2019-05-07 14:29:35

by Vasily Gorbik

Subject: [PATCH] latent_entropy: avoid build error when plugin cflags are not set

Some architectures set up CFLAGS for linux decompressor phase from
scratch and do not include GCC_PLUGINS_CFLAGS. Since "latent_entropy"
variable declaration is generated by the plugin code itself including
linux/random.h in decompressor code then would cause a build
error. E.g. on s390:

In file included from ./include/linux/net.h:22,
from ./include/linux/skbuff.h:29,
from ./include/linux/if_ether.h:23,
from ./arch/s390/include/asm/diag.h:12,
from arch/s390/boot/startup.c:8:
./include/linux/random.h: In function 'add_latent_entropy':
./include/linux/random.h:26:39: error: 'latent_entropy' undeclared
(first use in this function); did you mean 'add_latent_entropy'?
26 | add_device_randomness((const void *)&latent_entropy,
| ^~~~~~~~~~~~~~
| add_latent_entropy
./include/linux/random.h:26:39: note: each undeclared identifier is
reported only once for each function it appears in

The build error is triggered by commit a80313ff91ab ("s390/kernel:
introduce .dma sections") which made it into 5.2 merge window.

To address that avoid using CONFIG_GCC_PLUGIN_LATENT_ENTROPY in
favour of LATENT_ENTROPY_PLUGIN definition which is defined as a
part of gcc plugins cflags and hence reflect more accurately when gcc
plugin is active. Besides that it is also used for similar purpose in
linux/compiler-gcc.h for latent_entropy attribute definition.

Signed-off-by: Vasily Gorbik <[email protected]>
---
include/linux/random.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/random.h b/include/linux/random.h
index 445a0ea4ff49..d4eb9b3789ad 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -20,7 +20,7 @@ struct random_ready_callback {

extern void add_device_randomness(const void *, unsigned int);

-#if defined(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) && !defined(__CHECKER__)
+#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
static inline void add_latent_entropy(void)
{
add_device_randomness((const void *)&latent_entropy,
--
2.18.0.13.gd42ae10

2019-05-07 16:18:51

by Kees Cook

Subject: Re: [PATCH] latent_entropy: avoid build error when plugin cflags are not set

On Tue, May 7, 2019 at 7:28 AM Vasily Gorbik <[email protected]> wrote:
> Some architectures set up CFLAGS for linux decompressor phase from
> scratch and do not include GCC_PLUGINS_CFLAGS. Since "latent_entropy"
> variable declaration is generated by the plugin code itself including
> linux/random.h in decompressor code then would cause a build
> error. E.g. on s390:
>
> In file included from ./include/linux/net.h:22,
> from ./include/linux/skbuff.h:29,
> from ./include/linux/if_ether.h:23,
> from ./arch/s390/include/asm/diag.h:12,
> from arch/s390/boot/startup.c:8:
> ./include/linux/random.h: In function 'add_latent_entropy':
> ./include/linux/random.h:26:39: error: 'latent_entropy' undeclared
> (first use in this function); did you mean 'add_latent_entropy'?
> 26 | add_device_randomness((const void *)&latent_entropy,
> | ^~~~~~~~~~~~~~
> | add_latent_entropy
> ./include/linux/random.h:26:39: note: each undeclared identifier is
> reported only once for each function it appears in
>
> The build error is triggered by commit a80313ff91ab ("s390/kernel:
> introduce .dma sections") which made it into 5.2 merge window.
>
> To address that avoid using CONFIG_GCC_PLUGIN_LATENT_ENTROPY in
> favour of LATENT_ENTROPY_PLUGIN definition which is defined as a
> part of gcc plugins cflags and hence reflect more accurately when gcc
> plugin is active. Besides that it is also used for similar purpose in
> linux/compiler-gcc.h for latent_entropy attribute definition.
>
> Signed-off-by: Vasily Gorbik <[email protected]>

Thanks for fixing this! Do you want to take it via the s390 tree?

Acked-by: Kees Cook <[email protected]>

-Kees

> ---
> include/linux/random.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/random.h b/include/linux/random.h
> index 445a0ea4ff49..d4eb9b3789ad 100644
> --- a/include/linux/random.h
> +++ b/include/linux/random.h
> @@ -20,7 +20,7 @@ struct random_ready_callback {
>
> extern void add_device_randomness(const void *, unsigned int);
>
> -#if defined(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) && !defined(__CHECKER__)
> +#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
> static inline void add_latent_entropy(void)
> {
> add_device_randomness((const void *)&latent_entropy,
> --
> 2.18.0.13.gd42ae10
>


--
Kees Cook

2019-05-08 06:37:04

by Martin Schwidefsky

Subject: Re: [PATCH] latent_entropy: avoid build error when plugin cflags are not set

On Tue, 7 May 2019 09:16:29 -0700
Kees Cook <[email protected]> wrote:

> On Tue, May 7, 2019 at 7:28 AM Vasily Gorbik <[email protected]> wrote:
> > Some architectures set up CFLAGS for linux decompressor phase from
> > scratch and do not include GCC_PLUGINS_CFLAGS. Since "latent_entropy"
> > variable declaration is generated by the plugin code itself including
> > linux/random.h in decompressor code then would cause a build
> > error. E.g. on s390:
> >
> > In file included from ./include/linux/net.h:22,
> > from ./include/linux/skbuff.h:29,
> > from ./include/linux/if_ether.h:23,
> > from ./arch/s390/include/asm/diag.h:12,
> > from arch/s390/boot/startup.c:8:
> > ./include/linux/random.h: In function 'add_latent_entropy':
> > ./include/linux/random.h:26:39: error: 'latent_entropy' undeclared
> > (first use in this function); did you mean 'add_latent_entropy'?
> > 26 | add_device_randomness((const void *)&latent_entropy,
> > | ^~~~~~~~~~~~~~
> > | add_latent_entropy
> > ./include/linux/random.h:26:39: note: each undeclared identifier is
> > reported only once for each function it appears in
> >
> > The build error is triggered by commit a80313ff91ab ("s390/kernel:
> > introduce .dma sections") which made it into 5.2 merge window.
> >
> > To address that avoid using CONFIG_GCC_PLUGIN_LATENT_ENTROPY in
> > favour of LATENT_ENTROPY_PLUGIN definition which is defined as a
> > part of gcc plugins cflags and hence reflect more accurately when gcc
> > plugin is active. Besides that it is also used for similar purpose in
> > linux/compiler-gcc.h for latent_entropy attribute definition.
> >
> > Signed-off-by: Vasily Gorbik <[email protected]>
>
> Thanks for fixing this! Do you want to take it via the s390 tree?
>
> Acked-by: Kees Cook <[email protected]>

Sure, I can take it via the s390 tree.

> > ---
> > include/linux/random.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/random.h b/include/linux/random.h
> > index 445a0ea4ff49..d4eb9b3789ad 100644
> > --- a/include/linux/random.h
> > +++ b/include/linux/random.h
> > @@ -20,7 +20,7 @@ struct random_ready_callback {
> >
> > extern void add_device_randomness(const void *, unsigned int);
> >
> > -#if defined(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) && !defined(__CHECKER__)
> > +#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
> > static inline void add_latent_entropy(void)
> > {
> > add_device_randomness((const void *)&latent_entropy,
> > --
> > 2.18.0.13.gd42ae10
> >
>
>


--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.