kernel: Lookup and print symbols for addresses in backtraces

.gitignore

@@ -2,6 +2,7 @@ Luna.iso
 toolchain/
 build/
 initrd/boot/moon
+initrd/ksyms
 env-local.sh
 initrd/bin/**
 base/usr/bin/**

kernel/CMakeLists.txt

@@ -8,6 +8,7 @@ set(SOURCES
     src/Log.cpp
     src/Pledge.cpp
     src/cxxabi.cpp
+    src/Symbols.cpp
     src/video/Framebuffer.cpp
     src/video/TextConsole.cpp
     src/memory/MemoryManager.cpp
@@ -150,4 +151,6 @@ target_include_directories(moon PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/gen)
 
 target_link_options(moon PRIVATE LINKER:-T ${CMAKE_CURRENT_LIST_DIR}/moon.ld -nostdlib -nodefaultlibs)
 
+add_custom_command(TARGET moon POST_BUILD COMMAND ${LUNA_ROOT}/tools/generate-symbols.sh)
+
 install(FILES "${CMAKE_CURRENT_BINARY_DIR}/moon" DESTINATION ${LUNA_ROOT}/initrd/boot)

kernel/src/Symbols.cpp

@@ -0,0 +1,95 @@
+#include "Symbols.h"
+#include "Log.h"
+#include "arch/MMU.h"
+#include "boot/bootboot.h"
+#include "fs/InitRD.h"
+#include <luna/Scanf.h>
+#include <luna/TarStream.h>
+#include <luna/Vector.h>
+
+extern const BOOTBOOT bootboot;
+
+static bool g_symbols_loaded = false;
+
+struct Symbol
+{
+    u64 address;
+    char symbol[256];
+};
+
+Vector<Symbol> g_symbols;
+
+extern const u8 kernel_start;
+extern const u8 kernel_end;
+
+static int sscanf(const char* str, const char* format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+
+    int rc = scanf_impl(str, format, ap);
+
+    va_end(ap);
+
+    return rc;
+}
+
+namespace Symbols
+{
+    Result<void> load()
+    {
+        const u64 virtual_initrd_address = MMU::translate_physical_address(bootboot.initrd_ptr);
+
+        TarStream stream;
+        stream.initialize((void*)virtual_initrd_address, bootboot.initrd_size);
+
+        TarStream::Entry file;
+        while (TRY(stream.read_next_entry(file)))
+        {
+            if (file.name.view() == "ksyms")
+            {
+                char* string = strtok(const_cast<char*>((const char*)file.data()), "\n");
+                if (!string) return {};
+
+                do {
+                    Symbol symbol;
+                    memset(symbol.symbol, 0, sizeof(symbol.symbol));
+
+                    char unused;
+                    int nread;
+
+                    sscanf(string, "%lx %c %n", &symbol.address, &unused, &nread);
+                    strlcpy(symbol.symbol, string + nread, sizeof(symbol));
+
+                    TRY(g_symbols.try_append(symbol));
+                } while ((string = strtok(nullptr, "\n")));
+
+                kinfoln("Successfully loaded %zu kernel debug symbols", g_symbols.size());
+
+                g_symbols_loaded = true;
+                return {};
+            }
+        }
+
+        return {};
+    }
+
+    StringView lookup(u64 address)
+    {
+        if (!g_symbols_loaded) return StringView {};
+        if (address < (u64)&kernel_start) return StringView {};
+        if (address >= (u64)&kernel_end) return StringView {};
+
+        for (isize i = (isize)g_symbols.size() - 1; i >= 0; i--)
+        {
+            if (g_symbols[i].address < address)
+            {
+                usize index = i + 1;
+                if (index == g_symbols.size()) return StringView {};
+                return StringView { g_symbols[index].symbol };
+            }
+        }
+
+        return StringView {};
+    }
+}

kernel/src/Symbols.h

@@ -0,0 +1,9 @@
+#pragma once
+#include <luna/StringView.h>
+#include <luna/Types.h>
+
+namespace Symbols
+{
+    Result<void> load();
+    StringView lookup(u64 address);
+}

kernel/src/arch/x86_64/CPU.cpp

@@ -1,5 +1,6 @@
 #include "arch/CPU.h"
 #include "Log.h"
+#include "Symbols.h"
 #include "api/Mouse.h"
 #include "arch/Keyboard.h"
 #include "arch/Timer.h"
@@ -368,7 +369,7 @@ namespace CPU
             rbp,
             [](u64 instruction, void* arg) {
                 int* ptr = (int*)arg;
-                kinfoln("#%d at %p", *ptr, (void*)instruction);
+                kinfoln("#%d at %p in %s", *ptr, (void*)instruction, Symbols::lookup(instruction).chars());
                 (*ptr)++;
             },
             &frame_index);
@@ -387,7 +388,7 @@ namespace CPU
             regs,
             [](u64 instruction, void* arg) {
                 int* ptr = (int*)arg;
-                kinfoln("#%d at %p", *ptr, (void*)instruction);
+                kinfoln("#%d at %p in %s", *ptr, (void*)instruction, Symbols::lookup(instruction).chars());
                 (*ptr)++;
             },
             &frame_index);

kernel/src/main.cpp

@@ -1,4 +1,5 @@
 #include "Log.h"
+#include "Symbols.h"
 #include "arch/CPU.h"
 #include "arch/Timer.h"
 #include "binfmt/BinaryFormat.h"
@@ -53,6 +54,8 @@ void oom_thread()
         kinfoln("Current platform: %s", CPU::platform_string().chars());
         kinfoln("Current processor: %s", CPU::identify().value_or("(unknown)"_sv).chars());
 
+        Symbols::load();
+
         auto root = mark_critical(TmpFS::FileSystem::create(), "Failed to create initial ramfs");
         mark_critical(VFS::mount_root(root), "Failed to mount the initial ramfs as the root filesystem");
         mark_critical(InitRD::populate_vfs(), "Failed to load files from the initial ramdisk");

tools/generate-symbols.sh

@@ -6,8 +6,4 @@ source $(dirname $0)/env.sh
 
 cd $LUNA_ROOT
 
-rm -f initrd/sys/moon.sym
+nm -C -n $LUNA_BUILD_DIR/kernel/moon | grep -vE \\.Lubsan_data | awk '{ if ($2 != "a") print; }' | uniq > initrd/ksyms
-
-nm -C -n initrd/boot/moon | grep -vE \\.Lubsan_data | awk '{ if ($2 != "a") print; }' | uniq > initrd/sys/moon.sym
-
-chmod 400 initrd/sys/moon.sym