[PATCH v8 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>
v8:
 - Fix issues in ARM64 asm code
 - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
---
 arch/arm64/Kconfig               |  1 +
 arch/arm64/include/asm/ftrace.h  | 20 ++++++++++++++++++++
 arch/arm64/kernel/asm-offsets.c  | 12 ++++++++++++
 arch/arm64/kernel/entry-ftrace.S | 27 ++++++++++++++-------------
 4 files changed, 47 insertions(+), 13 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..5d2fb57e8a5f 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -170,4 +170,24 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
 }
 #endif /* ifndef __ASSEMBLY__ */
 
+#ifndef __ASSEMBLY__
+struct fgraph_ret_regs {
+	/* x0 - x7 */
+	unsigned long regs[8];
+
+	unsigned long fp;
+	unsigned long __unused;
+};
+
+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 /* __ASM_FTRACE_H */
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index ae345b06e9f7..f4f774e9a11f 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -198,5 +198,17 @@ int main(void)
 #ifdef CONFIG_FUNCTION_TRACER
   DEFINE(FTRACE_OPS_FUNC,		offsetof(struct ftrace_ops, func));
 #endif
+  BLANK();
+  DEFINE(FGRET_REGS_X0,			offsetof(struct fgraph_ret_regs, regs[0]));
+  DEFINE(FGRET_REGS_X1,			offsetof(struct fgraph_ret_regs, regs[1]));
+  DEFINE(FGRET_REGS_X2,			offsetof(struct fgraph_ret_regs, regs[2]));
+  DEFINE(FGRET_REGS_X3,			offsetof(struct fgraph_ret_regs, regs[3]));
+  DEFINE(FGRET_REGS_X4,			offsetof(struct fgraph_ret_regs, regs[4]));
+  DEFINE(FGRET_REGS_X5,			offsetof(struct fgraph_ret_regs, regs[5]));
+  DEFINE(FGRET_REGS_X6,			offsetof(struct fgraph_ret_regs, regs[6]));
+  DEFINE(FGRET_REGS_X7,			offsetof(struct fgraph_ret_regs, regs[7]));
+  DEFINE(FGRET_REGS_FP,			offsetof(struct fgraph_ret_regs, fp));
+  DEFINE(FGRET_REGS_SIZE,		sizeof(struct fgraph_ret_regs));
+  BLANK();
   return 0;
 }
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index 350ed81324ac..da1443bcf776 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -270,22 +270,23 @@ SYM_FUNC_END(ftrace_stub_graph)
  */
 SYM_CODE_START(return_to_handler)
 	/* save return value regs */
-	sub sp, sp, #64
-	stp x0, x1, [sp]
-	stp x2, x3, [sp, #16]
-	stp x4, x5, [sp, #32]
-	stp x6, x7, [sp, #48]
+	sub sp, sp, #FGRET_REGS_SIZE
+	stp x0, x1, [sp, #FGRET_REGS_X0]
+	stp x2, x3, [sp, #FGRET_REGS_X2]
+	stp x4, x5, [sp, #FGRET_REGS_X4]
+	stp x6, x7, [sp, #FGRET_REGS_X6]
+	str x29,    [sp, #FGRET_REGS_FP]	// parent's fp
 
-	mov	x0, x29			//     parent's fp
-	bl	ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
-	mov	x30, x0			// restore the original return address
+	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 */
-	ldp x0, x1, [sp]
-	ldp x2, x3, [sp, #16]
-	ldp x4, x5, [sp, #32]
-	ldp x6, x7, [sp, #48]
-	add sp, sp, #64
+	ldp x0, x1, [sp, #FGRET_REGS_X0]
+	ldp x2, x3, [sp, #FGRET_REGS_X2]
+	ldp x4, x5, [sp, #FGRET_REGS_X4]
+	ldp x6, x7, [sp, #FGRET_REGS_X6]
+	add sp, sp, #FGRET_REGS_SIZE
 
 	ret
 SYM_CODE_END(return_to_handler)
-- 
2.25.1