linux-kernel - Re: [PATCH v2 4/6] livepatch: Add sample livepatch module

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Date: Wed, 22 May 2024 13:37:15 +0200
From: Petr Mladek <pmladek@...e.com>
To: Lukas Hruska <lhruska@...e.cz>
Cc: mbenes@...e.cz, jpoimboe@...nel.org, joe.lawrence@...hat.com,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-kbuild@...r.kernel.org, mpdesouza@...e.com,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH v2 4/6] livepatch: Add sample livepatch module

On Thu 2024-05-16 15:30:07, Lukas Hruska wrote:
> From: Josh Poimboeuf <jpoimboe@...hat.com>
> 
> Add a new livepatch sample in samples/livepatch/ to make use of symbols
> that must be post-processed to enable load-time relocation resolution.
> As the new sample is to be used as an example, it is annotated with
> KLP_RELOC_SYMBOL macro.
> 
> The livepatch sample updates the function cmdline_proc_show to print the
> string referenced by the symbol saved_command_line appended by the
> string "livepatch=1".
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> Signed-off-by: Lukas Hruska <lhruska@...e.cz>
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> ---
>  samples/livepatch/Makefile                  |  1 +
>  samples/livepatch/livepatch-extern-symbol.c | 84 +++++++++++++++++++++
>  2 files changed, 85 insertions(+)
>  create mode 100644 samples/livepatch/livepatch-extern-symbol.c
> 
> diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile
> index 9f853eeb6140..f2b41f4d6c16 100644
> --- a/samples/livepatch/Makefile
> +++ b/samples/livepatch/Makefile
> @@ -6,3 +6,4 @@ obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o
>  obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-demo.o
>  obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-mod.o
>  obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-busymod.o
> +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-annotated-sample.o

It seems that the sample has been renamed without updating
the Makefile rule. There should be:

+obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-extern-symbol.o

Otherwise, I get:

make[4]: *** No rule to make target 'samples/livepatch/livepatch-annotated-sample.o', needed by 'samples/livepatch/'.  Stop.
make[3]: *** [scripts/Makefile.build:485: samples/livepatch] Error 2
make[2]: *** [scripts/Makefile.build:485: samples] Error 2
make[1]: *** [/prace/kernel/linux/Makefile:1921: .] Error 2
make: *** [Makefile:240: __sub-make] Error 2

> diff --git a/samples/livepatch/livepatch-extern-symbol.c b/samples/livepatch/livepatch-extern-symbol.c
> new file mode 100644
> index 000000000000..276a43d157b4
> --- /dev/null
> +++ b/samples/livepatch/livepatch-extern-symbol.c
> @@ -0,0 +1,84 @@

The test module works as expected after fixing the Makefile.

Best Regards,
Petr