linux-kernel - [PATCH] kgdb: Fix to kill breakpoints on initmem after boot

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Message-Id: <20210224081652.587785-1-sumit.garg@linaro.org>
Date:   Wed, 24 Feb 2021 13:46:52 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     kgdb-bugreport@...ts.sourceforge.net
Cc:     akpm@...ux-foundation.org, mhiramat@...nel.org,
        rostedt@...dmis.org, daniel.thompson@...aro.org,
        jason.wessel@...driver.com, dianders@...omium.org,
        peterz@...radead.org, stefan.saecherl@....de,
        qy15sije@....cs.fau.de, linux-kernel@...r.kernel.org,
        Sumit Garg <sumit.garg@...aro.org>
Subject: [PATCH] kgdb: Fix to kill breakpoints on initmem after boot

Currently breakpoints in kernel .init.text section are not handled
correctly while allowing to remove them even after corresponding pages
have been freed.

Fix it via killing .init.text section breakpoints just prior to initmem
pages being freed.

Suggested-by: Doug Anderson <dianders@...omium.org>
Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
---
 include/linux/kgdb.h      |  2 ++
 init/main.c               |  1 +
 kernel/debug/debug_core.c | 11 +++++++++++
 3 files changed, 14 insertions(+)

diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 57b8885708e5..3aa503ef06fc 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -361,9 +361,11 @@ extern atomic_t			kgdb_active;
 extern bool dbg_is_early;
 extern void __init dbg_late_init(void);
 extern void kgdb_panic(const char *msg);
+extern void kgdb_free_init_mem(void);
 #else /* ! CONFIG_KGDB */
 #define in_dbg_master() (0)
 #define dbg_late_init()
 static inline void kgdb_panic(const char *msg) {}
+static inline void kgdb_free_init_mem(void) { }
 #endif /* ! CONFIG_KGDB */
 #endif /* _KGDB_H_ */
diff --git a/init/main.c b/init/main.c
index c68d784376ca..a446ca3d334e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1417,6 +1417,7 @@ static int __ref kernel_init(void *unused)
 	async_synchronize_full();
 	kprobe_free_init_mem();
 	ftrace_free_init_mem();
+	kgdb_free_init_mem();
 	free_initmem();
 	mark_readonly();
 
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index 229dd119f430..319381e95d1d 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -465,6 +465,17 @@ int dbg_remove_all_break(void)
 	return 0;
 }
 
+void kgdb_free_init_mem(void)
+{
+	int i;
+
+	/* Clear init memory breakpoints. */
+	for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) {
+		if (init_section_contains((void *)kgdb_break[i].bpt_addr, 0))
+			kgdb_break[i].state = BP_UNDEFINED;
+	}
+}
+
 #ifdef CONFIG_KGDB_KDB
 void kdb_dump_stack_on_cpu(int cpu)
 {
-- 
2.25.1