start initial irq handling

+ Still lots todo, and I'm not entirely sure how I should handle program
  space switches (mainly since the kernel uses the process' stack, maybe
		  it shouldn't?)

3 files changed, 66 insertions, 4 deletions

diff --git a/arch/riscv64/kernel/head.S b/arch/riscv64/kernel/head.S
new file mode 100644
index 0000000..b8ad295
--- /dev/null
+++ b/arch/riscv64/kernel/head.S
@@ -0,0 +1,64 @@
+#include <csr.h>
+
+.section .text
+.global handle_irq
+handle_irq:
+	addi    sp,sp,-144
+	sd      ra,136(sp)
+	sd      t0,128(sp)
+	sd      t1,120(sp)
+	sd      t2,112(sp)
+	sd      s0,104(sp)
+	sd      a0,96(sp)
+	sd      a1,88(sp)
+	sd      a2,80(sp)
+	sd      a3,72(sp)
+	sd      a4,64(sp)
+	sd      a5,56(sp)
+	sd      a6,48(sp)
+	sd      a7,40(sp)
+	sd      t3,32(sp)
+	sd      t4,24(sp)
+	sd      t5,16(sp)
+	sd      t6,8(sp)
+	addi    s0,sp,144
+	/* load supervisor cause */
+	csrr s4, CSR_SCAUSE
+	/* interrupts fall through, exceptions jump */
+	bge s4, zero, handle_exception
+	/* TODO: handle interrupts */
+	j restore_all
+
+handle_exception:
+	li t0, EXC_SYSCALL
+	/* system exceptions fall through, syscalls jump */
+	beq s4, t0, handle_syscall
+	j	restore_all
+
+handle_syscall:
+	jal	syscall_dispatch
+	j	restore_noreturn
+
+restore_all:
+	ld      a0,96(sp)
+
+restore_noreturn:
+	ld      ra,136(sp)
+	ld      t0,128(sp)
+	ld      t1,120(sp)
+	ld      t2,112(sp)
+	ld      s0,104(sp)
+	ld      a1,88(sp)
+	ld      a2,80(sp)
+	ld      a3,72(sp)
+	ld      a4,64(sp)
+	ld      a5,56(sp)
+	ld      a6,48(sp)
+	ld      a7,40(sp)
+	ld      t3,32(sp)
+	ld      t4,24(sp)
+	ld      t5,16(sp)
+	ld      t6,8(sp)
+	addi    sp,sp,144
+	/* assume supervisor for now */
+	sret
diff --git a/arch/riscv64/kernel/irq.c b/arch/riscv64/kernel/irq.c
index 27e0bd0..d350426 100644
--- a/arch/riscv64/kernel/irq.c
+++ b/arch/riscv64/kernel/irq.c
@@ -13,10 +13,8 @@ void init_irq(void *fdt)
 	info("CSR_SIE: %lx\n", s);
 }
 
-__aligned(4) void handle_irq()
+void handle_sys_irq()
 {
-	while (1)
-		;
 }
 
 /* very simple for now */
diff --git a/arch/riscv64/kernel/proc.c b/arch/riscv64/kernel/proc.c
index ef8f24e..66325ec 100644
--- a/arch/riscv64/kernel/proc.c
+++ b/arch/riscv64/kernel/proc.c
@@ -5,7 +5,7 @@
 stat_t jump_to_userspace(struct tcb *t, int argc, char **argv)
 {
 	csr_write(CSR_SEPC, t->entry);
-	__asm__ volatile("mv sp, %0\n" : "=r"(t->proc_stack)::"memory");
+	__asm__ volatile("mv sp, %0\n" ::"r"(t->proc_stack_top) : "memory");
 	__asm__ volatile("sret\n" ::: "memory");
 	/* we should never reach this */
 	return ERR_ADDR;