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

Add ftrace_regs definition for x86_64 in the ftrace header to
clarify what register will be accessible from ftrace_regs.

Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
---
 Changes in v3:
  - Add rip to be saved.
 Changes in v2:
  - Newly added.
---
 arch/x86/include/asm/ftrace.h |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 897cf02c20b1..415cf7a2ec2c 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -36,6 +36,12 @@ static inline unsigned long ftrace_call_adjust(unsigned long 
addr)
 
 #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
 struct ftrace_regs {
+       /*
+        * On the x86_64, the ftrace_regs saves;
+        * rax, rcx, rdx, rdi, rsi, r8, r9, rbp, rip and rsp.
+        * Also orig_ax is used for passing direct trampoline address.
+        * x86_32 doesn't support ftrace_regs.
+        */
        struct pt_regs          regs;
 };
 


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