Created attachment 126911 [details]
Patch: enabling getcpu on arm32

SUMMARY


STEPS TO REPRODUCE
1. 

run the following code on an arm-32 platform (in my case, a raspberry pi).

#include ....

int main () {
  printf("getcpu = %d\n", sched_getcpu());
  return 0;
}

OBSERVED RESULT

==19515== Memcheck, a memory error detector
==19515== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==19515== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==19515== Command: ./getcpu
==19515== 
--19515-- WARNING: unhandled arm-linux syscall: 345
--19515-- You may be able to write your own handler.
--19515-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
--19515-- Nevertheless we consider this a bug.  Please report
--19515-- it at http://valgrind.org/support/bug_reports.html.
getcpu = -1
==19515== 
==19515== HEAP SUMMARY:
==19515==     in use at exit: 0 bytes in 0 blocks
==19515==   total heap usage: 1 allocs, 1 frees, 4,096 bytes allocated
==19515== 
==19515== All heap blocks were freed -- no leaks are possible
==19515== 
==19515== For lists of detected and suppressed errors, rerun with: -s
==19515== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)


EXPECTED RESULT

==19525== Memcheck, a memory error detector
==19525== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==19525== Using Valgrind-3.16.0.GIT and LibVEX; rerun with -h for copyright info
==19525== Command: ./getcpu
==19525== 
getcpu = 0
==19525== 
==19525== HEAP SUMMARY:
==19525==     in use at exit: 0 bytes in 0 blocks
==19525==   total heap usage: 1 allocs, 1 frees, 4,096 bytes allocated
==19525== 
==19525== All heap blocks were freed -- no leaks are possible
==19525== 
==19525== For lists of detected and suppressed errors, rerun with: -s
==19525== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)


ADDITIONAL INFORMATION


I reached this situation while debugging a dotnet application.

The patch is attached. By just simply uncommenting the syscall on syswrap-arm-linux.c, it was possible to make it work and return the correct output.

Regards.