Using gdb in buildroot

v5 of this series, addressing Samuel's comment about 'target remote'.

Best regards,
Thomas

From: Thomas Petazzoni <[email protected]>

This commit slightly improves the external toolchain backend, and the gdb build logic to create a file named $(STAGING_DIR)/usr/share/buildroot/gdbinit which can be used as a gdbinit file using gdb -x option. This allows gdb to automatically use the proper sysroot to find libraries.

The initial insight for this patch comes from the report of Oded Hanson <[email protected]>, who found an issue with the Eclipse Buildroot plugin, which was setting a solib-path in gdb, but not a sysroot. Setting a solib-path was enough to find shared libraries, but not the dynamic linker. And since Eclipse doesn't allow to set the sysroot in any other way than giving a gdbinit file, it makes sense to have Buildroot generate a gdbinit file (which can be used in other situations than Eclipse).

To achieve this, this commit introduces a gen_gdbinit_file helper in toolchain/helpers.mk, and uses it for the internal toolchain and external toolchain backends.

---
v3: retain proper authorship of ThomasP
v2: update commit message

 package/gdb/gdb.mk                                 | 2 ++
 toolchain/helpers.mk                               | 7 +++++++
 toolchain/toolchain-external/toolchain-external.mk | 7 +++++++
 3 files changed, 16 insertions(+)

@@ -126,5 +126,7 @@ endef
 
 HOST_GDB_POST_INSTALL_HOOKS += HOST_GDB_ADD_SYMLINK
 
+HOST_GDB_POST_INSTALL_HOOKS += gen_gdbinit_file
+
 $(eval $(autotools-package))
 $(eval $(host-autotools-package))

@@ -355,3 +355,10 @@ check_unusable_toolchain = \
 		echo "such as Buildroot." ; \
 		exit 1 ; \
 	fi
+
+#
+# Generate gdbinit file for use with Buildroot
+#
+gen_gdbinit_file = \
+	mkdir -p $(STAGING_DIR)/usr/share/buildroot/ ; \
+	echo "set sysroot $(STAGING_DIR)" > $(STAGING_DIR)/usr/share/buildroot/gdbinit

@@ -651,6 +651,12 @@ define TOOLCHAIN_EXTERNAL_SANITIZE_KERNE
 		-e 's@#(ifndef|define|endif[ \t]*/[*])[ \t]*_UAPI@#\1 @'
 endef
 
+define TOOLCHAIN_EXTERNAL_INSTALL_GDBINIT
+	if test -f $(TARGET_CROSS)gdb ; then \
+		$(call gen_gdbinit_file) ; \
+	fi
+endef
+
 # Even though we're installing things in both the staging, the host
 # and the target directory, we do everything within the
 # install-staging step, arbitrarily.

@@ -659,6 +665,7 @@ define TOOLCHAIN_EXTERNAL_INSTALL_STAGIN
 	$(TOOLCHAIN_EXTERNAL_INSTALL_BFIN_FDPIC)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_BFIN_FLAT)
 	$(TOOLCHAIN_EXTERNAL_INSTALL_WRAPPER)
+	$(TOOLCHAIN_EXTERNAL_INSTALL_GDBINIT)
 endef
 
 $(eval $(generic-package))

From: Thomas Petazzoni <[email protected]>

---
v4: add 'target remote' command line (Samuel)
v3: retain proper authorship of ThomasP
v2: some rewording, taking into account the comment of Baruch, also clarifying the example command (typically foo is not in the buildroot root).

 docs/manual/advanced.txt                 |   2 +
 docs/manual/using-buildroot-debugger.txt |  53 +++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 0 deletions(-)
 create mode 100644 docs/manual/using-buildroot-debugger.txt

@@ -5,6 +5,8 @@
 
 include::using-buildroot-toolchain.txt[]
 
+include::using-buildroot-debugger.txt[]
+
 include::ccache-support.txt[]
 
 include::download-location.txt[]