Implement stabilize_sig_stack

winsup/cygwin/Makefile.am

@@ -25,6 +25,10 @@ if TARGET_X86_64
 AM_CCASFLAGS=-D_WIN64
 endif
 
+if TARGET_AARCH64
+AM_CCASFLAGS=-Wa,-march=armv8.1-a
+endif
+
 target_builddir=@target_builddir@
 newlib_build=$(target_builddir)/newlib
 

winsup/cygwin/scripts/gendef

@@ -399,7 +399,48 @@ _sigdelayed_end:
 
 	.seh_proc stabilize_sig_stack
 stabilize_sig_stack:
+	// prologue
+	stp	fp, lr, [sp, #-0x10]!		// save FP and LR registers
+	.seh_save_fplr_x 16
+	stp	x19, x20, [sp, #-0x10]!
+	.seh_save_regp_x x19, 16
 	.seh_endprologue
+
+	ldr	x9, [x18, #0x8]		// load thread local storage base address
+	mov	x19, #_cygtls.current_sig	// load the _cygtls.current_sig offset
+	add x19, x9, x19	// final address of current_sig
+	mov	x20, #_cygtls.incyg	// load the _cygtls.incyg offset
+	add x20, x9, x20	// final address of incyg
+
+1:
+	// check if there is a current signal to handle 
+	ldr	w9, [x19]			// load current_sig
+	cbz	w9, 2f				// if no current signal, jump to cleanup
+
+	mov w9, #1				// specify increment
+	staddl w9, [x20]		// atomically increment incyg with a lock
+
+	// prepare arguments and call signal handler
+	mov	x0, #_cygtls.start_offset	// load the _cygtls.start_offset offset
+	add	x0, x10, x0			// final address of start_offset
+	bl	_ZN7_cygtls19call_signal_handlerEv
+
+	// decrement incyg counter
+	mov w9, #-1				// specify decrement
+	staddl w9, [x20]		// atomically decrement incyg with a lock
+
+	// go to the beginning to handle another signal
+	b	1b
+2:
+	ldr	x0, [x18, #0x8]		// return TLS address in x0 (return value)
+
+	// epilogue
+	.seh_startepilogue
+	ldp	x19, x20, [sp], #0x10
+	.seh_save_regp_x x19, 16
+	ldp	fp, lr, [sp], #0x10
+	.seh_save_fplr_x 16
+	.seh_endepilogue
 	ret
 	.seh_endproc
 EOF
@@ -555,8 +596,43 @@ sigsetjmp:
 	.globl  setjmp
 	.seh_proc setjmp
 setjmp:
+	// prologue
+	stp	fp, lr, [sp, #-0x10]!		// save FP and LR registers
 	.seh_endprologue
-	mov x0, 0
+
+	// save callee-saved registers from jump buffer
+	stp	x19, x20, [x0, #0x08]		// save x19 and x20
+	stp	x21, x22, [x0, #0x18]		// save x21 and x22
+	stp	x23, x24, [x0, #0x28]		// save x23 and x24
+	stp	x25, x26, [x0, #0x38]		// save x25 and x26
+	stp	x27, x28, [x0, #0x48]		// save x27 and x28
+	stp	fp, lr, [x0, #0x58]		// save x29 (frame pointer) and x30 (link register)
+	mov	x1, sp				// get the current stack pointer
+	str	x1, [x0, #0x68]			// save SP
+	mrs	x1, fpcr			// get floating-point control register
+	str	x1, [x0, #0x70]			// save FPCR
+	mrs	x1, fpsr			// get floating-point status register
+	str	x1, [x0, #0x78]			// save FPSR
+
+
+	// save floating-point registers (d8-d15)
+	stp	d8, d9, [x0, #0x80]
+	stp	d10, d11, [x0, #0x90]
+	stp	d12, d13, [x0, #0xA0]
+	stp	d14, d15, [x0, #0xB0]
+
+	bl	stabilize_sig_stack		// call stabilize_sig_stack (returns TLS in x0)
+
+	// store the stack pointer to ...
+	ldr	x2, =_cygtls.stackptr
+	add	x2, x0, x2
+	ldr	x3, [x2]
+	// TODO: Save the value somewhere.
+
+	mov	w0, #0				// return 0
+
+	// epilogue
+	ldp	fp, lr, [sp], #0x10		// restore saved FP and LR registers
 	ret
 	.seh_endproc
 
@@ -570,7 +646,56 @@ siglongjmp:
 	.globl  longjmp
 	.seh_proc longjmp
 longjmp:
+	// prologue
+	stp	fp, lr, [sp, #-0x20]!		// save FP and LR registers, allocate additional 16 bytes for function arguments
+	stp	x0, x1, [sp, #0x10]		// save function arguments (jump buffer and return value)
+	mov	fp, sp				// establishing frame chain
 	.seh_endprologue
+1:
+	bl	stabilize_sig_stack		// call stabilize_sig_stack which returns TLS pointer in x0
+	ldr	x2, [sp, #0x10]			// get jump buffer pointer from stack
+	ldr	x10, [x2]			// get old signal stack from jump buffer
+
+	// restore stack pointer in TLS
+	ldr	x11, =_cygtls.stackptr
+	add	x11, x0, x11
+	str	x10, [x11]
+
+	// we're not in cygwin anymore, clear "in cygwin" flag
+	ldr	x11, =_cygtls.incyg
+	add	x11, x0, x11
+	mov	w12, #0
+	str	w12, [x11]
+
+	// get saved return value before SP is restored
+	ldr	x0, [sp, #0x10]
+
+	// restore callee-saved registers from jump buffer
+	ldp	x19, x20, [x2, #0x08]		// restore x19, x20
+	ldp	x21, x22, [x2, #0x18]		// restore x21, x22
+	ldp	x23, x24, [x2, #0x28]		// restore x23, x24
+	ldp	x25, x26, [x2, #0x38]		// restore x25, x26
+	ldp	x27, x28, [x2, #0x48]		// restore x27, x28
+	ldp	fp, lr, [x2, #0x58]		// restore x29 (frame pointer) and x30 (link register)
+	ldr	x10, [x2, #0x68]		// get saved stack pointer
+	mov	sp, x10				// restore stack pointer
+	ldr	x10, [x2, #0x70]		// load floating-point control register
+	msr	fpcr, x10			// restore FPCR
+	ldr	x10, [x2, #0x78]		// load floating-point status register
+	msr	fpsr, x10			// restore FPSR
+
+	// restore floating-point registers (d8-d15)
+	ldp	d8, d9, [x2, #0x80]
+	ldp	d10, d11, [x2, #0x90]
+	ldp	d12, d13, [x2, #0xA0]
+	ldp	d14, d15, [x2, #0xB0]
+
+	// ensure return value is non-zero (C standard requirement)
+	cbnz	x0, 0f
+	mov	x0, #1
+0:
+	// epilogue
+	add	sp, sp, #0x10			// FP and LR are already restored, just restore SP as it would be popped
 	ret
 	.seh_endproc
 EOF