linux-kernel - [PATCH v3 3/3] kernel: debug: Centralize dbg_[de]activate_sw

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Message-Id: <20200927211531.1380577-4-daniel.thompson@linaro.org>
Date:   Sun, 27 Sep 2020 22:15:31 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Jason Wessel <jason.wessel@...driver.com>,
        Douglas Anderson <dianders@...omium.org>
Cc:     Daniel Thompson <daniel.thompson@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>, sumit.garg@...aro.org,
        pmladek@...e.com, sergey.senozhatsky@...il.com, will@...nel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        kgdb-bugreport@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        patches@...aro.org
Subject: [PATCH v3 3/3] kernel: debug: Centralize dbg_[de]activate_sw_breakpoints

During debug trap execution we expect dbg_deactivate_sw_breakpoints()
to be paired with an dbg_activate_sw_breakpoint(). Currently although
the calls are paired correctly they are needlessly smeared across three
different functions. Worse this also results in code to drive polled I/O
being called with breakpoints activated which, in turn, needlessly
increases the set of functions that will recursively trap if breakpointed.

Fix this by moving the activation of breakpoints into the debug core.

Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>
Reviewed-by: Douglas Anderson <dianders@...omium.org>
---
 kernel/debug/debug_core.c       | 2 ++
 kernel/debug/gdbstub.c          | 1 -
 kernel/debug/kdb/kdb_debugger.c | 2 --
 3 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index faa1f99ce65a..e4339fd82db0 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -768,6 +768,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
 		}
 	}
 
+	dbg_activate_sw_breakpoints();
+
 	/* Call the I/O driver's post_exception routine */
 	if (dbg_io_ops->post_exception)
 		dbg_io_ops->post_exception();
diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
index cc3c43dfec44..e9a9c3097089 100644
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -1061,7 +1061,6 @@ int gdb_serial_stub(struct kgdb_state *ks)
 				error_packet(remcom_out_buffer, -EINVAL);
 				break;
 			}
-			dbg_activate_sw_breakpoints();
 			fallthrough;	/* to default processing */
 		default:
 default_handle:
diff --git a/kernel/debug/kdb/kdb_debugger.c b/kernel/debug/kdb/kdb_debugger.c
index 53a0df6e4d92..0220afda3200 100644
--- a/kernel/debug/kdb/kdb_debugger.c
+++ b/kernel/debug/kdb/kdb_debugger.c
@@ -147,7 +147,6 @@ int kdb_stub(struct kgdb_state *ks)
 		return DBG_PASS_EVENT;
 	}
 	kdb_bp_install(ks->linux_regs);
-	dbg_activate_sw_breakpoints();
 	/* Set the exit state to a single step or a continue */
 	if (KDB_STATE(DOING_SS))
 		gdbstub_state(ks, "s");
@@ -167,7 +166,6 @@ int kdb_stub(struct kgdb_state *ks)
 		 * differently vs the gdbstub
 		 */
 		kgdb_single_step = 0;
-		dbg_deactivate_sw_breakpoints();
 		return DBG_SWITCH_CPU_EVENT;
 	}
 	return kgdb_info[ks->cpu].ret_state;
-- 
2.25.4