linux-kernel - Re: [PATCH v3] x86/efi: Correct ident mapping of efi old

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Message-ID: <20170517033945.GD29117@x1>
Date:   Wed, 17 May 2017 11:39:45 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Dave Young <dyoung@...hat.com>
Cc:     linux-kernel@...r.kernel.org, bp@...en8.de, bhsharma@...hat.com,
        rja@....com, Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Garnier <thgarnie@...gle.com>,
        Kees Cook <keescook@...omium.org>, x86@...nel.org,
        linux-efi@...r.kernel.org
Subject: Re: [PATCH v3] x86/efi: Correct ident mapping of efi old_map when
 kalsr enabled

On 05/17/17 at 11:35am, Baoquan He wrote:
> On 05/17/17 at 10:55am, Dave Young wrote:
> > Hi, Baoquan
> > >  arch/x86/platform/efi/efi_64.c | 69 +++++++++++++++++++++++++++++++++++++-----
> > >  1 file changed, 61 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> > > index c488625..c9dffec 100644
> > > --- a/arch/x86/platform/efi/efi_64.c
> > > +++ b/arch/x86/platform/efi/efi_64.c
> > > @@ -71,11 +71,13 @@ static void __init early_code_mapping_set_exec(int executable)
> > >  
> > >  pgd_t * __init efi_call_phys_prolog(void)
> > >  {
> > > -	unsigned long vaddress;
> > > -	pgd_t *save_pgd;
> > > +	unsigned long vaddr, addr_pgd, addr_p4d, addr_pud;
> > > +	pgd_t *save_pgd, *pgd_k, *pgd_efi;
> > > +	p4d_t *p4d, *p4d_k, *p4d_efi;
> > > +	pud_t *pud;
> > >  
> > >  	int pgd;
> > > -	int n_pgds;
> > > +	int n_pgds, i, j;
> > >  
> > >  	if (!efi_enabled(EFI_OLD_MEMMAP)) {
> > >  		save_pgd = (pgd_t *)read_cr3();
> > > @@ -88,10 +90,44 @@ pgd_t * __init efi_call_phys_prolog(void)
> > >  	n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE);
> > >  	save_pgd = kmalloc_array(n_pgds, sizeof(*save_pgd), GFP_KERNEL);
> > >  
> > > +	/*
> > > +	 * Build 1:1 ident mapping for old_map usage. It needs to be noticed
> > > +	 * that PAGE_OFFSET is PGDIR_SIZE aligned with KASLR disabled, while
> > > +	 * PUD_SIZE ALIGNED with KASLR enabled. So for a given physical
> > > +	 * address X, the pud_index(X) != pud_index(__va(X)), we can only copy
> > > +	 * pud entry of __va(X) to fill in pud entry of X to build 1:1 mapping
> > > +	 * . Means here we can only reuse pmd table of direct mapping.
> > > +	 */
> > >  	for (pgd = 0; pgd < n_pgds; pgd++) {
> > > -		save_pgd[pgd] = *pgd_offset_k(pgd * PGDIR_SIZE);
> > > -		vaddress = (unsigned long)__va(pgd * PGDIR_SIZE);
> > > -		set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), *pgd_offset_k(vaddress));
> > > +		addr_pgd = (unsigned long)(pgd * PGDIR_SIZE);
> > > +		vaddr = (unsigned long)__va(pgd * PGDIR_SIZE);
> > > +		pgd_efi = pgd_offset_k(addr_pgd);
> > > +		save_pgd[pgd] = *pgd_efi;
> > > +		p4d =  p4d_alloc(&init_mm, pgd_efi, addr_pgd);
> > > +
> > > +		if (!p4d) {
> > > +			pr_err("Failed to allocate p4d table \n");
> > > +			goto out;
> > > +		}
> > > +		for(i=0; i<PTRS_PER_P4D; i++) {
> > 
> > There is code style issue here and other for loop later..
> 
> Oops, I forget running scripts/checkpatch.pl to check patch. Will change
> and post v4. May post with sgi v4 fix about the sgi uv mmioh region
			     ~~~~~~sgi uv
> issue, have discussed with HPE SGI developer about that.
> 
> Thanks for pointing it out!
> 
> Thanks
> Baoquan
> 
> > 
> > > +			addr_p4d = addr_pgd + i * P4D_SIZE;
> > > +			p4d_efi = p4d + p4d_index(addr_p4d);
> > > +			pud = pud_alloc(&init_mm, p4d_efi, addr_p4d);
> > > +			if (!pud) {
> > > +				pr_err("Failed to allocate pud table \n");
> > > +				goto out;
> > > +			}
> > > +			for(j=0; j<PTRS_PER_PUD; j++) {
> > > +				addr_pud = addr_p4d + j * PUD_SIZE;
> > > +				if (addr_pud > (max_pfn << PAGE_SHIFT))
> > > +					break;
> > > +				vaddr = (unsigned long)__va(addr_pud);
> > > +
> > > +				pgd_k = pgd_offset_k(vaddr);
> > > +				p4d_k = p4d_offset(pgd_k, vaddr);
> > > +				pud[j] = *pud_offset(p4d_k, vaddr);
> > > +			}
> > > +		}
> > >  	}
> > >  out:
> > >  	__flush_tlb_all();
> > > @@ -104,8 +140,11 @@ void __init efi_call_phys_epilog(pgd_t *save_pgd)
> > >  	/*
> > >  	 * After the lock is released, the original page table is restored.
> > >  	 */
> > > -	int pgd_idx;
> > > +	int pgd_idx, i;
> > >  	int nr_pgds;
> > > +	pgd_t *pgd;
> > > +        p4d_t *p4d;
> > > +        pud_t *pud;
> > >  
> > >  	if (!efi_enabled(EFI_OLD_MEMMAP)) {
> > >  		write_cr3((unsigned long)save_pgd);
> > > @@ -115,9 +154,23 @@ void __init efi_call_phys_epilog(pgd_t *save_pgd)
> > >  
> > >  	nr_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT) , PGDIR_SIZE);
> > >  
> > > -	for (pgd_idx = 0; pgd_idx < nr_pgds; pgd_idx++)
> > > +	for (pgd_idx = 0; pgd_idx < nr_pgds; pgd_idx++) {
> > > +		pgd = pgd_offset_k(pgd_idx * PGDIR_SIZE);
> > >  		set_pgd(pgd_offset_k(pgd_idx * PGDIR_SIZE), save_pgd[pgd_idx]);
> > >  
> > > +		if (!(pgd_val(*pgd) & _PAGE_PRESENT))
> > > +			continue;
> > > +		for(i=0; i<PTRS_PER_P4D; i++) {
> > > +			p4d = p4d_offset(pgd, pgd_idx * PGDIR_SIZE + i * P4D_SIZE);
> > > +			if (!(p4d_val(*p4d) & _PAGE_PRESENT))
> > > +				continue;
> > > +			pud = (pud_t*)p4d_page_vaddr(*p4d);
> > > +			pud_free(&init_mm, pud);
> > > +                }
> > > +		p4d = (p4d_t*)pgd_page_vaddr(*pgd);
> > > +		p4d_free(&init_mm, p4d);
> > > +	}
> > > +
> > >  	kfree(save_pgd);
> > >  
> > >  	__flush_tlb_all();
> > > -- 
> > > 2.5.5
> > > 
> > 
> > Thanks
> > Dave