[PATCH v7 4/8] arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

[Donglin Peng]

The commit d4815c5d1bbd ("function_graph: Support recording and
printing the return value of function") laid the groundwork for the
for the funcgraph-retval, and this modification makes it available
on the ARM64 platform.

We introduce a new structure called fgraph_ret_regs for the ARM64
platform to hold return registers and the frame pointer. We then
fill its content in the return_to_handler and pass its address to
the function ftrace_return_to_handler to record the return value.

Signed-off-by: Donglin Peng <pengdonglin@xxxxxxxxxxxxxx>
---
 arch/arm64/Kconfig               |  1 +
 arch/arm64/include/asm/ftrace.h  | 23 +++++++++++++++++++++++
 arch/arm64/kernel/entry-ftrace.S |  9 +++++----
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1023e896d46b..48856d230800 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -195,6 +195,7 @@ config ARM64
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_ERROR_INJECTION
+	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_GCC_PLUGINS
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 1c2672bbbf37..f68dcc41be3b 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -170,4 +170,27 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
 }
 #endif /* ifndef __ASSEMBLY__ */
 
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
+struct fgraph_ret_regs {
+	/* x0 - x7 */
+	u64 regs[8];
+
+	u64 fp;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->regs[0];
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+	return ret_regs->fp;
+}
+#endif
+
+#endif
+
 #endif /* __ASM_FTRACE_H */
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index 350ed81324ac..8ac6f952e68f 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -270,14 +270,15 @@ SYM_FUNC_END(ftrace_stub_graph)
  */
 SYM_CODE_START(return_to_handler)
 	/* save return value regs */
-	sub sp, sp, #64
+	sub sp, sp, #72
 	stp x0, x1, [sp]
 	stp x2, x3, [sp, #16]
 	stp x4, x5, [sp, #32]
 	stp x6, x7, [sp, #48]
+	str x29,    [sp, #64]		//     parent's fp
 
-	mov	x0, x29			//     parent's fp
-	bl	ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
+	mov	x0, sp
+	bl	ftrace_return_to_handler// addr = ftrace_return_to_hander(regs);
 	mov	x30, x0			// restore the original return address
 
 	/* restore return value regs */
@@ -285,7 +286,7 @@ SYM_CODE_START(return_to_handler)
 	ldp x2, x3, [sp, #16]
 	ldp x4, x5, [sp, #32]
 	ldp x6, x7, [sp, #48]
-	add sp, sp, #64
+	add sp, sp, #72
 
 	ret
 SYM_CODE_END(return_to_handler)
-- 
2.25.1