[PATCH] arm: dma-mapping: Fix mapping size value
ritesh.harjani at gmail.com
Sat Apr 19 04:25:30 PDT 2014
In explaining the issue below, made a mistake of taking PAGE_SIZE
instead of PAGE_SHIFT (mistake mentioned inline).
Although numerical values and patch is correct.
On Sat, Apr 19, 2014 at 4:49 PM, Ritesh Harjani
<ritesh.harjani at gmail.com> wrote:
> I am finding an oops after following commit. I am on 3.10.30 kernel but applied
> all the latest patches from arch/arm/mm/dma-mapping.c
> I added some debug logs to see what is the error, on which I found that we are
> incorrectly setting mapping->size value.
> Please take a look at this and correct me if I am wrong here.
> FAULTY COMMIT:
> commit 68efd7d2fb32c2606f1da318b6a851
> Author: Marek Szyprowski <m.szyprowski at samsung.com>
> Date: Tue Feb 25 13:01:09 2014 +0100
> arm: dma-mapping: remove order parameter from arm_iommu_create_mapping()
> OOPS LOGS:
> [26.898145] __alloc_iova#LINE: 1097 start = 0x3500
> [26.898159] __alloc_iova#LINE:1136 iova = 0x53500000
> [26.898170] __alloc_iova#LINE:1138 mapping->base= 0x50000000
> [26.898181] __alloc_iova#LINE:1140 mapping->size = 0x1000000, i = 0
> [26.924442] __free_iova, bitmap_index = 3
> [Ritesh]: bitmap_index should be 0 for address 0x53500000. see in alloc_iova
> [26.924454] __free_iova,addr = 0x53500000
> [26.924463] __free_iova,mapping->base = 0x50000000
> [26.924472] __free_iova,mapping->size = 0x1000000
> [26.924482] __free_iova,bitmap_base = 0x53000000
> [26.924490] __free_iova, start = 0x500
> [Ritesh]: start should be 0x3500 for address 0x53500000. see in alloc_iova
> [26.924533] Unable to handle kernel NULL pointer dereference at virtual
> address 000000a0
> [26.924543] pgd = e7a84000
> [26.924558] [000000a0] *pgd=00000000
> [26.924572] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
> [26.924598] Modules linked in:
> [26.924613] CPU: 1 PID: 2263 Comm: BufferLiberator Not tainted 3.10.30+
> [26.924624] task: e7370a40 ti: e6e06000 task.ti: e6e06000
> [26.924644] PC is at bitmap_clear+0x48/0xd0
> [26.924659] LR is at __iommu_remove_mapping+0x130/0x164
> [26.924673] pc : [<c02d0814>] lr : [<c001bd30>] psr: 20000093
> [26.924673] sp : e6e07e20 ip : ffffffff fp : e6e07e3c
> [26.924682] r10: 00000500 r9 : c1333ea8 r8 : 80000013
> [26.924692] r7 : ffffffff r6 : 00000321 r5 : 000000a0 r4 : 00000028
> [26.924707] r3 : 00000000 r2 : 00000341 r1 : 00000500 r0 : 00000000
> [26.924730] Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment
> [26.924742] Control: 10c5387d Table: 77a8406a DAC: 00000015
> See below on how this is wrong:
> here iova_base = 0x50000000
> iova_size = 0x20000000
> => bits needed to map = 131072.
> => bitmap_size = 0x4000
> since bitmap_size > PAGE_SIZE
> => bitmap_size = PAGE_SIZE, extensions = 4;
> Now, mapping->size is currently set as bitmap_size << PAGE_SHIFT.
> =>mapping->size = 0x1000000.
> mapping->size is the IOVA size, which one bitmap can address.
> Now mapping->size * extensions should be size (0x20000000).
> which is not true, => our bitmap_size is set wrong.
> it should be (mapping->bits << PAGE_SIZE) or say
It should be PAGE_SHIFT here.
> (BITS_PER_BYTE * bitmap_size << PAGE_SIZE)
It should be PAGE_SHIFT here.
> => (8 * 0x1000) << 12) = 0x8000000
> With this IOVA_SIZE = extensions * mapping->size = 0x20000000
> Currently mapping->size is wrongly set resulting
> in OOPS (atleast we see OOPS with extension 4).
> Fix this.
> Signed-off-by: Ritesh Harjani <ritesh.harjani at gmail.com>
> arch/arm/mm/dma-mapping.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f62aa06..d1701a2 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1963,8 +1963,8 @@ arm_iommu_create_mapping(struct bus_type *bus,
> dma_addr_t base, size_t size)
> mapping->nr_bitmaps = 1;
> mapping->extensions = extensions;
> mapping->base = base;
> - mapping->size = bitmap_size << PAGE_SHIFT;
> mapping->bits = BITS_PER_BYTE * bitmap_size;
> + mapping->size = mapping->bits << PAGE_SHIFT;
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