On 2018-05-07 15:35, Ralf Ramsauer wrote:
> On 05/07/2018 03:25 PM, Jan Kiszka wrote:
>> On 2018-05-07 14:12, Ralf Ramsauer wrote:
>>> Don't jump directly to inmate_main from assembly, jump to c_entry.
>>>
>>> At the moment, c_entry does nothing else than jumping to inmate_main and
>>> ending up in an endless loop if inmate_main returns.
>>>
>>> Later we can use c_entry to do platform independant setup/checks.
>>>
>>> Signed-off-by: Ralf Ramsauer <[email protected]>
>>> ---
>>>  inmates/lib/arm-common/Makefile.lib | 2 +-
>>>  inmates/lib/arm/header.S            | 2 +-
>>>  inmates/lib/arm64/header.S          | 2 +-
>>>  inmates/lib/setup.c                 | 9 +++++++++
>>>  inmates/lib/x86/Makefile            | 2 +-
>>>  inmates/lib/x86/header.S            | 2 +-
>>>  6 files changed, 14 insertions(+), 5 deletions(-)
>>>  create mode 100644 inmates/lib/setup.c
>>>
>>> diff --git a/inmates/lib/arm-common/Makefile.lib 
>>> b/inmates/lib/arm-common/Makefile.lib
>>> index fb3b6585..9edb2d9f 100644
>>> --- a/inmates/lib/arm-common/Makefile.lib
>>> +++ b/inmates/lib/arm-common/Makefile.lib
>>> @@ -36,7 +36,7 @@
>>>  # THE POSSIBILITY OF SUCH DAMAGE.
>>>  #
>>>  
>>> -objs-y := ../string.o ../cmdline.o
>>> +objs-y := ../string.o ../cmdline.o ../setup.o
>>>  objs-y += printk.o gic.o timer.o
>>>  objs-y += uart-jailhouse.o uart-pl011.o uart-8250.o uart-8250-8.o
>>>  objs-y += uart-xuartps.o uart-mvebu.o uart-hscif.o uart-scifa.o uart-imx.o
>>> diff --git a/inmates/lib/arm/header.S b/inmates/lib/arm/header.S
>>> index d0a8f219..be1d23a8 100644
>>> --- a/inmates/lib/arm/header.S
>>> +++ b/inmates/lib/arm/header.S
>>> @@ -85,6 +85,6 @@ __reset_entry:
>>>  
>>>  2: ldr     sp, =stack_top
>>>  
>>> -   b       inmate_main
>>> +   b       c_entry
>>>  
>>>     .ltorg
>>> diff --git a/inmates/lib/arm64/header.S b/inmates/lib/arm64/header.S
>>> index e284aa5a..011aeb63 100644
>>> --- a/inmates/lib/arm64/header.S
>>> +++ b/inmates/lib/arm64/header.S
>>> @@ -57,7 +57,7 @@ __reset_entry:
>>>  
>>>     isb
>>>  
>>> -   b       inmate_main
>>> +   b       c_entry
>>>  
>>>  handle_irq:
>>>     bl      vector_irq
>>> diff --git a/inmates/lib/setup.c b/inmates/lib/setup.c
>>> new file mode 100644
>>> index 00000000..ed35b6f8
>>> --- /dev/null
>>> +++ b/inmates/lib/setup.c
>>> @@ -0,0 +1,9 @@
>>> +#include <inmate.h>
>>> +
>>> +void __attribute__((noreturn)) c_entry(void);
>>> +
>>> +void __attribute__((noreturn)) c_entry(void)
>>> +{
>>> +   inmate_main();
>>> +   spin_forever();
>>
>> When spin_forever/halt used like that, we should ensure first that
>> interrupts are disabled.
> 
> Hmm, yes, they could be disabled. Though they shouldn't harm us.
> 
> What about a architecture-dependent stop() or stop_machine() function
> that first disables IRQs and then enters halt()?
> 
> Do you also want to deinitialise the GIC? Shouldn't be necessary, though.

If we just define this as stop(), I see no point in doing it in c_entry
anymore. Then there will be only one user, and that one can also just
return to header and let it handle the stop.

> 
>>
>>> +}
>>> diff --git a/inmates/lib/x86/Makefile b/inmates/lib/x86/Makefile
>>> index de4d74b7..6561d0cf 100644
>>> --- a/inmates/lib/x86/Makefile
>>> +++ b/inmates/lib/x86/Makefile
>>> @@ -41,7 +41,7 @@ include $(INMATES_LIB)/Makefile.lib
>>>  always := lib.a lib32.a
>>>  
>>>  TARGETS := header.o hypercall.o ioapic.o printk.o smp.o
>>> -TARGETS += ../pci.o ../string.o ../cmdline.o
>>> +TARGETS += ../pci.o ../string.o ../cmdline.o ../setup.o
>>>  TARGETS_64_ONLY := int.o mem.o pci.o timing.o
>>>  
>>>  ccflags-y := -ffunction-sections
>>> diff --git a/inmates/lib/x86/header.S b/inmates/lib/x86/header.S
>>> index 95c7a5a4..1df4345b 100644
>>> --- a/inmates/lib/x86/header.S
>>> +++ b/inmates/lib/x86/header.S
>>> @@ -116,7 +116,7 @@ start64:
>>>     mov $bss_qwords,%rcx
>>>     rep stosq
>>>  
>>> -   mov $inmate_main,%rbx
>>> +   mov $c_entry,%rbx
>>>  
>>>  call_entry:
>>>     mov $stack_top,%rsp
>>>
>>
>> x86 has assembly code after the call that also does cli; hlt. That can
>> go when moving it to C.
> 
> Ack.
> 
>>
>> And you forgot header-32.S on x86.
> 
> Ups, sorry.
> 
>>
>> Might be worth checking at some point if there is more to convert,
>> though we would then need arch_c_entry() as well.
> 
> Yeah, I also thought of that. But at the moment there's nothing arch
> dependent. And my uart patches won't introduce anything architecture
> dependent as well. Maybe there will be something in the future, but it's
> not a big issue to add an arch_c_entry() hook.
> 

Right, was more a note to eventually check the existing logic again. Or
thinking of it when adding more (like cache enabling).

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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