As its name suggest this option prevents gcc from auto inlining
small functions. This is very important if one wants to obtain
traces with accurate call sites.

Without this option, gcc will collapse some small functions,
even when not marked as 'inline' thus making impossible to
correlate the trace caller address to the real function it belongs.

Of course, the resultant kernel is slower and slightly smaller,
but that's not an issue if the focus is on tracing accuracy.

Cc: Michal Marek <redacted>
Signed-off-by: Ezequiel Garcia <redacted>
---
 Makefile          |    4 ++++
 lib/Kconfig.debug |   11 +++++++++++
 2 files changed, 15 insertions(+), 0 deletions(-)

diff --git a/Makefile b/Makefile
index ddf5be9..df6045a 100644
--- a/Makefile
+++ b/Makefile

@@ -561,6 +561,10 @@ else
 KBUILD_CFLAGS	+= -O2
 endif
 
+ifdef CONFIG_DISABLE_GCC_AUTOMATIC_INLINING
+KBUILD_CFLAGS	+= -fno-inline-small-functions
+endif
+
 include $(srctree)/arch/$(SRCARCH)/Makefile
 
 ifdef CONFIG_READABLE_ASM

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2403a63..c8fd50f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug

@@ -1265,6 +1265,17 @@ config LATENCYTOP
 source mm/Kconfig.debug
 source kernel/trace/Kconfig
 
+config DISABLE_GCC_AUTOMATIC_INLINING
+	bool "Disable gcc automatic inlining"