linux-hardened/kernel/gcov/Kconfig
Arnd Bergmann cc62242079 gcov: disable for COMPILE_TEST
Enabling gcov is counterproductive to compile testing: it significantly
increases the kernel image size, compile time, and it produces lots
of false positive "may be used uninitialized" warnings as the result
of missed optimizations.

This is in line with how UBSAN_SANITIZE_ALL and PROFILE_ALL_BRANCHES
work, both of which have similar problems.

With an ARM allmodconfig kernel, I see the build time drop from
283 minutes CPU time to 225 minutes, and the vmlinux size drops
from 43MB to 26MB.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
2016-05-10 17:12:49 +02:00

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menu "GCOV-based kernel profiling"
config GCOV_KERNEL
bool "Enable gcov-based kernel profiling"
depends on DEBUG_FS
select CONSTRUCTORS if !UML
default n
---help---
This option enables gcov-based code profiling (e.g. for code coverage
measurements).
If unsure, say N.
Additionally specify CONFIG_GCOV_PROFILE_ALL=y to get profiling data
for the entire kernel. To enable profiling for specific files or
directories, add a line similar to the following to the respective
Makefile:
For a single file (e.g. main.o):
GCOV_PROFILE_main.o := y
For all files in one directory:
GCOV_PROFILE := y
To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
is specified, use:
GCOV_PROFILE_main.o := n
and:
GCOV_PROFILE := n
Note that the debugfs filesystem has to be mounted to access
profiling data.
config ARCH_HAS_GCOV_PROFILE_ALL
def_bool n
config GCOV_PROFILE_ALL
bool "Profile entire Kernel"
depends on !COMPILE_TEST
depends on GCOV_KERNEL
depends on ARCH_HAS_GCOV_PROFILE_ALL
default n
---help---
This options activates profiling for the entire kernel.
If unsure, say N.
Note that a kernel compiled with profiling flags will be significantly
larger and run slower. Also be sure to exclude files from profiling
which are not linked to the kernel image to prevent linker errors.
choice
prompt "Specify GCOV format"
depends on GCOV_KERNEL
default GCOV_FORMAT_AUTODETECT
---help---
The gcov format is usually determined by the GCC version, but there are
exceptions where format changes are integrated in lower-version GCCs.
In such a case use this option to adjust the format used in the kernel
accordingly.
If unsure, choose "Autodetect".
config GCOV_FORMAT_AUTODETECT
bool "Autodetect"
---help---
Select this option to use the format that corresponds to your GCC
version.
config GCOV_FORMAT_3_4
bool "GCC 3.4 format"
---help---
Select this option to use the format defined by GCC 3.4.
config GCOV_FORMAT_4_7
bool "GCC 4.7 format"
---help---
Select this option to use the format defined by GCC 4.7.
endchoice
endmenu