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Commit 255364f7 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman
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staging: comedi: support vm_access_process for mmap'd buffer 



If a process that has mmap'd a COMEDI buffer is being run under a
debugger such as GDB, the buffer contents are inaccessible from the
debugger.  Support the `access()` VM operation to allow the buffer
contents to be accessed by another process.

Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e44adf05

drivers/staging/comedi/comedi_buf.c

+24 −0
Original line number Diff line number Diff line
@@ -161,6 +161,30 @@ int comedi_buf_map_put(struct comedi_buf_map *bm) 
	return 1;

}



/* helper for "access" vm operation */

int comedi_buf_map_access(struct comedi_buf_map *bm, unsigned long offset,

			  void *buf, int len, int write)

{

	unsigned int pgoff = offset & ~PAGE_MASK;

	unsigned long pg = offset >> PAGE_SHIFT;

	int done = 0;



	while (done < len && pg < bm->n_pages) {

		int l = min_t(int, len - done, PAGE_SIZE - pgoff);

		void *b = bm->page_list[pg].virt_addr + pgoff;



		if (write)

			memcpy(b, buf, l);

		else

			memcpy(buf, b, l);

		buf += l;

		done += l;

		pg++;

		pgoff = 0;

	}

	return done;

}



/* returns s->async->buf_map and increments its kref refcount */

struct comedi_buf_map *

comedi_buf_map_from_subdev_get(struct comedi_subdevice *s)

drivers/staging/comedi/comedi_fops.c

+15 −0
Original line number Diff line number Diff line
@@ -2165,9 +2165,24 @@ static void comedi_vm_close(struct vm_area_struct *area) 
	comedi_buf_map_put(bm);

}



static int comedi_vm_access(struct vm_area_struct *vma, unsigned long addr,

			    void *buf, int len, int write)

{

	struct comedi_buf_map *bm = vma->vm_private_data;

	unsigned long offset =

	    addr - vma->vm_start + (vma->vm_pgoff << PAGE_SHIFT);



	if (len < 0)

		return -EINVAL;

	if (len > vma->vm_end - addr)

		len = vma->vm_end - addr;

	return comedi_buf_map_access(bm, offset, buf, len, write);

}



static const struct vm_operations_struct comedi_vm_ops = {

	.open = comedi_vm_open,

	.close = comedi_vm_close,

	.access = comedi_vm_access,

};



static int comedi_mmap(struct file *file, struct vm_area_struct *vma)

drivers/staging/comedi/comedi_internal.h

+2 −0
Original line number Diff line number Diff line
@@ -29,6 +29,8 @@ void comedi_buf_reset(struct comedi_subdevice *s); 
bool comedi_buf_is_mmapped(struct comedi_subdevice *s);

void comedi_buf_map_get(struct comedi_buf_map *bm);

int comedi_buf_map_put(struct comedi_buf_map *bm);

int comedi_buf_map_access(struct comedi_buf_map *bm, unsigned long offset,

			  void *buf, int len, int write);

struct comedi_buf_map *comedi_buf_map_from_subdev_get(

		struct comedi_subdevice *s);

unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s);