Initial dump of Castle sources

1 files changed, 63 insertions, 0 deletions

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+; This source code in this file is licensed to You by Castle Technology
+; Limited ("Castle") and its licensors on contractual terms and conditions
+; ("Licence") which entitle you freely to modify and/or to distribute this
+; source code subject to Your compliance with the terms of the Licence.
+; 
+; This source code has been made available to You without any warranties
+; whatsoever. Consequently, Your use, modification and distribution of this
+; source code is entirely at Your own risk and neither Castle, its licensors
+; nor any other person who has contributed to this source code shall be
+; liable to You for any loss or damage which You may suffer as a result of
+; Your use, modification or distribution of this source code.
+; 
+; Full details of Your rights and obligations are set out in the Licence.
+; You should have received a copy of the Licence with this source code file.
+; If You have not received a copy, the text of the Licence is available
+; online at www.castle-technology.co.uk/riscosbaselicence.htm
+; 
+; > s.asmcall RCC 24-Mar-88
+;
+; This makes it possible to call code which scribbles on all the
+; registers with a standard ARM procedure call, e.g. from C.
+;
+; If the code called also scribbles on lk, you must regain control
+; by forcing it to branch to asmcall_exit.
+;
+; NB it relies on scribbling on memory addressed pc-relative, so it
+; won't work if the code area is not writable.
+;
+
+r0  RN	0
+r1  RN	1
+r2  RN	2
+r3  RN	3
+r4  RN	4
+ip  RN 12
+lk  RN 14
+pc  RN 15
+
+    AREA |C$$code|, CODE, READONLY
+    EXPORT  asmcall_call
+    EXPORT  asmcall_exit
+
+asmcall_savedregs
+	DCD	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0  ; 11 words for registers
+asmcall_call
+	;  Enter with r0: thing to call
+	;	      r1, r2, r3: parameters for it
+
+	ADR	ip, asmcall_savedregs
+	STMIA	ip, {r4-lk}
+	MOV	ip, r0
+	MOV	r0, r1
+	MOV	r1, r2
+	MOV	r2, r3
+	MOV	lk, pc
+	MOV	pc, ip
+asmcall_exit
+	NOP		; 2 spurious instructions here in case the caller
+	NOP		; forgets to allow for prefetch ...
+	ADR	ip, asmcall_savedregs
+	LDMIA	ip, {r4-lk}
+	MOV	pc, lk
+    END