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, 41 insertions, 4 deletions

diff --git a/libc/sysdeps/linux/xtensa/sysdep.h b/libc/sysdeps/linux/xtensa/sysdep.h
index 4873a413d..ce2b0a0d6 100644
--- a/libc/sysdeps/linux/xtensa/sysdep.h
+++ b/libc/sysdeps/linux/xtensa/sysdep.h
@@ -28,13 +28,24 @@
 #define ASM_TYPE_DIRECTIVE(name, typearg) .type name, typearg
 #define ASM_SIZE_DIRECTIVE(name) .size name, . - name
 
+#if defined(__XTENSA_WINDOWED_ABI__)
+#define abi_entry(reg, frame_size) entry reg, frame_size
+#define abi_ret retw
+#elif defined(__XTENSA_CALL0_ABI__)
+#define abi_entry(reg, frame_size)
+#define abi_ret ret
+#else
+#error Unsupported Xtensa ABI
+#endif
+
+
 #define	ENTRY(name)							\
   ASM_GLOBAL_DIRECTIVE C_SYMBOL_NAME(name);				\
   ASM_TYPE_DIRECTIVE (C_SYMBOL_NAME(name), @function);			\
   .align ALIGNARG(2);							\
   LITERAL_POSITION;							\
   C_LABEL(name)								\
-  entry sp, FRAMESIZE;							\
+  abi_entry(sp, FRAMESIZE);						\
   CALL_MCOUNT
 
 #define	HIDDEN_ENTRY(name)						\
@@ -44,7 +55,7 @@
   .align ALIGNARG(2);							\
   LITERAL_POSITION;							\
   C_LABEL(name)								\
-  entry sp, FRAMESIZE;							\
+  abi_entry(sp, FRAMESIZE);						\
   CALL_MCOUNT
 
 #undef END
@@ -73,7 +84,13 @@
 #endif
 
 #ifndef FRAMESIZE
+#if defined(__XTENSA_WINDOWED_ABI__)
 #define FRAMESIZE 16
+#elif defined(__XTENSA_CALL0_ABI__)
+#define FRAMESIZE 0
+#else
+#error Unsupported Xtensa ABI
+#endif
 #endif
 #define CALL_MCOUNT		/* Do nothing.  */
 
@@ -118,7 +135,7 @@
   END (name)
 
 #undef	ret_NOERRNO
-#define ret_NOERRNO retw
+#define ret_NOERRNO abi_ret
 
 /* The function has to return the error code.  */
 #undef	PSEUDO_ERRVAL
@@ -133,7 +150,7 @@
   END (name)
 
 #undef	ret_ERRVAL
-#define ret_ERRVAL retw
+#define ret_ERRVAL abi_ret
 
 #if defined _LIBC_REENTRANT
 # if defined USE___THREAD
@@ -151,6 +168,8 @@
 	movi	a2, -1;							      \
 	j	.Lpseudo_end;
 # else /* !USE___THREAD */
+
+#if defined(__XTENSA_WINDOWED_ABI__)
 #  define SYSCALL_ERROR_HANDLER						      \
 0:	neg	a2, a2;							      \
 	mov	a6, a2;							      \
@@ -159,6 +178,24 @@
 	s32i	a2, a6, 0;						      \
 	movi	a2, -1;							      \
 	j	.Lpseudo_end;
+#elif defined(__XTENSA_CALL0_ABI__)
+#  define SYSCALL_ERROR_HANDLER						      \
+0:	neg	a2, a2;							      \
+	addi	a1, a1, -16;						      \
+	s32i	a0, a1, 0;						      \
+	s32i	a2, a1, 4;						      \
+	movi	a0, __errno_location@PLT;				      \
+	callx0	a0;						              \
+	l32i	a0, a1, 0;						      \
+	l32i	a3, a1, 4;						      \
+	addi	a1, a1, 16;						      \
+	s32i	a3, a2, 0;						      \
+	movi	a2, -1;							      \
+	j	.Lpseudo_end;
+#else
+#error Unsupported Xtensa ABI
+#endif
+
 # endif /* !USE___THREAD */
 #else /* !_LIBC_REENTRANT */
 #define SYSCALL_ERROR_HANDLER						      \