Messages in this thread | | | From | Nick Desaulniers <> | Date | Mon, 11 Sep 2023 13:49:22 -0700 | Subject | Re: [PATCH v2] init: fix -Wmissing-variable-declarations clang warning |
| |
On Mon, Sep 11, 2023 at 1:46 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Tue, Sep 5, 2023 at 3:43 PM Justin Stitt <justinstitt@google.com> wrote: > > > > When building x86/defconfig with Clang-18 I encounter the following warning: > > | init/main.c:189:13: warning: no previous extern declaration for non-static variable 'envp_init' [-Wmissing-variable-declarations] > > | 189 | const char *envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, }; > > | init/main.c:189:7: note: declare 'static' if the variable is not intended to be used outside of this translation unit > > | 189 | const char *envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, }; > > > > Make `envp_init` static and provide `handle_initrd` its own copy. > > > > This silences the warning and makes the code more readable as you no > > longer have to track down extern definitions inside of `handle_initrd`. > > It is now more self-contained. > > But this is now creating duplicate string arrays in the kernel image. > > Why can't this be: > 1. declared in include/linux/initrd.h > 2. defined in init/main.c > 3. referenced in init/do_mounts.c > > The extern declaration in init/do_mounts_initrd.c isn't even correct! > It's missing a `const`! That's the kind of monkey business this > warning is trying to help avoid. C has headers for this reason, let's > use them. > > Perhaps users of call_usermodehelper_setup need an update, or > envp_init actually should not be const.
I prefer v1 as the basis; though as kbuild test robot noted to you, there are other references to envp_init that now need to be cleaned up in addition.
When you say you build tested v1, I assume you only built init/main.o and not vmlinux. Make sure to build test ALL files which refer to variables you've modified.
call_usermodehelper_setup and its callers either need to be cleaned up, or we should consider dropping const.
> > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1920 > > Signed-off-by: Justin Stitt <justinstitt@google.com> > > --- > > The kernel test robot didn't like v1 of this patch and I prefer Kees' > > approach to simplifying this code anyways so I'm sending this v2. > > Hopefully the CI builds clean (as I am locally using their repro). > > > > Changes in v2: > > - Make envp_init static and provide handle_initrd() with a copy (thanks Kees) > > - Rebase onto mainline (2dde18cd1d8fa) > > - Link to v1: https://lore.kernel.org/r/20230830-missingvardecl2-init-main-c-v1-1-59007a637259@google.com > > --- > > Note: build-tested only. > > > > It should be noted that `handle_initrd` has been marked as deprecated > > and perhaps the entire thing can be removed as per it's own message: > > | using deprecated initrd support, will be removed in 2021. > > --- > > init/do_mounts_initrd.c | 4 ++-- > > init/main.c | 2 +- > > 2 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c > > index 425f4bcf4b77..154bd0de85a6 100644 > > --- a/init/do_mounts_initrd.c > > +++ b/init/do_mounts_initrd.c > > @@ -87,7 +87,7 @@ static void __init handle_initrd(char *root_device_name) > > { > > struct subprocess_info *info; > > static char *argv[] = { "linuxrc", NULL, }; > > - extern char *envp_init[]; > > + static char *envp[] = { "HOME=/", "TERM=linux", NULL, }; > > int error; > > > > pr_warn("using deprecated initrd support, will be removed in 2021.\n"); > > @@ -100,7 +100,7 @@ static void __init handle_initrd(char *root_device_name) > > init_mkdir("/old", 0700); > > init_chdir("/old"); > > > > - info = call_usermodehelper_setup("/linuxrc", argv, envp_init, > > + info = call_usermodehelper_setup("/linuxrc", argv, envp, > > GFP_KERNEL, init_linuxrc, NULL, NULL); > > if (!info) > > return; > > diff --git a/init/main.c b/init/main.c > > index ad920fac325c..9a473107bb8f 100644 > > --- a/init/main.c > > +++ b/init/main.c > > @@ -186,7 +186,7 @@ static int __init set_reset_devices(char *str) > > __setup("reset_devices", set_reset_devices); > > > > static const char *argv_init[MAX_INIT_ARGS+2] = { "init", NULL, }; > > -const char *envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, }; > > +static const char *envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, }; > > static const char *panic_later, *panic_param; > > > > static bool __init obsolete_checksetup(char *line) > > > > --- > > base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c > > change-id: 20230830-missingvardecl2-init-main-c-93dc1013ff8a > > > > Best regards, > > -- > > Justin Stitt <justinstitt@google.com> > > > > > -- > Thanks, > ~Nick Desaulniers
-- Thanks, ~Nick Desaulniers
| |