Add basic breakpoint support to kdb

sys/amd64/debug.c

@@ -160,6 +160,89 @@ Debug_Backtrace(int argc, const char *argv[])
 
 REGISTER_DBGCMD(backtrace, "Print backtrace", Debug_Backtrace);
 
+static void
+Debug_SetBreakpoint(int argc, const char *argv[])
+{
+    if (argc != 2) {
+	kprintf("bkpt [ADDR]");
+	return;
+    }
+
+    uint64_t addr = Debug_StrToInt(argv[1]);
+
+    uint32_t flags = read_dr7();
+
+    if (!(flags & DR7_DR0G)) {
+	write_dr0(addr);
+	write_dr7(flags | DR7_DR0G);
+    } else if (!(flags & DR7_DR1G)) {
+	write_dr1(addr);
+	write_dr7(flags | DR7_DR1G);
+    } else if (!(flags & DR7_DR2G)) {
+	write_dr2(addr);
+	write_dr7(flags | DR7_DR2G);
+    } else if (!(flags & DR7_DR3G)) {
+	write_dr3(addr);
+	write_dr7(flags | DR7_DR3G);
+    } else {
+	kprintf("No more breakpoints left!\n");
+    }
+}
+
+REGISTER_DBGCMD(bkpt, "Set breakpoint", Debug_SetBreakpoint);
+
+static void
+Debug_ClearBreakpoint(int argc, const char *argv[])
+{
+    if (argc != 2) {
+	kprintf("clrbkpt [0-3]");
+	return;
+    }
+
+    uint32_t flags = read_dr7();
+    switch (argv[1][0]) {
+	case '0':
+	    flags &= ~DR7_DR0G;
+	    break;
+	case '1':
+	    flags &= ~DR7_DR1G;
+	    break;
+	case '2':
+	    flags &= ~DR7_DR2G;
+	    break;
+	case '3':
+	    flags &= ~DR7_DR3G;
+	    break;
+	default:
+	    kprintf("Specify a breakpoint between 0-3\n");
+    }
+
+    write_dr7(flags);
+}
+
+REGISTER_DBGCMD(clrbkpt, "Clear breakpoint", Debug_ClearBreakpoint);
+
+static void
+Debug_ListBreakpoints(int argc, const char *argv[])
+{
+    uint32_t flags = read_dr7();
+
+    if (flags & DR7_DR0G) {
+	kprintf("DR0: 0x%lx\n", read_dr0());
+    }
+    if (flags & DR7_DR1G) {
+	kprintf("DR1: 0x%lx\n", read_dr1());
+    }
+    if (flags & DR7_DR2G) {
+	kprintf("DR2: 0x%lx\n", read_dr2());
+    }
+    if (flags & DR7_DR3G) {
+	kprintf("DR3: 0x%lx\n", read_dr3());
+    }
+}
+
+REGISTER_DBGCMD(bkpts, "List breakpoint", Debug_ListBreakpoints);
+
 static void
 Debug_Reboot(int argc, const char *argv[])
 {

sys/amd64/include/amd64.h

@@ -191,6 +191,15 @@ typedef struct XSAVEArea
  * Debug Registers
  */
 
+#define DR7_DR0L    0x00000001
+#define DR7_DR0G    0x00000002
+#define DR7_DR1L    0x00000004
+#define DR7_DR1G    0x00000008
+#define DR7_DR2L    0x00000010
+#define DR7_DR2G    0x00000020
+#define DR7_DR3L    0x00000040
+#define DR7_DR3G    0x00000080
+
 /*
  * MSRs
  */