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[209.85.217.52]) by smtp.gmail.com with ESMTPSA id s3sm9988330uao.0.2020.05.11.15.52.31 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 May 2020 15:52:31 -0700 (PDT) Received: by mail-vs1-f52.google.com with SMTP id x136so6711675vsx.2 for ; Mon, 11 May 2020 15:52:31 -0700 (PDT) X-Received: by 2002:a67:c40c:: with SMTP id c12mr13653102vsk.106.1589237114125; Mon, 11 May 2020 15:45:14 -0700 (PDT) MIME-Version: 1.0 References: <20200428211351.85055-1-dianders@chromium.org> <20200428141218.v3.5.I22067ad43e77ddfd4b64c2d49030628480f9e8d9@changeid> <20200511145908.GA22040@willie-the-truck> In-Reply-To: <20200511145908.GA22040@willie-the-truck> From: Doug Anderson Date: Mon, 11 May 2020 15:45:02 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 05/11] arm64: Add call_break_hook() to early_brk64() for early kgdb To: Will Deacon Cc: Jason Wessel , Daniel Thompson , Greg Kroah-Hartman , Andy Gross , kgdb-bugreport@lists.sourceforge.net, Catalin Marinas , linux-serial@vger.kernel.org, Sumit Garg , Jonathan Corbet , Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , Frank Rowand , bp@alien8.de, Bjorn Andersson , Jiri Slaby , Alexios Zavras , Allison Randal , Dave Martin , "Eric W. Biederman" , James Morse , Mark Rutland , Masami Hiramatsu , jinho lim , Linux ARM , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Hi, On Mon, May 11, 2020 at 7:59 AM Will Deacon wrote: > > Hi Doug, > > On Tue, Apr 28, 2020 at 02:13:45PM -0700, Douglas Anderson wrote: > > diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c > > index 48222a4760c2..59c353dfc8e9 100644 > > --- a/arch/arm64/kernel/debug-monitors.c > > +++ b/arch/arm64/kernel/debug-monitors.c > > @@ -297,7 +297,7 @@ void unregister_kernel_break_hook(struct break_hook *hook) > > unregister_debug_hook(&hook->node); > > } > > > > -static int call_break_hook(struct pt_regs *regs, unsigned int esr) > > +int call_break_hook(struct pt_regs *regs, unsigned int esr) > > { > > struct break_hook *hook; > > struct list_head *list; > > diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c > > index cf402be5c573..a8173f0c1774 100644 > > --- a/arch/arm64/kernel/traps.c > > +++ b/arch/arm64/kernel/traps.c > > @@ -1044,6 +1044,9 @@ int __init early_brk64(unsigned long addr, unsigned int esr, > > if ((comment & ~KASAN_BRK_MASK) == KASAN_BRK_IMM) > > return kasan_handler(regs, esr) != DBG_HOOK_HANDLED; > > #endif > > + if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED) > > + return 0; > > I think this just means we're not running debug_traps_init() early enough, > and actually the KASAN early handler is unnecessary too. > > If we call debug_traps_init() directly from setup_arch() and drop the > arch_initcall(), can we then drop early_brk64 entirely? It seems to work in my testing. ...but the worry I have is the comment right before trap_init(). It says: /* This registration must happen early, before debug_traps_init(). */ By moving debug_traps_init() early we're violating that comment. Do I just remove that comment, or was there a good reason for it? ...or am I reading it wrong and I should have read it as if it said: /* NOTE: this registration happens early, before debug_traps_init(). */ ...then removing it is fine. Maybe that's right? I coded this up and put it on the Chrome OS gerrit at . I'm happy to post this on the list as a loner patch to replace this one or spin the whole series depending on what people want. -Doug