From d920eaa4c4559f59be7b4c2d26fa0a2e1aaa3da9 Mon Sep 17 00:00:00 2001
From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Date: Wed, 16 Feb 2022 15:37:38 +0000
Subject: [PATCH] ARM: Fix kgdb breakpoint for Thumb2
Git-commit: d920eaa4c4559f59be7b4c2d26fa0a2e1aaa3da9
Patch-mainline: v5.17-rc7
References: git-fixes

The kgdb code needs to register an undef hook for the Thumb UDF
instruction that will fault in order to be functional on Thumb2
platforms.

Reported-by: Johannes Stezenbach <js@sig21.net>
Tested-by: Johannes Stezenbach <js@sig21.net>
Fixes: 5cbad0ebf45c ("kgdb: support for ARCH=arm")
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 arch/arm/kernel/kgdb.c | 36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
index 7bd30c0a4280..22f937e6f3ff 100644
--- a/arch/arm/kernel/kgdb.c
+++ b/arch/arm/kernel/kgdb.c
@@ -154,22 +154,38 @@ static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr)
 	return 0;
 }
 
-static struct undef_hook kgdb_brkpt_hook = {
+static struct undef_hook kgdb_brkpt_arm_hook = {
 	.instr_mask		= 0xffffffff,
 	.instr_val		= KGDB_BREAKINST,
-	.cpsr_mask		= MODE_MASK,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
 	.cpsr_val		= SVC_MODE,
 	.fn			= kgdb_brk_fn
 };
 
-static struct undef_hook kgdb_compiled_brkpt_hook = {
+static struct undef_hook kgdb_brkpt_thumb_hook = {
+	.instr_mask		= 0xffff,
+	.instr_val		= KGDB_BREAKINST & 0xffff,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
+	.cpsr_val		= PSR_T_BIT | SVC_MODE,
+	.fn			= kgdb_brk_fn
+};
+
+static struct undef_hook kgdb_compiled_brkpt_arm_hook = {
 	.instr_mask		= 0xffffffff,
 	.instr_val		= KGDB_COMPILED_BREAK,
-	.cpsr_mask		= MODE_MASK,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
 	.cpsr_val		= SVC_MODE,
 	.fn			= kgdb_compiled_brk_fn
 };
 
+static struct undef_hook kgdb_compiled_brkpt_thumb_hook = {
+	.instr_mask		= 0xffff,
+	.instr_val		= KGDB_COMPILED_BREAK & 0xffff,
+	.cpsr_mask		= PSR_T_BIT | MODE_MASK,
+	.cpsr_val		= PSR_T_BIT | SVC_MODE,
+	.fn			= kgdb_compiled_brk_fn
+};
+
 static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 {
 	struct pt_regs *regs = args->regs;
@@ -210,8 +226,10 @@ int kgdb_arch_init(void)
 	if (ret != 0)
 		return ret;
 
-	register_undef_hook(&kgdb_brkpt_hook);
-	register_undef_hook(&kgdb_compiled_brkpt_hook);
+	register_undef_hook(&kgdb_brkpt_arm_hook);
+	register_undef_hook(&kgdb_brkpt_thumb_hook);
+	register_undef_hook(&kgdb_compiled_brkpt_arm_hook);
+	register_undef_hook(&kgdb_compiled_brkpt_thumb_hook);
 
 	return 0;
 }
@@ -224,8 +242,10 @@ int kgdb_arch_init(void)
  */
 void kgdb_arch_exit(void)
 {
-	unregister_undef_hook(&kgdb_brkpt_hook);
-	unregister_undef_hook(&kgdb_compiled_brkpt_hook);
+	unregister_undef_hook(&kgdb_brkpt_arm_hook);
+	unregister_undef_hook(&kgdb_brkpt_thumb_hook);
+	unregister_undef_hook(&kgdb_compiled_brkpt_arm_hook);
+	unregister_undef_hook(&kgdb_compiled_brkpt_thumb_hook);
 	unregister_die_notifier(&kgdb_notifier);
 }
 
-- 
2.31.1