[PATCH 5.4 46/64] ARM: Fix kgdb breakpoint for Thumb2

Greg Kroah-Hartman
2022-03-07T09:33:35Z

From: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

commit d920eaa4c4559f59be7b4c2d26fa0a2e1aaa3da9 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm/kernel/kgdb.c | 36 ++++++++++++++++++++++++++++--------
1 file changed, 28 insertions(+), 8 deletions(-)

--- a/arch/arm/kernel/kgdb.c
+++ b/arch/arm/kernel/kgdb.c
@@ -154,22 +154,38 @@ static int kgdb_compiled_brk_fn(struct p
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);
}