user_visible_state: Add LAR support

1 files changed, 32 insertions, 7 deletions

diff --git a/user_visible_state.c b/user_visible_state.c
index 055de34..bf289e5 100644
--- a/user_visible_state.c
+++ b/user_visible_state.c
@@ -61,18 +61,43 @@ static void show_rdtscp(void)
 	printf("RDTSCP: cpu %d\n", cpu);
 }
 
-static void show_seglimit(uint16_t index)
+static void show_segment(uint16_t index)
 {
-	uint32_t okay = 0, limit;
+	uint32_t has_limit = 0, has_ar = 0, limit, ar;
 	asm ("lsl %[index], %[limit]\n\t"
 	     "jnz 1f\n\t"
-	     "mov $1, %[okay]\n\t"
+	     "mov $1, %[has_limit]\n\t"
 	     "1:"
-	     : [limit] "=r" (limit), [okay] "+rm" (okay)
+	     : [limit] "=r" (limit), [has_limit] "+rm" (has_limit)
 	     : [index] "r" ((index << 3) + 3));
-	if (okay) {
-		printf("GDT entry %02hu limit: 0x%08X\n", index, limit);
+	asm ("larl %[index], %[ar]\n\t"
+	     "jnz 1f\n\t"
+	     "mov $1, %[has_ar]\n\t"
+	     "1:"
+	     : [ar] "=r" (ar), [has_ar] "+rm" (has_ar)
+	     : [index] "r" ((index << 3) + 3));
+
+	if (!has_limit && !has_ar)
+		return;
+
+	printf("GDT entry %02hu", index);
+
+	if (has_limit)
+		printf(" limit: 0x%08X", limit);
+
+	if (has_ar) {
+#define ARBITS(low, high) ((ar >> low) & ((1 << (high - low + 1)) - 1))
+#define ARSTR(bit, str) (ARBITS(bit,bit) ? " " str : "")
+		printf(" access rights: 0x%08X (type=%d DPL=%d%s%s%s%s%s%s)",
+		       ar, ARBITS(8,11), ARBITS(13,14),
+		       ARSTR(12, "S"), ARSTR(15, "P"),
+		       ARSTR(20, "software-available"),
+		       ARSTR(21, "L"), ARSTR(22, "D/B"), ARSTR(23, "G"));
+#undef ARSTR
+#undef ARBITS
 	}
+
+	printf("\n");
 }
 
 int main()
@@ -84,5 +109,5 @@ int main()
 	show_flags();
 	show_rdtscp();
 	for (int i = 0; i <= gdtlimit; i++)
-		show_seglimit(i);
+		show_segment(i);
 }