libc: core: add mitigation for a potential bochs issue in strtoll

lib/libc/core/stdlib/strtoll.c

@@ -28,14 +28,14 @@
  * SUCH DAMAGE.
  */
 
+#include <assert.h>
 #include <ctype.h>
 #include <errno.h>
 #include <limits.h>
+#include <magenta/log.h>
+#include <stdio.h>
 
-long long strtoll(
-	const char *restrict ptr,
-	char **restrict endptr,
-	register int base)
+long long strtoll(const char *restrict ptr, char **restrict endptr, int base)
 {
 	const char *s = ptr;
 	long long acc;
@@ -64,8 +64,31 @@ long long strtoll(
 		base = c == '0' ? 8 : 10;
 	}
 
-	cutoff = (long long)LLONG_MAX / (long long)base;
-	cutlim = (long long)LLONG_MAX % (long long)base;
+	/* XXX cannot just divide by base here. Doing so results in a #DE
+	 * exception when running under Bochs. Not sure if this is a bug in the
+	 * kernel or in Bochs, but this switch statement is here as a workaround
+	 * until the issue is resolved. */
+	switch (base) {
+	case 2:
+		cutoff = (long long)LLONG_MAX / (long long)2;
+		cutlim = (long long)LLONG_MAX % (long long)2;
+		break;
+	case 8:
+		cutoff = (long long)LLONG_MAX / (long long)8;
+		cutlim = (long long)LLONG_MAX % (long long)8;
+		break;
+	case 10:
+		cutoff = (long long)LLONG_MAX / (long long)10;
+		cutlim = (long long)LLONG_MAX % (long long)10;
+		break;
+	case 16:
+		cutoff = (long long)LLONG_MAX / (long long)16;
+		cutlim = (long long)LLONG_MAX % (long long)16;
+		break;
+	default:
+		return -1;
+	}
+
 	for (acc = 0, any = 0;; c = *s++) {
 		if (isdigit(c)) {
 			c -= '0';