[Buildroot] [PATCH V2] package: gdb: Add helping kernel gdb functions compilation

[Buildroot] [PATCH V2] package: gdb: Add helping kernel gdb functions compilation

[Michael Trimarchi]

In order to use all the features of KGDB it's nice to have
the possibility to source the vmlinux-gdb.py file. The
generation of this file depend on CONFIG_GDB_SCRIPTS config
option. Add it in order to use gdb of vmlinux in output directory
including tx-* linux script

gdb-multiarch --tui output/build/<linux dir>/vmlinux
add-auto-load-safe-path output/build/<linux dir>
source output/build/<linux dir>/vmlinux-gdb.py

Linux needs to be compiled with DEBUG_INFO (without restrict
DEBUG_INFO) and kernel cmdline should be modified to wait
of kgdb if needed. As example

kgdboc_earlycon=ns16550a kgdboc=/dev/ttyS2 kgdbwait nokaslr

The test was done on am62x board over serial line. In order
to have it running properly we need to compile the agent-proxy

./output/host/bin/agent-proxy 4440 4441 0 /dev/ttyUSB0 115200

gdb can now having the debugging uart available using:

target remote localhost:4441

the 4440 is used by the console and 4441 is used to debug

[Yann E. MORIN: suggest to change the gdb.mk file instead,
 changing the kernel.mk file. ]

Suggested-by: Yann E. MORIN <yann.morin.1998@free.fr> 
Tested-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
---
V1->V2:
	- Yann really help to make it simple and move from
	  a kernel task to an enable configuration to gdb
---
 package/gdb/gdb.mk | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/package/gdb/gdb.mk b/package/gdb/gdb.mk
index 070598b385..0ebeb08dad 100644
--- a/package/gdb/gdb.mk
+++ b/package/gdb/gdb.mk
@@ -304,5 +304,9 @@ HOST_GDB_POST_INSTALL_HOOKS += HOST_GDB_ADD_SYMLINK
 
 HOST_GDB_POST_INSTALL_HOOKS += gen_gdbinit_file
 
+define HOST_GDB_LINUX_CONFIG_FIXUPS
+	$(call KCONFIG_ENABLE_OPT,CONFIG_GDB_SCRIPTS)
+endef
+
 $(eval $(autotools-package))
 $(eval $(host-autotools-package))
-- 
2.40.1

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Re: [Buildroot] [PATCH V2] package: gdb: Add helping kernel gdb functions compilation

[Thomas Petazzoni via buildroot]

Hello Michael,

I think the commit title is not very good/clear, and could be improved.
However, I have some more fundamental concern. See below.

On Sat,  9 Dec 2023 22:49:18 +0100
Michael Trimarchi <michael@amarulasolutions.com> wrote:

> diff --git a/package/gdb/gdb.mk b/package/gdb/gdb.mk
> index 070598b385..0ebeb08dad 100644
> --- a/package/gdb/gdb.mk
> +++ b/package/gdb/gdb.mk
> @@ -304,5 +304,9 @@ HOST_GDB_POST_INSTALL_HOOKS += HOST_GDB_ADD_SYMLINK
>  
>  HOST_GDB_POST_INSTALL_HOOKS += gen_gdbinit_file
>  
> +define HOST_GDB_LINUX_CONFIG_FIXUPS
> +	$(call KCONFIG_ENABLE_OPT,CONFIG_GDB_SCRIPTS)
> +endef

I'm not sure I like this. <pkg>_LINUX_CONFIG_FIXUPS is really meant to
be used to enable kernel options that are really/absolutely needed for
the package to work. I understand that CONFIG_GDB_SCRIPTS is not really
adding anything to the kernel image itself, but rather just to the
kernel build process, but still I believe it falls outside of the goal
of <pkg>_LINUX_CONFIG_FIXUPS.

In addition:

- Many people will want to use gdb and build a Linux kernel, but not
  necessarily want to debug the kernel. So "enabling gdb" does not
  imply "I want to debug the kernel"

- This patch does not account for the fairly common case of host gdb
  being provided by an external toolchain. In this situation, the user
  still has to enable CONFIG_GDB_SCRIPTS=y "manually" in his kernel
  configuration.

For all those reasons, and even though the change is simple and does no
harm, I believe it's not really useful and aligned with the intention
of <pkg>_LINUX_CONFIG_FIXUPS.

So I would personally be in favor of not accepting this patch.

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] [PATCH V2] package: gdb: Add helping kernel gdb functions compilation

[Michael Nazzareno Trimarchi]

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Hi Thomas

Il mer 13 dic 2023, 21:08 Thomas Petazzoni <thomas.petazzoni@bootlin.com>
ha scritto:

> Hello Michael,
>
> I think the commit title is not very good/clear, and could be improved.
> However, I have some more fundamental concern. See below.
>
> On Sat,  9 Dec 2023 22:49:18 +0100
> Michael Trimarchi <michael@amarulasolutions.com> wrote:
>
> > diff --git a/package/gdb/gdb.mk b/package/gdb/gdb.mk
> > index 070598b385..0ebeb08dad 100644
> > --- a/package/gdb/gdb.mk
> > +++ b/package/gdb/gdb.mk
> > @@ -304,5 +304,9 @@ HOST_GDB_POST_INSTALL_HOOKS += HOST_GDB_ADD_SYMLINK
> >
> >  HOST_GDB_POST_INSTALL_HOOKS += gen_gdbinit_file
> >
> > +define HOST_GDB_LINUX_CONFIG_FIXUPS
> > +     $(call KCONFIG_ENABLE_OPT,CONFIG_GDB_SCRIPTS)
> > +endef
>
> I'm not sure I like this. <pkg>_LINUX_CONFIG_FIXUPS is really meant to
> be used to enable kernel options that are really/absolutely needed for
> the package to work. I understand that CONFIG_GDB_SCRIPTS is not really
> adding anything to the kernel image itself, but rather just to the
> kernel build process, but still I believe it falls outside of the goal
> of <pkg>_LINUX_CONFIG_FIXUPS.
>
> In addition:
>
> - Many people will want to use gdb and build a Linux kernel, but not
>   necessarily want to debug the kernel. So "enabling gdb" does not
>   imply "I want to debug the kernel"
>
> - This patch does not account for the fairly common case of host gdb
>   being provided by an external toolchain. In this situation, the user
>   still has to enable CONFIG_GDB_SCRIPTS=y "manually" in his kernel
>   configuration.
>
> For all those reasons, and even though the change is simple and does no
> harm, I believe it's not really useful and aligned with the intention
> of <pkg>_LINUX_CONFIG_FIXUPS.
>
> So I would personally be in favor of not accepting this patch.
>
> Best regards,
>


My V1 was addressing your concern?

Michael

>
> Thomas Petazzoni
> --
> Thomas Petazzoni, co-owner and CEO, Bootlin
> Embedded Linux and Kernel engineering and training
> https://bootlin.com
>

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Re: [Buildroot] [PATCH V2] package: gdb: Add helping kernel gdb functions compilation

[Thomas Petazzoni via buildroot]

On Wed, 13 Dec 2023 21:17:34 +0100
Michael Nazzareno Trimarchi <michael@amarulasolutions.com> wrote:

> My V1 was addressing your concern?

No, your v1 was just adding a Buildroot option that allows to enable a
kernel option. This is useless, as you can simply enable the kernel
option in question, and it doesn't make any sense for Buildroot to
replicate 1:1 each kernel option as a Buildroot option. It only makes
sense to do so when enabling the kernel option requires that Buildroot
builds additional host tools/libraries. But for something as simple as
enabling CONFIG_GDB_SCRIPTS, just enable it in your kernel config.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] [PATCH V2] package: gdb: Add helping kernel gdb functions compilation

[Michael Nazzareno Trimarchi]

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Hi Tomas

Il mer 13 dic 2023, 21:24 Thomas Petazzoni <thomas.petazzoni@bootlin.com>
ha scritto:

> On Wed, 13 Dec 2023 21:17:34 +0100
> Michael Nazzareno Trimarchi <michael@amarulasolutions.com> wrote:
>
> > My V1 was addressing your concern?
>
> No, your v1 was just adding a Buildroot option that allows to enable a
> kernel option. This is useless, as you can simply enable the kernel
> option in question, and it doesn't make any sense for Buildroot to
> replicate 1:1 each kernel option as a Buildroot option. It only makes
> sense to do so when enabling the kernel option requires that Buildroot
> builds additional host tools/libraries. But for something as simple as
> enabling CONFIG_GDB_SCRIPTS, just enable it in your kernel config.
>

I don't think that I enable any option and I just run an other kernel
target. Yes but definitely I understand your point. My idea was to keeps
some tools build as option as the serial proxy.

Michael




> Thomas
> --
> Thomas Petazzoni, co-owner and CEO, Bootlin
> Embedded Linux and Kernel engineering and training
> https://bootlin.com
>

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Re: [Buildroot] [PATCH V2] package: gdb: Add helping kernel gdb functions compilation

[Yann E. MORIN]

Micheal, All,

On 2023-12-13 21:32 +0100, Michael Nazzareno Trimarchi spake thusly:
> Il mer 13 dic 2023, 21:24 Thomas Petazzoni <thomas.petazzoni@bootlin.com>
> ha scritto:
> > On Wed, 13 Dec 2023 21:17:34 +0100
> > Michael Nazzareno Trimarchi <michael@amarulasolutions.com> wrote:
> > > My V1 was addressing your concern?
> > No, your v1 was just adding a Buildroot option that allows to enable a
> > kernel option. This is useless, as you can simply enable the kernel
> > option in question, and it doesn't make any sense for Buildroot to
> > replicate 1:1 each kernel option as a Buildroot option. It only makes
> > sense to do so when enabling the kernel option requires that Buildroot
> > builds additional host tools/libraries. But for something as simple as
> > enabling CONFIG_GDB_SCRIPTS, just enable it in your kernel config.
> I don't think that I enable any option and I just run an other kernel
> target. Yes but definitely I understand your point. My idea was to keeps
> some tools build as option as the serial proxy.

Thomas' point is pretty fair, in fact, and it should have hit me as well
when I reviewed v1: if one wants to do kernel debugging, they should be
responsible for enabling all appropriate options in their kernel. One
such option will have this script installed.

Regards,
Yann E. MORIN.

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