Re: [PATCH 09/18] trace: disable function graph tracing with SCS

[Steven Rostedt]

On Fri, 18 Oct 2019 09:10:24 -0700
Sami Tolvanen <samitolvanen@xxxxxxxxxx> wrote:

> With CONFIG_FUNCTION_GRAPH_TRACER, function return addresses are
> modified in ftrace_graph_caller and prepare_ftrace_return to redirect
> control flow to ftrace_return_to_handler. This is incompatible with
> return address protection.
> 
> Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> ---
>  kernel/trace/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> index e08527f50d2a..b7e5e3bfa0f4 100644
> --- a/kernel/trace/Kconfig
> +++ b/kernel/trace/Kconfig
> @@ -161,6 +161,7 @@ config FUNCTION_GRAPH_TRACER
>  	depends on HAVE_FUNCTION_GRAPH_TRACER
>  	depends on FUNCTION_TRACER
>  	depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
> +	depends on ROP_PROTECTION_NONE

NAK, Put this in the arch code.

>  	default y
>  	help
>  	  Enable the kernel to trace a function at both its return

-- Steve


diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 41a9b4257b72..d68339987604 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -149,7 +149,7 @@ config ARM64
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_ERROR_INJECTION
-	select HAVE_FUNCTION_GRAPH_TRACER
+	select HAVE_FUNCTION_GRAPH_TRACER if ROP_PROTECTION_NONE
 	select HAVE_GCC_PLUGINS
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS
 	select HAVE_IRQ_TIME_ACCOUNTING