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[v5,01/34] tracing: Add a comment about ftrace_regs definition

Message ID 170290510399.220107.17645951919819438730.stgit@devnote2 (mailing list archive)
State Not Applicable
Headers show
Series tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph | expand

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Commit Message

Masami Hiramatsu (Google) Dec. 18, 2023, 1:11 p.m. UTC 
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 v3:
  - Add instruction pointer
 Changes in v2:
  - newly added.
---
 include/linux/ftrace.h |   26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

Comments

Mark Rutland Jan. 5, 2024, 5:12 p.m. UTC | #1 
On Mon, Dec 18, 2023 at 10:11:44PM +0900, Masami Hiramatsu (Google) wrote:
> 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>

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  Changes in v3:
>   - Add instruction pointer
>  Changes in v2:
>   - newly added.
> ---
>  include/linux/ftrace.h |   26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index e8921871ef9a..8b48fc621ea0 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -118,6 +118,32 @@ 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 call and return including the
> + *   frame pointer (the frame pointer is architecture/config dependent)
> + *   (e.g. rip, 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
> + * and instruction pointer (e.g. live patching.)
> + * On the function exit, only 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;
>  };
>
diff mbox series

Patch

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index e8921871ef9a..8b48fc621ea0 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -118,6 +118,32 @@  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 call and return including the
+ *   frame pointer (the frame pointer is architecture/config dependent)
+ *   (e.g. rip, 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
+ * and instruction pointer (e.g. live patching.)
+ * On the function exit, only 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;
 };