From 924758c6f8bcf463b5e996e5168d3a01779da912 Mon Sep 17 00:00:00 2001
From: Daniel Bertalan <dani@danielbertalan.dev>
Date: Sun, 2 Apr 2023 10:15:08 +0200
Subject: [PATCH] Toolchain+Meta: Support kernel debugging with host AArch64
 GDB

Previously, we would unconditionally build GDB from source for the
AArch64 toolchain. This commit makes it possible to use the system's
`gdb` binary if it supports the architecture, or `aarch64-elf-gdb` if
such a package is installed.

An `aarch64-elf-gdb` package will be available through Homebrew once
this PR is merged: https://github.com/Homebrew/homebrew-core/pull/127323
---
 Meta/debug-kernel.sh | 22 ++++++++++++----------
 Toolchain/BuildIt.sh | 24 ++++++++++++++++++++----
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/Meta/debug-kernel.sh b/Meta/debug-kernel.sh
index 63e8126b0b9..cefcb66a23b 100755
--- a/Meta/debug-kernel.sh
+++ b/Meta/debug-kernel.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 SCRIPT_DIR="$(dirname "${0}")"
 
@@ -9,16 +9,18 @@ fi
 # Set this environment variable to override the default debugger.
 #
 if [ -z "$SERENITY_KERNEL_DEBUGGER" ]; then
-    if [ "$SERENITY_ARCH" = "aarch64" ]; then
-        # Prepend the toolchain aarch64 bin directory so we pick up GDB from there
-        PATH="$SCRIPT_DIR/../Toolchain/Local/aarch64/bin:$PATH"
-        SERENITY_KERNEL_DEBUGGER="aarch64-pc-serenity-gdb"
+    # Prepend the toolchain bin directory so we pick up GDB from there
+    PATH="$SCRIPT_DIR/../Toolchain/Local/$SERENITY_ARCH/bin:$PATH"
+
+    if command -v "$SERENITY_ARCH-pc-serenity-gdb" >/dev/null; then
+        SERENITY_KERNEL_DEBUGGER="$SERENITY_ARCH-pc-serenity-gdb"
+    elif command -v "$SERENITY_ARCH-elf-gdb" >/dev/null; then
+        SERENITY_KERNEL_DEBUGGER="$SERENITY_ARCH-elf-gdb"
+    elif command -v gdb >/dev/null && gdb ex 'set architecture' -ex 'quit' | grep "${SERENITY_ARCH//_/-}"; then
+        SERENITY_KERNEL_DEBUGGER="gdb"
     else
-        if command -v x86_64-elf-gdb >/dev/null 2>&1; then
-            SERENITY_KERNEL_DEBUGGER="x86_64-elf-gdb"
-        else
-            SERENITY_KERNEL_DEBUGGER=gdb
-        fi
+        echo "Error: No suitable GDB installation found." >&2
+        exit 1
     fi
 fi
 
diff --git a/Toolchain/BuildIt.sh b/Toolchain/BuildIt.sh
index 3a0473c0304..16ea39befea 100755
--- a/Toolchain/BuildIt.sh
+++ b/Toolchain/BuildIt.sh
@@ -100,6 +100,21 @@ buildstep() {
     "$@" 2>&1 | sed $'s|^|\x1b[34m['"${NAME}"$']\x1b[39m |'
 }
 
+has_gdb() {
+    ARCH=$1
+    ARCH_DASH="${ARCH//_/-}"
+    if command -v gdb >/dev/null && gdb -ex 'set architecture' -ex 'quit' | grep "$ARCH_DASH"; then
+        return 0
+    else
+        command -v "$ARCH"-elf-gdb >/dev/null
+    fi
+}
+
+NEEDS_GDB=1
+if has_gdb "$ARCH"; then
+    NEEDS_GDB=0
+fi
+
 # === DEPENDENCIES ===
 buildstep dependencies echo "Checking whether 'make' is available..."
 if ! command -v ${MAKE:-make} >/dev/null; then
@@ -182,8 +197,9 @@ popd
 # === DOWNLOAD AND PATCH ===
 
 pushd "$DIR/Tarballs"
-    # Build aarch64-gdb for cross-debugging support on x86 systems
-    if [ "$ARCH" = "aarch64" ]; then
+    # Build gdb for cross-debugging support
+    if [ $NEEDS_GDB -eq 1 ]; then
+        echo "GDB not found for $ARCH. Will build it from source."
         md5=""
         if [ -e "$GDB_PKG" ]; then
             md5="$($MD5SUM $GDB_PKG | cut -f1 -d' ')"
@@ -221,7 +237,7 @@ pushd "$DIR/Tarballs"
         echo "Skipped downloading gcc"
     fi
 
-    if [ "$ARCH" = "aarch64" ]; then
+    if [ $NEEDS_GDB -eq 1 ]; then
         if [ -d ${GDB_NAME} ]; then
             rm -rf "${GDB_NAME}"
             rm -rf "$DIR/Build/$ARCH/$GDB_NAME"
@@ -319,7 +335,7 @@ mkdir -p "$DIR/Build/$ARCH"
 pushd "$DIR/Build/$ARCH"
     unset PKG_CONFIG_LIBDIR # Just in case
 
-    if [ "$ARCH" = "aarch64" ]; then
+    if [ $NEEDS_GDB -eq 1 ]; then
         rm -rf gdb
         mkdir -p gdb