linux-kernel - Re: [PATCH 0/6 v4] [GIT PULL] ftrace/x86: Ftrace cleanup and add support for -mfentry on x86

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Message-ID: <20170321185113.5bf9b476@vmware.local.home>
Date:   Tue, 21 Mar 2017 18:51:13 -0700
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...capital.net>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 0/6 v4] [GIT PULL] ftrace/x86: Ftrace cleanup and add
 support for -mfentry on x86_32


Bah, I forgot to add the "v4" in the subject (like I did for this
email).

-- Steve


On Tue, 21 Mar 2017 21:35:02 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> [
>  Ingo, Thomas or H.Peter,
> 
>  I believe this is all set to go now. I updated those patches that
> Linus commented on and I don't believe there are any more issues. I
> ran this through several tests (although some of my tests are failing
> due to bugs introduced by others in 4.11-rc2). You can take this as a
> patch series, or you can pull from my tree defined below. It's based
> on 4.11-rc2 as I noticed that tip/x86/core is rather outdated, and
> Linus is fine with basing off of his tagged releases.
> ]
> 
> 
> With the issues of gcc screwing around with the mcount stack frame
> causing function graph tracer to panic on x86_32, and with Linus
> saying that we should start deprecating mcount (at least on x86), I
> figured that x86_32 needs to support fentry.
> 
> First, I renamed mcount_64.S to ftrace_64.S. As we want to get away
> from mcount, having the ftrace code in a file called mcount seems
> rather backwards.
> 
> Next I moved the ftrace code out of entry_32.S. It's not in entry_64.S
> and it does not belong in entry_32.S.
> 
> I noticed that the x86_32 code has the same issue as the x86_64 did
> in the past with respect to a stack frame. I fixed that just for the
> main ftrace_caller. The ftrace_regs_caller is rather special, and so
> is function graph tracing.
> 
> I realized the ftrace_regs_caller code was complex due to me
> aggressively saving flags, even though I could still do push, lea and
> mov without changing them. That made the logic a little nicer.
> 
> Finally I added the fentry code.
> 
> I tested this with an older compiler (for mcount) with and without
> FRAME_POINTER set. I also did it with a new compiler (with fentry),
> with and without FRAME_POINTER. I tested function tracing, stack
> tracing, function_graph tracing, and kprobes (as that uses the
> ftrace_regs_caller).
> 
> Please pull (or take the patch series) from:
> 
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
> tip/x86/ftrace
> 
> Head SHA1: e086b1da846b8e53f4de11e38d02d05b1ec5db58
> 
> 
> Steven Rostedt (VMware) (6):
>       ftrace/x86_64: Rename mcount_64.S to ftrace_64.S
>       ftrace/x86_32: Move the ftrace specific code out of entry_32.S
>       ftrace/x86_32: Add stack frame pointer to ftrace_caller
>       ftrace/x86_32: Clean up ftrace_regs_caller
>       ftrace/x86_32: Add -mfentry support to x86_32 with
> DYNAMIC_FTRACE set ftrace/x86: Use Makefile logic instead of #ifdef
> for compiling ftrace_*.o
> 
> ----
> Changes since v3:
> 
>   * Changed comment about regs being skipped (Josh Poimboeuf)
> 
>   * Change subject line to fix typo (Josh Poimboeuf)
> 
> 
>  arch/x86/Kconfig                             |   2 +-
>  arch/x86/entry/entry_32.S                    | 169 ------------------
>  arch/x86/kernel/Makefile                     |   5 +-
>  arch/x86/kernel/ftrace_32.S                  | 246
> +++++++++++++++++++++++++++ arch/x86/kernel/{mcount_64.S =>
> ftrace_64.S} |   4 - 5 files changed, 250 insertions(+), 176
> deletions(-) create mode 100644 arch/x86/kernel/ftrace_32.S
>  rename arch/x86/kernel/{mcount_64.S => ftrace_64.S} (99%)
> 
> Diff against v3:
> 
> 
> diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
> index 4d52e0d49e26..de50c9084d16 100644
> --- a/arch/x86/kernel/ftrace_32.S
> +++ b/arch/x86/kernel/ftrace_32.S
> @@ -167,7 +167,7 @@ GLOBAL(ftrace_regs_call)
>  	popl	%gs
>  
>  	/* use lea to not affect flags */
> -	lea	3*4(%esp), %esp			/* Skip
> orig_ax, ip and flags */
> +	lea	3*4(%esp), %esp			/* Skip
> orig_ax, ip and cs */ 
>  	jmp	.Lftrace_ret
>  #else /* ! CONFIG_DYNAMIC_FTRACE */