From 0fada277147ffc6d694aa32162f51198d4f10d94 Mon Sep 17 00:00:00 2001

From: Jamie Iles <jamie@nuviainc.com>

Date: Mon, 12 Oct 2020 14:04:46 +0100

Subject: [PATCH] ACPI: debug: don't allow debugging when ACPI is disabled

Git-commit: 0fada277147ffc6d694aa32162f51198d4f10d94

Patch-mainline: v5.10-rc1

References: git-fixes

If ACPI is disabled then loading the acpi_dbg module will result in the

following splat when lock debugging is enabled.

  DEBUG_LOCKS_WARN_ON(lock->magic != lock)

  WARNING: CPU: 0 PID: 1 at kernel/locking/mutex.c:938 __mutex_lock+0xa10/0x1290

  Kernel panic - not syncing: panic_on_warn set ...

  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc8+ #103

  Hardware name: linux,dummy-virt (DT)

  Call trace:

   dump_backtrace+0x0/0x4d8

   show_stack+0x34/0x48

   dump_stack+0x174/0x1f8

   panic+0x360/0x7a0

   __warn+0x244/0x2ec

   report_bug+0x240/0x398

   bug_handler+0x50/0xc0

   call_break_hook+0x160/0x1d8

   brk_handler+0x30/0xc0

   do_debug_exception+0x184/0x340

   el1_dbg+0x48/0xb0

   el1_sync_handler+0x170/0x1c8

   el1_sync+0x80/0x100

   __mutex_lock+0xa10/0x1290

   mutex_lock_nested+0x6c/0xc0

   acpi_register_debugger+0x40/0x88

   acpi_aml_init+0xc4/0x114

   do_one_initcall+0x24c/0xb10

   kernel_init_freeable+0x690/0x728

   kernel_init+0x20/0x1e8

   ret_from_fork+0x10/0x18

This is because acpi_debugger.lock has not been initialized as

acpi_debugger_init() is not called when ACPI is disabled.  Fail module

loading to avoid this and any subsequent problems that might arise by

trying to debug AML when ACPI is disabled.

Fixes: 8cfb0cdf07e2 ("ACPI / debugger: Add IO interface to access debugger functionalities")

Reviewed-by: Hanjun Guo <guohanjun@huawei.com>

Signed-off-by: Jamie Iles <jamie@nuviainc.com>

Cc: 4.10+ <stable@vger.kernel.org> # 4.10+

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/acpi/acpi_dbg.c |    3 +++

 1 file changed, 3 insertions(+)

--- a/drivers/acpi/acpi_dbg.c

+++ b/drivers/acpi/acpi_dbg.c

@@ -757,6 +757,9 @@ int __init acpi_aml_init(void)

 		goto err_exit;

 	}

+	if (acpi_disabled)

+		return -ENODEV;

+

 	/* Initialize AML IO interface */

 	mutex_init(&acpi_aml_io.lock);

 	init_waitqueue_head(&acpi_aml_io.wait);