linux-kernel - [PATCH 4/5] arm64: Handle TRAP

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Date:	Tue,  2 Aug 2016 11:00:08 +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>,
	Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Yang Shi <yang.shi@...aro.org>
Subject: [PATCH 4/5] arm64: Handle TRAP_BRKPT for user mode as well

uprobe is registered at break_hook with a unique ESR code. So, when a
TRAP_BRKPT occurs, call_break_hook checks if it was for uprobe. If not,
then send a SIGTRAP to user.

Signed-off-by: Pratyush Anand <panand@...hat.com>
---
 arch/arm64/kernel/debug-monitors.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index fae2f57a92b7..466d199498b5 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -326,16 +326,20 @@ NOKPROBE_SYMBOL(call_break_hook);
 static int brk_handler(unsigned long addr, unsigned int esr,
 		       struct pt_regs *regs)
 {
-	if (user_mode(regs)) {
-		send_user_sigtrap(TRAP_BRKPT);
-	}
+	bool handler_found = false;
+
 #ifdef	CONFIG_KPROBES
-	else if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
-		if (kprobe_breakpoint_handler(regs, esr) != DBG_HOOK_HANDLED)
-			return -EFAULT;
+	if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
+		if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED)
+			handler_found = true;
 	}
 #endif
-	else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
+	if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
+		handler_found = true;
+
+	if (!handler_found && user_mode(regs)) {
+		send_user_sigtrap(TRAP_BRKPT);
+	} else if (!handler_found) {
 		pr_warn("Unexpected kernel BRK exception at EL1\n");
 		return -EFAULT;
 	}
-- 
2.5.5