kernel: send user interrupt on page fault

I really should just rename interrupts to something else.

This is inspired by Plan9 and meant to make debugging easier, as the
dying process can take a stacktrace etc.

It kinda sucks that the default handler now depends on fprintf, which is quite
a bit of code, but whatever.

1 files changed, 26 insertions, 0 deletions

diff --git a/src/kernel/arch/amd64/interrupts/isr.c b/src/kernel/arch/amd64/interrupts/isr.c
index 15993b2..75e9dc6 100644
--- a/src/kernel/arch/amd64/interrupts/isr.c
+++ b/src/kernel/arch/amd64/interrupts/isr.c
@@ -74,6 +74,32 @@ isr_stage3(uint8_t inr, IsrFrame *sf)
 		log_interrupt(inr, sf);
 		cpu_halt();
 	} else { /* in user */
+		if (inr == PageFault) {
+			char buf[64];
+			int len = snprintf(
+				buf, sizeof(buf),
+				"sys: fault %s ip=%p cr2=%p", /* format inspired by plan9 */
+				(sf->errcode & 2) ? "write" : "read",
+				sf->iret.ip,
+				getcr2()
+			);
+
+			/* save registers (ignoring SSE) */
+			proc_cur->regs = sf->regs;
+			proc_cur->regs.rsp = sf->iret.sp;
+			proc_cur->regs.rip = sf->iret.ip;
+			proc_cur->regs.flags = sf->iret.flags;
+
+			proc_intr(proc_cur, buf, len);
+			proc_intr_deliver(proc_cur);
+
+			/* restore */
+			sf->regs = proc_cur->regs;
+			sf->iret.sp = proc_cur->regs.rsp;
+			sf->iret.ip = proc_cur->regs.rip;
+			sf->iret.flags = proc_cur->regs.flags;
+			return;
+		}
 		proc_kill(proc_cur, inr);
 		proc_switch_any();
 	}