Christian König christian.koenig@amd.com writes:
Am 05.12.2016 um 08:27 schrieb Daniel Vetter:
On Sat, Dec 03, 2016 at 03:47:00PM +0100, Nicolai Stange wrote:
Since commit 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"), a struct drm_device's ->control member is always NULL.
In the case of CONFIG_DEBUG_FS=y, radeon_debugfs_add_files() accesses ->control->debugfs_root though. This results in the following Oops:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 IP: radeon_debugfs_add_files+0x90/0x100 [radeon] PGD 0 Oops: 0000 [#1] SMP [...] Call Trace: ? work_on_cpu+0xb0/0xb0 radeon_fence_driver_init+0x120/0x150 [radeon] si_init+0x122/0xd50 [radeon] ? _raw_spin_unlock_irq+0x2c/0x40 ? device_pm_check_callbacks+0xb3/0xc0 radeon_device_init+0x958/0xda0 [radeon] radeon_driver_load_kms+0x9a/0x210 [radeon] drm_dev_register+0xa9/0xd0 [drm] drm_get_pci_dev+0x9c/0x1e0 [drm] radeon_pci_probe+0xb8/0xe0 [radeon] [...]
Fix this by omitting the drm_debugfs_create_files() call for the control minor debugfs directory which is now non-existent anyway.
Fixes: 8a357d10043c ("drm: Nerf DRM_CONTROL nodes") Signed-off-by: Nicolai Stange nicstange@gmail.com
Applied to drm-misc with Dave's irc ack, thanks for your patch.
If it's still worth it the patch is Reviewed-by: Christian König christian.koenig@amd.com.
On the other hand when ->control is always NULL, why do we still have ->control anyway?
Yes, I was wondering about that, too.
Quoting from 8a357d10043c ("drm: Nerf DRM_CONTROL nodes"):
Since I don't like dead uabi, let's remove it. But since this would be a really big change I think it's better to start out small by simply not registering anything. We can garbage-collect the dead code later on, once we're sure it's really not used anywhere.
I'd too prefer compile time errors by purging ->control here. Daniel?
And BTW: Please double check the other drivers as well.
# git grep '->control' -- drivers/gpu/ drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control->debugfs_root, drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control); drivers/gpu/drm/amd/amdgpu/amdgpu_device.c: adev->ddev->control);
Oops.
drivers/gpu/drm/amd/amdkfd/kfd_dbgdev.c: ib_packet->control = (1 << 23) | (1 << 31) | drivers/gpu/drm/drm_drv.c: return &dev->control;
That's drm_minor_get_slot(dev, type), but grepping for DRM_MINOR_CONTROL doesn't yield anything -> dead code.
drivers/gpu/drm/gma500/psb_intel_sdvo.c: switch (sdvo->controlled_output) { drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS0; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS1; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= type; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB0; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB1; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS0; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS1; drivers/gpu/drm/gma500/psb_intel_sdvo.c: psb_intel_sdvo->controlled_output = 0; drivers/gpu/drm/i915/intel_sdvo.c: switch (sdvo->controlled_output) { drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS0; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_TMDS1; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= type; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB0; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_RGB1; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS0; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output |= SDVO_OUTPUT_LVDS1; drivers/gpu/drm/i915/intel_sdvo.c: intel_sdvo->controlled_output = 0; drivers/gpu/drm/msm/msm_debugfs.c: ret = late_init_minor(dev->control);
Not an oops but dead code.
drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control->debugfs_root, drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control); drivers/gpu/drm/qxl/qxl_debugfs.c: qdev->ddev->control);
Oops.
I'll send compile-only tested patches either tonight or tomorrow. Shall they cover the oopses only or the dead code as well?
Thanks,
Nicolai