summaryrefslogtreecommitdiff
path: root/arch/x86/Kconfig
diff options
context:
space:
mode:
authorSteven Rostedt (VMware) <rostedt@goodmis.org>2019-05-10 12:05:46 -0400
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2019-05-10 12:33:03 -0400
commit518049d9d3e25dcd7be6e3d728e86f292ad0c922 (patch)
treefdc458e59447517e471a9113d8f32f11cb4d4a8d /arch/x86/Kconfig
parenta15fd609ad53a631a927c6680e8fb606f42a712b (diff)
ftrace/x86_32: Remove support for non DYNAMIC_FTRACE
When DYNAMIC_FTRACE is enabled in the kernel, all the functions that can be traced by the function tracer have a "nop" placeholder at the start of the function. When function tracing is enabled, the nop is converted into a call to the tracing infrastructure where the functions get traced. This also allows for specifying specific functions to trace, and a lot of infrastructure is built on top of this. When DYNAMIC_FTRACE is not enabled, all the functions have a call to the ftrace trampoline. A check is made to see if a function pointer is the ftrace_stub or not, and if it is not, it calls the function pointer to trace the code. This adds over 10% overhead to the kernel even when tracing is disabled. When an architecture supports DYNAMIC_FTRACE there really is no reason to use the static tracing. I have kept non DYNAMIC_FTRACE available in x86 so that the generic code for non DYNAMIC_FTRACE can be tested. There is no reason to support non DYNAMIC_FTRACE for both x86_64 and x86_32. As the non DYNAMIC_FTRACE for x86_32 does not even support fentry, and we want to remove mcount completely, there's no reason to keep non DYNAMIC_FTRACE around for x86_32. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/Kconfig')
-rw-r--r--arch/x86/Kconfig11
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5ad92419be19..0544041ae3a2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -31,6 +31,17 @@ config X86_64
select X86_DEV_DMA_OPS
select ARCH_HAS_SYSCALL_WRAPPER
+config FORCE_DYNAMIC_FTRACE
+ def_bool y
+ depends on X86_32
+ depends on FUNCTION_TRACER
+ select DYNAMIC_FTRACE
+ help
+ We keep the static function tracing (!DYNAMIC_FTRACE) around
+ in order to test the non static function tracing in the
+ generic code, as other architectures still use it. But we
+ only need to keep it around for x86_64. No need to keep it
+ for x86_32. For x86_32, force DYNAMIC_FTRACE.
#
# Arch settings
#