From: Joe Stringer <joe@ovn.org>
To: linux-kernel@vger.kernel.org
Cc: Ian Abbott <abbotti@mev.co.uk>, Arnd Bergmann <arnd@arndb.de>,
Michal Nazarewicz <mina86@mina86.com>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] compiler: Don't perform compiletime_assert with -O0.
Date: Tue, 29 Aug 2017 16:01:14 -0700
Message-ID: <20170829230114.11662-1-joe@ovn.org> (raw)
Recent changes[0] to make use of __compiletime_assert() from
container_of() increased the usage of this macro, allowing developers to
notice type conflicts in usage of container_of() at compile time.
However, the implementation of __compiletime_assert relies on compiler
optimizations to report an error. This means that if a developer uses
"-O0" with any code that performs container_of(), the compiler will
always report an error regardless of whether there is an actual problem
in the code.
This patch disables compile_time_assert when optimizations are disabled
to allow such code to compile with CFLAGS="-O0".
Example compilation failure:
./include/linux/compiler.h:547:38: error: call to ‘__compiletime_assert_94’ declared with attribute error: pointer type mismatch in container_of()
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
./include/linux/compiler.h:530:4: note: in definition of macro ‘__compiletime_assert’
prefix ## suffix(); \
^~~~~~
./include/linux/compiler.h:547:2: note: in expansion of macro ‘_compiletime_assert’
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:46:37: note: in expansion of macro ‘compiletime_assert’
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
./include/linux/kernel.h:860:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^~~~~~~~~~~~~~~~
[0] http://lkml.kernel.org/r/20170525120316.24473-7-abbotti@mev.co.uk
Signed-off-by: Joe Stringer <joe@ovn.org>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
include/linux/compiler.h | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index eca8ad75e28b..b67e5ec9b810 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -517,7 +517,8 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
# define __compiletime_error_fallback(condition) do { } while (0)
#endif
-#define __compiletime_assert(condition, msg, prefix, suffix) \
+#ifdef __OPTIMIZE__
+# define __compiletime_assert(condition, msg, prefix, suffix) \
do { \
bool __cond = !(condition); \
extern void prefix ## suffix(void) __compiletime_error(msg); \
@@ -525,6 +526,9 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
prefix ## suffix(); \
__compiletime_error_fallback(__cond); \
} while (0)
+#else
+# define __compiletime_assert(condition, msg, prefix, suffix)
+#endif
#define _compiletime_assert(condition, msg, prefix, suffix) \
__compiletime_assert(condition, msg, prefix, suffix)
--
2.14.1
next reply index
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-29 23:01 Joe Stringer [this message]
2017-08-30 10:26 ` Michal Nazarewicz
2017-08-30 18:03 ` Joe Stringer
2017-08-30 22:59 ` Andrew Morton
2017-08-30 23:22 ` Joe Stringer
2017-08-31 2:16 ` Michael Ellerman
2017-08-31 6:52 ` Joe Stringer
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170829230114.11662-1-joe@ovn.org \
--to=joe@ovn.org \
--cc=abbotti@mev.co.uk \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mina86@mina86.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
LKML Archive on lore.kernel.org
Archives are clonable:
git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git
git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git
git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git
git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git
git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git
git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git
git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git
git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git
git clone --mirror https://lore.kernel.org/lkml/8 lkml/git/8.git
git clone --mirror https://lore.kernel.org/lkml/9 lkml/git/9.git
# If you have public-inbox 1.1+ installed, you may
# initialize and index your mirror using the following commands:
public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \
linux-kernel@vger.kernel.org
public-inbox-index lkml
Example config snippet for mirrors
Newsgroup available over NNTP:
nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel
AGPL code for this site: git clone https://public-inbox.org/public-inbox.git