Messages in this thread | | | Subject | Re: [PATCH v1 ] ALSA: core: memalloc: add page alignment for iram | From | Lars-Peter Clausen <> | Date | Thu, 17 Dec 2020 11:44:27 +0100 |
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On 12/17/20 11:14 AM, Takashi Iwai wrote: > On Thu, 17 Dec 2020 10:55:42 +0100, > Takashi Iwai wrote: >> On Thu, 17 Dec 2020 10:43:45 +0100, >> Lars-Peter Clausen wrote: >>> On 12/17/20 5:15 PM, Robin Gong wrote: >>>> Since mmap for userspace is based on page alignment, add page alignment >>>> for iram alloc from pool, otherwise, some good data located in the same >>>> page of dmab->area maybe touched wrongly by userspace like pulseaudio. >>>> >>> I wonder, do we also have to align size to be a multiple of PAGE_SIZE >>> to avoid leaking unrelated data? >> Hm, a good question. Basically the PCM buffer size itself shouldn't >> be influenced by that (i.e. no hw-constraint or such is needed), but >> the padding should be cleared indeed. I somehow left those to the >> allocator side, but maybe it's safer to clear the whole buffer in >> sound/core/memalloc.c commonly. > That said, something like below (totally untested). > We might pass the pass-aligned size to dmab->bytes field instead of > keeping the original value, too.
We'd need this for those APIs that also pass the size to the free() function. Like dma_free_coherent() and free_pages_exact(), but maybe those round up internally as well.
I had a quick look and I could not find any place were the code relies on the requested buffer size being stored in dmab->bytes. In fact we already reuse the buffer if there is an allocated buffer that is larger than the requested buffer (See snd_pcm_lib_malloc_pages), so this should be OK.
> > > Takashi > > --- > --- a/sound/core/memalloc.c > +++ b/sound/core/memalloc.c > @@ -126,6 +126,7 @@ static inline gfp_t snd_mem_get_gfp_flags(const struct device *dev, > int snd_dma_alloc_pages(int type, struct device *device, size_t size, > struct snd_dma_buffer *dmab) > { > + size_t orig_size = size; > gfp_t gfp; > > if (WARN_ON(!size)) > @@ -133,6 +134,7 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size, > if (WARN_ON(!dmab)) > return -ENXIO; > > + size = PAGE_ALIGN(size); > dmab->dev.type = type; > dmab->dev.dev = device; > dmab->bytes = 0; > @@ -177,7 +179,8 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size, > } > if (! dmab->area) > return -ENOMEM; > - dmab->bytes = size; > + memset(dmab->area, 0, size); > + dmab->bytes = orig_size; > return 0; > } > EXPORT_SYMBOL(snd_dma_alloc_pages);
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