From dbacb0ef670d057a2c52c0e1e642bab727f6b4cb Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Tue, 26 Jan 2016 21:51:05 -0500 Subject: kconfig option for TRIM_UNUSED_KSYMS The config option to enable it all. Signed-off-by: Nicolas Pitre Acked-by: Rusty Russell --- init/Kconfig | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index e0d26162432e..29d74d3f8044 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2012,6 +2012,22 @@ config MODULE_COMPRESS_XZ endchoice +config TRIM_UNUSED_KSYMS + bool "Trim unused exported kernel symbols" + depends on MODULES && !UNUSED_SYMBOLS + help + The kernel and some modules make many symbols available for + other modules to use via EXPORT_SYMBOL() and variants. Depending + on the set of modules being selected in your kernel configuration, + many of those exported symbols might never be used. + + This option allows for unused exported symbols to be dropped from + the build. In turn, this provides the compiler more opportunities + (especially when using LTO) for optimizing the code and reducing + binary size. This might have some security advantages as well. + + If unsure say N. + endif # MODULES config MODULES_TREE_LOOKUP -- cgit v1.2.3 From 877417e6ffb9578e8580abf76a71e15732473456 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Mon, 25 Apr 2016 17:35:27 +0200 Subject: Kbuild: change CC_OPTIMIZE_FOR_SIZE definition CC_OPTIMIZE_FOR_SIZE disables the often useful -Wmaybe-unused warning, because that causes a ridiculous amount of false positives when combined with -Os. This means a lot of warnings don't show up in testing by the developers that should see them with an 'allmodconfig' kernel that has CC_OPTIMIZE_FOR_SIZE enabled, but only later in randconfig builds that don't. This changes the Kconfig logic around CC_OPTIMIZE_FOR_SIZE to make it a 'choice' statement defaulting to CC_OPTIMIZE_FOR_PERFORMANCE that gets added for this purpose. The allmodconfig and allyesconfig kernels now default to -O2 with the maybe-unused warning enabled. Signed-off-by: Arnd Bergmann Signed-off-by: Michal Marek --- init/Kconfig | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index 29d74d3f8044..f224dae6e37d 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1283,6 +1283,17 @@ source "usr/Kconfig" endif +choice + prompt "Compiler optimization level" + default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE + +config CC_OPTIMIZE_FOR_PERFORMANCE + bool "Optimize for performance" + help + This is the default optimization level for the kernel, building + with the "-O2" compiler flag for best performance and most + helpful compile-time warnings. + config CC_OPTIMIZE_FOR_SIZE bool "Optimize for size" help @@ -1291,6 +1302,8 @@ config CC_OPTIMIZE_FOR_SIZE If unsure, say N. +endchoice + config SYSCTL bool -- cgit v1.2.3