| From | "Masami Hiramatsu (Google)" <> | Subject | [RFC PATCH v2 01/31] tracing: Add a comment about ftrace_regs definition | Date | Wed, 8 Nov 2023 23:24:32 +0900 |
| |
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
To clarify what will be expected on ftrace_regs, add a comment to the architecture independent definition of the ftrace_regs.
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> --- Changes in v2: - newly added. --- include/linux/ftrace.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index e8921871ef9a..b174af91d8be 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -118,6 +118,31 @@ extern int ftrace_enabled; #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS +/** + * ftrace_regs - ftrace partial/optimal register set + * + * ftrace_regs represents a group of registers which is used at the + * function entry and exit. There are three types of registers. + * + * - Registers for passing the parameters to callee, including the stack + * pointer. (e.g. rcx, rdx, rdi, rsi, r8, r9 and rsp on x86_64) + * - Registers for passing the return values to caller. + * (e.g. rax and rdx on x86_64) + * - Registers for hooking the function return including the frame pointer + * (the frame pointer is architecture/config dependent) + * (e.g. rbp and rsp for x86_64) + * + * Also, architecture dependent fields can be used for internal process. + * (e.g. orig_ax on x86_64) + * + * On the function entry, those registers will be restored except for + * the stack pointer, so that user can change the function parameters. + * On the function exit, onlu registers which is used for return values + * are restored. + * + * NOTE: user *must not* access regs directly, only do it via APIs, because + * the member can be changed according to the architecture. + */ struct ftrace_regs { struct pt_regs regs; };
|