On 11/28/2025 9:02 PM, Greg KH wrote:
> On Fri, Nov 28, 2025 at 04:04:28PM +0530, Ekansh Gupta wrote:
>> Currently, FastRPC only supports mapping buffers allocated by the
>> kernel. This limits flexibility for applications that allocate memory
>> in userspace using rpcmem or DMABUF and need to share it with the DSP.
>> Add support for mapping and unmapping userspace-allocated buffers to
>> the DSP through SMMU. This includes handling map requests for rpcmem
>> and DMABUF-backed memory and providing corresponding unmap
>> functionality.
>>
>> Signed-off-by: Ekansh Gupta <[email protected]>
>> ---
>> drivers/misc/fastrpc.c | 96 +++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 85 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> index 9bf76e224852..feba79913763 100644
>> --- a/drivers/misc/fastrpc.c
>> +++ b/drivers/misc/fastrpc.c
>> @@ -1854,8 +1854,10 @@ static int fastrpc_req_munmap_impl(struct
>> fastrpc_user *fl, struct fastrpc_buf *
>> static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
>> {
>> struct fastrpc_buf *buf = NULL, *iter, *b;
>> + struct fastrpc_map *map = NULL, *iterm, *m;
>> struct fastrpc_req_munmap req;
>> struct device *dev = fl->sctx->dev;
>> + int err;
>>
>> if (copy_from_user(&req, argp, sizeof(req)))
>> return -EFAULT;
>> @@ -1869,13 +1871,41 @@ static int fastrpc_req_munmap(struct fastrpc_user
>> *fl, char __user *argp)
>> }
>> spin_unlock(&fl->lock);
>>
>> - if (!buf) {
>> - dev_err(dev, "mmap\t\tpt 0x%09llx [len 0x%08llx] not in list\n",
>> + if (buf) {
>> + err = fastrpc_req_munmap_impl(fl, buf);
>> + if (err) {
>> + spin_lock(&fl->lock);
>> + list_add_tail(&buf->node, &fl->mmaps);
>> + spin_unlock(&fl->lock);
>> + }
>> + return err;
>> + }
>> +
>> + spin_lock(&fl->lock);
>> + list_for_each_entry_safe(iterm, m, &fl->maps, node) {
>> + if (iterm->raddr == req.vaddrout) {
>> + map = iterm;
>> + list_del(&iterm->node);
>> + break;
>> + }
>> + }
>> + spin_unlock(&fl->lock);
>> + if (!map) {
>> + dev_dbg(dev, "buffer/map not found addr 0x%09llx, len
>> 0x%08llx\n",
>> req.vaddrout, req.size);
> Never print out kernel pointers "raw" like this, use the real %p tags
> instead. Odd that the current code does this, that is not good and is
> probably a "information leak" somehow.
>
> Can you fix that up first so it can be backported properly?
Thanks for pointing this out, I'll fix this before refactoring.
>
>> return -EINVAL;
>> }
>>
>> - return fastrpc_req_munmap_impl(fl, buf);
>> + err = fastrpc_req_munmap_dsp(fl, map->raddr, map->size);
>> + if (err) {
>> + dev_dbg(dev, "unmmap\tpt fd = %d, 0x%09llx error\n", map->fd,
>> map->raddr);
> Same here. Also, no need for a \t in a kernel log message.
Ack.
>
>> + spin_lock(&fl->lock);
>> + list_add_tail(&map->node, &fl->maps);
>> + spin_unlock(&fl->lock);
>> + } else {
>> + fastrpc_map_put(map);
>> + }
>> + return err;
>> }
>>
>> static int fastrpc_req_map_dsp(struct fastrpc_user *fl, u64 phys,
>> @@ -1989,25 +2019,69 @@ static int fastrpc_req_buf_alloc(struct fastrpc_user
>> *fl,
>> return err;
>> }
>>
>> -static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
>> +static int fastrpc_req_map_create(struct fastrpc_user *fl,
>> + struct fastrpc_req_mmap req,
>> + char __user *argp)
>> {
>> - struct fastrpc_req_mmap req;
>> + struct fastrpc_map *map = NULL;
>> + struct device *dev = fl->sctx->dev;
>> + u64 raddr = 0;
>> int err;
>>
>> - if (copy_from_user(&req, argp, sizeof(req)))
>> - return -EFAULT;
>> + err = fastrpc_map_create(fl, req.fd, req.size, 0, &map);
>> + if (err) {
>> + dev_err(dev, "failed to map buffer, fd = %d\n", req.fd);
>> + return err;
>> + }
>>
>> - if (req.flags != ADSP_MMAP_ADD_PAGES && req.flags !=
>> ADSP_MMAP_REMOTE_HEAP_ADDR) {
>> - dev_err(fl->sctx->dev, "flag not supported 0x%x\n", req.flags);
>> + err = fastrpc_req_map_dsp(fl, map->phys, map->size, req.flags,
>> + req.vaddrin, &raddr);
>> + if (err)
>> + goto err_invoke;
>>
>> - return -EINVAL;
>> + /* update the buffer to be able to deallocate the memory on the DSP */
>> + map->raddr = (u64)raddr;
>> +
>> + /* let the client know the address to use */
>> + req.vaddrout = raddr;
>> + dev_dbg(dev, "mmap\t\tpt 0x%09llx OK [len 0x%08llx]\n",
>> + map->raddr, map->size);
>> +
>> + if (copy_to_user((void __user *)argp, &req, sizeof(req))) {
> argp is already a user pointer, no need to cast it again, right?
yes, right.
>
>> + err = -EFAULT;
>> + goto err_copy;
>> }
>>
>> - err = fastrpc_req_buf_alloc(fl, req, argp);
>> + return 0;
>> +err_copy:
>> + fastrpc_req_munmap_dsp(fl, map->raddr, map->size);
>> +err_invoke:
>> + fastrpc_map_put(map);
>>
>> return err;
>> }
>>
>> +static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
>> +{
>> + struct fastrpc_req_mmap req;
>> + int err;
>> +
>> + if (copy_from_user(&req, argp, sizeof(req)))
>> + return -EFAULT;
>> +
>> + if ((req.flags == ADSP_MMAP_ADD_PAGES ||
>> + req.flags == ADSP_MMAP_REMOTE_HEAP_ADDR)) {
>> + err = fastrpc_req_buf_alloc(fl, req, argp);
>> + if (err)
>> + return err;
>> + } else {
>> + err = fastrpc_req_map_create(fl, req, argp);
> You changed the logic here from what used to happen if req.flags was not
> set to those two values. Are you _sure_ you mean to do that? If so,
> how does userspace know? Why don't you have a new flag for the new
> type of memory you want to map?
The userspace follows the same logic for all the flags other than the defined
flags
where a buffer is allocated using DMA-BUF and then mapped onto DSP using this
IOCTL call.
Do you see any concerns with this?
Thanks,
Ekansh
>
> thanks,
>
> greg k-h
