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

Steven Rostedt
2019-10-18T17:01:41Z

On Fri, 18 Oct 2019 09:10:24 -0700
Sami Tolvanen <samitolvanen@google.com> 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@google.com>
> ---
> 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