[PATCH 01/12] drm/amdgpu: implement vm_operations_struct.access

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Hi Felix,

in theory all ranges should be limited by the VMA, the TTM mapping code 
makes that assumption as well.

But I agree that we better be save than sorry.

Additional to that one thing which stand out:
> +    r = ttm_bo_kmap(bo, 0, bo->num_pages, &map);

Please try to avoid mapping the whole BO if you want to access only some 
bytes. That in turn usually result in changing the page tables which is 
a bit invasive for the ptrace callback.

In general we should try to avoid accessing more than one page at once.

Regards,
Christian.

Am 12.07.2017 um 08:26 schrieb axie:
> Hi Felix,
>
> I think you might want to add a boundary check to limit the ptrace 
> access inside the BO.
>
> Otherwise there may be a potential security leak allowing others to 
> access the whole memory by using ptrace system call.
>
> -Alex Bin
>
>
> On 2017-07-12 01:37 AM, Felix Kuehling wrote:
>> Any comments on this one?
>>
>> This was requested by the HSA runtime team a long time ago as a
>> debugging feature. It allows gdb to access the content of CPU-mapped
>> BOs. I imagine this may be useful for user mode driver developers.
>>
>> Does anyone dare to give me a Reviewed-by?
>>
>> Regards,
>>    Felix
>>
>>
>> On 17-07-03 05:11 PM, Felix Kuehling wrote:
>>> Allows gdb to access contents of user mode mapped BOs.
>>>
>>> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 130 
>>> +++++++++++++++++++++++++++++++-
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h |   2 +
>>>   2 files changed, 131 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>> index 15148f1..3f927c2 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>>> @@ -1237,6 +1237,134 @@ void amdgpu_ttm_set_active_vram_size(struct 
>>> amdgpu_device *adev, u64 size)
>>>       man->size = size >> PAGE_SHIFT;
>>>   }
>>>   +static struct vm_operations_struct amdgpu_ttm_vm_ops;
>>> +static const struct vm_operations_struct *ttm_vm_ops /* = NULL;
>>> +                              * (appease checkpatch) */;
>>> +static int amdgpu_ttm_bo_access_vram(struct amdgpu_bo *abo,
>>> +                     unsigned long offset,
>>> +                     void *buf, int len, int write)
>>> +{
>>> +    struct amdgpu_device *adev = amdgpu_ttm_adev(abo->tbo.bdev);
>>> +    struct drm_mm_node *nodes = abo->tbo.mem.mm_node;
>>> +    uint32_t value = 0;
>>> +    int result = 0;
>>> +    uint64_t pos;
>>> +    unsigned long flags;
>>> +
>>> +    while (offset >= (nodes->size << PAGE_SHIFT)) {
>>> +        offset -= nodes->size << PAGE_SHIFT;
>>> +        ++nodes;
>>> +    }
>>> +    pos = (nodes->start << PAGE_SHIFT) + offset;
>>> +
>>> +    while (len && pos < adev->mc.mc_vram_size) {
>>> +        uint64_t aligned_pos = pos & ~(uint64_t)3;
>>> +        uint32_t bytes = 4 - (pos & 3);
>>> +        uint32_t shift = (pos & 3) * 8;
>>> +        uint32_t mask = 0xffffffff << shift;
>>> +
>>> +        if (len < bytes) {
>>> +            mask &= 0xffffffff >> (bytes - len) * 8;
>>> +            bytes = len;
>>> +        }
>>> +
>>> +        spin_lock_irqsave(&adev->mmio_idx_lock, flags);
>>> +        WREG32(mmMM_INDEX, ((uint32_t)aligned_pos) | 0x80000000);
>>> +        WREG32(mmMM_INDEX_HI, aligned_pos >> 31);
>>> +        if (!write || mask != 0xffffffff)
>>> +            value = RREG32(mmMM_DATA);
>>> +        if (write) {
>>> +            value &= ~mask;
>>> +            value |= (*(uint32_t *)buf << shift) & mask;
>>> +            WREG32(mmMM_DATA, value);
>>> +        }
>>> +        spin_unlock_irqrestore(&adev->mmio_idx_lock, flags);
>>> +        if (!write) {
>>> +            value = (value & mask) >> shift;
>>> +            memcpy(buf, &value, bytes);
>>> +        }
>>> +
>>> +        result += bytes;
>>> +        buf = (uint8_t *)buf + bytes;
>>> +        pos += bytes;
>>> +        len -= bytes;
>>> +        if (pos >= (nodes->start + nodes->size) << PAGE_SHIFT) {
>>> +            ++nodes;
>>> +            pos = (nodes->start << PAGE_SHIFT);
>>> +        }
>>> +    }
>>> +
>>> +    return result;
>>> +}
>>> +
>>> +static int amdgpu_ttm_bo_access_kmap(struct amdgpu_bo *abo,
>>> +                     unsigned long offset,
>>> +                     void *buf, int len, int write)
>>> +{
>>> +    struct ttm_buffer_object *bo = &abo->tbo;
>>> +    struct ttm_bo_kmap_obj map;
>>> +    void *ptr;
>>> +    bool is_iomem;
>>> +    int r;
>>> +
>>> +    r = ttm_bo_kmap(bo, 0, bo->num_pages, &map);
>>> +    if (r)
>>> +        return r;
>>> +    ptr = (uint8_t *)ttm_kmap_obj_virtual(&map, &is_iomem) + offset;
>>> +    WARN_ON(is_iomem);
>>> +    if (write)
>>> +        memcpy(ptr, buf, len);
>>> +    else
>>> +        memcpy(buf, ptr, len);
>>> +    ttm_bo_kunmap(&map);
>>> +
>>> +    return len;
>>> +}
>>> +
>>> +static int amdgpu_ttm_vm_access(struct vm_area_struct *vma, 
>>> unsigned long addr,
>>> +                void *buf, int len, int write)
>>> +{
>>> +    unsigned long offset = (addr) - vma->vm_start;
>>> +    struct ttm_buffer_object *bo = vma->vm_private_data;
>>> +    struct amdgpu_bo *abo = container_of(bo, struct amdgpu_bo, tbo);
>>> +    unsigned domain;
>>> +    int result;
>>> +
>>> +    result = amdgpu_bo_reserve(abo, false);
>>> +    if (result != 0)
>>> +        return result;
>>> +
>>> +    domain = amdgpu_mem_type_to_domain(bo->mem.mem_type);
>>> +    if (domain == AMDGPU_GEM_DOMAIN_VRAM)
>>> +        result = amdgpu_ttm_bo_access_vram(abo, offset,
>>> +                           buf, len, write);
>>> +    else
>>> +        result = amdgpu_ttm_bo_access_kmap(abo, offset,
>>> +                           buf, len, write);
>>> +    amdgpu_bo_unreserve(abo);
>>> +
>>> +    return len;
>>> +}
>>> +
>>> +int amdgpu_bo_mmap(struct file *filp, struct vm_area_struct *vma,
>>> +           struct ttm_bo_device *bdev)
>>> +{
>>> +    int r;
>>> +
>>> +    r = ttm_bo_mmap(filp, vma, bdev);
>>> +    if (unlikely(r != 0))
>>> +        return r;
>>> +
>>> +    if (unlikely(ttm_vm_ops == NULL)) {
>>> +        ttm_vm_ops = vma->vm_ops;
>>> +        amdgpu_ttm_vm_ops = *ttm_vm_ops;
>>> +        amdgpu_ttm_vm_ops.access = &amdgpu_ttm_vm_access;
>>> +    }
>>> +    vma->vm_ops = &amdgpu_ttm_vm_ops;
>>> +
>>> +    return 0;
>>> +}
>>> +
>>>   int amdgpu_mmap(struct file *filp, struct vm_area_struct *vma)
>>>   {
>>>       struct drm_file *file_priv;
>>> @@ -1250,7 +1378,7 @@ int amdgpu_mmap(struct file *filp, struct 
>>> vm_area_struct *vma)
>>>       if (adev == NULL)
>>>           return -EINVAL;
>>>   -    return ttm_bo_mmap(filp, vma, &adev->mman.bdev);
>>> +    return amdgpu_bo_mmap(filp, vma, &adev->mman.bdev);
>>>   }
>>>     int amdgpu_copy_buffer(struct amdgpu_ring *ring, uint64_t 
>>> src_offset,
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>> index 776a20a..1eb605c 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>> @@ -73,6 +73,8 @@ int amdgpu_fill_buffer(struct amdgpu_bo *bo,
>>>               struct dma_fence **fence);
>>>     int amdgpu_mmap(struct file *filp, struct vm_area_struct *vma);
>>> +int amdgpu_bo_mmap(struct file *filp, struct vm_area_struct *vma,
>>> +           struct ttm_bo_device *bdev);
>>>   bool amdgpu_ttm_is_bound(struct ttm_tt *ttm);
>>>   int amdgpu_ttm_bind(struct ttm_buffer_object *bo, struct 
>>> ttm_mem_reg *bo_mem);
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>
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