* ColdFire and Thread-Local Storage
@ 2014-01-28 15:49 Sebastian Huber
2014-01-28 19:15 ` Ian Lance Taylor
0 siblings, 1 reply; 5+ messages in thread
From: Sebastian Huber @ 2014-01-28 15:49 UTC (permalink / raw)
To: gcc-help
Hi,
it seems GCC uses this ColdFire TLS ABI:
https://lists.debian.org/debian-68k/2007/11/msg00071.html
Here we have a function
void *__m68k_read_tp(void)
which must return the thread pointer in register a0.
I have to implement this function. Is there a way to instruct GCC to return
the value in register a0 instead of d0 or do I have to use assembler to
implement this function?
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.huber@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ColdFire and Thread-Local Storage
2014-01-28 15:49 ColdFire and Thread-Local Storage Sebastian Huber
@ 2014-01-28 19:15 ` Ian Lance Taylor
2014-01-29 7:51 ` Sebastian Huber
0 siblings, 1 reply; 5+ messages in thread
From: Ian Lance Taylor @ 2014-01-28 19:15 UTC (permalink / raw)
To: Sebastian Huber; +Cc: gcc-help
On Tue, Jan 28, 2014 at 7:49 AM, Sebastian Huber
<sebastian.huber@embedded-brains.de> wrote:
>
> it seems GCC uses this ColdFire TLS ABI:
>
> https://lists.debian.org/debian-68k/2007/11/msg00071.html
>
> Here we have a function
>
> void *__m68k_read_tp(void)
>
> which must return the thread pointer in register a0.
>
> I have to implement this function. Is there a way to instruct GCC to return
> the value in register a0 instead of d0 or do I have to use assembler to
> implement this function?
I believe that on m68k GNU/Linux a function that returns a pointer
will normally return the value in a0.
Ian
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ColdFire and Thread-Local Storage
2014-01-28 19:15 ` Ian Lance Taylor
@ 2014-01-29 7:51 ` Sebastian Huber
2014-01-29 19:50 ` Norbert Lange
0 siblings, 1 reply; 5+ messages in thread
From: Sebastian Huber @ 2014-01-29 7:51 UTC (permalink / raw)
To: Ian Lance Taylor; +Cc: gcc-help
On 2014-01-28 20:15, Ian Lance Taylor wrote:
> On Tue, Jan 28, 2014 at 7:49 AM, Sebastian Huber
> <sebastian.huber@embedded-brains.de> wrote:
>>
>> it seems GCC uses this ColdFire TLS ABI:
>>
>> https://lists.debian.org/debian-68k/2007/11/msg00071.html
>>
>> Here we have a function
>>
>> void *__m68k_read_tp(void)
>>
>> which must return the thread pointer in register a0.
>>
>> I have to implement this function. Is there a way to instruct GCC to return
>> the value in register a0 instead of d0 or do I have to use assembler to
>> implement this function?
>
> I believe that on m68k GNU/Linux a function that returns a pointer
> will normally return the value in a0.
>
> Ian
>
The function
void *__m68k_read_tp(void)
{
const Thread_Control *executing = _Thread_Get_executing();
return (char *) executing->Start.tls_area +
_TLS_Get_thread_control_block_area_size((uintptr_t) _TLS_Alignment)
+ 0x7000;
}
translates to
__m68k_read_tp:
move.l #_TLS_Alignment,%d0
moveq #8,%d1
move.l _Per_CPU_Information+18,%a0
cmp.l %d0,%d1
jls .L2
moveq #8,%d0
.L2:
add.l #28672,%d0
add.l 194(%a0),%d0
rts
I use now:
void __m68k_read_tp(void)
{
const Thread_Control *executing = _Thread_Get_executing();
void *tp = (char *) executing->Start.tls_area +
_TLS_Get_thread_control_block_area_size((uintptr_t) _TLS_Alignment)
+ 0x7000;
__asm__ volatile (
"move.l %0, %%a0"
:
: "d" (tp)
);
}
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.huber@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ColdFire and Thread-Local Storage
2014-01-29 7:51 ` Sebastian Huber
@ 2014-01-29 19:50 ` Norbert Lange
2014-01-30 10:43 ` Sebastian Huber
0 siblings, 1 reply; 5+ messages in thread
From: Norbert Lange @ 2014-01-29 19:50 UTC (permalink / raw)
To: gcc-help
Hello,
its been some time since I looked at the TLS conventions and I only done
this on ARM.
But I would strongly advise you to implement the function in asm, on ARM
you arent allowed to change any register except the one you return and I
would bet its the same on other architectures.
Norbert
Am 29.01.2014, 08:51 Uhr, schrieb Sebastian Huber
<sebastian.huber@embedded-brains.de>:
> On 2014-01-28 20:15, Ian Lance Taylor wrote:
>> On Tue, Jan 28, 2014 at 7:49 AM, Sebastian Huber
>> <sebastian.huber@embedded-brains.de> wrote:
>>>
>>> it seems GCC uses this ColdFire TLS ABI:
>>>
>>> https://lists.debian.org/debian-68k/2007/11/msg00071.html
>>>
>>> Here we have a function
>>>
>>> void *__m68k_read_tp(void)
>>>
>>> which must return the thread pointer in register a0.
>>>
>>> I have to implement this function. Is there a way to instruct GCC to
>>> return
>>> the value in register a0 instead of d0 or do I have to use assembler to
>>> implement this function?
>>
>> I believe that on m68k GNU/Linux a function that returns a pointer
>> will normally return the value in a0.
>>
>> Ian
>>
>
> The function
>
> void *__m68k_read_tp(void)
> {
> const Thread_Control *executing = _Thread_Get_executing();
>
> return (char *) executing->Start.tls_area +
> _TLS_Get_thread_control_block_area_size((uintptr_t) _TLS_Alignment)
> + 0x7000;
> }
>
> translates to
>
> __m68k_read_tp:
> move.l #_TLS_Alignment,%d0
> moveq #8,%d1
> move.l _Per_CPU_Information+18,%a0
> cmp.l %d0,%d1
> jls .L2
> moveq #8,%d0
> .L2:
> add.l #28672,%d0
> add.l 194(%a0),%d0
> rts
>
> I use now:
>
> void __m68k_read_tp(void)
> {
> const Thread_Control *executing = _Thread_Get_executing();
> void *tp = (char *) executing->Start.tls_area +
> _TLS_Get_thread_control_block_area_size((uintptr_t) _TLS_Alignment)
> + 0x7000;
>
> __asm__ volatile (
> "move.l %0, %%a0"
> :
> : "d" (tp)
> );
> }
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: ColdFire and Thread-Local Storage
2014-01-29 19:50 ` Norbert Lange
@ 2014-01-30 10:43 ` Sebastian Huber
0 siblings, 0 replies; 5+ messages in thread
From: Sebastian Huber @ 2014-01-30 10:43 UTC (permalink / raw)
To: gcc-help
Hello Norbert,
thanks for the warning.
On 2014-01-29 20:50, Norbert Lange wrote:
> its been some time since I looked at the TLS conventions and I only done this
> on ARM.
> But I would strongly advise you to implement the function in asm, on ARM you
> arent allowed to change any register except the one you return and I would bet
> its the same on other architectures.
Yes, this is true for ARM, here __aeabi_read_tp() can clobber only r0. On m68k
the situation is different:
https://lists.debian.org/debian-68k/2007/11/msg00071.html
"This TLS ABI defines a function __m68k_read_tp, provided by libc.
This returns the thread pointer in register a0 (not d0) and may
clobber other call-clobbered registers. The compiler will generate
calls to this function for the initial exec and local exec models."
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.huber@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschÀftliche Mitteilung im Sinne des EHUG.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2014-01-28 15:49 ColdFire and Thread-Local Storage Sebastian Huber
2014-01-28 19:15 ` Ian Lance Taylor
2014-01-29 7:51 ` Sebastian Huber
2014-01-29 19:50 ` Norbert Lange
2014-01-30 10:43 ` Sebastian Huber
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