diff --git a/support/Makefile b/support/Makefile
index 9b50eac117..91b940c379 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -76,6 +76,7 @@ libsupport-routines = \
   support_quote_string \
   support_record_failure \
   support_run_diff \
+  support_scramble_registers \
   support_select_modifies_timeout \
   support_select_normalizes_timeout \
   support_set_small_thread_stack_size \
diff --git a/support/support.h b/support/support.h
index d20051da4d..3d049575d0 100644
--- a/support/support.h
+++ b/support/support.h
@@ -233,6 +233,11 @@ void support_stack_free (struct support_stack *stack);
    The returned value is the lowest file descriptor number.  */
 int support_open_dev_null_range (int num, int flags, mode_t mode);
 
+/* Write arbitrary values to all registers that can be written do, to
+   avoid assumptions about initial register contents in test
+   cases.  */
+void support_scramble_registers (void);
+
 __END_DECLS
 
 #endif /* SUPPORT_H */
diff --git a/support/support_scramble_registers.c b/support/support_scramble_registers.c
new file mode 100644
index 0000000000..d5e2d3fd6d
--- /dev/null
+++ b/support/support_scramble_registers.c
@@ -0,0 +1,29 @@
+/* scramble any call-not-preserved registers
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include "scramble-regs.h"
+
+void
+support_scramble_registers(void)
+{
+#ifdef SCRAMBLE_REGS
+  SCRAMBLE_REGS;
+#endif
+}
diff --git a/support/support_test_main.c b/support/support_test_main.c
index 60307fd68e..0ccb182791 100644
--- a/support/support_test_main.c
+++ b/support/support_test_main.c
@@ -269,6 +269,8 @@ adjust_exit_status (int status)
 int
 support_test_main (int argc, char **argv, const struct test_config *config)
 {
+  support_scramble_registers();
+
   if (test_main_called)
     {
       printf ("error: test_main called for a second time\n");
diff --git a/sysdeps/generic/scramble-regs.h b/sysdeps/generic/scramble-regs.h
new file mode 100644
index 0000000000..e3c158d475
--- /dev/null
+++ b/sysdeps/generic/scramble-regs.h
@@ -0,0 +1,36 @@
+/* scramble any call-not-preserved registers, target portion.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Example target-specific usage:
+
+   #define SCRAMBLE_REGS \
+     asm volatile ("movl %0, %%eax" :: "i" (1235) : "%eax"); \
+     asm volatile ("movl %0, %%edx" :: "i" (3579) : "%edx");
+
+   Targets are encouraged to create their own target-specific sub-definitions, like
+   
+   #ifndef SCRAMBLE_REGS_FPU
+   #define SCRAMBLE_REGS_FPU
+   #endif
+   #define SCRAMBLE_REGS \
+     SCRAMBLE_REGS_FPU \
+     asm volatile ("..."); \
+
+*/
+
+/* #define SCRAMBLE_REGS */
diff --git a/sysdeps/powerpc/scramble-regs.h b/sysdeps/powerpc/scramble-regs.h
new file mode 100644
index 0000000000..8480ac0da3
--- /dev/null
+++ b/sysdeps/powerpc/scramble-regs.h
@@ -0,0 +1,30 @@
+/* scramble any call-not-preserved registers, powerpc version
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#define SCRAMBLE_REGS		       \
+  asm volatile ("li 0, %0" :: "i" (0x1235) : "0"); \
+  asm volatile ("li 3, %0" :: "i" (0x1235) : "3"); \
+  asm volatile ("li 4, %0" :: "i" (0x1235) : "4"); \
+  asm volatile ("li 5, %0" :: "i" (0x1235) : "5"); \
+  asm volatile ("li 6, %0" :: "i" (0x1235) : "6"); \
+  asm volatile ("li 7, %0" :: "i" (0x1235) : "7"); \
+  asm volatile ("li 8, %0" :: "i" (0x1235) : "8"); \
+  asm volatile ("li 9, %0" :: "i" (0x1235) : "9"); \
+  asm volatile ("li 10, %0" :: "i" (0x1235) : "10"); \
+  asm volatile ("li 11, %0" :: "i" (0x1235) : "11"); \
+  asm volatile ("li 12, %0" :: "i" (0x1235) : "12");
diff --git a/sysdeps/riscv/scramble-regs.h b/sysdeps/riscv/scramble-regs.h
new file mode 100644
index 0000000000..85bc1d501c
--- /dev/null
+++ b/sysdeps/riscv/scramble-regs.h
@@ -0,0 +1,34 @@
+/* scramble any call-not-preserved registers, powerpc version
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#define SCRAMBLE_REGS		       \
+  asm volatile ("li t0, %0" :: "i" (0x13579bdf) : "t0"); \
+  asm volatile ("li t1, %0" :: "i" (0x13579bdf) : "t1"); \
+  asm volatile ("li t2, %0" :: "i" (0x13579bdf) : "t2"); \
+  asm volatile ("li t3, %0" :: "i" (0x13579bdf) : "t3"); \
+  asm volatile ("li t4, %0" :: "i" (0x13579bdf) : "t4"); \
+  asm volatile ("li t5, %0" :: "i" (0x13579bdf) : "t5"); \
+  asm volatile ("li t6, %0" :: "i" (0x13579bdf) : "t6"); \
+  asm volatile ("li a0, %0" :: "i" (0x13579bdf) : "a0"); \
+  asm volatile ("li a1, %0" :: "i" (0x13579bdf) : "a1"); \
+  asm volatile ("li a2, %0" :: "i" (0x13579bdf) : "a2"); \
+  asm volatile ("li a3, %0" :: "i" (0x13579bdf) : "a3"); \
+  asm volatile ("li a4, %0" :: "i" (0x13579bdf) : "a4"); \
+  asm volatile ("li a5, %0" :: "i" (0x13579bdf) : "a5"); \
+  asm volatile ("li a6, %0" :: "i" (0x13579bdf) : "a6"); \
+  asm volatile ("li a7, %0" :: "i" (0x13579bdf) : "a7");
diff --git a/sysdeps/x86_64/scramble-regs.h b/sysdeps/x86_64/scramble-regs.h
new file mode 100644
index 0000000000..3993c3b843
--- /dev/null
+++ b/sysdeps/x86_64/scramble-regs.h
@@ -0,0 +1,31 @@
+/* scramble any call-not-preserved registers, x86_64 version
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* SysV ABI: preserve EBX, ESP, EBP and R12-R15.  */
+
+#define SCRAMBLE_REGS		       \
+  asm volatile ("movl %0, %%eax" :: "i" (0x12345679) : "%eax");	\
+  asm volatile ("movl %0, %%ecx" :: "i" (0x12345679) : "%ecx");	\
+  asm volatile ("movl %0, %%edx" :: "i" (0x12345679) : "%edx");	\
+  asm volatile ("movl %0, %%esi" :: "i" (0x12345679) : "%esi");	\
+  asm volatile ("movl %0, %%edi" :: "i" (0x12345679) : "%edi");	\
+  asm volatile ("mov %0, %%r8"  :: "i" (0x12345679) : "%r8");	\
+  asm volatile ("mov %0, %%r9"  :: "i" (0x12345679) : "%r9");	\
+  asm volatile ("mov %0, %%r10" :: "i" (0x12345679) : "%r10");	\
+  asm volatile ("mov %0, %%r11" :: "i" (0x12345679) : "%r11");	\
+
