On 10/6/26 21:36, Matt Evans wrote: > Allow exporters to set the name of buffers, during export or for > subsequent updates. This is useful to express buffer-specific debug > information, indicate state particular to the exporter's usage, etc. > Only exporters and userspace are expected to set names; it isn't > sensible for importers to do it. > > Originally, the static dma_buf_set_name() was used for > DMA_BUF_SET_NAME ioctls, taking a __user string parameter. Export > this function as a generic set-name helper, taking a kernel-allocated > string. The SET_NAME ioctls now locally duplicate the __user string, > and use the new function to set the name. > > Signed-off-by: Matt Evans <[email protected]>
Reviewed-by: Christian König <[email protected]> > --- > drivers/dma-buf/dma-buf.c | 84 +++++++++++++++++++++++++-------------- > include/linux/dma-buf.h | 16 +++++--- > 2 files changed, 64 insertions(+), 36 deletions(-) > > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index 4c9add51f9ef..b99da4ff2ef6 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c > @@ -404,34 +404,6 @@ static __poll_t dma_buf_poll(struct file *file, > poll_table *poll) > return events; > } > > -/** > - * dma_buf_set_name - Set a name to a specific dma_buf to track the usage. > - * It could support changing the name of the dma-buf if the same > - * piece of memory is used for multiple purpose between different devices. > - * > - * @dmabuf: [in] dmabuf buffer that will be renamed. > - * @buf: [in] A piece of userspace memory that contains the name of > - * the dma-buf. > - * > - * Returns 0 on success. If the dma-buf buffer is already attached to > - * devices, return -EBUSY. > - * > - */ > -static long dma_buf_set_name(struct dma_buf *dmabuf, const char __user *buf) > -{ > - char *name = strndup_user(buf, DMA_BUF_NAME_LEN); > - > - if (IS_ERR(name)) > - return PTR_ERR(name); > - > - spin_lock(&dmabuf->name_lock); > - kfree(dmabuf->name); > - dmabuf->name = name; > - spin_unlock(&dmabuf->name_lock); > - > - return 0; > -} > - > #if IS_ENABLED(CONFIG_SYNC_FILE) > static long dma_buf_export_sync_file(struct dma_buf *dmabuf, > void __user *user_data) > @@ -577,8 +549,19 @@ static long dma_buf_ioctl(struct file *file, > return ret; > > case DMA_BUF_SET_NAME_A: > - case DMA_BUF_SET_NAME_B: > - return dma_buf_set_name(dmabuf, (const char __user *)arg); > + case DMA_BUF_SET_NAME_B: { > + char *name = strndup_user((const char __user *)arg, > + DMA_BUF_NAME_LEN); > + > + if (IS_ERR(name)) > + return PTR_ERR(name); > + > + ret = dma_buf_set_name(dmabuf, name); > + if (ret) > + kfree(name); > + > + return ret; > + } > > #if IS_ENABLED(CONFIG_SYNC_FILE) > case DMA_BUF_IOCTL_EXPORT_SYNC_FILE: > @@ -874,6 +857,42 @@ void dma_buf_put(struct dma_buf *dmabuf) > } > EXPORT_SYMBOL_NS_GPL(dma_buf_put, "DMA_BUF"); > > +/** > + * dma_buf_set_name - Set a dmabuf's name > + * @dmabuf: [in] dmabuf buffer that will be renamed. > + * @name: [in] The name of the dma-buf, allocated with kmalloc() or > + * similar. This takes ownership of the allocation > + * on success, which will be kfree()d when the > + * dmabuf is released or a new name assigned. > + * > + * Intended to be used by the exporter to set a name for debug > + * purposes. This can also change an existing name if the same piece > + * of memory is used for multiple purposes over time. Importers > + * should NOT use this function to overwrite the name. > + * > + * Return: 0 on success, -EINVAL if the name is NULL, or -E2BIG if the > + * name (including terminator) exceeds DMA_BUF_NAME_LEN. > + */ > +int dma_buf_set_name(struct dma_buf *dmabuf, char *name) > +{ > + if (!name) > + return -EINVAL; > + > + /* dmabuffs_dname() won't use the string if the length > + * (including terminator) exceeds DMA_BUF_NAME_LEN: > + */ > + if (strlen(name) >= DMA_BUF_NAME_LEN) > + return -E2BIG; > + > + spin_lock(&dmabuf->name_lock); > + kfree(dmabuf->name); > + dmabuf->name = name; > + spin_unlock(&dmabuf->name_lock); > + > + return 0; > +} > +EXPORT_SYMBOL_NS_GPL(dma_buf_set_name, "DMA_BUF"); > + > static int dma_buf_wrap_sg_table(struct sg_table **sg_table) > { > struct scatterlist *to_sg, *from_sg; > @@ -1004,6 +1023,11 @@ dma_buf_pin_on_map(struct dma_buf_attachment *attach) > * functions: > * > * - dma_buf_invalidate_mappings() > + * > + * 4. Exporters must not hold the dma-buf reservation lock when calling these > + * functions: > + * > + * - dma_buf_set_name() > */ > > /** > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > index d15b2b31d3c9..0f88132c0654 100644 > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h > @@ -342,12 +342,14 @@ struct dma_buf { > /** > * @name: > * > - * Userspace-provided name. Default value is NULL. If not NULL, > - * length cannot be longer than DMA_BUF_NAME_LEN, including NIL > - * char. Useful for accounting and debugging. Read/Write accesses > - * are protected by @name_lock > - * > - * See the IOCTLs DMA_BUF_SET_NAME or DMA_BUF_SET_NAME_A/B > + * Exporter or userspace-provided name. Default value is > + * NULL. If not NULL, length cannot be longer than > + * DMA_BUF_NAME_LEN, including NIL char. Useful for accounting > + * and debugging. Read/Write accesses are protected by > + * @name_lock > + * > + * See dma_buf_set_name(), and the IOCTLs DMA_BUF_SET_NAME or > + * DMA_BUF_SET_NAME_A/B > */ > const char *name; > > @@ -571,6 +573,8 @@ void dma_buf_fd_install(struct dma_buf *dmabuf, int fd); > struct dma_buf *dma_buf_get(int fd); > void dma_buf_put(struct dma_buf *dmabuf); > > +int dma_buf_set_name(struct dma_buf *dmabuf, char *name); > + > struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *, > enum dma_data_direction); > void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
