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, 17 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/xtensa/__longjmp.S b/libc/sysdeps/linux/xtensa/__longjmp.S
index 4d55906db..acc0b4ff2 100644
--- a/libc/sysdeps/linux/xtensa/__longjmp.S
+++ b/libc/sysdeps/linux/xtensa/__longjmp.S
@@ -48,6 +48,7 @@
 
 ENTRY (__longjmp)
 
+#if defined(__XTENSA_WINDOWED_ABI__)
 	/* Invalidate all but the current window.  Reading and writing
 	   special registers WINDOWBASE and WINDOWSTART are
 	   privileged operations, so user processes must call the
@@ -120,6 +121,22 @@ ENTRY (__longjmp)
 	movnez	a2, a3, a3
 
 	retw
+#elif defined(__XTENSA_CALL0_ABI__)
+	l32i	a0, a2, 0
+	l32i	a1, a2, 4
+	l32i	a12, a2, 8
+	l32i	a13, a2, 12
+	l32i	a14, a2, 16
+	l32i	a15, a2, 20
+
+	/* Return v ? v : 1.  */
+	movi	a2, 1
+	movnez	a2, a3, a3
+
+	ret
+#else
+#error Unsupported Xtensa ABI
+#endif
 END (__longjmp)
 
 libc_hidden_def (__longjmp)