[PATCH v6 25/36] arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_FREGS

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Enable CONFIG_HAVE_FUNCTION_GRAPH_FREGS on arm64. Note that this
depends on HAVE_DYNAMIC_FTRACE_WITH_ARGS which is enabled if the
compiler supports "-fpatchable-function-entry=2". If not, it
continue to use ftrace_ret_regs.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Changes in v3:
   - Newly added.
---
 arch/arm64/Kconfig               |    2 ++
 arch/arm64/include/asm/ftrace.h  |    6 ++++++
 arch/arm64/kernel/entry-ftrace.S |   28 ++++++++++++++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b071a00425d..beebc724dcae 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -192,6 +192,8 @@ config ARM64
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_ARGS \
 		if $(cc-option,-fpatchable-function-entry=2)
+	select HAVE_FUNCTION_GRAPH_FREGS \
+		if HAVE_DYNAMIC_FTRACE_WITH_ARGS
 	select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS \
 		if DYNAMIC_FTRACE_WITH_ARGS && DYNAMIC_FTRACE_WITH_CALL_OPS
 	select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS \
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index ab158196480c..efd5dbf74dd6 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -131,6 +131,12 @@ ftrace_regs_set_return_value(struct ftrace_regs *fregs,
 	fregs->regs[0] = ret;
 }
 
+static __always_inline unsigned long
+ftrace_regs_get_frame_pointer(struct ftrace_regs *fregs)
+{
+	return fregs->fp;
+}
+
 static __always_inline void
 ftrace_override_function_with_return(struct ftrace_regs *fregs)
 {
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index f0c16640ef21..d87ccdb9e678 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -328,6 +328,33 @@ SYM_FUNC_END(ftrace_stub_graph)
  * Run ftrace_return_to_handler() before going back to parent.
  * @fp is checked against the value passed by ftrace_graph_caller().
  */
+#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
+SYM_CODE_START(return_to_handler)
+	/* save ftrace_regs except for PC */
+	sub	sp, sp, #FREGS_SIZE
+	stp	x0, x1, [sp, #FREGS_X0]
+	stp	x2, x3, [sp, #FREGS_X2]
+	stp	x4, x5, [sp, #FREGS_X4]
+	stp	x6, x7, [sp, #FREGS_X6]
+	str	x8,     [sp, #FREGS_X8]
+	str	x29, [sp, #FREGS_FP]
+	str	x9,  [sp, #FREGS_LR]
+	str	x10, [sp, #FREGS_SP]
+
+	mov	x0, sp
+	bl	ftrace_return_to_handler	// addr = ftrace_return_to_hander(fregs);
+	mov	x30, x0				// restore the original return address
+
+	/* restore return value regs */
+	ldp x0, x1, [sp, #FREGS_X0]
+	ldp x2, x3, [sp, #FREGS_X2]
+	ldp x4, x5, [sp, #FREGS_X4]
+	ldp x6, x7, [sp, #FREGS_X6]
+	add sp, sp, #FREGS_SIZE
+
+	ret
+SYM_CODE_END(return_to_handler)
+#else /* !CONFIG_HAVE_FUNCTION_GRAPH_FREGS */
 SYM_CODE_START(return_to_handler)
 	/* save return value regs */
 	sub sp, sp, #FGRET_REGS_SIZE
@@ -350,4 +377,5 @@ SYM_CODE_START(return_to_handler)
 
 	ret
 SYM_CODE_END(return_to_handler)
+#endif /* CONFIG_HAVE_FUNCTION_GRAPH_FREGS */
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */