linux/include
Richard Fitzgerald fcbac39b7d kunit: Allow passing function pointer to kunit_activate_static_stub()
Swap the arguments to typecheck_fn() in kunit_activate_static_stub()
so that real_fn_addr can be either the function itself or a pointer
to that function.

This is useful to simplify redirecting static functions in a module.
Having to pass the actual function meant that it must be exported
from the module. Either making the 'static' and EXPORT_SYMBOL*()
conditional (which makes the code messy), or change it to always
exported (which increases the export namespace and prevents the
compiler inlining a trivial stub function in non-test builds).

With the original definition of kunit_activate_static_stub() the
address of real_fn_addr was passed to typecheck_fn() as the type to
be passed. This meant that if real_fn_addr was a pointer-to-function
it would resolve to a ** instead of a *, giving an error like this:

   error: initialization of ‘int (**)(int)’ from incompatible pointer
   type ‘int (*)(int)’ [-Werror=incompatible-pointer-types]
   kunit_activate_static_stub(test, add_one_fn_ptr, subtract_one);
      |                             ^~~~~~~~~~~~
   ./include/linux/typecheck.h:21:25: note: in definition of macro
   ‘typecheck_fn’
   21 | ({ typeof(type) __tmp = function; \

Swapping the arguments to typecheck_fn makes it take the type of a
pointer to the replacement function. Either a function or a pointer
to function can be assigned to that. For example:

static int some_function(int x)
{
    /* whatever */
}

int (* some_function_ptr)(int) = some_function;

static int replacement(int x)
{
    /* whatever */
}

Then:
  kunit_activate_static_stub(test, some_function, replacement);
yields:
  typecheck_fn(typeof(&replacement), some_function);

and:
  kunit_activate_static_stub(test, some_function_ptr, replacement);
yields:
  typecheck_fn(typeof(&replacement), some_function_ptr);

The two typecheck_fn() then resolve to:

  int (*__tmp)(int) = some_function;
and
  int (*__tmp)(int) = some_function_ptr;

Both of these are valid. In the first case the compiler inserts
an implicit '&' to take the address of the supplied function, and
in the second case the RHS is already a pointer to the same type.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
2024-01-03 09:06:52 -07:00
..
acpi ACPI: PM: Add acpi_device_fix_up_power_children() function 2023-11-20 17:31:49 +01:00
asm-generic kunit: add KUNIT_INIT_TABLE to init linker section 2023-12-18 13:21:15 -07:00
clocksource
crypto
drm Merge tag 'drm-misc-fixes-2023-12-07' of git://anongit.freedesktop.org/drm/drm-misc into drm-fixes 2023-12-08 12:16:11 +10:00
dt-bindings linux-watchdog 6.7-rc1 tag 2023-11-09 13:54:25 -08:00
keys
kunit kunit: Allow passing function pointer to kunit_activate_static_stub() 2024-01-03 09:06:52 -07:00
kvm
linux kunit: add KUNIT_INIT_TABLE to init linker section 2023-12-18 13:21:15 -07:00
math-emu
media
memory
misc
net net/sched: act_ct: Take per-cb reference to tcf_ct_flow_table 2023-12-11 09:59:58 +00:00
pcmcia
ras
rdma RDMA/core: Fix umem iterator when PAGE_SIZE is greater then HCA pgsz 2023-12-04 20:02:41 -04:00
rv
scsi scsi: sd: Fix system start for ATA devices 2023-11-24 20:44:21 -05:00
soc IOMMU Updates for Linux v6.7 2023-11-09 13:37:28 -08:00
sound ALSA: cs35l41: Fix for old systems which do not support command 2023-11-20 12:37:01 +01:00
target
trace rxrpc: Fix RTT determination to use any ACK as a source 2023-11-17 02:50:33 +00:00
uapi fuse: Rename DIRECT_IO_RELAX to DIRECT_IO_ALLOW_MMAP 2023-12-04 10:14:39 +01:00
ufs
vdso
video
xen xen/events: reduce externally visible helper functions 2023-11-14 09:29:28 +01:00