From: Nick Desaulniers <ndesaulniers@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
Nicolas Pitre <npitre@baylibre.com>,
Luis Chamberlain <mcgrof@kernel.org>,
linux-modules@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Michal Marek <michal.lkml@markovi.net>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/7] modpost: use null string instead of NULL pointer for default namespace
Date: Mon, 25 Jul 2022 09:42:53 -0700 [thread overview]
Message-ID: <CAKwvOd=TCSWmG_sca9e49V-h3ZRdtP+cEazoO26vf475mJfyzg@mail.gmail.com> (raw)
In-Reply-To: <20220610183236.1272216-8-masahiroy@kernel.org>
On Fri, Jun 10, 2022 at 11:34 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> The default namespace is the null string, "".
>
> When set, the null string "" is converted to NULL:
>
> s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL;
>
> When printed, the NULL pointer is get back to the null string:
>
> sym->namespace ?: ""
>
> This saves 1 byte memory allocated for "", but loses the readability.
>
> In kernel-space, we strive to save memory, but modpost is a userspace
> tool used to build the kernel. On modern systems, such small piece of
> memory is not a big deal.
>
> Handle the namespace string as is.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Sorry for the late review. If this is still useful:
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Feel free to ping me via mail if I'm falling behind. Otherwise you
should join us on IRC. (#clangbuiltlinux on libera)
> ---
>
> scripts/mod/modpost.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 0db2cbb74a2a..5a1785645943 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -296,6 +296,13 @@ static bool contains_namespace(struct list_head *head, const char *namespace)
> {
> struct namespace_list *list;
>
> + /*
> + * The default namespace is null string "", which is always implicitly
> + * contained.
> + */
> + if (!namespace[0])
> + return true;
> +
> list_for_each_entry(list, head, list) {
> if (!strcmp(list->namespace, namespace))
> return true;
> @@ -371,7 +378,7 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod,
> s = alloc_symbol(name);
> s->module = mod;
> s->is_gpl_only = gpl_only;
> - s->namespace = namespace[0] ? NOFAIL(strdup(namespace)) : NULL;
> + s->namespace = NOFAIL(strdup(namespace));
> list_add_tail(&s->list, &mod->exported_symbols);
> hash_add_symbol(s);
>
> @@ -2117,8 +2124,7 @@ static void check_exports(struct module *mod)
> else
> basename = mod->name;
>
> - if (exp->namespace &&
> - !contains_namespace(&mod->imported_namespaces, exp->namespace)) {
> + if (!contains_namespace(&mod->imported_namespaces, exp->namespace)) {
> modpost_log(allow_missing_ns_imports ? LOG_WARN : LOG_ERROR,
> "module %s uses symbol %s from namespace %s, but does not import it.\n",
> basename, exp->name, exp->namespace);
> @@ -2201,7 +2207,7 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod)
> list_for_each_entry(sym, &mod->exported_symbols, list)
> buf_printf(buf, "KSYMTAB_ENTRY(%s, \"%s\", \"%s\");\n",
> sym->name, sym->is_gpl_only ? "_gpl" : "",
> - sym->namespace ?: "");
> + sym->namespace);
>
> if (!modversions)
> return;
> @@ -2471,7 +2477,7 @@ static void write_dump(const char *fname)
> buf_printf(&buf, "0x%08x\t%s\t%s\tEXPORT_SYMBOL%s\t%s\n",
> sym->crc, sym->name, mod->name,
> sym->is_gpl_only ? "_GPL" : "",
> - sym->namespace ?: "");
> + sym->namespace);
> }
> }
> write_buf(&buf, fname);
> --
> 2.32.0
>
--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2022-07-25 16:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-10 18:32 [PATCH 0/7] Unify <linux/export.h> and <asm/export.h>, remove EXPORT_DATA_SYMBOL() Masahiro Yamada
2022-06-10 18:32 ` [PATCH 1/7] modpost: fix section mismatch check for exported init/exit sections Masahiro Yamada
2022-06-10 18:32 ` [PATCH 2/7] modpost: put get_secindex() call inside sec_name() Masahiro Yamada
2022-06-10 21:41 ` Nick Desaulniers
2022-06-10 18:32 ` [PATCH 3/7] kbuild: generate struct kernel_symbol by modpost Masahiro Yamada
2022-06-11 18:47 ` Masahiro Yamada
2022-06-10 18:32 ` [PATCH 4/7] ia64,export.h: replace EXPORT_DATA_SYMBOL* with EXPORT_SYMBOL* Masahiro Yamada
2022-06-11 18:49 ` Masahiro Yamada
2022-06-10 18:32 ` [PATCH 5/7] checkpatch: warn if <asm/export.h> is included Masahiro Yamada
2022-06-11 1:33 ` Joe Perches
2022-06-11 18:56 ` Masahiro Yamada
2022-06-10 18:32 ` [PATCH 6/7] modpost: merge sym_update_namespace() into sym_add_exported() Masahiro Yamada
2022-06-10 22:26 ` Nick Desaulniers
2022-06-10 18:32 ` [PATCH 7/7] modpost: use null string instead of NULL pointer for default namespace Masahiro Yamada
2022-07-25 16:42 ` Nick Desaulniers [this message]
2022-06-11 18:51 ` [PATCH 0/7] Unify <linux/export.h> and <asm/export.h>, remove EXPORT_DATA_SYMBOL() Masahiro Yamada
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAKwvOd=TCSWmG_sca9e49V-h3ZRdtP+cEazoO26vf475mJfyzg@mail.gmail.com' \
--to=ndesaulniers@google.com \
--cc=ardb@kernel.org \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-modules@vger.kernel.org \
--cc=masahiroy@kernel.org \
--cc=mcgrof@kernel.org \
--cc=michal.lkml@markovi.net \
--cc=npitre@baylibre.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).