After several hours of debugging this obviously bogus but elaborate
gcc-7.0.1 warning,
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c: In function 'vchiq_complete_bulk':
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c:603:4: error: argument 2 null where non-null expected [-Werror=nonnull]
memcpy((char *)page_address(pages[0]) +
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pagelist->offset,
~~~~~~~~~~~~~~~~~
fragments,
~~~~~~~~~~
head_bytes);
~~~~~~~~~~~
In file included from include/linux/string.h:18:0,
from include/linux/bitmap.h:8,
from include/linux/cpumask.h:11,
from include/linux/interrupt.h:9,
from drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c:37:
arch/arm/include/asm/string.h:16:15: note: in a call to function 'memcpy' declared here
extern void * memcpy(void *, const void *, __kernel_size_t) __nocapture(2);
^~~~~~
I have concluded that gcc was technically right in the first place:
vchiq_complete_bulk is an externally visible function that calls
free_pagelist(), which in turn derives a pointer from the global
g_fragments_base variable.
g_fragments_base is initialized in vchiq_platform_init(), but
we only get there if of_property_read_u32() successfully reads the
cache line size. When CONFIG_OF is disabled, this always fails, and
g_fragments_base is guaranteed to be NULL when vchiq_complete_bulk()
gets called.
This adds a CONFIG_OF Kconfig dependency, which is also technically correct
but nonobvious, and thus seems like a good fit for the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
b3bd0f2849