kernel: implement _sys_intr_return

2 files changed, 42 insertions, 0 deletions

diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index 350f3ee..8be1080 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -413,6 +413,7 @@ static void proc_intr_deliver(Proc *p) {
 	d.rcx = p->regs.rcx;
 	d.rax = p->regs.rax;
 	d.rip = p->regs.rip;
+	d.flags = p->regs.flags;
 
 	// one more because the buffer itself isn't NUL terminated
 	// TODO ensure NUL termination
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 23a8883..ffd69b8 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -487,6 +487,46 @@ long _sys_duplex(hid_t from, hid_t to, int flags) {
 	return -1; // dummy
 }
 
+void _sys_intr_return(struct intr_data __user *intr, int flags) {
+	CpuRegs *r = &proc_cur->regs;
+	struct intr_data d;
+	if (flags != 0 || pcpy_from(proc_cur, &d, intr, sizeof(d)) < sizeof(d)) {
+		proc_kill(proc_cur, EFAULT);
+		proc_switch_any(); /* doesn't return */
+	}
+	r->r15 = d.r15;
+	r->r14 = d.r14;
+	r->r13 = d.r13;
+	r->r12 = d.r12;
+	r->r11 = d.r11;
+	r->r10 = d.r10;
+	r->r9  = d.r9;
+	r->r8  = d.r8;
+	r->rdi = d.rdi;
+	r->rsi = d.rsi;
+	r->rbp = d.rbp;
+	r->rsp = d.rsp;
+	r->rbx = d.rbx;
+	r->rdx = d.rdx;
+	r->rcx = d.rcx;
+	r->rax = d.rax;
+	r->rip = d.rip;
+	/* preserved flags: (see intel vol 1 3.4.3.)
+	 * 1<<0 = CF, carry flag
+	 * 1<<2 = PF, parity flag
+	 * 1<<4 = AC, auxilary carry
+	 * 1<<6 = ZF, zero flag
+	 * 1<<7 = SF, sign flag
+	 * 1<<11 = OF, overflow flag
+	 * 1<<10 = DF, direction flag
+	 */
+	static_assert(
+		((1<<0) | (1<<2) | (1<<4) | (1<<6) | (1<<7) | (1<<10) | (1<<11))
+		== 0xCD5
+	);
+	r->flags = (d.flags & 0xCD5) | (r->flags & ~0xCD5);
+}
+
 long _sys_execbuf(void __user *ubuf, size_t len) {
 	if (len == 0) SYSCALL_RETURN(0);
 	static_assert(EXECBUF_MAX_LEN <= KMALLOC_MAX);
@@ -544,6 +584,7 @@ long _syscall(long num, long a, long b, long c, long d, long e) {
 		break; case _SYS_TIME:	_sys_time(a);
 		break; case _SYS_GETNULL:	_sys_getnull(a);
 		break; case _SYS_DUPLEX:	_sys_duplex(a, b, c);
+		break; case _SYS_INTR_RETURN:	_sys_intr_return((userptr_t)a, b);
 		break; case _SYS_EXECBUF:	_sys_execbuf((userptr_t)a, b);
 		break; case _SYS_DEBUG_KLOG:	_sys_debug_klog((userptr_t)a, b);
 		break;