| Message ID | 20190719134303.7617-1-minwoo.im.dev@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | firmware: qcom_scm: fix error for incompatible pointer | expand |
Adding people who have worked on drivers/firmware/qcom_scm.c or DMA On 19/07/2019 15:43, Minwoo Im wrote: > The following error can happen when trying to build it: > > ``` > drivers/firmware/qcom_scm.c: In function ‘qcom_scm_assign_mem’: > drivers/firmware/qcom_scm.c:460:47: error: passing argument 3 of ‘dma_alloc_coherent’ from incompatible pointer type [-Werror=incompatible-pointer-types] > ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL); > ^ > In file included from drivers/firmware/qcom_scm.c:12:0: > ./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’ > static inline void *dma_alloc_coherent(struct device *dev, size_t size, > ^~~~~~~~~~~~~~~~~~ > ``` > > We just can cast phys_addr_t to dma_addr_t here. IME, casting is rarely a proper solution. > diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c > index 2ddc118dba1b..7f6c841fa200 100644 > --- a/drivers/firmware/qcom_scm.c > +++ b/drivers/firmware/qcom_scm.c > @@ -457,7 +457,8 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz, > ptr_sz = ALIGN(src_sz, SZ_64) + ALIGN(mem_to_map_sz, SZ_64) + > ALIGN(dest_sz, SZ_64); > > - ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL); > + ptr = dma_alloc_coherent(__scm->dev, ptr_sz, (dma_addr_t *) &ptr_phys, > + GFP_KERNEL); > if (!ptr) > return -ENOMEM; >
On Mon, Jul 22, 2019 at 10:38:55AM +0200, Marc Gonzalez wrote: > > In file included from drivers/firmware/qcom_scm.c:12:0: > > ./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’ > > static inline void *dma_alloc_coherent(struct device *dev, size_t size, > > ^~~~~~~~~~~~~~~~~~ > > ``` > > > > We just can cast phys_addr_t to dma_addr_t here. > > IME, casting is rarely a proper solution. *nod* ptr_phys probably should be a dma_addr_t. Unless this driver is so magic that it really wants a physical and not a dma address, in which case it needs to use alloc_pages instead of dma_alloc_coherent and then call page_to_phys on the returned page, and a very big comment explaining why it is so special.
On Mon 22 Jul 02:30 PDT 2019, Christoph Hellwig wrote: > On Mon, Jul 22, 2019 at 10:38:55AM +0200, Marc Gonzalez wrote: > > > In file included from drivers/firmware/qcom_scm.c:12:0: > > > ./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’ > > > static inline void *dma_alloc_coherent(struct device *dev, size_t size, > > > ^~~~~~~~~~~~~~~~~~ > > > ``` > > > > > > We just can cast phys_addr_t to dma_addr_t here. > > > > IME, casting is rarely a proper solution. > > *nod* > > ptr_phys probably should be a dma_addr_t. Unless this driver is so > magic that it really wants a physical and not a dma address, in which > case it needs to use alloc_pages instead of dma_alloc_coherent > and then call page_to_phys on the returned page, and a very big comment > explaining why it is so special. The scm call takes physical addresses (which happens to be 1:1 with DMA addresses for this driver). This allocation started off (downstream) as a simple kmalloc(), but while the scm call is being executed an access from Linux will cause a security violation (that's not handled gracefully). The properties of dma_alloc is closer, so that's where the code is today. Optimally this should be something like alloc_pages() and some mechanism for unmapping the pages during the call. But no one has come up with a suitable patch for that. But there's a patch from Stephen for this already (not doing a typecast). Apparently I missed merging this, so I'll do that. https://lore.kernel.org/linux-arm-msm/20190517210923.202131-2-swboyd@chromium.org/ Regards, Bjorn
> > > > We just can cast phys_addr_t to dma_addr_t here. > > > > > > IME, casting is rarely a proper solution. > > > > *nod* > > > > ptr_phys probably should be a dma_addr_t. Unless this driver is so > > magic that it really wants a physical and not a dma address, in which > > case it needs to use alloc_pages instead of dma_alloc_coherent > > and then call page_to_phys on the returned page, and a very big comment > > explaining why it is so special. > > The scm call takes physical addresses (which happens to be 1:1 with DMA > addresses for this driver). > > This allocation started off (downstream) as a simple kmalloc(), but > while the scm call is being executed an access from Linux will cause a > security violation (that's not handled gracefully). The properties of > dma_alloc is closer, so that's where the code is today. > > Optimally this should be something like alloc_pages() and some mechanism > for unmapping the pages during the call. But no one has come up with a > suitable patch for that. > > > But there's a patch from Stephen for this already (not doing a > typecast). Apparently I missed merging this, so I'll do that. > > https://lore.kernel.org/linux-arm-msm/20190517210923.202131-2-swboyd@chromium.org/ Bjron, I appreciate for checking this. And also thanks all you guys for the comments here! Thanks,
diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c index 2ddc118dba1b..7f6c841fa200 100644 --- a/drivers/firmware/qcom_scm.c +++ b/drivers/firmware/qcom_scm.c @@ -457,7 +457,8 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz, ptr_sz = ALIGN(src_sz, SZ_64) + ALIGN(mem_to_map_sz, SZ_64) + ALIGN(dest_sz, SZ_64); - ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL); + ptr = dma_alloc_coherent(__scm->dev, ptr_sz, (dma_addr_t *) &ptr_phys, + GFP_KERNEL); if (!ptr) return -ENOMEM;
The following error can happen when trying to build it: ``` drivers/firmware/qcom_scm.c: In function ‘qcom_scm_assign_mem’: drivers/firmware/qcom_scm.c:460:47: error: passing argument 3 of ‘dma_alloc_coherent’ from incompatible pointer type [-Werror=incompatible-pointer-types] ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL); ^ In file included from drivers/firmware/qcom_scm.c:12:0: ./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’ static inline void *dma_alloc_coherent(struct device *dev, size_t size, ^~~~~~~~~~~~~~~~~~ ``` We just can cast phys_addr_t to dma_addr_t here. Cc: Andy Gross <agross@kernel.org> Cc: David Brown <david.brown@linaro.org> Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com> --- drivers/firmware/qcom_scm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)