[Buildroot] [PATCH 0 of 2 v4] Using gdb in buildroot

[Buildroot] [PATCH 0 of 2 v4] Using gdb in buildroot

[Thomas De Schampheleire]

Sorry for the mess. This time a proper v4, addressing Samuel's comments.

Best regards, 
Thomas

[Buildroot] [PATCH 1 of 2 v4] toolchain: generate a gdbinit file

[Thomas De Schampheleire]

From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

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 <OHanson@xsightsys.com>, 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.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[ThomasDS: minor updates in commit message]
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>

---
v4: no changes
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(+)

diff --git a/package/gdb/gdb.mk b/package/gdb/gdb.mk
--- a/package/gdb/gdb.mk
+++ b/package/gdb/gdb.mk
@@ -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))
diff --git a/toolchain/helpers.mk b/toolchain/helpers.mk
--- a/toolchain/helpers.mk
+++ b/toolchain/helpers.mk
@@ -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
diff --git a/toolchain/toolchain-external/toolchain-external.mk b/toolchain/toolchain-external/toolchain-external.mk
--- a/toolchain/toolchain-external/toolchain-external.mk
+++ b/toolchain/toolchain-external/toolchain-external.mk
@@ -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))

[Buildroot] [PATCH 2 of 2 v4] docs/manual: document how to use the cross debugger

[Thomas De Schampheleire]

From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[ThomasDS: some rewording, add <buildroot> path prefix in example]
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>

---
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

diff --git a/docs/manual/advanced.txt b/docs/manual/advanced.txt
--- a/docs/manual/advanced.txt
+++ b/docs/manual/advanced.txt
@@ -5,6 +5,8 @@
 
 include::using-buildroot-toolchain.txt[]
 
+include::using-buildroot-debugger.txt[]
+
 include::ccache-support.txt[]
 
 include::download-location.txt[]
diff --git a/docs/manual/using-buildroot-debugger.txt b/docs/manual/using-buildroot-debugger.txt
new file mode 100644
--- /dev/null
+++ b/docs/manual/using-buildroot-debugger.txt
@@ -0,0 +1,53 @@
+// -*- mode:doc; -*-
+// vim: set syntax=asciidoc:
+
+=== Using +gdb+ in Buildroot
+
+Buildroot allows to do cross-debugging, where the debugger runs on the
+build machine and communicates with +gdbserver+ on the target to
+control the execution of the program.
+
+To achieve this:
+
+* If you are using an _internal toolchain_ (built by Buildroot), you
+  must enable +BR2_PACKAGE_HOST_GDB+, +BR2_PACKAGE_GDB+ and
+  +BR2_PACKAGE_GDB_SERVER+. This ensures that both the cross gdb and
+  gdbserver get built, and that gdbserver gets installed to your target.
+
+* If you are using an _external toolchain_, you should enable
+  +BR2_TOOLCHAIN_EXTERNAL_GDB_SERVER_COPY+, which will copy the
+  gdbserver included with the external toolchain to the target. If your
+  external toolchain does not have a cross gdb or gdbserver, it is also
+  possible to let Buildroot build them, by enabling the same options as
+  for the _internal toolchain backend_.
+
+Now, to start debugging a program called +foo+, you should run on the
+target:
+
+----------------------------
+gdbserver :2345 foo
+----------------------------
+
+This will cause +gdbserver+ to listen on TCP port 2345 for a connection
+from the cross gdb.
+
+Then, on the host, you should start the cross gdb using the following
+command line:
+
+----------------------------
+<buildroot>/output/host/usr/bin/<tuple>-gdb -x <buildroot>/output/staging/usr/share/buildroot/gdbinit foo
+----------------------------
+
+Of course, +foo+ must be available in the current directory, built
+with debugging symbols. Typically you start this command from the
+directory where +foo+ is built (and not from +output/target/+ as the
+binaries in that directory are stripped).
+
+The +<buildroot>/output/staging/usr/share/buildroot/gdbinit+ file will tell the
+cross gdb where to find the libraries of the target.
+
+Finally, to connect to the target from the cross gdb:
+
+----------------------------
+(gdb) target remote <target ip address>:2345
+----------------------------

[Buildroot] [PATCH 0 of 2 v4] Using gdb in buildroot

[Peter Korsgaard]

>>>>> "Thomas" == Thomas De Schampheleire <patrickdepinguin@gmail.com> writes:

 > Sorry for the mess. This time a proper v4, addressing Samuel's comments.

Committed both, thanks.

-- 
Bye, Peter Korsgaard