[bug report] drm/amdgpu: add ring buffer information in devcoredump

[Christian König]

Am 15.03.24 um 20:08 schrieb Khatri, Sunil:
>
> Thanks for pointing these. I do have some doubt and i raised inline.
>
> On 3/15/2024 8:46 PM, Dan Carpenter wrote:
>> Hello Sunil Khatri,
>>
>> Commit 42742cc541bb ("drm/amdgpu: add ring buffer information in
>> devcoredump") from Mar 11, 2024 (linux-next), leads to the following
>> Smatch static checker warning:
>>
>> 	drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c:219 amdgpu_devcoredump_read()
>> 	error: we previously assumed 'coredump->adev' could be null (see line 206)
>>
>> drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c
>>      171 static ssize_t
>>      172 amdgpu_devcoredump_read(char *buffer, loff_t offset, size_t count,
>>      173                         void *data, size_t datalen)
>>      174 {
>>      175         struct drm_printer p;
>>      176         struct amdgpu_coredump_info *coredump = data;
>>      177         struct drm_print_iterator iter;
>>      178         int i;
>>      179
>>      180         iter.data = buffer;
>>      181         iter.offset = 0;
>>      182         iter.start = offset;
>>      183         iter.remain = count;
>>      184
>>      185         p = drm_coredump_printer(&iter);
>>      186
>>      187         drm_printf(&p, "**** AMDGPU Device Coredump ****\n");
>>      188         drm_printf(&p, "version: " AMDGPU_COREDUMP_VERSION "\n");
>>      189         drm_printf(&p, "kernel: " UTS_RELEASE "\n");
>>      190         drm_printf(&p, "module: " KBUILD_MODNAME "\n");
>>      191         drm_printf(&p, "time: %lld.%09ld\n", coredump->reset_time.tv_sec,
>>      192                         coredump->reset_time.tv_nsec);
>>      193
>>      194         if (coredump->reset_task_info.pid)
>>      195                 drm_printf(&p, "process_name: %s PID: %d\n",
>>      196                            coredump->reset_task_info.process_name,
>>      197                            coredump->reset_task_info.pid);
>>      198
>>      199         if (coredump->ring) {
>>      200                 drm_printf(&p, "\nRing timed out details\n");
>>      201                 drm_printf(&p, "IP Type: %d Ring Name: %s\n",
>>      202                            coredump->ring->funcs->type,
>>      203                            coredump->ring->name);
>>      204         }
>>      205
>>      206         if (coredump->adev) {
>>                      ^^^^^^^^^^^^^^
>> Check for NULL
> This is the check for NULL. Is there any issue here ?
>>      207                 struct amdgpu_vm_fault_info *fault_info =
>>      208                         &coredump->adev->vm_manager.fault_info;
>>      209
>>      210                 drm_printf(&p, "\n[%s] Page fault observed\n",
>>      211                            fault_info->vmhub ? "mmhub" : "gfxhub");
>>      212                 drm_printf(&p, "Faulty page starting at address: 0x%016llx\n",
>>      213                            fault_info->addr);
>>      214                 drm_printf(&p, "Protection fault status register: 0x%x\n\n",
>>      215                            fault_info->status);
>>      216         }
>>      217
>>      218         drm_printf(&p, "Ring buffer information\n");
>> --> 219         for (int i = 0; i < coredump->adev->num_rings; i++) {
>>                                      ^^^^^^^^^^^^^^
>> Unchecked dereference
> Agree
>>      220                 int j = 0;
>>      221                 struct amdgpu_ring *ring = coredump->adev->rings[i];
>>      222
>>      223                 drm_printf(&p, "ring name: %s\n", ring->name);
>>      224                 drm_printf(&p, "Rptr: 0x%llx Wptr: 0x%llx RB mask: %x\n",
>>      225                            amdgpu_ring_get_rptr(ring),
>>      226                            amdgpu_ring_get_wptr(ring),
>>      227                            ring->buf_mask);
>>      228                 drm_printf(&p, "Ring size in dwords: %d\n",
>>      229                            ring->ring_size / 4);
>>      230                 drm_printf(&p, "Ring contents\n");
>>      231                 drm_printf(&p, "Offset \t Value\n");
>>      232
>>      233                 while (j < ring->ring_size) {
>>      234                         drm_printf(&p, "0x%x \t 0x%x\n", j, ring->ring[j/4]);
>>      235                         j += 4;
>>      236                 }
>>      237         }
>>      238
>>      239         if (coredump->reset_vram_lost)
>>      240                 drm_printf(&p, "VRAM is lost due to GPU reset!\n");
>>      241         if (coredump->adev->reset_info.num_regs) {
>>                      ^^^^^^^^^^^^^^
>> Here too
> Agree.
>>      242                 drm_printf(&p, "AMDGPU register dumps:\nOffset:     Value:\n");
>>      243
>>      244                 for (i = 0; i < coredump->adev->reset_info.num_regs; i++)
>>      245                         drm_printf(&p, "0x%08x: 0x%08x\n",
>>      246                                    coredump->adev->reset_info.reset_dump_reg_list[i],
>>      247                                    coredump->adev->reset_info.reset_dump_reg_value[i]);
>>      248         }
>>      249
>>      250         return count - iter.remain;
>>      251 }
>
>
> Although adev is a global structure and never in the code it is being 
> checked for NULL as it wont be NULL until the driver is unloaded. I 
> can add a check  for adev in the beginning of the function 
> amdgpu_devcoredump_read for completeness of the tool but still not 
> very sure of it.
>
> Christian and Alex Do you agree with my understanding the adev does 
> really need a validation for NULL. I dint see throughout the code adev 
> to be validated for NULL. Do you recommend to add a check for NULL for 
> adev in the above mentioned function/places.
>

No, that doesn't make sense. adev is mandatory to be around for the core 
dump to be valid and accessible.

Without a device you don't have a core dump in the first place.

Regards,
Christian.

> Regards Sunil
>
>> regards,
>> dan carpenter
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