diff mbox series

[v7,1/4] drm/panthor: Introduce BO labeling

Message ID 20250411150357.3308921-2-adrian.larumbe@collabora.com (mailing list archive)
State New
Headers show
Series Panthor BO tagging and GEMS debug display | expand

Commit Message

Adrián Larumbe April 11, 2025, 3:03 p.m. UTC 
Add a new character string Panthor BO field, and a function that allows
setting it from within the driver.

Driver takes care of freeing the string when it's replaced or no longer
needed at object destruction time, but allocating it is the responsibility
of callers.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_gem.c | 39 +++++++++++++++++++++++++++
 drivers/gpu/drm/panthor/panthor_gem.h | 17 ++++++++++++
 2 files changed, 56 insertions(+)

Comments

Steven Price April 14, 2025, 9:50 a.m. UTC | #1 
Hi Adrián,

On 11/04/2025 16:03, Adrián Larumbe wrote:
> Add a new character string Panthor BO field, and a function that allows
> setting it from within the driver.
> 
> Driver takes care of freeing the string when it's replaced or no longer
> needed at object destruction time, but allocating it is the responsibility
> of callers.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
>  drivers/gpu/drm/panthor/panthor_gem.c | 39 +++++++++++++++++++++++++++
>  drivers/gpu/drm/panthor/panthor_gem.h | 17 ++++++++++++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
> index 8244a4e6c2a2..af0ac17f357f 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.c
> +++ b/drivers/gpu/drm/panthor/panthor_gem.c
> @@ -2,6 +2,7 @@
>  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
>  /* Copyright 2023 Collabora ltd. */
>  
> +#include <linux/cleanup.h>
>  #include <linux/dma-buf.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/err.h>
> @@ -18,6 +19,14 @@ static void panthor_gem_free_object(struct drm_gem_object *obj)
>  	struct panthor_gem_object *bo = to_panthor_bo(obj);
>  	struct drm_gem_object *vm_root_gem = bo->exclusive_vm_root_gem;
>  
> +	/*
> +	 * Label might have been allocated with kstrdup_const(),
> +	 * we need to take that into account when freeing the memory
> +	 */
> +	kfree_const(bo->label.str);
> +
> +	mutex_destroy(&bo->label.lock);
> +
>  	drm_gem_free_mmap_offset(&bo->base.base);
>  	mutex_destroy(&bo->gpuva_list_lock);
>  	drm_gem_shmem_free(&bo->base);
> @@ -196,6 +205,7 @@ struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t
>  	obj->base.map_wc = !ptdev->coherent;
>  	mutex_init(&obj->gpuva_list_lock);
>  	drm_gem_gpuva_set_lock(&obj->base.base, &obj->gpuva_list_lock);
> +	mutex_init(&obj->label.lock);
>  
>  	return &obj->base.base;
>  }
> @@ -247,3 +257,32 @@ panthor_gem_create_with_handle(struct drm_file *file,
>  
>  	return ret;
>  }
> +
> +void
> +panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label)
> +{
> +	struct panthor_gem_object *bo = to_panthor_bo(obj);
> +	const char *old_label;
> +
> +	scoped_guard(mutex, &bo->label.lock) {
> +		old_label = bo->label.str;
> +		bo->label.str = label;
> +	}
> +
> +	kfree(old_label);

Shouldn't this be kfree_const()? I suspect as things stand we can't
trigger this bug but it's inconsistent.

> +}
> +
> +void
> +panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label)
> +{
> +	const char *str;
> +
> +	str = kstrdup_const(label, GFP_KERNEL);
> +	if (!str) {

In the next patch you permit user space to clear the label
(args->size==0) which means label==NULL and AFAICT kstrdup_const() will
return NULL in this case triggering this warning.

Thanks,
Steve

> +		/* Failing to allocate memory for a label isn't a fatal condition */
> +		drm_warn(bo->obj->dev, "Not enough memory to allocate BO label");
> +		return;
> +	}
> +
> +	panthor_gem_bo_set_label(bo->obj, str);
> +}
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
> index 1a363bb814f4..af0d77338860 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.h
> +++ b/drivers/gpu/drm/panthor/panthor_gem.h
> @@ -46,6 +46,20 @@ struct panthor_gem_object {
>  
>  	/** @flags: Combination of drm_panthor_bo_flags flags. */
>  	u32 flags;
> +
> +	/**
> +	 * @label: BO tagging fields. The label can be assigned within the
> +	 * driver itself or through a specific IOCTL.
> +	 */
> +	struct {
> +		/**
> +		 * @label.str: Pointer to NULL-terminated string,
> +		 */
> +		const char *str;
> +
> +		/** @lock.str: Protects access to the @label.str field. */
> +		struct mutex lock;
> +	} label;
>  };
>  
>  /**
> @@ -91,6 +105,9 @@ panthor_gem_create_with_handle(struct drm_file *file,
>  			       struct panthor_vm *exclusive_vm,
>  			       u64 *size, u32 flags, uint32_t *handle);
>  
> +void panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label);
> +void panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label);
> +
>  static inline u64
>  panthor_kernel_bo_gpuva(struct panthor_kernel_bo *bo)
>  {
Adrián Larumbe April 14, 2025, 7:43 p.m. UTC | #2 
Hi Steven,

On 14.04.2025 10:50, Steven Price wrote:
> Hi Adrián,
>
> On 11/04/2025 16:03, Adrián Larumbe wrote:
> > Add a new character string Panthor BO field, and a function that allows
> > setting it from within the driver.
> >
> > Driver takes care of freeing the string when it's replaced or no longer
> > needed at object destruction time, but allocating it is the responsibility
> > of callers.
> >
> > Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> > Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> > ---
> >  drivers/gpu/drm/panthor/panthor_gem.c | 39 +++++++++++++++++++++++++++
> >  drivers/gpu/drm/panthor/panthor_gem.h | 17 ++++++++++++
> >  2 files changed, 56 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
> > index 8244a4e6c2a2..af0ac17f357f 100644
> > --- a/drivers/gpu/drm/panthor/panthor_gem.c
> > +++ b/drivers/gpu/drm/panthor/panthor_gem.c
> > @@ -2,6 +2,7 @@
> >  /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
> >  /* Copyright 2023 Collabora ltd. */
> >
> > +#include <linux/cleanup.h>
> >  #include <linux/dma-buf.h>
> >  #include <linux/dma-mapping.h>
> >  #include <linux/err.h>
> > @@ -18,6 +19,14 @@ static void panthor_gem_free_object(struct drm_gem_object *obj)
> >  	struct panthor_gem_object *bo = to_panthor_bo(obj);
> >  	struct drm_gem_object *vm_root_gem = bo->exclusive_vm_root_gem;
> >
> > +	/*
> > +	 * Label might have been allocated with kstrdup_const(),
> > +	 * we need to take that into account when freeing the memory
> > +	 */
> > +	kfree_const(bo->label.str);
> > +
> > +	mutex_destroy(&bo->label.lock);
> > +
> >  	drm_gem_free_mmap_offset(&bo->base.base);
> >  	mutex_destroy(&bo->gpuva_list_lock);
> >  	drm_gem_shmem_free(&bo->base);
> > @@ -196,6 +205,7 @@ struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t
> >  	obj->base.map_wc = !ptdev->coherent;
> >  	mutex_init(&obj->gpuva_list_lock);
> >  	drm_gem_gpuva_set_lock(&obj->base.base, &obj->gpuva_list_lock);
> > +	mutex_init(&obj->label.lock);
> >
> >  	return &obj->base.base;
> >  }
> > @@ -247,3 +257,32 @@ panthor_gem_create_with_handle(struct drm_file *file,
> >
> >  	return ret;
> >  }
> > +
> > +void
> > +panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label)
> > +{
> > +	struct panthor_gem_object *bo = to_panthor_bo(obj);
> > +	const char *old_label;
> > +
> > +	scoped_guard(mutex, &bo->label.lock) {
> > +		old_label = bo->label.str;
> > +		bo->label.str = label;
> > +	}
> > +
> > +	kfree(old_label);
>
> Shouldn't this be kfree_const()? I suspect as things stand we can't
> trigger this bug but it's inconsistent.

This could only be called either from the set_label() ioctl, in which case
old_label could be NULL or a pointer to a string obtained from strdup(); or from
panthor_gem_kernel_bo_set_label(). In the latter case, it could only ever be
NULL, since we don't reassign kernel BO labels, so it'd be safe too.

However I do agree that it's not consistent, and then in the future perhaps
relabelling kernel BO's might be justified, so I'll change it to kfree_const().

> > +}
> > +
> > +void
> > +panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label)
> > +{
> > +	const char *str;
> > +
> > +	str = kstrdup_const(label, GFP_KERNEL);
> > +	if (!str) {
>
> In the next patch you permit user space to clear the label
> (args->size==0) which means label==NULL and AFAICT kstrdup_const() will
> return NULL in this case triggering this warning.

Kernel and UM-exposed BO's should never experience cross-labelling, so in theory
this scenario ought to be impossible. The only way panthor_gem_kernel_bo_set_label()
might take NULL in the 'label' argument is that someone called panthor_kernel_bo_create()
with NULL for its name 'argument'.

I think as a defensive check, I could do something as follows

void
panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label)
{
	const char *str;

	/* We should never attempt labelling a UM-exposed GEM object */
	if (drm_WARN_ON(bo->obj->dev, &bo->obj->handle_count > 0))
		return;

	if (!label)
		return;

       [...]
}

> Thanks,
> Steve
>
> > +		/* Failing to allocate memory for a label isn't a fatal condition */
> > +		drm_warn(bo->obj->dev, "Not enough memory to allocate BO label");
> > +		return;
> > +	}
> > +
> > +	panthor_gem_bo_set_label(bo->obj, str);
> > +}
> > diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
> > index 1a363bb814f4..af0d77338860 100644
> > --- a/drivers/gpu/drm/panthor/panthor_gem.h
> > +++ b/drivers/gpu/drm/panthor/panthor_gem.h
> > @@ -46,6 +46,20 @@ struct panthor_gem_object {
> >
> >  	/** @flags: Combination of drm_panthor_bo_flags flags. */
> >  	u32 flags;
> > +
> > +	/**
> > +	 * @label: BO tagging fields. The label can be assigned within the
> > +	 * driver itself or through a specific IOCTL.
> > +	 */
> > +	struct {
> > +		/**
> > +		 * @label.str: Pointer to NULL-terminated string,
> > +		 */
> > +		const char *str;
> > +
> > +		/** @lock.str: Protects access to the @label.str field. */
> > +		struct mutex lock;
> > +	} label;
> >  };
> >
> >  /**
> > @@ -91,6 +105,9 @@ panthor_gem_create_with_handle(struct drm_file *file,
> >  			       struct panthor_vm *exclusive_vm,
> >  			       u64 *size, u32 flags, uint32_t *handle);
> >
> > +void panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label);
> > +void panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label);
> > +
> >  static inline u64
> >  panthor_kernel_bo_gpuva(struct panthor_kernel_bo *bo)
> >  {

Adrian Larumbe
diff mbox series

Patch

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index 8244a4e6c2a2..af0ac17f357f 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -2,6 +2,7 @@ 
 /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
 /* Copyright 2023 Collabora ltd. */
 
+#include <linux/cleanup.h>
 #include <linux/dma-buf.h>
 #include <linux/dma-mapping.h>
 #include <linux/err.h>
@@ -18,6 +19,14 @@  static void panthor_gem_free_object(struct drm_gem_object *obj)
 	struct panthor_gem_object *bo = to_panthor_bo(obj);
 	struct drm_gem_object *vm_root_gem = bo->exclusive_vm_root_gem;
 
+	/*
+	 * Label might have been allocated with kstrdup_const(),
+	 * we need to take that into account when freeing the memory
+	 */
+	kfree_const(bo->label.str);
+
+	mutex_destroy(&bo->label.lock);
+
 	drm_gem_free_mmap_offset(&bo->base.base);
 	mutex_destroy(&bo->gpuva_list_lock);
 	drm_gem_shmem_free(&bo->base);
@@ -196,6 +205,7 @@  struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t
 	obj->base.map_wc = !ptdev->coherent;
 	mutex_init(&obj->gpuva_list_lock);
 	drm_gem_gpuva_set_lock(&obj->base.base, &obj->gpuva_list_lock);
+	mutex_init(&obj->label.lock);
 
 	return &obj->base.base;
 }
@@ -247,3 +257,32 @@  panthor_gem_create_with_handle(struct drm_file *file,
 
 	return ret;
 }
+
+void
+panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label)
+{
+	struct panthor_gem_object *bo = to_panthor_bo(obj);
+	const char *old_label;
+
+	scoped_guard(mutex, &bo->label.lock) {
+		old_label = bo->label.str;
+		bo->label.str = label;
+	}
+
+	kfree(old_label);
+}
+
+void
+panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label)
+{
+	const char *str;
+
+	str = kstrdup_const(label, GFP_KERNEL);
+	if (!str) {
+		/* Failing to allocate memory for a label isn't a fatal condition */
+		drm_warn(bo->obj->dev, "Not enough memory to allocate BO label");
+		return;
+	}
+
+	panthor_gem_bo_set_label(bo->obj, str);
+}
diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
index 1a363bb814f4..af0d77338860 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.h
+++ b/drivers/gpu/drm/panthor/panthor_gem.h
@@ -46,6 +46,20 @@  struct panthor_gem_object {
 
 	/** @flags: Combination of drm_panthor_bo_flags flags. */
 	u32 flags;
+
+	/**
+	 * @label: BO tagging fields. The label can be assigned within the
+	 * driver itself or through a specific IOCTL.
+	 */
+	struct {
+		/**
+		 * @label.str: Pointer to NULL-terminated string,
+		 */
+		const char *str;
+
+		/** @lock.str: Protects access to the @label.str field. */
+		struct mutex lock;
+	} label;
 };
 
 /**
@@ -91,6 +105,9 @@  panthor_gem_create_with_handle(struct drm_file *file,
 			       struct panthor_vm *exclusive_vm,
 			       u64 *size, u32 flags, uint32_t *handle);
 
+void panthor_gem_bo_set_label(struct drm_gem_object *obj, const char *label);
+void panthor_gem_kernel_bo_set_label(struct panthor_kernel_bo *bo, const char *label);
+
 static inline u64
 panthor_kernel_bo_gpuva(struct panthor_kernel_bo *bo)
 {