[kernel] Improve debugcon & panic display

Several minor changes related to debug output.

- Colorize the debugcon logger like the userspace one.
- Display the process and thread for each cpu in the panic display
- Skip the panic() frame in panic back traces
- Don't try to follow obviously bad (non-canonical) stack frame pointers

src/kernel/assert.cpp

@@ -13,9 +13,6 @@ install(uintptr_t entrypoint, util::const_buffer symbol_data)
     symbol_table = symbol_data.pointer;
 }
 
-extern uint32_t *apic_icr;
-extern void const *symbol_table;
-
 [[ noreturn ]]
 void panic(
         const char *message,

src/kernel/debugcon.cpp

@@ -7,6 +7,7 @@
 namespace debugcon {
 
 namespace {
+    static const uint8_t level_colors[] = {0x00, 0x09, 0x01, 0x0b, 0x0f, 0x07, 0x08};
     const char *level_names[] = {"", "fatal", "error", "warn", "info", "verbose", "spam"};
     const char *area_names[] = {
 #define LOG(name, lvl) #name ,
@@ -19,9 +20,9 @@ namespace {
         asm ( "rep outsb;" :: "c"(size), "d"(port), "S"(msg) );
     }
 
-    inline void debug_newline() {
-        static const char *newline = "\r\n";
-        asm ( "rep outsb;" :: "c"(2), "d"(port), "S"(newline) );
+    inline void debug_endline() {
+        static const char *newline = "\e[38;5;0m\r\n";
+        asm ( "rep outsb;" :: "c"(11), "d"(port), "S"(newline) );
     }
 } // anon namespace
 
@@ -29,12 +30,16 @@ void
 output(j6_log_entry *entry)
 {
     char buffer [256];
-    size_t dlen = util::format({buffer, sizeof(buffer)}, "%7s %7s| ",
-            area_names[entry->area], level_names[entry->severity]);
+    size_t dlen = util::format({buffer, sizeof(buffer)}, "\e[38;5;%dm%7s %7s\e[38;5;14m|\e[38;5;%dm ",
+            level_colors[entry->severity],
+            area_names[entry->area],
+            level_names[entry->severity],
+            level_colors[entry->severity]);
+
     debug_out(buffer, dlen);
 
     debug_out(entry->message, entry->bytes - sizeof(j6_log_entry));
-    debug_newline();
+    debug_endline();
 }
 
 void

src/kernel/panic.serial/display.cpp

@@ -2,6 +2,8 @@
 
 #include "cpu.h"
 #include "display.h"
+#include "objects/process.h"
+#include "objects/thread.h"
 #include "serial.h"
 #include "symbol_table.h"
 
@@ -36,11 +38,25 @@ print_header(
 void
 print_cpu(serial_port &out, cpu_data &cpu)
 {
+    uint32_t process = cpu.process ? cpu.process->obj_id() : 0;
+    uint32_t thread = cpu.thread ? cpu.thread->obj_id() : 0;
+
     out.write("\n \e[0;31m==[ CPU: ");
-    char cpuid[7];
-    util::format({cpuid, sizeof(cpuid)}, "%4d", cpu.id + 1); // gdb uses 1-based CPU indices
-    out.write(cpuid);
-    out.write(" ]====================================================================\n");
+
+    char buffer[64];
+    util::format({buffer, sizeof(buffer)}, "%4d <%02lx:%02lx>",
+            cpu.id + 1, process, thread);
+    out.write(buffer);
+
+    out.write(" ]=============================================================\n");
+}
+
+template <typename T> inline bool
+canonical(T p)
+{
+    static constexpr uintptr_t mask = 0xffff800000000000;
+    uintptr_t addr = reinterpret_cast<uintptr_t>(p);
+    return (addr & mask) == mask || (addr & mask) == 0;
 }
 
 void
@@ -49,10 +65,10 @@ print_callstack(serial_port &out, symbol_table &syms, frame const *fp)
     char message[512];
     unsigned count = 0;
 
-    while (fp && fp->return_addr) {
+    while (canonical(fp) && fp && fp->return_addr) {
         char const *name = syms.find_symbol(fp->return_addr);
         if (!name)
-            name = "<unknown>";
+            name = canonical(fp->return_addr) ? "<unknown>" : "<corrupt>";
 
         util::format({message, sizeof(message)},
             " \e[0;33mframe %2d: <0x%016lx> \e[1;33m%s\n",

src/kernel/panic.serial/main.cpp

@@ -19,7 +19,7 @@ panicking::serial_port &com1 = __com1_storage.value;
 util::no_construct<panicking::symbol_table> __syms_storage;
 panicking::symbol_table &syms = __syms_storage.value;
 
-constexpr int order = __ATOMIC_ACQ_REL;
+static constexpr int order = __ATOMIC_ACQ_REL;
 
 extern "C"
 void panic_handler(const cpu_state *regs)
@@ -41,7 +41,7 @@ void panic_handler(const cpu_state *regs)
         asm ("pause");
 
     panicking::frame const *fp = nullptr;
-    asm ( "mov %%rbp, %0" : "=r" (fp) );
+    asm ( "movq (%%rbp), %0" : "=r" (fp) );
 
     if (panic)
         print_header(com1, panic->message, panic->function,