linux-kernel - Re: [PATCH -tip v3 4/7] kprobes: Ignore break

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Date:   Fri, 18 May 2018 08:16:36 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Laura Abbott <labbott@...hat.com>, Josef Bacik <jbacik@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: Re: [PATCH -tip v3 4/7] kprobes: Ignore break_handler

* Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Ignore break_handler related code because it was only
> used by jprobe and jprobe is removed.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  Documentation/kprobes.txt |    2 +-
>  kernel/kprobes.c          |   39 +++++----------------------------------
>  2 files changed, 6 insertions(+), 35 deletions(-)

Even after all these changes there's quite a bit of ->break_handler() use:

triton:~/tip> git grep -w break_handler
arch/arc/kernel/kprobes.c:              if (p->break_handler && p->break_handler(p, regs)) {
arch/arm/probes/kprobes/core.c:                  * for calling the break_handler below on re-entry,
arch/arm/probes/kprobes/core.c:         if (cur->break_handler && cur->break_handler(cur, regs)) {
arch/arm64/kernel/probes/kprobes.c:                      * for calling the break_handler below on re-entry,
arch/arm64/kernel/probes/kprobes.c:             if (cur_kprobe->break_handler  &&
arch/arm64/kernel/probes/kprobes.c:                  cur_kprobe->break_handler(cur_kprobe, regs)) {
arch/ia64/kernel/kprobes.c:                     if (p->break_handler && p->break_handler(p, regs)) {
arch/mips/kernel/kprobes.c:                     if (p->break_handler && p->break_handler(p, regs))
arch/powerpc/kernel/kprobes.c:                  if (p->break_handler && p->break_handler(p, regs)) {
arch/s390/kernel/kprobes.c:                      * for calling the break_handler below on re-entry
arch/s390/kernel/kprobes.c:             if (p->break_handler && p->break_handler(p, regs)) {
arch/s390/kernel/kprobes.c:                      * break_handler "returns" to the original
arch/sh/kernel/kprobes.c:                       if (p->break_handler && p->break_handler(p, regs)) {
arch/sh/kernel/kprobes.c:                                       if (p->break_handler &&
arch/sh/kernel/kprobes.c:                                           p->break_handler(p, args->regs))
arch/sparc/kernel/kprobes.c:                    if (p->break_handler && p->break_handler(p, regs))
arch/x86/include/asm/kprobes.h:  * a post_handler or break_handler).
include/linux/kprobes.h:        kprobe_break_handler_t break_handler;

Nothing appears to be actually _setting_ the break_handler, so all of this is 
stale code as well which should be removed?

Thanks,

	Ingo