tests: add test for double-traps on rv64

We do have a number of test-case for various architectures exercising
their interrupt/exception logic. However, for the recently introduced
trap API we also want to exercise the logic for double traps on at least
one architecture.

Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Julian Ganz <neither@nut.email>
Message-ID: <20251027110344.2289945-31-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

tests/tcg/riscv64/Makefile.softmmu-target

@@ -24,5 +24,11 @@ EXTRA_RUNS += run-test-mepc-masking
 run-test-mepc-masking: test-mepc-masking
 	$(call run-test, $<, $(QEMU) $(QEMU_OPTS)$<)
 
+EXTRA_RUNS += run-plugin-doubletrap
+run-plugin-doubletrap: doubletrap
+	$(call run-test, $<, \
+	  $(QEMU) -plugin ../plugins/libdiscons.so -d plugin -D $<.pout \
+	  $(QEMU_OPTS)$<)
+
 # We don't currently support the multiarch system tests
 undefine MULTIARCH_TESTS

tests/tcg/riscv64/doubletrap.S

@@ -0,0 +1,73 @@
+	.option norvc
+
+	.text
+	.global _start
+_start:
+	# Set up vectored interrupts
+	lla	t0, trap
+	add	t0, t0, 1
+	csrw	mtvec, t0
+
+	# Enable sw interrupts
+	csrrsi	zero, mie, 0x8
+	csrrsi	zero, mstatus, 0x8
+
+	# Engage the double trap: we trigger an machine-level software
+	# interrupt, which will trap to an illegal instruction
+	lui	t1, 0x02000
+	li	t0, 1
+	sw	t0, 0(t1)
+
+	# If we still not went out via the software interrupt route after a
+	# short while, we failed the test.
+	lui	t0, 0x1
+0:
+	addi	t0, t0, -1
+	bnez	t0, 0b
+	j	fail
+
+trap:
+	j	illegal_insn # Exceptions
+	j	fail # Supervisor software interrupt
+	j	fail
+	.insn	i CUSTOM_0, 0, x0, x0, 0 # Machine software interrupt
+	j	fail
+	j	fail # Supervisor timer interrupt
+	j	fail
+	j	fail # Machine timer interrupt
+	j	fail
+	j	fail # Supervisor external interrupt
+	j	fail
+	j	fail # Machine external interrupt
+	j	fail
+	j	fail # Counter overflow interrupt
+	j	fail
+	j	fail
+
+illegal_insn:
+	# Check whether we really got an illegal instruction
+	csrr	t0, mcause
+	li	t1, 2
+	bne	t0, t1, fail
+	li	a0, 0
+	j	_exit
+fail:
+	li	a0, 1
+_exit:
+	lla	a1, semiargs
+	li	t0, 0x20026	# ADP_Stopped_ApplicationExit
+	sd	t0, 0(a1)
+	sd	a0, 8(a1)
+	li	a0, 0x20	# TARGET_SYS_EXIT_EXTENDED
+
+	# Semihosting call sequence
+	.balign	16
+	slli	zero, zero, 0x1f
+	ebreak
+	srai	zero, zero, 0x7
+	j	.
+
+	.data
+	.balign	16
+semiargs:
+	.space	16