| Message ID | 20210826123032.1732926-5-jens.wiklander@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | Asynchronous notifications from secure world | expand |
On Thu, 26 Aug 2021 at 18:00, Jens Wiklander <jens.wiklander@linaro.org> wrote: > > Adds tee_dev_open_helper() and tee_dev_ctx_put() to make it easier to > create a driver internal struct tee_context without the usual > tee_device_get() on the struct tee_device as that adds a circular > reference counter dependency and would prevent the struct tee_device > from ever being released again. Can you elaborate regarding the circular dependency issue you are referring to? IIUC, lifespan for struct tee_device would look like below with normal teedev_open(): optee_probe() { ... tee_device_alloc() <- teedev->num_users = 1 tee_device_register() optee_notif_init() <- tee_device_get() ... } optee_remove() { ... optee_notif_uninit() <- tee_device_put() tee_device_unregister() <- tee_device_put() ... } -Sumit > > Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org> > --- > drivers/tee/tee_core.c | 33 ++++++++++++++++++++++++--------- > include/linux/tee_drv.h | 27 +++++++++++++++++++++++++++ > 2 files changed, 51 insertions(+), 9 deletions(-) > > diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c > index 85102d12d716..3beb682684a8 100644 > --- a/drivers/tee/tee_core.c > +++ b/drivers/tee/tee_core.c > @@ -43,14 +43,11 @@ static DEFINE_SPINLOCK(driver_lock); > static struct class *tee_class; > static dev_t tee_devt; > > -static struct tee_context *teedev_open(struct tee_device *teedev) > +struct tee_context *tee_dev_open_helper(struct tee_device *teedev) > { > int rc; > struct tee_context *ctx; > > - if (!tee_device_get(teedev)) > - return ERR_PTR(-EINVAL); > - > ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); > if (!ctx) { > rc = -ENOMEM; > @@ -66,10 +63,30 @@ static struct tee_context *teedev_open(struct tee_device *teedev) > return ctx; > err: > kfree(ctx); > - tee_device_put(teedev); > return ERR_PTR(rc); > > } > +EXPORT_SYMBOL_GPL(tee_dev_open_helper); > + > +void tee_dev_ctx_put(struct tee_context *ctx) > +{ > + teedev_ctx_put(ctx); > +} > +EXPORT_SYMBOL_GPL(tee_dev_ctx_put); > + > +static struct tee_context *teedev_open(struct tee_device *teedev) > +{ > + struct tee_context *ctx; > + > + if (!tee_device_get(teedev)) > + return ERR_PTR(-EINVAL); > + > + ctx = tee_dev_open_helper(teedev); > + if (IS_ERR(ctx)) > + tee_device_put(teedev); > + > + return ctx; > +} > > void teedev_ctx_get(struct tee_context *ctx) > { > @@ -90,10 +107,8 @@ static void teedev_ctx_release(struct kref *ref) > > void teedev_ctx_put(struct tee_context *ctx) > { > - if (ctx->releasing) > - return; > - > - kref_put(&ctx->refcount, teedev_ctx_release); > + if (ctx && !ctx->releasing) > + kref_put(&ctx->refcount, teedev_ctx_release); > } > > static void teedev_close_context(struct tee_context *ctx) > diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h > index 3ebfea0781f1..00a31ff03049 100644 > --- a/include/linux/tee_drv.h > +++ b/include/linux/tee_drv.h > @@ -458,6 +458,33 @@ static inline int tee_shm_get_id(struct tee_shm *shm) > */ > struct tee_shm *tee_shm_get_from_id(struct tee_context *ctx, int id); > > +/** > + * tee_dev_open_helper() - helper function to make a struct tee_context > + * @teedev: Device to open > + * > + * Creates the struct tee_context without increasing the reference counter > + * on @teedev. This is needed for instance when a driver need an internal > + * struct tee_context to operate on. By skipping the reference counter > + * the circular dependency is broken. > + * > + * Note that this struct tee_context need special care when freeing in > + * order to avoid the normal put on the struct tee_device. > + * tee_dev_ctx_put() is the best choice for this. > + * > + * @returns a pointer 'struct tee_context' on success or an ERR_PTR on failure > + */ > +struct tee_context *tee_dev_open_helper(struct tee_device *teedev); > + > +/** > + * tee_dev_ctx_put() - helper function to release a struct tee_context > + * @ctx: The struct tee_context to release > + * > + * Note that this function doesn't do a tee_device_put() on the internal > + * struct tee_device so this function should normal only be used when > + * releasing a struct tee_context obtained with tee_dev_open_helper(). > + */ > +void tee_dev_ctx_put(struct tee_context *ctx); > + > /** > * tee_client_open_context() - Open a TEE context > * @start: if not NULL, continue search after this context > -- > 2.31.1 >
On Fri, Aug 27, 2021 at 8:23 AM Sumit Garg <sumit.garg@linaro.org> wrote: > > On Thu, 26 Aug 2021 at 18:00, Jens Wiklander <jens.wiklander@linaro.org> wrote: > > > > Adds tee_dev_open_helper() and tee_dev_ctx_put() to make it easier to > > create a driver internal struct tee_context without the usual > > tee_device_get() on the struct tee_device as that adds a circular > > reference counter dependency and would prevent the struct tee_device > > from ever being released again. > > Can you elaborate regarding the circular dependency issue you are > referring to? IIUC, lifespan for struct tee_device would look like > below with normal teedev_open(): > > optee_probe() { > ... > tee_device_alloc() <- teedev->num_users = 1 > tee_device_register() > optee_notif_init() <- tee_device_get() > ... > } > > optee_remove() { > ... > optee_notif_uninit() <- tee_device_put() > tee_device_unregister() <- tee_device_put() > ... > } You're right, it works just as well without this patch. teedev_close_context() and teedev_open() must be exported in another patch though. I'll replace this patch with such a patch in the next patch set. Thanks, Jens > > -Sumit > > > > > Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org> > > --- > > drivers/tee/tee_core.c | 33 ++++++++++++++++++++++++--------- > > include/linux/tee_drv.h | 27 +++++++++++++++++++++++++++ > > 2 files changed, 51 insertions(+), 9 deletions(-) > > > > diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c > > index 85102d12d716..3beb682684a8 100644 > > --- a/drivers/tee/tee_core.c > > +++ b/drivers/tee/tee_core.c > > @@ -43,14 +43,11 @@ static DEFINE_SPINLOCK(driver_lock); > > static struct class *tee_class; > > static dev_t tee_devt; > > > > -static struct tee_context *teedev_open(struct tee_device *teedev) > > +struct tee_context *tee_dev_open_helper(struct tee_device *teedev) > > { > > int rc; > > struct tee_context *ctx; > > > > - if (!tee_device_get(teedev)) > > - return ERR_PTR(-EINVAL); > > - > > ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); > > if (!ctx) { > > rc = -ENOMEM; > > @@ -66,10 +63,30 @@ static struct tee_context *teedev_open(struct tee_device *teedev) > > return ctx; > > err: > > kfree(ctx); > > - tee_device_put(teedev); > > return ERR_PTR(rc); > > > > } > > +EXPORT_SYMBOL_GPL(tee_dev_open_helper); > > + > > +void tee_dev_ctx_put(struct tee_context *ctx) > > +{ > > + teedev_ctx_put(ctx); > > +} > > +EXPORT_SYMBOL_GPL(tee_dev_ctx_put); > > + > > +static struct tee_context *teedev_open(struct tee_device *teedev) > > +{ > > + struct tee_context *ctx; > > + > > + if (!tee_device_get(teedev)) > > + return ERR_PTR(-EINVAL); > > + > > + ctx = tee_dev_open_helper(teedev); > > + if (IS_ERR(ctx)) > > + tee_device_put(teedev); > > + > > + return ctx; > > +} > > > > void teedev_ctx_get(struct tee_context *ctx) > > { > > @@ -90,10 +107,8 @@ static void teedev_ctx_release(struct kref *ref) > > > > void teedev_ctx_put(struct tee_context *ctx) > > { > > - if (ctx->releasing) > > - return; > > - > > - kref_put(&ctx->refcount, teedev_ctx_release); > > + if (ctx && !ctx->releasing) > > + kref_put(&ctx->refcount, teedev_ctx_release); > > } > > > > static void teedev_close_context(struct tee_context *ctx) > > diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h > > index 3ebfea0781f1..00a31ff03049 100644 > > --- a/include/linux/tee_drv.h > > +++ b/include/linux/tee_drv.h > > @@ -458,6 +458,33 @@ static inline int tee_shm_get_id(struct tee_shm *shm) > > */ > > struct tee_shm *tee_shm_get_from_id(struct tee_context *ctx, int id); > > > > +/** > > + * tee_dev_open_helper() - helper function to make a struct tee_context > > + * @teedev: Device to open > > + * > > + * Creates the struct tee_context without increasing the reference counter > > + * on @teedev. This is needed for instance when a driver need an internal > > + * struct tee_context to operate on. By skipping the reference counter > > + * the circular dependency is broken. > > + * > > + * Note that this struct tee_context need special care when freeing in > > + * order to avoid the normal put on the struct tee_device. > > + * tee_dev_ctx_put() is the best choice for this. > > + * > > + * @returns a pointer 'struct tee_context' on success or an ERR_PTR on failure > > + */ > > +struct tee_context *tee_dev_open_helper(struct tee_device *teedev); > > + > > +/** > > + * tee_dev_ctx_put() - helper function to release a struct tee_context > > + * @ctx: The struct tee_context to release > > + * > > + * Note that this function doesn't do a tee_device_put() on the internal > > + * struct tee_device so this function should normal only be used when > > + * releasing a struct tee_context obtained with tee_dev_open_helper(). > > + */ > > +void tee_dev_ctx_put(struct tee_context *ctx); > > + > > /** > > * tee_client_open_context() - Open a TEE context > > * @start: if not NULL, continue search after this context > > -- > > 2.31.1 > >
diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c index 85102d12d716..3beb682684a8 100644 --- a/drivers/tee/tee_core.c +++ b/drivers/tee/tee_core.c @@ -43,14 +43,11 @@ static DEFINE_SPINLOCK(driver_lock); static struct class *tee_class; static dev_t tee_devt; -static struct tee_context *teedev_open(struct tee_device *teedev) +struct tee_context *tee_dev_open_helper(struct tee_device *teedev) { int rc; struct tee_context *ctx; - if (!tee_device_get(teedev)) - return ERR_PTR(-EINVAL); - ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); if (!ctx) { rc = -ENOMEM; @@ -66,10 +63,30 @@ static struct tee_context *teedev_open(struct tee_device *teedev) return ctx; err: kfree(ctx); - tee_device_put(teedev); return ERR_PTR(rc); } +EXPORT_SYMBOL_GPL(tee_dev_open_helper); + +void tee_dev_ctx_put(struct tee_context *ctx) +{ + teedev_ctx_put(ctx); +} +EXPORT_SYMBOL_GPL(tee_dev_ctx_put); + +static struct tee_context *teedev_open(struct tee_device *teedev) +{ + struct tee_context *ctx; + + if (!tee_device_get(teedev)) + return ERR_PTR(-EINVAL); + + ctx = tee_dev_open_helper(teedev); + if (IS_ERR(ctx)) + tee_device_put(teedev); + + return ctx; +} void teedev_ctx_get(struct tee_context *ctx) { @@ -90,10 +107,8 @@ static void teedev_ctx_release(struct kref *ref) void teedev_ctx_put(struct tee_context *ctx) { - if (ctx->releasing) - return; - - kref_put(&ctx->refcount, teedev_ctx_release); + if (ctx && !ctx->releasing) + kref_put(&ctx->refcount, teedev_ctx_release); } static void teedev_close_context(struct tee_context *ctx) diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h index 3ebfea0781f1..00a31ff03049 100644 --- a/include/linux/tee_drv.h +++ b/include/linux/tee_drv.h @@ -458,6 +458,33 @@ static inline int tee_shm_get_id(struct tee_shm *shm) */ struct tee_shm *tee_shm_get_from_id(struct tee_context *ctx, int id); +/** + * tee_dev_open_helper() - helper function to make a struct tee_context + * @teedev: Device to open + * + * Creates the struct tee_context without increasing the reference counter + * on @teedev. This is needed for instance when a driver need an internal + * struct tee_context to operate on. By skipping the reference counter + * the circular dependency is broken. + * + * Note that this struct tee_context need special care when freeing in + * order to avoid the normal put on the struct tee_device. + * tee_dev_ctx_put() is the best choice for this. + * + * @returns a pointer 'struct tee_context' on success or an ERR_PTR on failure + */ +struct tee_context *tee_dev_open_helper(struct tee_device *teedev); + +/** + * tee_dev_ctx_put() - helper function to release a struct tee_context + * @ctx: The struct tee_context to release + * + * Note that this function doesn't do a tee_device_put() on the internal + * struct tee_device so this function should normal only be used when + * releasing a struct tee_context obtained with tee_dev_open_helper(). + */ +void tee_dev_ctx_put(struct tee_context *ctx); + /** * tee_client_open_context() - Open a TEE context * @start: if not NULL, continue search after this context
Adds tee_dev_open_helper() and tee_dev_ctx_put() to make it easier to create a driver internal struct tee_context without the usual tee_device_get() on the struct tee_device as that adds a circular reference counter dependency and would prevent the struct tee_device from ever being released again. Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org> --- drivers/tee/tee_core.c | 33 ++++++++++++++++++++++++--------- include/linux/tee_drv.h | 27 +++++++++++++++++++++++++++ 2 files changed, 51 insertions(+), 9 deletions(-)