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, 20 insertions, 2 deletions

diff --git a/src/libc/intr.c b/src/libc/intr.c
index 12e6f4c..e751fa1 100644
--- a/src/libc/intr.c
+++ b/src/libc/intr.c
@@ -1,4 +1,5 @@
 #include <camellia/intr.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -9,6 +10,23 @@ void intr_set(void (*fn)(struct intr_data *)) {
 	_intr = fn ? fn : intr_null;
 }
 
-void intr_default(struct intr_data *) {
-	exit(-1);
+/* does haystack begin with needle? */
+static
+bool strprefix(const char *haystack, const char *needle)
+{
+	for (;; haystack++, needle++) {
+		if (*needle == '\0') return true;
+		/* note that *haystack == '\0' implies *needle != *haystack */
+		if (*needle != *haystack) return false;
+	}
+}
+
+__attribute__((visibility("hidden")))
+extern char __executable_start[];
+
+void intr_default(struct intr_data *d) {
+	if (strprefix(d->msg, "sys: ")) {
+		fprintf(stderr, "%s: %s (base %p)\n", getprogname(), d->msg, __executable_start);
+	}
+	exit(1);
 }