linux-kernel - Re: Crash on FSL Book3E due to pte_pgprot()? (was Re: [PATCH v3 12/24] powerpc/mm: use pte helpers in generic code)

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Date:   Wed, 17 Oct 2018 11:12:08 +0000
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Geoff Levand <geoff@...radead.org>,
        Jens Axboe <axboe@...nel.dk>,
        Kumar Gala <galak@...nel.crashing.org>,
        Li Yang <leoyang.li@....com>,
        Nicholas Piggin <npiggin@...il.com>,
        Paul Mackerras <paulus@...ba.org>,
        Scott Wood <oss@...error.net>, aneesh.kumar@...ux.vnet.ibm.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-block@...r.kernel.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, dri-devel@...ts.freedesktop.org
Subject: Re: Crash on FSL Book3E due to pte_pgprot()? (was Re: [PATCH v3
 12/24] powerpc/mm: use pte helpers in generic code)



On 10/17/2018 10:32 AM, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@....fr> writes:
>> On 10/17/2018 12:59 AM, Michael Ellerman wrote:
> ...
>>> The question is what's the right way to fix it? Should pte_pgprot() not
>>> be filtering those bits out on book3e?
>>
>> I think we should not use pte_pggrot() for that then. What about the
>> below fix ?
> 
> Thanks, that almost works.
> 
> pte_mkprivileged() also needs to not strip _PAGE_BAP_SR.

Oops, I missed it allthough I knew it. Patch below.

From: Christophe Leroy <christophe.leroy@....fr>
Date: Wed, 17 Oct 2018 10:46:24 +0000
Subject: [PATCH] powerpc/book3e: redefine pte_mkprivileged() and 
pte_mkuser()
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Mackerras 
<paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org

Book3e defines both _PAGE_USER and _PAGE_PRIVILEGED, so the nohash
default pte_mkprivileged() and pte_mkuser() are not usable.

This patch redefines them for book3e.

Fixes: a0da4bc166f2 ("powerpc/mm: Allow platforms to redefine some helpers")
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
  arch/powerpc/include/asm/nohash/pte-book3e.h | 14 ++++++++++++++
  1 file changed, 14 insertions(+)

diff --git a/arch/powerpc/include/asm/nohash/pte-book3e.h 
b/arch/powerpc/include/asm/nohash/pte-book3e.h
index 58eef8cb569d..fb4297dff3e2 100644
--- a/arch/powerpc/include/asm/nohash/pte-book3e.h
+++ b/arch/powerpc/include/asm/nohash/pte-book3e.h
@@ -109,5 +109,19 @@
  #define PAGE_READONLY	__pgprot(_PAGE_BASE | _PAGE_USER)
  #define PAGE_READONLY_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)

+static inline pte_t pte_mkprivileged(pte_t pte)
+{
+	return __pte((pte_val(pte) & ~_PAGE_USER) | _PAGE_PRIVILEGED);
+}
+
+#define pte_mkprivileged pte_mkprivileged
+
+static inline pte_t pte_mkuser(pte_t pte)
+{
+	return __pte((pte_val(pte) & ~_PAGE_PRIVILEGED) | _PAGE_USER);
+}
+
+#define pte_mkuser pte_mkuser
+
  #endif /* __KERNEL__ */
  #endif /*  _ASM_POWERPC_NOHASH_PTE_BOOK3E_H */
-- 
2.13.3



> 
> 
> But there's also a use of pte_pgprot() in mm/memory.c, and I think that
> is also broken now that we don't add PAGE_KERNEL back in.
> 
> Aneesh is going to do a patch to make pte_pgprot() only mask the PFN
> which is what other arches do.

Yes I saw it, that's ok for me.

Christophe

> 
> cheers
> 
>> From: Christophe Leroy <christophe.leroy@....fr>
>> Date: Wed, 17 Oct 2018 05:56:25 +0000
>> Subject: [PATCH] powerpc/mm: don't use pte_pgprot() in ioremap_prot()
>>
>> pte_pgprot() filters out some required flags like _PAGE_PRESENT.
>>
>> This patch replaces pte_pgprot() by __pgprot(pte_val())
>> in ioremap_prot()
>>
>> Fixes: 26973fa5ac0e ("powerpc/mm: use pte helpers in generic code")
>> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
>> ---
>>    arch/powerpc/mm/pgtable_32.c | 3 ++-
>>    arch/powerpc/mm/pgtable_64.c | 4 ++--
>>    2 files changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
>> index 5877f5aa8f5d..a606e2f4937b 100644
>> --- a/arch/powerpc/mm/pgtable_32.c
>> +++ b/arch/powerpc/mm/pgtable_32.c
>> @@ -122,7 +122,8 @@ ioremap_prot(phys_addr_t addr, unsigned long size,
>> unsigned long flags)
>>    	pte = pte_exprotect(pte);
>>    	pte = pte_mkprivileged(pte);
>>
>> -	return __ioremap_caller(addr, size, pte_pgprot(pte),
>> __builtin_return_address(0));
>> +	return __ioremap_caller(addr, size, __pgprot(pte_val(pte)),
>> +				__builtin_return_address(0));
>>    }
>>    EXPORT_SYMBOL(ioremap_prot);
>>
>> diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
>> index fb1375c07e8c..836bf436cabb 100644
>> --- a/arch/powerpc/mm/pgtable_64.c
>> +++ b/arch/powerpc/mm/pgtable_64.c
>> @@ -245,8 +245,8 @@ void __iomem * ioremap_prot(phys_addr_t addr,
>> unsigned long size,
>>    	pte = pte_mkprivileged(pte);
>>
>>    	if (ppc_md.ioremap)
>> -		return ppc_md.ioremap(addr, size, pte_pgprot(pte), caller);
>> -	return __ioremap_caller(addr, size, pte_pgprot(pte), caller);
>> +		return ppc_md.ioremap(addr, size, __pgprot(pte_val(pte)), caller);
>> +	return __ioremap_caller(addr, size, __pgprot(pte_val(pte)), caller);
>>    }
>>
>>
>> -- 
>> 2.13.3