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[v10,03/36] x86: tracing: Add ftrace_regs definition in the header

Message ID 171509091569.162236.17928081833857878443.stgit@devnote2 (mailing list archive)
State Not Applicable
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Commit Message

Masami Hiramatsu (Google) May 7, 2024, 2:08 p.m. UTC 
From: Masami Hiramatsu (Google) <mhiramat@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) <mhiramat@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(+)

Comments

Steven Rostedt May 23, 2024, 11:14 p.m. UTC | #1 
On Tue,  7 May 2024 23:08:35 +0900
"Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@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) <mhiramat@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 cf88cc8cc74d..c88bf47f46da 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.

Should add a comment that if fregs->regs.cs is set, then all of the pt_regs
is valid. And x86_32 does support ftrace_regs, it just doesn't support
having a subset of it.

-- Steve


> +	 */
>  	struct pt_regs		regs;
>  };
>
Masami Hiramatsu (Google) May 24, 2024, 1:37 a.m. UTC | #2 
On Thu, 23 May 2024 19:14:59 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue,  7 May 2024 23:08:35 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat@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) <mhiramat@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 cf88cc8cc74d..c88bf47f46da 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.
> 
> Should add a comment that if fregs->regs.cs is set, then all of the pt_regs
> is valid.

But what about rbx and r1*? Only regs->cs should be care for pt_regs?
Or, did you mean "the ftrace_regs is valid"?

> And x86_32 does support ftrace_regs, it just doesn't support
> having a subset of it.

Oh, thanks. I'll update the comment about x86_32.

Thank you,

> 
> -- Steve
> 
> 
> > +	 */
> >  	struct pt_regs		regs;
> >  };
> >  
> 
>
Steven Rostedt May 24, 2024, 2:31 p.m. UTC | #3 
On Fri, 24 May 2024 10:37:54 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> > >  
> > >  #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.  
> > 
> > Should add a comment that if fregs->regs.cs is set, then all of the pt_regs
> > is valid.  
> 
> But what about rbx and r1*? Only regs->cs should be care for pt_regs?
> Or, did you mean "the ftrace_regs is valid"?

Yeah, on x86_64 ftrace_regs uses regs.cs to denote if it is valid or not:

static __always_inline struct pt_regs *
arch_ftrace_get_regs(struct ftrace_regs *fregs)
{
	/* Only when FL_SAVE_REGS is set, cs will be non zero */
	if (!fregs->regs.cs)
		return NULL;
	return &fregs->regs;
}


-- Steve
diff mbox series

Patch

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index cf88cc8cc74d..c88bf47f46da 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;
 };