[glibc] powerpc64le/power9: guard power9 strcmp against rtld usage [BZ# 25905]

[glibc] powerpc64le/power9: guard power9 strcmp against rtld usage [BZ# 25905]

[Paul E. Murphy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4a4db1de2f0fd936b583698dcc1b1c12a71828c8

commit 4a4db1de2f0fd936b583698dcc1b1c12a71828c8
Author: Paul E. Murphy <murphyp@linux.vnet.ibm.com>
Date:   Fri May 1 14:30:42 2020 -0500

    powerpc64le/power9: guard power9 strcmp against rtld usage [BZ# 25905]
    
    strcmp is used while resolving PLT references.  Vector registers
    should not be used during this.  The P9 strcmp makes heavy use of
    vector registers, so it should be avoided in rtld.
    
    This prevents quiet vector register corruption when glibc is configured
    with --disable-multi-arch and --with-cpu=power9.  This can be seen with
    test-float64x-compat_totalordermag during the first call into
    totalordermagf64x@GLIBC_2.27.
    
    Add a guard to fallback to the power8 implementation when building
    power9 strcmp for libraries other than libc.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 sysdeps/powerpc/powerpc64/le/power9/rtld-strcmp.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sysdeps/powerpc/powerpc64/le/power9/rtld-strcmp.S b/sysdeps/powerpc/powerpc64/le/power9/rtld-strcmp.S
new file mode 100644
index 0000000000..afdb492b3d
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/le/power9/rtld-strcmp.S
@@ -0,0 +1,2 @@
+/* Fallback to P8 which does not use vector regs for rtld.  */
+#include <sysdeps/powerpc/powerpc64/power8/strcmp.S>