linux-kernel - [PATCH] ftrace: Allow WITH_ARGS flavour of graph tracer with shadow call stack

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Message-Id: <20221209143402.3332369-1-ardb@kernel.org>
Date:   Fri,  9 Dec 2022 15:34:02 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
        will@...nel.org, rostedt@...dmis.org, samitolvanen@...gle.com,
        keescook@...omium.org, mhiramat@...nel.org,
        Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH] ftrace: Allow WITH_ARGS flavour of graph tracer with shadow call stack

The recent switch on arm64 from DYNAMIC_FTRACE_WITH_REGS to
DYNAMIC_FTRACE_WITH_ARGS failed to take into account that we currently
require the former in order to allow the function graph tracer to be
enabled in combination with shadow call stacks. This means that this is
no longer permitted at all, in spite of the fact that either flavour of
ftrace works perfectly fine in this combination.

Given that arm64 is the only arch that implements shadow call stacks in
the first place, let's update the condition to just reflect the arm64
change. When other architectures adopt shadow call stack support, this
can be revisited if needed.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 072a1b39e3afd0d1..683f365b5e31c856 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -635,7 +635,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK
 config SHADOW_CALL_STACK
 	bool "Shadow Call Stack"
 	depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
-	depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
+	depends on DYNAMIC_FTRACE_WITH_ARGS || !FUNCTION_GRAPH_TRACER
 	help
 	  This option enables the compiler's Shadow Call Stack, which
 	  uses a shadow stack to protect function return addresses from
-- 
2.35.1