linux-kernel - [PATCH 3/7] arm64: Add call_break_hook() to early

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Message-Id: <20200410151632.3.I22067ad43e77ddfd4b64c2d49030628480f9e8d9@changeid>
Date:   Fri, 10 Apr 2020 15:17:22 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     jason.wessel@...driver.com, daniel.thompson@...aro.org,
        gregkh@...uxfoundation.org
Cc:     hpa@...or.com, kgdb-bugreport@...ts.sourceforge.net,
        corbet@....net, frowand.list@...il.com, tglx@...utronix.de,
        jslaby@...e.com, linux-serial@...r.kernel.org, mingo@...hat.com,
        will@...nel.org, bjorn.andersson@...aro.org, agross@...nel.org,
        bp@...en8.de, catalin.marinas@....com,
        Douglas Anderson <dianders@...omium.org>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Allison Randal <allison@...utok.net>,
        Dave Martin <Dave.Martin@....com>,
        Enrico Weigelt <info@...ux.net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        James Morse <james.morse@....com>,
        Mark Rutland <mark.rutland@....com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        jinho lim <jordan.lim@...sung.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/7] arm64: Add call_break_hook() to early_brk64() for early kgdb

In order to make early kgdb work properly we need early_brk64() to be
able to call into it.  This is as easy as adding a call into
call_break_hook() just like we do later in the normal brk_handler().

Once we do this we can let kgdb know that it can break into the
debugger a little earlier (specifically when parsing early_param's).

NOTE: without this patch it turns out that arm64 can't do breakpoints
even at dbg_late_init(), so if we decide something about this patch is
wrong we might need to move dbg_late_init() a little later.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
---

 arch/arm64/include/asm/debug-monitors.h | 2 ++
 arch/arm64/kernel/debug-monitors.c      | 2 +-
 arch/arm64/kernel/kgdb.c                | 5 +++++
 arch/arm64/kernel/traps.c               | 3 +++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
index 7619f473155f..2d82a0314d29 100644
--- a/arch/arm64/include/asm/debug-monitors.h
+++ b/arch/arm64/include/asm/debug-monitors.h
@@ -97,6 +97,8 @@ void unregister_user_break_hook(struct break_hook *hook);
 void register_kernel_break_hook(struct break_hook *hook);
 void unregister_kernel_break_hook(struct break_hook *hook);
 
+int call_break_hook(struct pt_regs *regs, unsigned int esr);
+
 u8 debug_monitors_arch(void);
 
 enum dbg_active_el {
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/kgdb.c b/arch/arm64/kernel/kgdb.c
index 43119922341f..96a47af870bc 100644
--- a/arch/arm64/kernel/kgdb.c
+++ b/arch/arm64/kernel/kgdb.c
@@ -301,6 +301,11 @@ static struct notifier_block kgdb_notifier = {
 	.priority	= -INT_MAX,
 };
 
+extern bool kgdb_arch_can_debug_early(void)
+{
+	return true;
+}
+
 /*
  * kgdb_arch_init - Perform any architecture specific initialization.
  * This function will handle the initialization of any architecture
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;
+
 	return bug_handler(regs, esr) != DBG_HOOK_HANDLED;
 }
 
-- 
2.26.0.110.g2183baf09c-goog