Re: [PATCH v3 1/2] objtool: Add --Werror

Nathan Chancellor
2025-01-14T17:24:33Z

On Mon, Jan 13, 2025 at 02:05:15PM +0000, Brendan Jackman wrote:
> At present objtool only prints to the terminal when observing "fatal
> warnings". This option lets you have it produce an error instead.
>
> The use case for this is noinstr validation; so far I've never seen any
> false warnings here, but it quite often detects real bugs. It would
> be useful for the build to fail when I have those bugs.
>
> Signed-off-by: Brendan Jackman <jackmanb@google.com>
> ---
> tools/objtool/builtin-check.c | 6 ++++++
> tools/objtool/check.c | 7 ++-----
> tools/objtool/include/objtool/builtin.h | 1 +
> 3 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
> index 387d56a7f5fb8da8435d0a3f5c05eeee66932c9b..0b28082df90710ff7127327deb857c0548f378c7 100644
> --- a/tools/objtool/builtin-check.c
> +++ b/tools/objtool/builtin-check.c
> @@ -94,6 +94,12 @@ static const struct option check_options[] = {
> OPT_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
> OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
> OPT_BOOLEAN('v', "verbose", &opts.verbose, "verbose warnings"),
> + /*
> + * For now, don't fail the kernel build on fatal warnings by default.
> + * These errors are still fairly common due to the growing matrix of
> + * supported toolchains and their recent pace of change.
> + */
> + OPT_BOOLEAN(0, "Werror", &opts.werror, "fail on fatal warnings"),
>
> OPT_END(),
> };
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 76060da755b5c51cda3a669d8245d7d004e25f22..e44135293eb45f908e00359d84d954cfeddd266f 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -4944,10 +4944,7 @@ int check(struct objtool_file *file)
> }
>
> out:
> - /*
> - * For now, don't fail the kernel build on fatal warnings. These
> - * errors are still fairly common due to the growing matrix of
> - * supported toolchains and their recent pace of change.
> - */
> + if (opts.werror && warnings)

It might be a good idea to print a message here about why the build is
failing, in lieu of turning all "objtool: warning:" messages into
"objtool: error:" messages ala -Werror for C compilers, which does not
seem simple on quick glance. Otherwise, I am not entirely sure it will
be obvious to people why a build like allmodconfig may start failing if
this configuration gets turned on.

https://lore.kernel.org/Z4X8j%2FqJj7ib0vkh@rli9-mobl/

> + return 1;
> return 0;
> }
> diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
> index fcca6662c8b4b5e0048e54fada8694cc2e6ebc34..97d668010efadfa05bb6e25e1967a7d72bf77815 100644
> --- a/tools/objtool/include/objtool/builtin.h
> +++ b/tools/objtool/include/objtool/builtin.h
> @@ -38,6 +38,7 @@ struct opts {
> bool sec_address;
> bool stats;
> bool verbose;
> + bool werror;
> };
>
> extern struct opts opts;
>
> --
> 2.47.1.613.gc27f4b7a9f-goog
>