +{
> > +	int ret;
> > +	void *temp_page;
> > +
> > +	/* Handling 1st block is less than header size */
> > +	if (hdr_bytes < sizeof(efi_capsule_header_t)) {
> > +		if (!cap_info->pages) {
> > +			cap_info->pages = kzalloc(sizeof(void *),
> GFP_KERNEL);
> > +			if (!cap_info->pages) {
> > +				pr_debug("%s: kzalloc() failed\n", __func__);
> > +				return -ENOMEM;
> > +			}
> > +		}
> 
> This function would be much more simple if you handled the above
> condition differently.
> 
> Instead of having code in efi_capsule_setup_info() to allocate the
> initial ->pages memory, why not just allocate it in efi_capsule_open()
> at the same time as you allocate the private_data? You can then
> free it in efi_capsule_release() (you're leaking it at the moment).
> 
> You are always going to need at least one element in ->pages for
> successful operation, so you might as well allocate it up front.

Just want to double check I understand you correctly. Do you mean
I should free ->pages during close(2) but not free the ->pages[X] if
there is any successfully submitted?

> 
> > +	} else {
> > +		/* Reset back to the correct offset of header */
> > +		efi_capsule_header_t *cap_hdr = kbuff - cap_info->count;
> > +		size_t pages_needed = ALIGN(cap_hdr->imagesize,
> PAGE_SIZE) >>
> > +					    PAGE_SHIFT;
> > +
> > +		if (pages_needed == 0) {
> > +			pr_err("%s: pages count invalid\n", __func__);
> > +			return -EINVAL;
> > +		}
> > +
> > +		/* Check if the capsule binary supported */
> > +		mutex_lock(&capsule_loader_lock);
> > +		ret = efi_capsule_supported(cap_hdr->guid, cap_hdr->flags,
> > +					    cap_hdr->imagesize,
> > +					    &cap_info->reset_type);
> > +		mutex_unlock(&capsule_loader_lock);
> > +		if (ret) {
> > +			pr_err("%s: efi_capsule_supported() failed\n",
> > +			       __func__);
> > +			return ret;
> > +		}
> > +
> > +		cap_info->total_size = cap_hdr->imagesize;
> > +		temp_page = krealloc(cap_info->pages,
> > +				     pages_needed * sizeof(void *),
> > +				     GFP_KERNEL | __GFP_ZERO);
> > +		if (!temp_page) {
> > +			pr_debug("%s: krealloc() failed\n", __func__);
> > +			return -ENOMEM;
> > +		}
> > +
> > +		cap_info->pages = temp_page;
> > +		cap_info->header_obtained = 1;
> 
> This should be 'true', not 1.

Noted.

> 
> > +	}
> > +
> > +	return 0;
> > +}
> >
> > +
> > +/**
> > + * efi_capsule_submit_update - invoke the efi_capsule_update API once
> binary
> > + *			       upload done
> > + * @cap_info: pointer to current instance of capsule_info structure
> > + **/
> > +static ssize_t efi_capsule_submit_update(struct capsule_info *cap_info)
> > +{
> > +	int ret;
> > +	void *cap_hdr_temp;
> > +
> > +	cap_hdr_temp = kmap(cap_info->pages[0]);
> > +	if (!cap_hdr_temp) {
> > +		pr_debug("%s: kmap() failed\n", __func__);
> > +		return -EFAULT;
> > +	}
> > +
> > +	mutex_lock(&capsule_loader_lock);
> > +	ret = efi_capsule_update(cap_hdr_temp, cap_info->pages);
> > +	mutex_unlock(&capsule_loader_lock);
> > +	kunmap(cap_info->pages[0]);
> > +	if (ret) {
> > +		pr_err("%s: efi_capsule_update() failed\n", __func__);
> > +		return ret;
> > +	}
> > +
> > +	/* Indicate capsule binary uploading is done */
> > +	cap_info->index = NO_FURTHER_WRITE_ACTION;
> > +	pr_info("%s: Successfully upload capsule file with reboot type '%s'\n",
> > +		__func__, !cap_info->reset_type ? "RESET_COLD" :
> > +		cap_info->reset_type == 1 ? "RESET_WARM" :
> > +		"RESET_SHUTDOWN");
> > +	return 0;
> > +}
> > +
> > +/**
> > + * efi_capsule_write - store the capsule binary and pass it to
> > + *		       efi_capsule_update() API
> > + * @file: file pointer
> > + * @buff: buffer pointer
> > + * @count: number of bytes in @buff
> > + * @offp: not used
> > + *
> > + *	Expectation:
> > + *	- User space tool should start at the beginning of capsule binary and
> > + *	  pass data in sequential.
> > + *	- User should close and re-open this file note in order to upload more
> > + *	  capsules.
> > + *	- Any error occurred, user should close the file and restart the
> > + *	  operation for the next try otherwise -EIO will be returned until the
> > + *	  file is closed.
> > + *	- EFI capsule header must be located at the beginning of capsule
> binary
> > + *	  file and passed in as 1st block write.
> > + **/
> > +static ssize_t efi_capsule_write(struct file *file, const char __user *buff,
> > +				 size_t count, loff_t *offp)
> > +{
> > +	int ret = 0;
> > +	struct capsule_info *cap_info = file->private_data;
> > +	struct page *kbuff_page = NULL;
> > +	void *kbuff = NULL;
> > +	size_t write_byte;
> > +
> > +	if (count == 0)
> > +		return 0;
> > +
> > +	/* Return error while NO_FURTHER_WRITE_ACTION is flagged */
> > +	if (cap_info->index < 0)
> > +		return -EIO;
> > +
> > +	/* Only alloc a new page when previous page is full */
> > +	if (!cap_info->page_bytes_remain) {
> > +		kbuff_page = alloc_page(GFP_KERNEL);
> > +		if (!kbuff_page) {
> > +			pr_debug("%s: alloc_page() failed\n", __func__);
> > +			ret = -ENOMEM;
> > +			goto failed;
> > +		}
> > +		cap_info->page_bytes_remain = PAGE_SIZE;
> > +	} else {
> > +		kbuff_page = cap_info->pages[--cap_info->index];
> > +	}
> 
> This shuffling and unshuffling of cap_info->index seems kinda crazy to
> me because you're treating the current page differently from the rest,
> which complicates the error paths too (you shouldn't need
> __free_page() *and* efi_free_all_buff_pages()).
> 
> Why not make cap_info->index always index the last page? That way you
> could do,
> 
> 	if (!cap_info->page_bytes_remain) {
> 		cap_info->pages[++cap_info->index] = alloc_page()
> 		cap_info->page_bytes_remain = PAGE_SIZE;
> 	}
> 
> 	kbuff_page = cap_info->pages[cap_info->index];
> 
> ?

Noted.

> 
> > +
> > +	kbuff = kmap(kbuff_page);
> > +	if (!kbuff) {
> > +		pr_debug("%s: kmap() failed\n", __func__);
> > +		ret = -EFAULT;
> > +		goto fail_freepage;
> > +	}
> > +	kbuff += PAGE_SIZE - cap_info->page_bytes_remain;
> > +
> > +	/* Copy capsule binary data from user space to kernel space buffer
> */
> > +	write_byte = min_t(size_t, count, cap_info->page_bytes_remain);
> > +	if (copy_from_user(kbuff, buff, write_byte)) {
> > +		pr_debug("%s: copy_from_user() failed\n", __func__);
> > +		ret = -EFAULT;
> > +		goto fail_unmap;
> > +	}
> > +	cap_info->page_bytes_remain -= write_byte;
> > +
> > +	/* Setup capsule binary info structure */
> > +	if (!cap_info->header_obtained) {
> > +		ret = efi_capsule_setup_info(cap_info, kbuff,
> > +					     cap_info->count + write_byte);
> > +		if (ret)
> > +			goto fail_unmap;
> > +	}
> > +
> > +	cap_info->pages[cap_info->index++] = kbuff_page;
> > +	cap_info->count += write_byte;
> > +	kunmap(kbuff_page);
> > +
> > +	/* Submit the full binary to efi_capsule_update() API */
> > +	if (cap_info->header_obtained &&
> > +	    cap_info->count >= cap_info->total_size) {
> > +		if (cap_info->count > cap_info->total_size) {
> > +			pr_err("%s: upload size exceeded header defined
> size\n",
> > +			       __func__);
> > +			ret = -EINVAL;
> > +			goto failed;
> > +		}
> > +
> > +		ret = efi_capsule_submit_update(cap_info);
> > +		if (ret)
> > +			goto failed;
> > +	}
> > +
> > +	return write_byte;
> > +
> > +fail_unmap:
> > +	kunmap(kbuff_page);
> > +fail_freepage:
> > +	__free_page(kbuff_page);
> > +failed:
> > +	efi_free_all_buff_pages(cap_info);
> > +	return ret;
> > +}
> > +
> > +/**
> > + * efi_capsule_flush - called by file close or file flush
> > + * @file: file pointer
> > + * @id: not used
> > + *
> > + *	If capsule being uploaded partially, calling this function will be
> > + *	treated as uploading canceled and will free up those completed
> buffer
> > + *	pages and then return -ECANCELED.
> > + **/
> > +static int efi_capsule_flush(struct file *file, fl_owner_t id)
> > +{
> > +	int ret = 0;
> > +	struct capsule_info *cap_info = file->private_data;
> > +
> > +	if (cap_info->index > 0) {
> > +		pr_err("%s: capsule upload not complete\n", __func__);
> > +		efi_free_all_buff_pages(cap_info);
> > +		ret = -ECANCELED;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +/**
> > + * efi_capsule_release - called by file close
> > + * @inode: not used
> > + * @file: file pointer
> > + *
> > + *	We would not free the successful submitted buffer pages here due
> to
> > + *	efi update require system reboot with data maintained.
> > + **/
> > +static int efi_capsule_release(struct inode *inode, struct file *file)
> > +{
> > +	kfree(file->private_data);
> > +	file->private_data = NULL;
> > +	return 0;
> > +}
> > +
> > +/**
> > + * efi_capsule_open - called by file open
> > + * @inode: not used
> > + * @file: file pointer
> > + *
> > + *	Will allocate each capsule_info memory for each file open call.
> > + *	This provided the capability to support multiple file open feature
> > + *	where user is not needed to wait for others to finish in order to
> > + *	upload their capsule binary.
> > + **/
> > +static int efi_capsule_open(struct inode *inode, struct file *file)
> > +{
> > +	struct capsule_info *cap_info;
> > +
> > +	cap_info = kzalloc(sizeof(*cap_info), GFP_KERNEL);
> > +	if (!cap_info)
> > +		return -ENOMEM;
> > +
> > +	file->private_data = cap_info;
> > +
> 
> Please allocate one ->pages element here (void *). You need at least
> one for this code to work and you can easily free it in
> efi_capsule_release() if it still exists. It would also simplfy
> efi_capsule_setup_info() immensely.

Note.

Thanks & Regards,
Wilson