xtensa: support call0 ABI

Most changes are mechanical replacement of 'retw' instruction with
'abi_ret' macro, defined to 'retw' or 'ret' according to ABI.
Assembly code that makes calls is duplicated for call0 ABI with changed
register numbers for parameters/return value and call instruction.
'entry' instructions are replaced with 'abi_entry' macro.

More interesting changes:
- non-leaf assembly functions (e.g. _dl_tlsdesc_dynamic,
  _dl_linux_resolve, SYSCALL_ERROR_HANDLER, PSEUDO) now need to preserve
  registers around intermediate calls they make, use temporary stack
  frame for that;
- setjmp/longjmp only need to save and restore return address, stack
  pointer and callee-saved registers in the jmpbuf;
- __clone and syscall functions had hardcoded offsets to parameter
  passed on stack, on call0 ABI they don't need stack frame, so the
  offset is different. Replace these offsets with FRAMESIZE macro.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/libc/sysdeps/linux/xtensa/syscall.S b/libc/sysdeps/linux/xtensa/syscall.S
index 0e1a5d0be..790a8d018 100644
--- a/libc/sysdeps/linux/xtensa/syscall.S
+++ b/libc/sysdeps/linux/xtensa/syscall.S
@@ -26,7 +26,7 @@
  */
 
 ENTRY (syscall)
-	l32i	a9, a1, 16	/* load extra argument from stack */
+	l32i	a9, a1, FRAMESIZE/* load extra argument from stack */
 	mov	a8, a7
 	mov	a7, a3		/* preserve a3 in a7 */
 	mov	a3, a4
@@ -37,5 +37,5 @@ ENTRY (syscall)
 	movi    a4, -4095
 	bgeu    a2, a4, SYSCALL_ERROR_LABEL
 .Lpseudo_end:
-	retw
+	abi_ret
 PSEUDO_END (syscall)