linux-kernel - Re: [PATCH v3] modpost: check for static EXPORT

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Message-ID: <1b6f749c-2a25-219a-3eb3-0f2c7a542426@linux.com>
Date:   Tue, 30 Jul 2019 09:59:56 +0300
From:   Denis Efremov <efremov@...ux.com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Emil Velikov <emil.l.velikov@...il.com>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] modpost: check for static EXPORT_SYMBOL* functions

On 30.07.2019 01:26, Stephen Rothwell wrote:
> Hi Denis,
> 
> On Mon, 29 Jul 2019 17:18:01 +0300 Denis Efremov <efremov@...ux.com> wrote:
>>
>> This patch adds a check to warn about static EXPORT_SYMBOL* functions
>> during the modpost. In most of the cases, a static symbol marked for
>> exporting is an odd combination that should be fixed either by deleting
>> the exporting mark or by removing the static attribute and adding the
>> appropriate declaration to headers.
> 
> OK, this is now in linux-next and I am getting what look like false
> positives :-(
> 
> My powerpc builds produce these:
> 
> WARNING: "ahci_em_messages" [vmlinux] is the static EXPORT_SYMBOL_GPL
> WARNING: "ftrace_set_clr_event" [vmlinux] is the static EXPORT_SYMBOL_GPL
> WARNING: "empty_zero_page" [vmlinux] is the static EXPORT_SYMBOL
> WARNING: "jiffies" [vmlinux] is the static EXPORT_SYMBOL
> 
> empty_zero_page (at least) is not static.  It is defined in assembler ...

This could be fixed either by adding the type, for example:
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -478,6 +478,7 @@ EXPORT_SYMBOL(phys_base)

         __PAGE_ALIGNED_BSS
  NEXT_PAGE(empty_zero_page)
+.type empty_zero_page, STT_OBJECT
         .skip PAGE_SIZE
  EXPORT_SYMBOL(empty_zero_page)

Or by updating the check in the patch:
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1988,7 +1988,9 @@ static void read_symbols(const char *modname)
                 unsigned char bind = ELF_ST_BIND(sym->st_info);
                 unsigned char type = ELF_ST_TYPE(sym->st_info);

-               if (type == STT_OBJECT || type == STT_FUNC) {
+               if (type == STT_OBJECT ||
+                   type == STT_FUNC ||
+                   type == STT_NOTYPE) {

Do I need to resend the whole patch or create new "patch-on-patch"?

Denis