Implement the fcontext asm for sparc64

build/Jamfile.v2

@@ -508,6 +508,30 @@ alias asm_sources
      <toolset>gcc
    ;
 
+# SPARC64
+# SPARC64/SYSV/ELF
+alias asm_sources
+   : asm/make_sparc64_sysv_elf_gas.S
+     asm/jump_sparc64_sysv_elf_gas.S
+     asm/ontop_sparc64_sysv_elf_gas.S
+   : <abi>sysv
+     <address-model>64
+     <architecture>sparc
+     <binary-format>elf
+     <toolset>clang
+   ;
+
+alias asm_sources
+   : asm/make_sparc64_sysv_elf_gas.S
+     asm/jump_sparc64_sysv_elf_gas.S
+     asm/ontop_sparc64_sysv_elf_gas.S
+   : <abi>sysv
+     <address-model>64
+     <architecture>sparc
+     <binary-format>elf
+     <toolset>gcc
+   ;
+
 # S390X
 # S390X/SYSV/ELF
 alias asm_sources

src/asm/jump_sparc64_sysv_elf_gas.S

@@ -0,0 +1,51 @@
+/*
+       Copyright Claudio Jeker 2024
+   Distributed under the Boost Software License, Version 1.0.
+      (See accompanying file LICENSE_1_0.txt or copy at
+          http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+/*
+ * typedef void*	fcontext_t;
+ *
+ * struct transfer_t {
+ *	fcontext_t	fctx;
+ *	void	*	data;
+ * };
+ *
+ * transfer_t jump_fcontext(fcontext_t const to, void *vp);
+ */
+#define CC64FSZ 176
+#define BIAS 2047
+#define SP 128
+#define I7 136
+
+.file "jump_sparc64_sysv_elf_gas.S"
+.text
+.align  4
+.global jump_fcontext
+.type   jump_fcontext, %function
+jump_fcontext:
+	# prepare stack
+	save	%sp, -CC64FSZ, %sp
+
+	# store framepointer and return address in slots reserved
+	# for arguments
+	stx %fp, [%sp + BIAS + SP]
+	stx %i7, [%sp + BIAS + I7]
+	mov %sp, %o0
+	# force flush register windows to stack and with that save context
+	flushw
+	# get SP (pointing to new context-data) from %i0 param
+	mov %i0, %sp
+	# load framepointer and return address from context
+	ldx [%sp + BIAS + SP], %fp
+	ldx [%sp + BIAS + I7], %i7
+
+	ret
+	 restore %o0, %g0, %o0
+	# restore old %sp (pointing to old context-data) in %o0
+	# *data stored in %o1 was not modified
+.size	jump_fcontext,.-jump_fcontext
+# Mark that we don't need executable stack.
+.section .note.GNU-stack,"",%progbits

src/asm/make_sparc64_sysv_elf_gas.S

@@ -0,0 +1,68 @@
+/*
+       Copyright Claudio Jeker 2024
+   Distributed under the Boost Software License, Version 1.0.
+      (See accompanying file LICENSE_1_0.txt or copy at
+          http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+/*
+ * fcontext_t *make_fcontext(void *sp, size_t size, void (*fn)(transfer_t));
+ */
+#define CC64FSZ 176
+#define BIAS 2047
+#define FP 112
+#define SP 128
+#define I7 136
+
+.file "make_sparc64_sysv_elf_gas.S"
+.text
+.align  4
+.global make_fcontext
+.type   make_fcontext, %function
+make_fcontext:
+	save	%sp, -CC64FSZ, %sp
+
+	# shift address in %i0 (allocated stack) to lower 16 byte boundary
+	and	%i0, -0xf, %i0
+
+	# reserve space for two frames on the stack
+	# the first frame is for the call the second one holds the data
+	# for jump_fcontext
+	sub	%i0, 2 * CC64FSZ, %i0
+
+	# third argument of make_fcontext() is the context-function to call
+	# store it in the first stack frame, also clear %fp there to indicate
+	# the end of the stack.
+	stx	%i2, [%i0 + CC64FSZ + I7]
+	stx	%g0, [%i0 + CC64FSZ + FP]
+
+	# On OpenBSD stackghost prevents overriding the return address on
+	# a stack frame. So this code uses an extra trampoline to load
+	# to call the context-function and then do the _exit(0) dance.
+	# Extract the full address of the trampoline via pc relative addressing
+1:
+	rd	%pc, %l0
+	add	%l0, (trampoline - 1b - 8), %l0
+	stx	%l0, [%i0 + I7]
+
+	# Save framepointer to first stack frame but first substract the BIAS
+	add	%i0, CC64FSZ - BIAS, %l0
+	stx	%l0, [%i0 + SP]
+
+	# Return context-data which is also includes the BIAS
+	ret
+	 restore %i0, -BIAS, %o0
+
+trampoline:
+	ldx	[%sp + BIAS + I7], %l0
+
+	# no need to setup transfer_t, already in %o0 and %o1
+	jmpl	%l0, %o7
+	 nop
+
+	call	_exit
+	 clr	%o0
+	unimp
+.size	make_fcontext,.-make_fcontext
+# Mark that we don't need executable stack.
+.section .note.GNU-stack,"",%progbits

src/asm/ontop_sparc64_sysv_elf_gas.S

@@ -0,0 +1,50 @@
+/*
+       Copyright Claudio Jeker 2024
+   Distributed under the Boost Software License, Version 1.0.
+      (See accompanying file LICENSE_1_0.txt or copy at
+          http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+/*
+ * transfer_t ontop_fcontext(fcontext_t const to, void *vp, transfer_t (*fn)(transfer_t));
+ */
+#define CC64FSZ 176
+#define BIAS 2047
+#define SP 128
+#define I7 136
+
+.file "ontop_sparc64_sysv_elf_gas.S"
+.text
+.align  4
+.global ontop_fcontext
+.type   ontop_fcontext, %function
+ontop_fcontext:
+	# prepare stack
+	save	%sp, -CC64FSZ, %sp
+
+	# store framepointer and return address in slots reserved
+	# for arguments
+	stx %fp, [%sp + BIAS + SP]
+	stx %i7, [%sp + BIAS + I7]
+	mov %sp, %o0
+	# force flush register windows to stack and with that save context
+	flushw
+	# get SP (pointing to new context-data) from %i0 param
+	mov %i0, %sp
+	# load framepointer and return address from context
+	ldx [%sp + BIAS + SP], %fp
+	ldx [%sp + BIAS + I7], %i7
+
+	# ontop_fcontext requires to directly call a function on top of the
+	# current frame so restore register window before doing the jump
+	# to the context function which then is in %o2. Do not clobber
+	# %o7 in the jump so that (*fn)() returns to that address.
+	restore %o0, %g0, %o0
+	# restore old %sp (pointing to old context-data) in %o0
+	# *data stored in %o1 was not modified
+
+	jmpl %o2, %g0
+	 nop
+.size	jump_fcontext,.-jump_fcontext
+# Mark that we don't need executable stack.
+.section .note.GNU-stack,"",%progbits