[linux-next:master 10679/10701] arch/x86/mm/pgtable.c:427:2: warning: ISO C90 forbids variable length array 'u_pmds'

[linux-next:master 10679/10701] arch/x86/mm/pgtable.c:427:2: warning: ISO C90 forbids variable length array 'u_pmds'

[kbuild test robot]

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   fb57b1fabcb28f358901b2df90abd2b48abc1ca8
commit: 0e19fc1c40bd7516d5a30a459db4f49d48910847 [10679/10701] mm: consolidate pgd_index() and pgd_offset{_k}() definitions
config: i386-randconfig-r013-20200521 (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce (this is a W=1 build):
        git checkout 0e19fc1c40bd7516d5a30a459db4f49d48910847
        # save the attached .config to linux build tree
        make ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@intel.com>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

arch/x86/mm/pgtable.c: In function 'pgd_alloc':
>> arch/x86/mm/pgtable.c:427:2: warning: ISO C90 forbids variable length array 'u_pmds' [-Wvla]
pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS];
^~~~~
>> arch/x86/mm/pgtable.c:428:2: warning: ISO C90 forbids variable length array 'pmds' [-Wvla]
pmd_t *pmds[MAX_PREALLOCATED_PMDS];
^~~~~

vim +/u_pmds +427 arch/x86/mm/pgtable.c

1db491f77b6ed0 Fenghua Yu          2015-01-15  423  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  424  pgd_t *pgd_alloc(struct mm_struct *mm)
1ec1fe73dfb711 Ingo Molnar         2008-03-19  425  {
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  426  	pgd_t *pgd;
184d47f0fd3651 Kees Cook           2018-10-08 @427  	pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS];
184d47f0fd3651 Kees Cook           2018-10-08 @428  	pmd_t *pmds[MAX_PREALLOCATED_PMDS];
1ec1fe73dfb711 Ingo Molnar         2008-03-19  429  
1db491f77b6ed0 Fenghua Yu          2015-01-15  430  	pgd = _pgd_alloc();
1ec1fe73dfb711 Ingo Molnar         2008-03-19  431  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  432  	if (pgd == NULL)
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  433  		goto out;
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  434  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  435  	mm->pgd = pgd;
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  436  
f59dbe9ca6707e Joerg Roedel        2018-07-18  437  	if (preallocate_pmds(mm, pmds, PREALLOCATED_PMDS) != 0)
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  438  		goto out_free_pgd;
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  439  
f59dbe9ca6707e Joerg Roedel        2018-07-18  440  	if (preallocate_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS) != 0)
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  441  		goto out_free_pmds;
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  442  
f59dbe9ca6707e Joerg Roedel        2018-07-18  443  	if (paravirt_pgd_alloc(mm) != 0)
f59dbe9ca6707e Joerg Roedel        2018-07-18  444  		goto out_free_user_pmds;
f59dbe9ca6707e Joerg Roedel        2018-07-18  445  
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  446  	/*
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  447  	 * Make sure that pre-populating the pmds is atomic with
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  448  	 * respect to anything walking the pgd_list, so that they
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  449  	 * never see a partially populated pgd.
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  450  	 */
a79e53d85683c6 Andrea Arcangeli    2011-02-16  451  	spin_lock(&pgd_lock);
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  452  
617d34d9e5d832 Jeremy Fitzhardinge 2010-09-21  453  	pgd_ctor(mm, pgd);
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  454  	pgd_prepopulate_pmd(mm, pgd, pmds);
f59dbe9ca6707e Joerg Roedel        2018-07-18  455  	pgd_prepopulate_user_pmd(mm, pgd, u_pmds);
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  456  
a79e53d85683c6 Andrea Arcangeli    2011-02-16  457  	spin_unlock(&pgd_lock);
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  458  
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  459  	return pgd;
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  460  
f59dbe9ca6707e Joerg Roedel        2018-07-18  461  out_free_user_pmds:
f59dbe9ca6707e Joerg Roedel        2018-07-18  462  	free_pmds(mm, u_pmds, PREALLOCATED_USER_PMDS);
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  463  out_free_pmds:
f59dbe9ca6707e Joerg Roedel        2018-07-18  464  	free_pmds(mm, pmds, PREALLOCATED_PMDS);
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  465  out_free_pgd:
1db491f77b6ed0 Fenghua Yu          2015-01-15  466  	_pgd_free(pgd);
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  467  out:
d8d5900ef8afc5 Jeremy Fitzhardinge 2008-06-25  468  	return NULL;
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  469  }
4f76cd382213b2 Jeremy Fitzhardinge 2008-03-17  470  

:::::: The code at line 427 was first introduced by commit
:::::: 184d47f0fd365108bd06ab26cdb3450b716269fd x86/mm: Avoid VLA in pgd_alloc()

:::::: TO: Kees Cook <keescook@chromium.org>
:::::: CC: Ingo Molnar <mingo@kernel.org>

---
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