[Valgrind-developers] memcheck/tests/overlap test failing on Debian 9/glibc 2.24

[Philippe W. <phi...@sk...>]

14 valgrind regression tests are failing on Debian 9/x86_64
(all tests were succesful on Debian 8).

memcheck/tests/overlap tests fails because valgrind does not detect
anymore memcpy calls with overlapping arguments.

As far as I can see, this is because memcpy on avx+erms+... CPUs
is (with glibc 2.24) implemented by calling an optimised memmove
implementation:

(gdb) bt
#0   () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:210
#1  0x000055555555478e in main () at redirf.c:22
(gdb) list redirf.c:22
17	      x[i] = 0;
18	
19	   }
20	
21	   memcpy(x+50, x, 20);    // no overlap
22	   memcpy(x+70, x, 10);    // no overlap
23	   return 0;
24	}
(gdb) 


The redir mechanism of valgrind then redirects the memcpy calls to
its memmove vg_replace_mem.c, that does not detect overlap.
This somewhat sounds like the return of 
https://bugs.kde.org/show_bug.cgi?id=275284


Is that failure also seen on other x86_64 glibc 2.24 or 2.25 systems ?

Is there any way to improve the redir mechanism to e.g. redirect at
the level of the call to 
   callq  0x555555554580 <memcpy@plt>
rather than redirecting later at the ifunc function that points to
__memmove_avx_unaligned_erms ?

Any other idea ?

Philippe