linux-kernel - Re: [PATCH 05/15] x86_32: Provide consistent pt

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Message-ID: <20190611081433.GP3436@hirez.programming.kicks-ass.net>
Date:   Tue, 11 Jun 2019 10:14:33 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andy Lutomirski <luto@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jason Baron <jbaron@...mai.com>, Jiri Kosina <jkosina@...e.cz>,
        David Laight <David.Laight@...LAB.COM>,
        Borislav Petkov <bp@...en8.de>,
        Julia Cartwright <julia@...com>, Jessica Yu <jeyu@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Nadav Amit <namit@...are.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Edward Cree <ecree@...arflare.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH 05/15] x86_32: Provide consistent pt_regs

On Fri, Jun 07, 2019 at 03:32:15PM -0400, Josh Poimboeuf wrote:
> On Wed, Jun 05, 2019 at 03:07:58PM +0200, Peter Zijlstra wrote:
> > Currently pt_regs on x86_32 has an oddity in that kernel regs
> > (!user_mode(regs)) are short two entries (esp/ss). This means that any
> > code trying to use them (typically: regs->sp) needs to jump through
> > some unfortunate hoops.
> > 
> > Change the entry code to fix this up and create a full pt_regs frame.
> > 
> > This then simplifies various trampolines in ftrace and kprobes, the
> > stack unwinder, ptrace, kdump and kgdb.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> >
> > ---
> >  arch/x86/entry/entry_32.S         |  105 ++++++++++++++++++++++++++++++++++----
> >  arch/x86/include/asm/kexec.h      |   17 ------
> >  arch/x86/include/asm/ptrace.h     |   17 ------
> >  arch/x86/include/asm/stacktrace.h |    2 
> >  arch/x86/kernel/crash.c           |    8 --
> >  arch/x86/kernel/ftrace_32.S       |   77 +++++++++++++++------------
> >  arch/x86/kernel/kgdb.c            |    8 --
> >  arch/x86/kernel/kprobes/common.h  |    4 -
> >  arch/x86/kernel/kprobes/core.c    |   29 ++++------
> >  arch/x86/kernel/kprobes/opt.c     |   20 ++++---
> >  arch/x86/kernel/process_32.c      |   16 +----
> >  arch/x86/kernel/ptrace.c          |   29 ----------
> >  arch/x86/kernel/time.c            |    3 -
> >  arch/x86/kernel/unwind_frame.c    |   32 +----------
> >  arch/x86/kernel/unwind_orc.c      |    2 
> >  15 files changed, 178 insertions(+), 191 deletions(-)
> 
> I recall writing some of this code (some of the kernel_stack_pointer
> removal stuff) so please give me a shout-out ;-)

Absolutely, sorry for not doing that. I've added:

 "Much thanks to Josh for help with the cleanups!"