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Subject[PATCH v8 3/8] ARM: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
Date
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
ARM platform.

We introduce a new structure called fgraph_ret_regs for the ARM 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@sangfor.com.cn>
---
v8:
- Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
---
arch/arm/Kconfig | 1 +
arch/arm/include/asm/ftrace.h | 18 ++++++++++++++++++
arch/arm/kernel/entry-ftrace.S | 6 +++++-
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e24a9820e12f..73061379855a 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -98,6 +98,7 @@ config ARM
select HAVE_FAST_GUP if ARM_LPAE
select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
select HAVE_FUNCTION_ERROR_INJECTION
+ select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER if !XIP_KERNEL
select HAVE_GCC_PLUGINS
diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 7e9251ca29fe..2ab4bee21d79 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -77,4 +77,22 @@ static inline bool arch_syscall_match_sym_name(const char *sym,

#endif /* ifndef __ASSEMBLY__ */

+
+#ifndef __ASSEMBLY__
+struct fgraph_ret_regs {
+ unsigned long regs[4];
+ unsigned long 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 /* _ASM_ARM_FTRACE */
diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
index 3e7bcaca5e07..5f1e74555b25 100644
--- a/arch/arm/kernel/entry-ftrace.S
+++ b/arch/arm/kernel/entry-ftrace.S
@@ -257,11 +257,15 @@ ENDPROC(ftrace_graph_regs_caller)

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(return_to_handler)
+ sub sp, sp, #4
stmdb sp!, {r0-r3}
- add r0, sp, #16 @ sp at exit of instrumented routine
+ add r0, sp, #20 @ sp at exit of instrumented routine
+ str r0, [sp, #16]
+ mov r0, sp
bl ftrace_return_to_handler
mov lr, r0 @ r0 has real ret addr
ldmia sp!, {r0-r3}
+ add sp, sp, #4 @ skip fp
ret lr
ENDPROC(return_to_handler)
#endif
--
2.25.1
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