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

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Date:   Fri, 7 Jun 2019 15:32:15 -0400
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 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 ;-)

Otherwise:

Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh