[PATCH 5.4 346/389] gcc-plugins: Undefine LATENT_ENTROPY_PLUGIN when plugin disabled for a file

Greg Kroah-Hartman
2022-08-23T11:59:26Z

From: Andrew Donnellan <ajd@linux.ibm.com>

commit 012e8d2034f1bda8863435cd589636e618d6a659 upstream.

Commit 36d4b36b6959 ("lib/nodemask: inline next_node_in() and
node_random()") refactored some code by moving node_random() from
lib/nodemask.c to include/linux/nodemask.h, thus requiring nodemask.h to
include random.h, which conditionally defines add_latent_entropy()
depending on whether the macro LATENT_ENTROPY_PLUGIN is defined.

This broke the build on powerpc, where nodemask.h is indirectly included
in arch/powerpc/kernel/prom_init.c, part of the early boot machinery that
is excluded from the latent entropy plugin using
DISABLE_LATENT_ENTROPY_PLUGIN. It turns out that while we add a gcc flag
to disable the actual plugin, we don't undefine LATENT_ENTROPY_PLUGIN.

This leads to the following:

CC arch/powerpc/kernel/prom_init.o
In file included from ./include/linux/nodemask.h:97,
from ./include/linux/mmzone.h:17,
from ./include/linux/gfp.h:7,
from ./include/linux/xarray.h:15,
from ./include/linux/radix-tree.h:21,
from ./include/linux/idr.h:15,
from ./include/linux/kernfs.h:12,
from ./include/linux/sysfs.h:16,
from ./include/linux/kobject.h:20,
from ./include/linux/pci.h:35,
from arch/powerpc/kernel/prom_init.c:24:
./include/linux/random.h: In function 'add_latent_entropy':
./include/linux/random.h:25:46: error: 'latent_entropy' undeclared (first use in this function); did you mean 'add_latent_entropy'?
25 | add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy));
| ^~~~~~~~~~~~~~
| add_latent_entropy
./include/linux/random.h:25:46: note: each undeclared identifier is reported only once for each function it appears in
make[2]: *** [scripts/Makefile.build:249: arch/powerpc/kernel/prom_init.o] Fehler 1
make[1]: *** [scripts/Makefile.build:465: arch/powerpc/kernel] Fehler 2
make: *** [Makefile:1855: arch/powerpc] Error 2

Change the DISABLE_LATENT_ENTROPY_PLUGIN flags to undefine
LATENT_ENTROPY_PLUGIN for files where the plugin is disabled.

Cc: Yury Norov <yury.norov@gmail.com>
Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216367
Link: https://lore.kernel.org/linuxppc-dev/alpine.DEB.2.22.394.2208152006320.289321@ramsan.of.borg/
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220816051720.44108-1-ajd@linux.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
scripts/Makefile.gcc-plugins | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -6,7 +6,7 @@ gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_EN
gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) \
+= -DLATENT_ENTROPY_PLUGIN
ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
- DISABLE_LATENT_ENTROPY_PLUGIN += -fplugin-arg-latent_entropy_plugin-disable
+ DISABLE_LATENT_ENTROPY_PLUGIN += -fplugin-arg-latent_entropy_plugin-disable -ULATENT_ENTROPY_PLUGIN
endif
export DISABLE_LATENT_ENTROPY_PLUGIN