lkml.org 
[lkml]   [2018]   [Oct]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 1/1] iommu/arm-smmu-v3: eliminate a potential memory corruption on Hi16xx soc
From
Date
On 15/10/18 09:36, Zhen Lei wrote:
> ITS translation register map:
> 0x0000-0x003C Reserved
> 0x0040 GITS_TRANSLATER
> 0x0044-0xFFFC Reserved
>
> The standard GITS_TRANSLATER register in ITS is only 4 bytes, but Hisilicon
> expands the next 4 bytes to carry some IMPDEF information. That means, 8 bytes
> data will be written to MSIAddress each time.
>
> MSIAddr: |----4bytes----|----4bytes----|
> | MSIData | IMPDEF |
>
> There is no problem for ITS, because the next 4 bytes space is reserved in ITS.
> But it will overwrite the 4 bytes memory following "sync_count". It's very
> luckly that the previous and the next neighbour of "sync_count" are both aligned
> by 8 bytes, so no problem is met now.
>
> It's good to explicitly add a workaround:
> 1. Add gcc __attribute__((aligned(8))) to make sure that "sync_count" is always
> aligned by 8 bytes.
> 2. Add a "u64" union member to make sure the 4 bytes padding is always exist.

Surely the u64 member inherently makes the union, and thus the u32
member as well, 64-bit-aligned anyway?

Robin.

> There is no functional change.
>
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
> drivers/iommu/arm-smmu-v3.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 5059d09..a07bc0d 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -586,7 +586,10 @@ struct arm_smmu_device {
>
> struct arm_smmu_strtab_cfg strtab_cfg;
>
> + union {
> + u64 padding; /* workaround for Hisilicon */
> u32 sync_count;
> + } __attribute__((aligned(8)));
>
> /* IOMMU core code handle */
> struct iommu_device iommu;
>

\
 
 \ /
  Last update: 2018-10-15 15:53    [W:0.069 / U:23.328 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site