test: Rpi4: Add gdbserver test

tests/Rpi4/README.md

@@ -41,3 +41,63 @@ Check Rpi4 pin out here (Alt4): https://pinout.xyz/pinout/jtag<br>
 |   RTCK        |       11          |       GPIO 23     |
 |   TDO         |       13          |       GPIO 24     |
 |   GND         |       18          |       Any Ground  |
+
+# Userspace debugging with gdbserver + Seer
+
+The image ships `gdbserver` and the `recursive-test` package, which installs
+`/usr/bin/math_toolkit` (the `../recursive_test` C++ program). It is built
+**statically, non-PIE, `-g -O0`, unstripped** on purpose: with no shared
+libraries and a fixed load address, remote debugging needs no sysroot, no
+shared-library relocation, and behaves identically in launch and `--attach`
+modes - which sidesteps the GDB-15-host / gdbserver-12-target `lmid`
+incompatibility in the svr4 library list.
+
+After a build, `debug-rpi4/` holds the matching unstripped binary plus the
+exact source tree the binary was compiled from. The on-Pi
+`/usr/bin/math_toolkit` and `debug-rpi4/math_toolkit` are byte-identical
+(check with `sha256sum`) - keep them in sync after every rebuild.
+
+### On the Raspberry Pi
+
+Connect the Pi's Ethernet and reach it over the network (see the IP section
+above; default LAN is `192.168.1.1`). Then, launch mode:
+
+```
+ssh root@<pi-ip>
+gdbserver --once :2345 /usr/bin/math_toolkit
+```
+
+or attach mode (program already running):
+
+```
+math_toolkit &
+gdbserver --once --attach :2345 $(pidof math_toolkit)
+```
+
+`--once` makes gdbserver exit cleanly when the session ends; re-run it before
+each new session.
+
+### On the host
+
+```
+seergdb --gdb-program gdb-multiarch \
+        --connect <pi-ip>:2345 \
+        --sym  /abs/path/tests/Rpi4/debug-rpi4/math_toolkit \
+               /abs/path/tests/Rpi4/debug-rpi4/math_toolkit
+```
+
+In Seer's gdb command list (Settings -> Configuration) or `~/.gdbinit`, before
+connecting:
+
+```
+set architecture aarch64
+set remotetimeout 60
+set mi-async on
+set non-stop off
+set substitute-path /workdir/openwrt/build_dir/target-aarch64_cortex-a72_musl/recursive-test-1.0 /abs/path/tests/Rpi4/debug-rpi4
+```
+
+Set a breakpoint (`break factorial(int)`, `break main`), press **Continue**
+(not Interrupt - Interrupt only does something once the program is running).
+`math_toolkit` loops every 2 s, so breakpoints in `factorial` / `fibonacci`
+hit repeatedly.

tests/Rpi4/build_Rpi4_owrt.sh

@@ -2,7 +2,7 @@
 
 # Script to build OpenWrt image for Raspberry Pi 4 with debug symbols
 # Assumes OpenWrt build environment is set up (docker)
-# I have tested with kernel version 6.15 but vmlinux symbol file is optimized out so feature Debug on init can't be 
+# I have tested with kernel version 6.15 but vmlinux symbol file is optimized out so feature Debug on init can't be
 # performed with kernel v6.15
 # It is recommended to use Linux kernel version 5.15
 
@@ -16,7 +16,7 @@ git config --global http.maxRequestBuffer 100M
 git config --global http.version HTTP/1.1
 git config --global http.maxRequests 100
 git config --global core.compression 0
-git config --global --unset http.proxy 
+git config --global --unset http.proxy
 git config --global --unset https.proxy
 # Define variables
 TOPDIR=$PWD
@@ -49,6 +49,19 @@ echo "Updating feeds..."
 ./scripts/feeds update -a
 ./scripts/feeds install -a
 
+# Add out-of-tree packages BEFORE any "make defconfig": defconfig silently drops
+# CONFIG_PACKAGE_* entries for packages that are not yet present in the tree, so
+# these must be copied in first or they never get built.
+# hello world kernel module
+rm -rf $HELLO_WORLD_DIR/helloworld
+cp -rfT $TOPDIR/helloworld_owrt $HELLO_WORLD_DIR/helloworld
+# myplatform kernel module
+rm -rf $HELLO_WORLD_DIR/myplatform
+cp -rfT $TOPDIR/myplatform_owrt $HELLO_WORLD_DIR/myplatform
+# recursive-test userspace program (math_toolkit) for gdbserver + Seer
+rm -rf $OPENWRT_DIR/package/utils/recursive-test
+cp -rfT $TOPDIR/recursive_test_owrt $OPENWRT_DIR/package/utils/recursive-test
+
 # Step 3: Configure OpenWrt for Raspberry Pi 4
 echo "Configuring OpenWrt for Raspberry Pi 4..."
 make defconfig
@@ -67,6 +80,9 @@ CONFIG_KALLSYMS_ALL=y
 CONFIG_DEBUG_KERNEL=y
 CONFIG_PACKAGE_kmod-helloworld=y
 CONFIG_PACKAGE_kmod-myplatform=y
+CONFIG_PACKAGE_iptables-nft=y
+CONFIG_PACKAGE_gdbserver=y
+CONFIG_PACKAGE_recursive-test=y
 EOF
 make defconfig
 
@@ -81,16 +97,25 @@ echo 'CONFIG_KALLSYMS_ALL=y' >> .config
 echo 'CONFIG_DEBUG_KERNEL=y' >> .config
 echo 'CONFIG_PACKAGE_kmod-helloworld=y' >> .config
 echo 'CONFIG_PACKAGE_kmod-myplatform=y' >> .config
+echo 'CONFIG_PACKAGE_iptables-nft=y' >> .config
+echo 'CONFIG_PACKAGE_gdbserver=y' >> .config
+echo 'CONFIG_PACKAGE_recursive-test=y' >> .config
 echo 'CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE=n' >> .config
 
 sed -i 's|CONFIG_KERNEL_DEBUG_INFO_REDUCED=y|CONFIG_KERNEL_DEBUG_INFO_REDUCED=n|g' .config
 
-# add hello world module
-rm -rf $HELLO_WORLD_DIR/helloworld
-cp -rfT $TOPDIR/helloworld_owrt $HELLO_WORLD_DIR/helloworld
-# add myplatform module
-rm -rf $HELLO_WORLD_DIR/myplatform
-cp -rfT $TOPDIR/myplatform_owrt $HELLO_WORLD_DIR/myplatform
+# Resolve dependencies for every option appended above (iptables-nft pulls in
+# kmod-nft-core / xtables-nft / kmod-ipt-core, etc.). Without this opkg fails
+# package/install with "cannot find dependency ...".
+make defconfig
+
+# Confirm the out-of-tree packages survived dependency resolution.
+grep -q '^CONFIG_PACKAGE_recursive-test=y' .config || { echo_red "recursive-test missing from .config"; exit 1; }
+
+# Force recursive-test to rebuild even when only its compile recipe changed
+# (OpenWrt's build stamp does not track the recipe text).
+make package/recursive-test/clean V=s || true
+
 # Path config.txt
 cp -f $TOPDIR/patches/config.txt $TOPDIR/openwrt/target/linux/bcm27xx/image/config.txt
 # Apply patched DTS with myplatform node
@@ -105,14 +130,17 @@ sed -i 's|# CONFIG_KALLSYMS_ALL is not set|CONFIG_KALLSYMS_ALL=y|g' \
             $OPENWRT_DIR/build_dir/target-aarch64_cortex-a72_musl/linux-bcm27xx_bcm2711/linux-5.15.132/.config
 echo 'CONFIG_IKCONFIG_PROC=y' >> $OPENWRT_DIR/build_dir/target-aarch64_cortex-a72_musl/linux-bcm27xx_bcm2711/linux-5.15.132/.config
 echo 'CONFIG_CORESIGHT_CPU_DEBUG=y' >> $OPENWRT_DIR/build_dir/target-aarch64_cortex-a72_musl/linux-bcm27xx_bcm2711/linux-5.15.132/.config
+sed -i 's|# CONFIG_GDB_SCRIPTS is not set|CONFIG_GDB_SCRIPTS=y|g' \
+            $OPENWRT_DIR/build_dir/target-aarch64_cortex-a72_musl/linux-bcm27xx_bcm2711/linux-5.15.132/.config
 
 sed -i 's|MAKEFLAGS += -rR|MAKEFLAGS += -g -rR|g' \
             $OPENWRT_DIR/build_dir/target-aarch64_cortex-a72_musl/linux-bcm27xx_bcm2711/linux-5.15.132/Makefile
 if grep -q "KBUILD_HOSTCFLAGS   := " $OPENWRT_DIR/build_dir/target-aarch64_cortex-a72_musl/linux-bcm27xx_bcm2711/linux-5.15.132/Makefile; then
     sed -i 's|KBUILD_HOSTCFLAGS   := |KBUILD_HOSTCFLAGS   := -g -O0 |g' \
             $OPENWRT_DIR/build_dir/target-aarch64_cortex-a72_musl/linux-bcm27xx_bcm2711/linux-5.15.132/Makefile
 fi
-# And recompile
+# And recompile. iptables-nft, gdbserver and recursive-test are already enabled
+# (with their dependencies) in .config above, so just rebuild.
 make -j4
 ########################################################################################################################
 # Check build result
@@ -126,4 +154,4 @@ if [ $? -eq 0 ]; then
 else
     echo_red "Build failed."
     exit 1
-fi
+fi

tests/Rpi4/recursive_test_owrt/Makefile

@@ -0,0 +1,53 @@
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=recursive-test
+PKG_VERSION:=1.0
+PKG_RELEASE:=1
+
+PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)-$(PKG_VERSION)
+
+include $(INCLUDE_DIR)/package.mk
+
+# Keep the installed binary unstripped so it can be debugged on-target and so a
+# host copy carries full symbols for Seer/GDB.
+RSTRIP:=:
+
+define Package/recursive-test
+  SECTION:=utils
+  CATEGORY:=Utilities
+  TITLE:=math_toolkit - recursion/struct test program for gdbserver + Seer
+  URL:=https://github.com/epasveer/seer
+endef
+
+define Package/recursive-test/description
+  A small C++ program (math_toolkit) with recursion, nested structs and a
+  long-running loop. Statically linked and non-PIE, built -g -O0, so remote
+  debugging on a Raspberry Pi 4 via gdbserver + Seer needs no shared-library
+  relocation and works identically in launch and --attach modes.
+endef
+
+define Build/Prepare
+	mkdir -p $(PKG_BUILD_DIR)
+	$(CP) ./src/*.cpp $(PKG_BUILD_DIR)/
+	$(CP) ./include $(PKG_BUILD_DIR)/
+endef
+
+define Build/Compile
+	$(TARGET_CXX) \
+		-g -O0 -Wall -Wextra \
+		-static -no-pie -fno-pie \
+		-I$(PKG_BUILD_DIR)/include \
+		-o $(PKG_BUILD_DIR)/math_toolkit \
+		$(PKG_BUILD_DIR)/main.cpp \
+		$(PKG_BUILD_DIR)/arithmetic.cpp \
+		$(PKG_BUILD_DIR)/advanced.cpp \
+		-pthread \
+		-Wl,--start-group -lstdc++ -lgcc -lgcc_eh -Wl,--end-group
+endef
+
+define Package/recursive-test/install
+	$(INSTALL_DIR) $(1)/usr/bin
+	$(INSTALL_BIN) $(PKG_BUILD_DIR)/math_toolkit $(1)/usr/bin/math_toolkit
+endef
+
+$(eval $(call BuildPackage,recursive-test))

tests/Rpi4/recursive_test_owrt/include/advanced.h

@@ -0,0 +1,34 @@
+#ifndef ADVANCED_H
+#define ADVANCED_H
+#include <iostream>
+#include <iostream>
+#include <chrono>
+#include <unistd.h>
+#include <string>
+#include <vector>
+
+struct childStruct
+{
+    int age;
+    std::string name;
+};
+
+struct parentStruct
+{
+    int age;
+    std::string name;
+    childStruct childArr[100];
+};
+
+struct familyStruct
+{
+    parentStruct dad;
+    int numberOfNumber;
+    char familyName[50];
+    parentStruct mom;
+};
+
+int factorial(int n);
+int fibonacci(int n);
+
+#endif

tests/Rpi4/recursive_test_owrt/include/arithmetic.h

@@ -0,0 +1,9 @@
+#ifndef ARITHMETIC_H
+#define ARITHMETIC_H
+
+int add(int a, int b);
+int subtract(int a, int b);
+int multiply(int a, int b);
+double divide(int a, int b);
+
+#endif