drm/amdgpu: Fix cat debugfs amdgpu_regs_didt causes kernel null pointer

  For 'AMDGPU_FAMILY_SI' family cards, in 'si_common_early_init' func, init
'didt_rreg' and 'didt_wreg' to 'NULL'. But in func
'amdgpu_debugfs_regs_didt_read/write', using 'RREG32_DIDT' 'WREG32_DIDT'
lacks of relevant judgment. And other 'amdgpu_ip_block_version' that use
these two definitions won't be added for 'AMDGPU_FAMILY_SI'.

So, add null pointer judgment before calling.

Signed-off-by: Lu Yao <yaolu@kylinos.cn>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
  

Am 22.11.23 um 10:35 schrieb Lu Yao:
> For 'AMDGPU_FAMILY_SI' family cards, in 'si_common_early_init' func, init
> 'didt_rreg' and 'didt_wreg' to 'NULL'. But in func
> 'amdgpu_debugfs_regs_didt_read/write', using 'RREG32_DIDT' 'WREG32_DIDT'
> lacks of relevant judgment. And other 'amdgpu_ip_block_version' that use
> these two definitions won't be added for 'AMDGPU_FAMILY_SI'.
>
> So, add null pointer judgment before calling.
>
> Signed-off-by: Lu Yao <yaolu@kylinos.cn>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index a53f436fa9f1..797d7d3bfd50 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -638,6 +638,11 @@ static ssize_t amdgpu_debugfs_regs_didt_read(struct file *f, char __user *buf,
>   	if (size & 0x3 || *pos & 0x3)
>   		return -EINVAL;
>   
> +	if (adev->didt_rreg == NULL) {
> +		dev_err(adev->dev, "%s adev->didt_rreg is null!\n", __FUNC__);

Please drop the dev_err(), this is not a device error but rather 
userspace using a functionality not applicable for this device type.

> +		return -EPERM;

Maybe rather use EOPNOTSUPP here.

Regards,
Christian.

> +	}
> +
>   	r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
>   	if (r < 0) {
>   		pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
> @@ -694,6 +699,11 @@ static ssize_t amdgpu_debugfs_regs_didt_write(struct file *f, const char __user
>   	if (size & 0x3 || *pos & 0x3)
>   		return -EINVAL;
>   
> +	if (adev->didt_wreg == NULL) {
> +		dev_err(adev->dev, "%s adev->didt_wreg is null!\n", __FUNC__);
> +		return -EPERM;
> +	}
> +
>   	r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
>   	if (r < 0) {
>   		pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
  

Hi Lu,

kernel test robot noticed the following build errors:

[auto build test ERROR on drm-misc/drm-misc-next]
[also build test ERROR on linus/master v6.7-rc2 next-20231124]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Lu-Yao/drm-amdgpu-Fix-cat-debugfs-amdgpu_regs_didt-causes-kernel-null-pointer/20231122-203138
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20231122093509.34302-1-yaolu%40kylinos.cn
patch subject: [PATCH] drm/amdgpu: Fix cat debugfs amdgpu_regs_didt causes kernel null pointer
config: x86_64-randconfig-001-20231123 (https://download.01.org/0day-ci/archive/20231124/202311241442.F0S4BazK-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231124/202311241442.F0S4BazK-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311241442.F0S4BazK-lkp@intel.com/

All errors (new ones prefixed by >>):

   warning: unknown warning option '-Wstringop-truncation'; did you mean '-Wstring-concatenation'? [-Wunknown-warning-option]
   warning: unknown warning option '-Wpacked-not-aligned'; did you mean '-Wpacked-non-pod'? [-Wunknown-warning-option]
>> drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c:642:55: error: use of undeclared identifier '__FUNC__'
                   dev_err(adev->dev, "%s adev->didt_rreg is null!\n", __FUNC__);
                                                                       ^
   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c:703:55: error: use of undeclared identifier '__FUNC__'
                   dev_err(adev->dev, "%s adev->didt_wreg is null!\n", __FUNC__);
                                                                       ^
   2 warnings and 2 errors generated.


vim +/__FUNC__ +642 drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c

   618	
   619	/**
   620	 * amdgpu_debugfs_regs_didt_read - Read from a DIDT register
   621	 *
   622	 * @f: open file handle
   623	 * @buf: User buffer to store read data in
   624	 * @size: Number of bytes to read
   625	 * @pos:  Offset to seek to
   626	 *
   627	 * The lower bits are the BYTE offset of the register to read.  This
   628	 * allows reading multiple registers in a single call and having
   629	 * the returned size reflect that.
   630	 */
   631	static ssize_t amdgpu_debugfs_regs_didt_read(struct file *f, char __user *buf,
   632						size_t size, loff_t *pos)
   633	{
   634		struct amdgpu_device *adev = file_inode(f)->i_private;
   635		ssize_t result = 0;
   636		int r;
   637	
   638		if (size & 0x3 || *pos & 0x3)
   639			return -EINVAL;
   640	
   641		if (adev->didt_rreg == NULL) {
 > 642			dev_err(adev->dev, "%s adev->didt_rreg is null!\n", __FUNC__);
   643			return -EPERM;
   644		}
   645	
   646		r = pm_runtime_get_sync(adev_to_drm(adev)->dev);
   647		if (r < 0) {
   648			pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
   649			return r;
   650		}
   651	
   652		r = amdgpu_virt_enable_access_debugfs(adev);
   653		if (r < 0) {
   654			pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
   655			return r;
   656		}
   657	
   658		while (size) {
   659			uint32_t value;
   660	
   661			value = RREG32_DIDT(*pos >> 2);
   662			r = put_user(value, (uint32_t *)buf);
   663			if (r)
   664				goto out;
   665	
   666			result += 4;
   667			buf += 4;
   668			*pos += 4;
   669			size -= 4;
   670		}
   671	
   672		r = result;
   673	out:
   674		pm_runtime_mark_last_busy(adev_to_drm(adev)->dev);
   675		pm_runtime_put_autosuspend(adev_to_drm(adev)->dev);
   676		amdgpu_virt_disable_access_debugfs(adev);
   677		return r;
   678	}
   679