treewide: refresh kmalloc_obj() conversionsgrafted

This is another run of the Coccinelle script for converting kmalloc()
family of allocations to kmalloc_obj() via the existing rules in
scripts/coccinelle/api/kmalloc_objs.cocci

This catches both the set of kmalloc() uses added since the first
kmalloc_obj() conversions in v7.0 and adds a large group missed in the
first pass due to Coccinelle not interacting well with the cleanup.h
scoped_...() family of macros[1]. I worked around this with spatch's
"--macro-file" argument to a file with all the scoped_...() macros mapped
to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control
flow indicator I could find.

Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc,
riscv, and s390 with no new warnings.

Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1]
Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2]
Signed-off-by: Kees Cook <kees+treewide@kernel.org>

1 files changed, 116 insertions, 0 deletions

diff --git a/Documentation/driver-api/driver-model/design-patterns.rst b/Documentation/driver-api/driver-model/design-patterns.rst
new file mode 100644
index 000000000..965b2b93b
--- /dev/null
+++ b/Documentation/driver-api/driver-model/design-patterns.rst
@@ -0,0 +1,116 @@
+=============================
+Device Driver Design Patterns
+=============================
+
+This document describes a few common design patterns found in device drivers.
+It is likely that subsystem maintainers will ask driver developers to
+conform to these design patterns.
+
+1. State Container
+2. container_of()
+
+
+1. State Container
+~~~~~~~~~~~~~~~~~~
+
+While the kernel contains a few device drivers that assume that they will
+only be probed() once on a certain system (singletons), it is custom to assume
+that the device the driver binds to will appear in several instances. This
+means that the probe() function and all callbacks need to be reentrant.
+
+The most common way to achieve this is to use the state container design
+pattern. It usually has this form::
+
+  struct foo {
+      spinlock_t lock; /* Example member */
+      (...)
+  };
+
+  static int foo_probe(...)
+  {
+      struct foo *foo;
+
+      foo = devm_kzalloc(dev, sizeof(*foo), GFP_KERNEL);
+      if (!foo)
+          return -ENOMEM;
+      spin_lock_init(&foo->lock);
+      (...)
+  }
+
+This will create an instance of struct foo in memory every time probe() is
+called. This is our state container for this instance of the device driver.
+Of course it is then necessary to always pass this instance of the
+state around to all functions that need access to the state and its members.
+
+For example, if the driver is registering an interrupt handler, you would
+pass around a pointer to struct foo like this::
+
+  static irqreturn_t foo_handler(int irq, void *arg)
+  {
+      struct foo *foo = arg;
+      (...)
+  }
+
+  static int foo_probe(...)
+  {
+      struct foo *foo;
+
+      (...)
+      ret = request_irq(irq, foo_handler, 0, "foo", foo);
+  }
+
+This way you always get a pointer back to the correct instance of foo in
+your interrupt handler.
+
+
+2. container_of()
+~~~~~~~~~~~~~~~~~
+
+Continuing on the above example we add an offloaded work::
+
+  struct foo {
+      spinlock_t lock;
+      struct workqueue_struct *wq;
+      struct work_struct offload;
+      (...)
+  };
+
+  static void foo_work(struct work_struct *work)
+  {
+      struct foo *foo = container_of(work, struct foo, offload);
+
+      (...)
+  }
+
+  static irqreturn_t foo_handler(int irq, void *arg)
+  {
+      struct foo *foo = arg;
+
+      queue_work(foo->wq, &foo->offload);
+      (...)
+  }
+
+  static int foo_probe(...)
+  {
+      struct foo *foo;
+
+      foo->wq = create_singlethread_workqueue("foo-wq");
+      INIT_WORK(&foo->offload, foo_work);
+      (...)
+  }
+
+The design pattern is the same for an hrtimer or something similar that will
+return a single argument which is a pointer to a struct member in the
+callback.
+
+container_of() is a macro defined in <linux/container_of.h>
+
+What container_of() does is to obtain a pointer to the containing struct from
+a pointer to a member by a simple subtraction using the offsetof() macro from
+standard C, which allows something similar to object oriented behaviours.
+Notice that the contained member must not be a pointer, but an actual member
+for this to work.
+
+We can see here that we avoid having global pointers to our struct foo *
+instance this way, while still keeping the number of parameters passed to the
+work function to a single pointer.