Re: "Failed to create /dev/root: -14" after commit e6978e4bf1 ("ARM: save and reset the address limit when entering an exception")

[Guenter Roeck]

On 08/03/2016 01:38 AM, Russell King - ARM Linux wrote:

On Tue, Aug 02, 2016 at 07:51:45PM -0700, Guenter Roeck wrote:

Hi,

I see the following crash when running a qemu arm 'kzm' runtime test with
the current mainline.
...
Failed to create /dev/root: -14

[ followed by panic ]

A complete log file is at [1].

I think it's because of those undefined instructions you're hitting
with the hw-breakpoint code... can you try the patch below please?

  arch/arm/kernel/entry-armv.S | 1 +
  1 file changed, 1 insertion(+)

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index bc5f50799d75..9f157e7c51e7 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -295,6 +295,7 @@ __und_svc_fault:
        bl      __und_fault

  __und_svc_finish:
+       get_thread_info tsk
        ldr     r5, [sp, #S_PSR]                @ Get SVC cpsr
        svc_exit r5                             @ return from exception
   UNWIND(.fnend                )

Yes, that fixes the problem.

Assuming you'll create a patch:

Tested-by: Guenter Roeck <li...@roeck-us.net>

Does that need to be addressed in qemu, or is it a Linux bug ?

Thanks,
Guenter