SEGFAULT @ 0xfffffffffffffffe

(gdb) x/16i  0x3ff6e60000   ## Trampoline code 
   0x3ff6e60000:	auipc	t0,0x0
   0x3ff6e60004:	addi	sp,sp,-32
   0x3ff6e60006:	sd	ra,16(sp)
   0x3ff6e60008:	sd	t0,8(sp)
   0x3ff6e6000a:	sd	sp,0(sp)
   0x3ff6e6000c:	auipc	t1,0x1c
   0x3ff6e60010:	ld	t2,0(t1)
   0x3ff6e60014:	jalr	t2
   0x3ff6e60016:	ld	ra,16(sp)
   0x3ff6e60018:	addi	sp,sp,32
   0x3ff6e6001a:	ret
   0x3ff6e6001c:	nop
   0x3ff6e6001e:	nop
   0x3ff6e60020:	unimp
   0x3ff6e60022:	unimp
   0x3ff6e60024:	unimp

(gdb) x/2x  0x3ff6e60028
0x3ff6e60028:	0x0000002a	0xaab68572


(gdb) x thunkEntry
0x2aaab68572 <thunkEntry>:	0x00088317

(gdb) x/12i thunkEntry
   0x2aaab68572 <thunkEntry>:    auipc	t1,0x88
   0x2aaab68576 <thunkEntry+4>:	 ld	t1,918(t1)
   0x2aaab6857a <thunkEntry+8>:	 ld	t1,0(t1)
   0x2aaab6857e <thunkEntry+12>: addi	sp,sp,-1008
   0x2aaab68582 <thunkEntry+16>: sd	a0,8(sp)
   0x2aaab68584 <thunkEntry+18>: ld	t1,1080(t1)
   0x2aaab68588 <thunkEntry+22>: sd	a0,24(sp)
   0x2aaab6858a <thunkEntry+24>: sd	a5,64(sp)
   0x2aaab6858c <thunkEntry+26>: sd	ra,1000(sp)
   0x2aaab68590 <thunkEntry+30>: sd	s0,992(sp)
   0x2aaab68594 <thunkEntry+34>: sd	s1,984(sp)
   0x2aaab68598 <thunkEntry+38>: sd	a1,32(sp)
...
(gdb) i b     ## Some breakpoints set (trampoline & thunkEntry), but not hit
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x0000002aaab686d8 in allocateExecutablePage at /usr/build/RiscV64vm/platforms/Cross/plugins/IA32ABI/riscv64abicc.c:325
	breakpoint already hit 1 time
2       breakpoint     keep y   0x0000002aaab671b2 in primAlienReplace at /usr/build/RiscV64vm/src/plugins/IA32ABI/IA32ABI.c:495
	breakpoint already hit 1 time
4       breakpoint     keep y   <PENDING>          primThunkEntry
5       breakpoint     keep y   0x0000002aaab68572 in thunkEntry at /usr/build/RiscV64vm/platforms/Cross/plugins/IA32ABI/riscv64abicc.c:185
6       breakpoint     keep y   <PENDING>          0x3ff6e60000
7       breakpoint     keep y   <PENDING>          0x3ff6e6000c
(gdb) 

vvv===vvv===vvv===vvv  Trampoline Setup Details  vvv===vvv===vvv===vvv 
'From Squeak5.3 of 12 May 2022 [latest update: #19481] on 29 July 2022 at 1:54:08 pm'!

!FFICallbackThunk methodsFor: 'private-instance initalization' stamp: 'KenD 7/29/2022 13:54'!
initializeRiscV64
"Initialize the receiver with a __ccall thunk.  The thunk calls thunkEntry in the Alien/IA32ABI plugin,
 whose source is in platforms/Cross/plugins/IA32ABI/riscv64abicc.c.  thunkEntry is the entry point
 for Callbacks. The objective of the thunk is to call thunkEntry with all arguments to the call of the
 thunk (registers and stack) as well as a pointer to the thunk itself.  thunkEntry is as follows:
	
  long long
    thunkEntry(long x0, long x1, long x2, long x3,
	       long x4, long x5, long x6, long x7,
	       double d0, double d1, double d2, double d3,
	       double d4, double d5, double d6, double d7,
	       void *thunkpPlus20, sqIntptr_t *stackp)

thunkEntry then collects the various arguments 
(thunk, integer register arguments, floating-point register arguments, stack pointer) 
in a VMCallbackContext and invokes the callback via invokeCallbackContext:."
"
  0 : 00000297  auipc	t0,0x0		Current PC = self codeAddress
  4 : 1101     	addi	sp,sp,-32	reserve 4 stack slots (1 for alignment)
  6 : e806      sd	ra,16(sp)	push Return Address
  8 : e416      sd	t0,8(sp)	push self codeAddress
  a : e00a      sd	sp,0(sp)	push current Stack Pointer
  c : 0001C317  auipc	t1,0x1c		PC+0x1c is address of &entryThunk
 10:  00033383  ld	t2,0(t1)	get &entryThunk in register
 14 : 9382      jalr	t2		Call entryThunk()
 16 : 60c2      ld	ra,16(sp)	Restore saved Return Address
 18 : 6105      addi	sp,sp,32	Restore Stack Pointer
 20 : 8082      ret			Return to Mamma
 22 : 0001      noop			--keep prefetch happy-- 
 24 : 0001	noop
 ... 
 28:   <@entryThunk>
"
	| addrTop wordReversedAddr |  "NB: upper & lower instructions swapped"
	self unsignedLongLongAt:  1 put: 16rE806110100000297.  "16r0"
	self unsignedLongLongAt:  9 put: 16r0001C317E00AE416.  "16r8"
	self unsignedLongLongAt: 17 put: 16r60C2938200033383. "16r10"
	self unsignedLongLongAt: 25 put: 16r0001000180826105. "16r18"
	addrTop := self primThunkEntryAddress >> 32.
	wordReversedAddr := ((self primThunkEntryAddress bitAnd: 16rFFFFFFFF) << 32) 
				bitOr: addrTop.
	self unsignedLongLongAt: 41 put: wordReversedAddr.
	self halt.
	self

	"self newCCall"! !
			^^^===^^^===^^^===^^^