[RFC PATCH -tip 2/9] ftrace/x86-64: support SAVE_REGS feature on x86-64

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

Add register saving/restoring sequence in ftrace_caller
on x86-64 for enabling SAVE_REGS feature.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
---

 arch/x86/include/asm/ftrace.h |    4 ++++
 arch/x86/kernel/entry_64.S    |   38 +++++++++++++++++++++++++++++++++-----
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 18d9005..ffb9564 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -32,6 +32,10 @@
 #define MCOUNT_ADDR		((long)(mcount))
 #define MCOUNT_INSN_SIZE	5 /* sizeof mcount call */
 
+#if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_X86_64)
+#define ARCH_SUPPORTS_FTRACE_SAVE_REGS 1
+#endif
+
 #ifndef __ASSEMBLY__
 extern void mcount(void);
 extern int modifying_ftrace_code;
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 320852d..6d0545b 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -73,21 +73,44 @@ ENTRY(mcount)
 	retq
 END(mcount)
 
+	.macro MCOUNT_SAVE_ALL
+	SAVE_ARGS (RSP-ORIG_RAX)
+	SAVE_REST
+	/* Adjust eflags, rsp and rip */
+	movq RSP(%rsp), %rdx
+	movq %rdx, EFLAGS(%rsp)
+	leaq SS+8(%rsp), %rdx
+	movq %rdx, RSP(%rsp)
+	movq SS(%rsp), %rdi
+	subq $MCOUNT_INSN_SIZE, %rdi
+	movq %rdi, RIP(%rsp)
+	.endm
+
+	.macro MCOUNT_RESTORE_ALL
+	/* store eflags into regs->rsp */
+	movq EFLAGS(%rsp), %rax
+	movq %rax, RSP(%rsp)
+	RESTORE_REST
+	RESTORE_ARGS 1, (RSP-ORIG_RAX)
+	.endm
+
 ENTRY(ftrace_caller)
+	CFI_STARTPROC	simple
+	pushfq_cfi
 	cmpl $0, function_trace_stop
-	jne  ftrace_stub
+	jne  ftrace_exit
 
-	MCOUNT_SAVE_FRAME
+	MCOUNT_SAVE_ALL
 
-	movq 0x38(%rsp), %rdi
 	movq 8(%rbp), %rsi
-	subq $MCOUNT_INSN_SIZE, %rdi
+	movq %rsp, %rdx
 
 GLOBAL(ftrace_call)
 	call ftrace_stub
 
-	MCOUNT_RESTORE_FRAME
+	MCOUNT_RESTORE_ALL
 
+	popfq_cfi
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 GLOBAL(ftrace_graph_call)
 	jmp ftrace_stub
@@ -95,6 +118,11 @@ GLOBAL(ftrace_graph_call)
 
 GLOBAL(ftrace_stub)
 	retq
+
+ftrace_exit:
+	popfq_cfi
+	retq
+	CFI_ENDPROC
 END(ftrace_caller)
 
 #else /* ! CONFIG_DYNAMIC_FTRACE */