riscv32: add setjmp/longjmp and sigreturn

Largely copied from riscv64 but required recalculation of offsets.

src/setjmp/riscv32/longjmp.S

@@ -0,0 +1,42 @@
+.global __longjmp
+.global _longjmp
+.global longjmp
+.type __longjmp, %function
+.type _longjmp,  %function
+.type longjmp,   %function
+__longjmp:
+_longjmp:
+longjmp:
+	lw s0,    0(a0)
+	lw s1,    4(a0)
+	lw s2,    8(a0)
+	lw s3,    12(a0)
+	lw s4,    16(a0)
+	lw s5,    20(a0)
+	lw s6,    24(a0)
+	lw s7,    28(a0)
+	lw s8,    32(a0)
+	lw s9,    36(a0)
+	lw s10,   40(a0)
+	lw s11,   44(a0)
+	lw sp,    48(a0)
+	lw ra,    52(a0)
+
+#ifndef __riscv_float_abi_soft
+	fld fs0,  56(a0)
+	fld fs1,  64(a0)
+	fld fs2,  72(a0)
+	fld fs3,  80(a0)
+	fld fs4,  88(a0)
+	fld fs5,  96(a0)
+	fld fs6,  104(a0)
+	fld fs7,  112(a0)
+	fld fs8,  120(a0)
+	fld fs9,  128(a0)
+	fld fs10, 136(a0)
+	fld fs11, 144(a0)
+#endif
+
+	seqz a0, a1
+	add a0, a0, a1
+	ret

src/setjmp/riscv32/setjmp.S

@@ -0,0 +1,41 @@
+.global __setjmp
+.global _setjmp
+.global setjmp
+.type __setjmp, %function
+.type _setjmp,  %function
+.type setjmp,   %function
+__setjmp:
+_setjmp:
+setjmp:
+	sw s0,    0(a0)
+	sw s1,    4(a0)
+	sw s2,    8(a0)
+	sw s3,    12(a0)
+	sw s4,    16(a0)
+	sw s5,    20(a0)
+	sw s6,    24(a0)
+	sw s7,    28(a0)
+	sw s8,    32(a0)
+	sw s9,    36(a0)
+	sw s10,   40(a0)
+	sw s11,   44(a0)
+	sw sp,    48(a0)
+	sw ra,    52(a0)
+
+#ifndef __riscv_float_abi_soft
+	fsd fs0,  56(a0)
+	fsd fs1,  64(a0)
+	fsd fs2,  72(a0)
+	fsd fs3,  80(a0)
+	fsd fs4,  88(a0)
+	fsd fs5,  96(a0)
+	fsd fs6,  104(a0)
+	fsd fs7,  112(a0)
+	fsd fs8,  120(a0)
+	fsd fs9,  128(a0)
+	fsd fs10, 136(a0)
+	fsd fs11, 144(a0)
+#endif
+
+	li a0, 0
+	ret

src/signal/riscv32/restore.s

@@ -0,0 +1,8 @@
+.global __restore
+.type __restore, %function
+__restore:
+.global __restore_rt
+.type __restore_rt, %function
+__restore_rt:
+	li a7, 139 # SYS_rt_sigreturn
+	ecall

src/signal/riscv32/sigsetjmp.s

@@ -0,0 +1,23 @@
+.global sigsetjmp
+.global __sigsetjmp
+.type sigsetjmp, %function
+.type __sigsetjmp, %function
+sigsetjmp:
+__sigsetjmp:
+	bnez a1, 1f
+	tail setjmp
+1:
+
+	sw ra, 152(a0)
+	sw s0, 164(a0)
+	mv s0, a0
+
+	call setjmp
+
+	mv a1, a0
+	mv a0, s0
+	lw s0, 164(a0)
+	lw ra, 152(a0)
+
+.hidden __sigsetjmp_tail
+	tail __sigsetjmp_tail