Implement support for `std::terminate` via `::abort`

6 files changed, 77 insertions, 17 deletions

diff --git a/arch/x86_64/src/boot/boot.s b/arch/x86_64/src/boot/boot.s
index 2aa30c6..710d4ce 100644
--- a/arch/x86_64/src/boot/boot.s
+++ b/arch/x86_64/src/boot/boot.s
@@ -82,6 +82,7 @@ global_descriptor_table_pointer:
  * We are going to print some messages in case we panic during boot, so we are
  * going to store them here as well
  */
+.global message_prefix_panic
 message_prefix_panic:
 .string "TeachOS Panic: "
 message_not_loaded_by_multiboot2:
@@ -109,6 +110,12 @@ vga_buffer_pointer: .long 0xb8000
 .align 16
 .code32
 
+.global halt
+halt:
+1:
+    hlt
+    jmp 1b
+
 /**
  * Print a given panic message and then halt the machine.
  *
@@ -129,7 +136,7 @@ _panic:
     call _print
     add $8, %esp
 
-    hlt
+    call halt
 
 /**
  * Print a message via the VGA buffer.
@@ -189,7 +196,7 @@ _start:
     lgdt (global_descriptor_table_pointer)
     jmp $global_descriptor_table_code,$_transition_to_long_mode
 
-    hlt
+    call halt
 
 /**
  * Assert that the CPU supports going into long mode.
@@ -354,4 +361,4 @@ _transition_to_long_mode:
     call _init
 
     call kernel_main
-    hlt
+    call halt
diff --git a/arch/x86_64/src/exception_handling/abort.cpp b/arch/x86_64/src/exception_handling/abort.cpp
new file mode 100644
index 0000000..dc40008
--- /dev/null
+++ b/arch/x86_64/src/exception_handling/abort.cpp
@@ -0,0 +1,17 @@
+#include "arch/exception_handling/panic.hpp"
+
+#include <cstdlib>
+
+namespace teachos::arch::exception_handling
+{
+
+  /**
+   * @brief Override for the newlib abort function.
+   *
+   * newlib defines @p ::abort as a weak symbol, thus allowing implementations to override it by simply providing a
+   * matching implementation. Since the default implemenatation calls a number of functions the kernel does not
+   * currently implement, @p ::abort gets overridden to simply panic.
+   */
+  extern "C" auto abort() -> void { panic("Terminate was called, possibly due to an unhandled exception"); }
+
+}  // namespace teachos::arch::exception_handling
\ No newline at end of file
diff --git a/arch/x86_64/src/exception_handling/assert.cpp b/arch/x86_64/src/exception_handling/assert.cpp
index b55da49..86696f8 100644
--- a/arch/x86_64/src/exception_handling/assert.cpp
+++ b/arch/x86_64/src/exception_handling/assert.cpp
@@ -1,4 +1,6 @@
-#include "arch/video/vga/text.hpp"
+#include "arch/exception_handling/assert.hpp"
+
+#include "arch/exception_handling/panic.hpp"
 
 namespace teachos::arch::exception_handling
 {
@@ -9,16 +11,6 @@ namespace teachos::arch::exception_handling
       return;
     }
 
-    video::vga::text::write("Assert failed: ", video::vga::text::common_attributes::green_on_black);
-    video::vga::text::write(message, video::vga::text::common_attributes::green_on_black);
-    for (;;)
-    {
-      // Trick the compiler into thinking the variable is changes at run time,
-      // to prevent the while loop being optimized away
-      // See
-      // https://stackoverflow.com/questions/9495856/how-to-prevent-g-from-optimizing-out-a-loop-controlled-by-a-variable-that-can
-      // for more information.
-      asm volatile("" : "+g"(condition));
-    }
+    panic("Assertion Violation: ", message);
   }
 }  // namespace teachos::arch::exception_handling
\ No newline at end of file
diff --git a/arch/x86_64/src/exception_handling/panic.cpp b/arch/x86_64/src/exception_handling/panic.cpp
new file mode 100644
index 0000000..56edfd5
--- /dev/null
+++ b/arch/x86_64/src/exception_handling/panic.cpp
@@ -0,0 +1,23 @@
+#include "arch/exception_handling/panic.hpp"
+
+#include "arch/kernel/halt.hpp"
+#include "arch/video/vga/text.hpp"
+
+namespace teachos::arch::exception_handling
+{
+
+  extern "C" char const message_prefix_panic[];
+
+  auto panic(char const * reason) -> void { panic(message_prefix_panic, reason); }
+
+  auto panic(char const * prefix, char const * reason) -> void
+  {
+    using video::vga::text::common_attributes::white_on_red;
+
+    video::vga::text::newline();
+    video::vga::text::write(prefix, white_on_red);
+    video::vga::text::write(reason, white_on_red);
+
+    kernel::halt();
+  };
+}  // namespace teachos::arch::exception_handling
\ No newline at end of file
diff --git a/arch/x86_64/src/kernel/main.cpp b/arch/x86_64/src/kernel/main.cpp
index 12498d0..babe251 100644
--- a/arch/x86_64/src/kernel/main.cpp
+++ b/arch/x86_64/src/kernel/main.cpp
@@ -165,7 +165,6 @@ namespace teachos::arch::kernel
     auto allocator = arch::memory::area_frame_allocator(kernel_start, kernel_end, multiboot_start, multiboot_end,
                                                         memory_areas, area_count);
 
-    // WATCH OUT: using optional::value() crashes the build... I think its because of missing exception handling
     auto last_allocated = allocator.allocate_frame();
     auto allocated = last_allocated;
     do
@@ -174,6 +173,6 @@ namespace teachos::arch::kernel
       allocated = allocator.allocate_frame();
     } while (allocated.has_value());
     video::vga::text::write("Allocated Frames", video::vga::text::common_attributes::green_on_black);
-    video::vga::text::write_number(allocated->frame_number, video::vga::text::common_attributes::green_on_black);
+    video::vga::text::write_number(allocated.value().frame_number, video::vga::text::common_attributes::green_on_black);
   }
 }  // namespace teachos::arch::kernel
diff --git a/arch/x86_64/src/video/vga/text.cpp b/arch/x86_64/src/video/vga/text.cpp
index a613c3b..c14de16 100644
--- a/arch/x86_64/src/video/vga/text.cpp
+++ b/arch/x86_64/src/video/vga/text.cpp
@@ -13,6 +13,8 @@ namespace teachos::arch::video::vga::text
   namespace
   {
     auto constexpr default_text_buffer_address = 0xb8000;
+    auto constexpr default_text_buffer_width = 80;
+    auto constexpr default_text_buffer_height = 25;
 
     extern "C" std::pair<char, attribute> * vga_buffer_pointer;
     auto constinit text_buffer = teachos::memory::asm_pointer{vga_buffer_pointer};
@@ -32,6 +34,26 @@ namespace teachos::arch::video::vga::text
     crtc::data_port::write(vga::crtc::data_port::read() | cursor_disable_byte);
   }
 
+  auto newline() -> void
+  {
+    auto base = reinterpret_cast<decltype(text_buffer)::pointer>(default_text_buffer_address);
+    auto & raw_buffer = *text_buffer;
+    auto current_line = (raw_buffer - base) / default_text_buffer_width;
+    auto next_line = current_line + 1;
+
+    if (next_line >= default_text_buffer_height)
+    {
+      auto begin = base + default_text_buffer_width;
+      auto end = base + default_text_buffer_width * default_text_buffer_height;
+      std::ranges::move(begin, end, base);
+      raw_buffer = base + current_line * default_text_buffer_width;
+    }
+    else
+    {
+      raw_buffer = base + next_line * default_text_buffer_width;
+    }
+  }
+
   auto write_char(char code_point, attribute attribute) -> void
   {
     auto & p = *text_buffer;