[PATCH v7 04/11] scs: disable when function graph tracing is enabled

Sami Tolvanen
2020-01-28T18:50:32Z

The graph tracer hooks returns by modifying frame records on the
(regular) stack, but with SCS the return address is taken from the
shadow stack, and the value in the frame record has no effect. As we
don't currently have a mechanism to determine the corresponding slot
on the shadow stack (and to pass this through the ftrace
infrastructure), for now let's disable SCS when the graph tracer is
enabled.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
arch/Kconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index 1b16aa9a3fe5..0d746373c52e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -530,6 +530,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK

config SHADOW_CALL_STACK
bool "Clang Shadow Call Stack"
+ depends on !FUNCTION_GRAPH_TRACER
depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
help
This option enables Clang's Shadow Call Stack, which uses a
--
2.25.0.341.g760bfbb309-goog