linux-kernel - [PATCH 3/5] arm64: Handle TRAP

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Date:	Tue,  2 Aug 2016 11:00:07 +0530
From:	Pratyush Anand <panand@...hat.com>
To:	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	catalin.marinas@....com, will.deacon@....com
Cc:	linux-kernel@...r.kernel.org, wcohen@...hat.com, oleg@...hat.com,
	dave.long@...aro.org, steve.capper@...aro.org,
	srikar@...ux.vnet.ibm.com, vijaya.kumar@...iumnetworks.com,
	Pratyush Anand <panand@...hat.com>,
	Anna-Maria Gleixner <anna-maria@...utronix.de>,
	Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Yang Shi <yang.shi@...aro.org>
Subject: [PATCH 3/5] arm64: Handle TRAP_HWBRKPT for user mode as well

uprobe registers a handler at step_hook. So, single_step_handler now
checks for user mode as well if there is a valid hook.

Signed-off-by: Pratyush Anand <panand@...hat.com>
---
 arch/arm64/kernel/debug-monitors.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 91fff48d0f57..fae2f57a92b7 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -246,6 +246,8 @@ static void send_user_sigtrap(int si_code)
 static int single_step_handler(unsigned long addr, unsigned int esr,
 			       struct pt_regs *regs)
 {
+	bool handler_found = false;
+
 	/*
 	 * If we are stepping a pending breakpoint, call the hw_breakpoint
 	 * handler first.
@@ -253,7 +255,14 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
 	if (!reinstall_suspended_bps(regs))
 		return 0;
 
-	if (user_mode(regs)) {
+#ifdef	CONFIG_KPROBES
+	if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
+		handler_found = true;
+#endif
+	if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
+		handler_found = true;
+
+	if (!handler_found && user_mode(regs)) {
 		send_user_sigtrap(TRAP_HWBKPT);
 
 		/*
@@ -263,15 +272,8 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
 		 * to the active-not-pending state).
 		 */
 		user_rewind_single_step(current);
-	} else {
-#ifdef	CONFIG_KPROBES
-		if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
-			return 0;
-#endif
-		if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
-			return 0;
-
-		pr_warning("Unexpected kernel single-step exception at EL1\n");
+	} else if (!handler_found) {
+		pr_warn("Unexpected kernel single-step exception at EL1\n");
 		/*
 		 * Re-enable stepping since we know that we will be
 		 * returning to regs.
-- 
2.5.5