[PATCH v4 0/2] add JTAG debugging support

[PATCH v4 0/2] add JTAG debugging support

[Oleksij Rempel]

changes v4:
- rebase against latest git next barebox
- make sure barebox header is not broken by PBL patch

Oleksij Rempel (1):
  add CONFIG_PBL_BREAK option

Rouven Czerwinski (1):
  add gdb helper scripts to load barebox symbols

 Documentation/user/debugging.rst        | 21 +++++++++
 Documentation/user/user-manual.rst      |  1 +
 arch/arm/cpu/common.c                   | 13 ++++++
 arch/arm/cpu/start.c                    |  2 +
 arch/arm/include/asm/barebox-arm-head.h |  7 +++
 arch/arm/include/asm/barebox-arm.h      |  1 +
 common/Kconfig                          |  8 ++++
 scripts/gdb/helper.py                   | 60 +++++++++++++++++++++++++
 8 files changed, 113 insertions(+)
 create mode 100644 Documentation/user/debugging.rst
 create mode 100644 scripts/gdb/helper.py

-- 
2.20.1


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[PATCH v4 1/2] add CONFIG_PBL_BREAK option

[Oleksij Rempel]

From: Oleksij Rempel <linux@rempel-privat.de>

With this option barebox will be build with breakpoint instruction
in early pbl stage.

Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
---
 arch/arm/cpu/common.c                   | 13 +++++++++++++
 arch/arm/cpu/start.c                    |  2 ++
 arch/arm/include/asm/barebox-arm-head.h |  7 +++++++
 arch/arm/include/asm/barebox-arm.h      |  1 +
 common/Kconfig                          |  8 ++++++++
 5 files changed, 31 insertions(+)

diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
index 821cafbf26..4a2b6734db 100644
--- a/arch/arm/cpu/common.c
+++ b/arch/arm/cpu/common.c
@@ -46,6 +46,19 @@ void sync_caches_for_execution(void)
 #define R_ARM_RELATIVE 23
 #define R_AARCH64_RELATIVE 1027
 
+void pbl_barebox_break(void)
+{
+	__asm__ __volatile__ (
+#ifdef CONFIG_PBL_BREAK
+		"bkpt #17\n"
+		"nop\n"
+#else
+		"nop\n"
+		"nop\n"
+#endif
+	);
+}
+
 /*
  * relocate binary to the currently running address
  */
diff --git a/arch/arm/cpu/start.c b/arch/arm/cpu/start.c
index 1b1659b315..c97b2770c4 100644
--- a/arch/arm/cpu/start.c
+++ b/arch/arm/cpu/start.c
@@ -168,6 +168,8 @@ __noreturn void barebox_non_pbl_start(unsigned long membase,
 
 	barrier();
 
+	pbl_barebox_break();
+
 	pr_debug("memory at 0x%08lx, size 0x%08lx\n", membase, memsize);
 
 	arm_endmem = endmem;
diff --git a/arch/arm/include/asm/barebox-arm-head.h b/arch/arm/include/asm/barebox-arm-head.h
index 5c6205c815..83a22c4d94 100644
--- a/arch/arm/include/asm/barebox-arm-head.h
+++ b/arch/arm/include/asm/barebox-arm-head.h
@@ -64,6 +64,13 @@ static inline void __barebox_arm_head(void)
 		".word 0x55555555\n"
 		".endr\n"
 		"2:\n"
+#ifdef CONFIG_PBL_BREAK
+		"bkpt #17\n"
+		"nop\n"
+#else
+		"nop\n"
+		"nop\n"
+#endif
 	);
 }
 static inline void barebox_arm_head(void)
diff --git a/arch/arm/include/asm/barebox-arm.h b/arch/arm/include/asm/barebox-arm.h
index a1e6bff3a3..9840482b23 100644
--- a/arch/arm/include/asm/barebox-arm.h
+++ b/arch/arm/include/asm/barebox-arm.h
@@ -55,6 +55,7 @@ static inline unsigned long global_variable_offset(void)
 }
 
 void setup_c(void);
+void pbl_barebox_break(void);
 void relocate_to_current_adr(void);
 void relocate_to_adr(unsigned long target);
 void __noreturn barebox_arm_entry(unsigned long membase, unsigned long memsize, void *boarddata);
diff --git a/common/Kconfig b/common/Kconfig
index f5777a304c..8aad5baecd 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -1287,6 +1287,14 @@ config DEBUG_INITCALLS
 	help
 	  If enabled this will print initcall traces.
 
+
+config PBL_BREAK
+	bool "Execute software break on pbl start"
+	depends on ARM
+	help
+	  If this enabled, barebox will be compiled with BKPT instruction
+	  on early pbl init. This option should be used only with JTAG debugger!
+
 endmenu
 
 config HAS_DEBUG_LL
-- 
2.20.1


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[PATCH v4 2/2] add gdb helper scripts to load barebox symbols

[Oleksij Rempel]

From: Rouven Czerwinski <r.czerwinski@pengutronix.de>

Add a gdb script with two helper functions which use the new
pbl_barebox_break symbol to calculate the current barebox load address
on the device and loads a barebox ELF file to this address.

Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
---
 Documentation/user/debugging.rst   | 21 +++++++++++
 Documentation/user/user-manual.rst |  1 +
 scripts/gdb/helper.py              | 60 ++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 Documentation/user/debugging.rst
 create mode 100644 scripts/gdb/helper.py

diff --git a/Documentation/user/debugging.rst b/Documentation/user/debugging.rst
new file mode 100644
index 0000000000..15cb439043
--- /dev/null
+++ b/Documentation/user/debugging.rst
@@ -0,0 +1,21 @@
+Debugging with OpenOCD
+======================
+
+Barebox can be configured to break on prebootloader and main barebox entry. This
+breakpoint can not be resumed and will stop the board to allow the user to
+attach a JTAG debugger with OpenOCD. Additionally, barebox provides helper
+scripts to load the symbols from the ELF binaries.
+The python scripts require `pyelftools`.
+To load the scripts into your gdb session, run the following command in the
+barebox directory:
+
+.. code-block:: none
+
+    (gdb) source scripts/gdb/helper.py
+
+This makes two new commands available in gdb, `bb-load-symbols` and
+`bb-skip-break`. `bb-load-symbols` can load either the main `barebox` file or
+one of the .pbl files in the image directories. The board needs to be stopped in
+either the prebootloader or main barebox breakpoint, and gdb needs to be
+connected to OpenOCD. To continue booting the board, `bb-skip-break` jumps over
+the breakpoint and continues the barebox execution.
diff --git a/Documentation/user/user-manual.rst b/Documentation/user/user-manual.rst
index 516b760b1b..f04981c3f0 100644
--- a/Documentation/user/user-manual.rst
+++ b/Documentation/user/user-manual.rst
@@ -33,6 +33,7 @@ Contents:
    system-reset
    state
    random
+   debugging
 
 * :ref:`search`
 * :ref:`genindex`
diff --git a/scripts/gdb/helper.py b/scripts/gdb/helper.py
new file mode 100644
index 0000000000..4041789890
--- /dev/null
+++ b/scripts/gdb/helper.py
@@ -0,0 +1,60 @@
+#!/usr/bin/env python
+
+import gdb
+
+try:
+    from elftools.elf.elffile import ELFFile
+    from elftools.common.exceptions import ELFError
+except ImportError:
+    gdb.write("The barebox helper requires pyelftools\n", gdb.STDERR)
+    exit(1)
+
+
+class BBSymbols(gdb.Command):
+
+    def __init__(self):
+        super(BBSymbols, self).__init__("bb-load-symbols", gdb.COMMAND_FILES,
+                                        gdb.COMPLETE_FILENAME)
+
+    def invoke(self, argument, from_tty):
+        path = argument
+        f = open(path, 'rb')
+
+        try:
+            elf = ELFFile(f)
+        except ELFError:
+            gdb.write("Selected file is not an ELF file\n", gdb.STDERR)
+            return
+
+        section = elf.get_section_by_name(".symtab")
+        if section is None:
+            gdb.write("Section .symtab not found\n", gdb.STDERR)
+            return
+        symbol = section.get_symbol_by_name("pbl_barebox_break")
+        if not symbol:
+            gdb.write("Symbol pbl_barebox_break in section {} in file {} not found\n"
+                      .format(section.name, self.path), gdb.STDERR)
+            return
+        symbol = symbol[0]
+        pc = gdb.parse_and_eval("$pc")
+        symbol_address = int(symbol.entry.st_value)
+        address = int(pc) - symbol_address + 1
+        gdb.execute("symbol-file")
+        gdb.execute("add-symbol-file {} {}".format(path, address))
+
+
+BBSymbols()
+
+
+class BBSkip(gdb.Command):
+
+    def __init__(self):
+        super(BBSkip, self).__init__("bb-skip-break", gdb.COMMAND_BREAKPOINTS)
+
+    def invoke(self, arg, from_tty):
+        pc = gdb.parse_and_eval("$pc")
+        nop_address = int(pc) + 2
+        gdb.execute("jump *{}".format(nop_address))
+
+
+BBSkip()
-- 
2.20.1


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Re: [PATCH v4 0/2] add JTAG debugging support

[Sascha Hauer]

On Mon, Jun 24, 2019 at 12:00:41PM +0200, Oleksij Rempel wrote:
> changes v4:
> - rebase against latest git next barebox
> - make sure barebox header is not broken by PBL patch
> 
> Oleksij Rempel (1):
>   add CONFIG_PBL_BREAK option
> 
> Rouven Czerwinski (1):
>   add gdb helper scripts to load barebox symbols

Applied, thanks

Sascha

> 
>  Documentation/user/debugging.rst        | 21 +++++++++
>  Documentation/user/user-manual.rst      |  1 +
>  arch/arm/cpu/common.c                   | 13 ++++++
>  arch/arm/cpu/start.c                    |  2 +
>  arch/arm/include/asm/barebox-arm-head.h |  7 +++
>  arch/arm/include/asm/barebox-arm.h      |  1 +
>  common/Kconfig                          |  8 ++++
>  scripts/gdb/helper.py                   | 60 +++++++++++++++++++++++++
>  8 files changed, 113 insertions(+)
>  create mode 100644 Documentation/user/debugging.rst
>  create mode 100644 scripts/gdb/helper.py
> 
> -- 
> 2.20.1
> 
> 
> _______________________________________________
> barebox mailing list
> barebox@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/barebox
> 

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