Re: [Linuxsampler-devel] problem to build linuxsampler 2.4.0 for armv7hl

[Philippe D. <phi...@la...>]

Le 18/06/2025 à 12:25, Christian Schoenebeck a écrit :
> On Tuesday, June 17, 2025 2:16:19 AM CEST Philippe DIDIER wrote:
>> Hi
> Hi Philippe,
>
>> We use to create rpms of gig linuxsampler gigedit and qsampler for i686
>> , x86_64 , aarch64  and  armv7hl...
>>
>> There's something wrong when we try to build linuxsampler 2.4.0 for
>> armv7hl :
>>
>> This concerns RTMath.cpp ... We get a build failure with this message :
>>
>> RTMath.cpp:79:19: error: invalid operand for instruction
>>       79 |     asm volatile ("mrs %0, cntvct_el0" : "=r"(t));
>>
>>
>> This is linked to the instructions from line 77 to 80 #elif
>> defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7S__) uint32_t t; asm
>> volatile ("mrs %0, cntvct_el0" : "=r"(t)); return t;
>>
>> Maybe we should use for ARM_ARCH_75
> Yeah, looks like that's an ARMv8 (a.k.a. ARM64) feature.
>
>> the same instruction as for ARMv6 ... that is :
>>       uint32_t t;
>>       asm volatile ("mrc p15, 0, %0, c15, c12, 1" : "=r" (t));
>>       return t;
> I think that also needs some correction. Can you test the following patch?
>
> Index: src/common/RTMath.cpp
> ===================================================================
> --- src/common/RTMath.cpp       (revision 4334)
> +++ src/common/RTMath.cpp       (working copy)
> @@ -74,16 +74,12 @@
>       uint64_t t;
>       asm volatile ("mrs %0, cntvct_el0" : "=r"(t));
>       return (time_stamp_t) t;
> -    #elif defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7S__)
> -    uint32_t t;
> -    asm volatile ("mrs %0, cntvct_el0" : "=r"(t));
> -    return t;
>       #elif defined(__APPLE__)
>       return (time_stamp_t) mach_absolute_time();
>       #elif defined(__arm__) /* ARMv6 and older */
>       # warning ARM 'mrc' instruction requires special runtime privileges!
>       uint32_t t;
> -    asm volatile ("mrc p15, 0, %0, c15, c12, 1" : "=r" (t));
> +    asm volatile ("mrc p15, 0, %0, c9, c13, 0" : "=r" (t));
>       return t;
>       #else // we don't want to use a slow generic solution
>       #  error "Sorry, LinuxSampler lacks time stamp code for your system."
>
> Would be good to know not only if it compiles, but whether it works at
> runtime. Because as you can see from the warning, special privileges or
> preceding system configuration steps might be required for this to work at
> all.
>
> If not, it's getting pretty ugly for the user. Since the sampler would first
> start without complaint and eventually after loading a sound the app would die
> with illegal instruction exception.
>
> /Christian
>
>
>
>
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Hi Christian

We have tested 2 patches (the first from me the second from an other 
packager) :


--- src/common/RTMath.cpp
+++ src/common/RTMath.cpp
@@ -75,9 +75,9 @@
      asm volatile ("mrs %0, cntvct_el0" : "=r"(t));
      return (time_stamp_t) t;
      #elif defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7S__)
-    uint32_t t;
-    asm volatile ("mrs %0, cntvct_el0" : "=r"(t));
-    return t;
+    uint32_t t;
+    asm volatile ("mrc p15, 0, %0, c15, c12, 1" : "=r" (t));
+    return t;
      #elif defined(__APPLE__)
      return (time_stamp_t) mach_absolute_time();
      #elif defined(__arm__) /* ARMv6 and older */



--- src/common/RTMath.cpp
+++ src/common/RTMath.cpp
@@ -75,9 +75,9 @@
      asm volatile ("mrs %0, cntvct_el0" : "=r"(t));
      return (time_stamp_t) t;
      #elif defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7S__)
-    uint32_t t;
-    asm volatile ("mrs %0, cntvct_el0" : "=r"(t));
-    return t;
+    uint32_t hi, lo;
+    asm volatile ("mrrc p15, 1, %0, %1, c14" : "=r"(lo), "=r" (hi));
+    return lo;
      #elif defined(__APPLE__)
      return (time_stamp_t) mach_absolute_time();
      #elif defined(__arm__) /* ARMv6 and older */


Both of them allow to compile for armv7hl on our BuildSystem
Nevertheless I choosed to apply the first one with
return t   and not      return lo
for coherency with the other arches


I'm gonna test to compile with

asm volatile ("mrc p15, 0, %0, c9, c13, 0" : "=r" (t));


Unfortunately we can't test the use on a real armv7hl system (using a 
virtual system is not enough)