Re: [PATCH 2/2] lib/vsprintf: reduce space taken by no_hash_pointers warning

Andy Shevchenko
2021-03-08T10:34:15Z

On Fri, Mar 05, 2021 at 08:42:06PM +0100, Marco Elver wrote:
> Move the no_hash_pointers warning string into __initconst section, so
> that it is discarded after init. Remove common start/end characters.
> Also remove repeated lines from the array, since the compiler can't
> remove duplicate strings for us since the array must appear in
> __initconst as defined.
>
> Note, a similar message appears in kernel/trace/trace.c, but compiling
> the feature is guarded by CONFIG_TRACING. It is not immediately obvious
> if a space-concious kernel would prefer CONFIG_TRACING=n. Therefore, it
> makes sense to keep the message for no_hash_pointers as __initconst, and
> not move the NOTICE-printing to a common function.

This seems to have 2-in-1 patch. Care to split?
Feel free to add
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
to the __initconst part, but the rest.

> Link: https://lkml.kernel.org/r/CAMuHMdULKZCJevVJcp7TxzLdWLjsQPhE8hqxhnztNi9bjT_cEw@mail.gmail.com
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Marco Elver <elver@google.com>
> ---
> lib/vsprintf.c | 30 +++++++++++++++++-------------
> 1 file changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 4a14889ccb35..1095689c9c97 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -2094,26 +2094,30 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
> bool no_hash_pointers __ro_after_init;
> EXPORT_SYMBOL_GPL(no_hash_pointers);
>
> +static const char no_hash_pointers_warning[8][55] __initconst = {
> + "******************************************************",
> + " NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE ",
> + " This system shows unhashed kernel memory addresses ",
> + " via the console, logs, and other interfaces. This ",
> + " might reduce the security of your system. ",
> + " If you see this message and you are not debugging ",
> + " the kernel, report this immediately to your system ",
> + " administrator! ",
> +};
> +
> static int __init no_hash_pointers_enable(char *str)
> {
> + /* Indices into no_hash_pointers_warning; -1 is an empty line. */
> + const int lines[] = { 0, 1, -1, 2, 3, 4, -1, 5, 6, 7, -1, 1, 0 };
> + int i;
> +
> if (no_hash_pointers)
> return 0;
>
> no_hash_pointers = true;
>
> - pr_warn("**********************************************************\n");
> - pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
> - pr_warn("** **\n");
> - pr_warn("** This system shows unhashed kernel memory addresses **\n");
> - pr_warn("** via the console, logs, and other interfaces. This **\n");
> - pr_warn("** might reduce the security of your system. **\n");
> - pr_warn("** **\n");
> - pr_warn("** If you see this message and you are not debugging **\n");
> - pr_warn("** the kernel, report this immediately to your system **\n");
> - pr_warn("** administrator! **\n");
> - pr_warn("** **\n");
> - pr_warn("** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **\n");
> - pr_warn("**********************************************************\n");
> + for (i = 0; i < ARRAY_SIZE(lines); i++)
> + pr_warn("**%54s**\n", i == -1 ? "" : no_hash_pointers_warning[lines[i]]);
>
> return 0;
> }
> --
> 2.30.1.766.gb4fecdf3b7-goog
>

--
With Best Regards,
Andy Shevchenko