[PATCH 1/2] kprobes: introduce ARCH_HANDLES_KPROBES_ON_FTRACE

[Heiko Carstens]

Allow architectures to implement handling of kprobes on function
tracer call sites on their own, without depending on common code.

This patch removes the kprobes check if a kprobe is being placed
on a function tracer call site and therefore gives full responsibility
of handling this correctly to the architecture.

Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
---
 arch/Kconfig     | 8 ++++++++
 kernel/kprobes.c | 3 ++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 05d7a8a458d5..e1a8e0edf03f 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -85,6 +85,14 @@ config KPROBES_ON_FTRACE
 	 passing of pt_regs to function tracing, then kprobes can
 	 optimize on top of function tracing.
 
+config ARCH_HANDLES_KPROBES_ON_FTRACE
+	def_bool n
+	help
+	 If an architecture can handle kprobes on function tracer call
+	 sites on own, then this option should be selected. This option
+	 removes the check which otherwise prevents to set kprobes on
+	 function tracer call sites.
+
 config UPROBES
 	def_bool n
 	select PERCPU_RWSEM
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 3995f546d0f3..4cc48aa67635 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1428,7 +1428,8 @@ static int check_kprobe_address_safe(struct kprobe *p,
 			return -EILSEQ;
 		p->flags |= KPROBE_FLAG_FTRACE;
 #else	/* !CONFIG_KPROBES_ON_FTRACE */
-		return -EINVAL;
+		if (!IS_ENABLED(CONFIG_ARCH_HANDLES_KPROBES_ON_FTRACE))
+			return -EINVAL;
 #endif
 	}
 
-- 
1.8.5.5

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