From 9e2483d78e09316a547368c133466ce167f3513c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Lov=C3=A9n?= <thomasloven@gmail.com>
Date: Tue, 6 Mar 2018 10:59:23 +0100
Subject: [PATCH] Halt-And-Catch-Fire macro

---
 src/kernel/boot/kmain.c    |  2 ++
 src/kernel/include/debug.h | 14 ++++++++++++++
 toolchain/gdbinit          | 18 ++++++++++++++++++
 3 files changed, 34 insertions(+)

diff --git a/src/kernel/boot/kmain.c b/src/kernel/boot/kmain.c
index 50dd904..aaec318 100644
--- a/src/kernel/boot/kmain.c
+++ b/src/kernel/boot/kmain.c
@@ -14,6 +14,8 @@ void kmain()
   debug_ok("This thing worked well!\n");
   debug_warning("Careful!\n");
   debug_error("Something went wrong!\n");
+
+  PANIC("Reached end of kernel main function\n");
   for(;;);
 }
 
diff --git a/src/kernel/include/debug.h b/src/kernel/include/debug.h
index 51a80ff..13bdf8d 100644
--- a/src/kernel/include/debug.h
+++ b/src/kernel/include/debug.h
@@ -22,3 +22,17 @@ void debug_printf(char *fmt, ...);
 void debug_puts(char *s);
 void debug_putsn(char *s, size_t n);
 void debug_putch(char c);
+
+#define S(x) #x
+#define S_(x) S(x)
+#define S__LINE__ S_(__LINE__)
+#define PANIC(...) \
+  do{ \
+    debug("\n\nKernel panic!\n%s:%d\n", __FILE__, __LINE__); \
+    debug(__VA_ARGS__); \
+    volatile int _override = 0; \
+    while(1){ \
+      asm("panic_breakpoint_" S__LINE__ ":"); \
+      if(_override) break; \
+    } \
+  }while(0)
diff --git a/toolchain/gdbinit b/toolchain/gdbinit
index 003a4c9..8f8ed31 100644
--- a/toolchain/gdbinit
+++ b/toolchain/gdbinit
@@ -11,6 +11,24 @@ target remote :1234
 set height 0
 set width 0
 
+# The PANIC() macro - defined in src/kernel/include/debug.h - creates
+# a label of the form panic_breakpoint_xxx, where xxx is a number.
+# Unfortunately, gdb can set breakpoints on FUNCTIONS based on regex, but
+# not on LABELS.
+# The following piece of python code runs objdump to extract all panic_breakpoint
+# labels, and set breakpoints for each.
+python
+import subprocess
+import os
+dump = subprocess.Popen(("objdump", "-t", os.environ['BUILDROOT'] + "sysroot/kernel"), stdout=subprocess.PIPE)
+lines = subprocess.check_output(('grep', 'panic_breakpoint'), stdin=dump.stdout)
+dump.wait()
+for line in lines.split('\n'):
+  name = line.split(' ')[-1]
+  if name:
+    gdb.execute('b ' + name, to_string=True)
+end
+
 define q
 monitor quit
 end