On 19/10/17 17:20, Boris Brezillon wrote:
> On Thu, 19 Oct 2017 17:11:34 +0300
> Roger Quadros <rogerq@xxxxxx> wrote:
>
>> On 19/10/17 16:51, Boris Brezillon wrote:
>>> On Thu, 19 Oct 2017 11:41:29 +0300
>>> Roger Quadros <rogerq@xxxxxx> wrote:
>>>
>>>> Since v4.12, NAND subpage writes were causing a NULL pointer
>>>> dereference on OMAP platforms (omap2-nand) using OMAP_ECC_BCH4_CODE_HW,
>>>> OMAP_ECC_BCH8_CODE_HW and OMAP_ECC_BCH16_CODE_HW.
>>>>
>>>> This is because for those ECC modes, omap_calculate_ecc_bch()
>>>> generates ECC bytes for the entire (multi-sector) page and this can
>>>> overflow the ECC buffer provided by nand_write_subpage_hwecc()
>>>> as it expects ecc.calculate() to return ECC bytes for just one sector.
>>>>
>>>> However, the root cause of the problem is present much before
>>>> v4.12 but was not seen then as NAND buffers were being allocated
>>>> as one big chunck prior to
>>>> commit 3deb9979c731 ("mtd: nand: allocate aligned buffers if NAND_OWN_BUFFERS is unset")
>>>>
>>>> Fix the issue by providing a OMAP optimized write_subpage() implementation.
>>>>
>>>> cc: <stable@xxxxxxxxxxxxxxx> # v4.12+
>>>> Signed-off-by: Roger Quadros <rogerq@xxxxxx>
>>>> ---
>>>> drivers/mtd/nand/omap2.c | 338 +++++++++++++++++++++++++++++++----------------
>>>> 1 file changed, 225 insertions(+), 113 deletions(-)
>>>>
>>>> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
>>>> index 54540c8..a0bd456 100644
>>>> --- a/drivers/mtd/nand/omap2.c
>>>> +++ b/drivers/mtd/nand/omap2.c
>>>> @@ -1133,129 +1133,172 @@ static u8 bch8_polynomial[] = {0xef, 0x51, 0x2e, 0x09, 0xed, 0x93, 0x9a, 0xc2,
>>>> 0x97, 0x79, 0xe5, 0x24, 0xb5};
>>>>
>>
>> <snip>
>>
>>>> +
>>>> +/**
>>>> * omap_read_page_bch - BCH ecc based page read function for entire page
>>>> * @mtd: mtd info structure
>>>> * @chip: nand chip info structure
>>>> @@ -2044,7 +2153,7 @@ static int omap_nand_probe(struct platform_device *pdev)
>>>> nand_chip->ecc.strength = 4;
>>>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>>>> nand_chip->ecc.correct = nand_bch_correct_data;
>>>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>>>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_sw;
>>>> mtd_set_ooblayout(mtd, &omap_sw_ooblayout_ops);
>>>> /* Reserve one byte for the OMAP marker */
>>>> oobbytes_per_step = nand_chip->ecc.bytes + 1;
>>>> @@ -2066,9 +2175,10 @@ static int omap_nand_probe(struct platform_device *pdev)
>>>> nand_chip->ecc.strength = 4;
>>>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>>>> nand_chip->ecc.correct = omap_elm_correct_data;
>>>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>>>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_multi;
>>>> nand_chip->ecc.read_page = omap_read_page_bch;
>>>> nand_chip->ecc.write_page = omap_write_page_bch;
>>>> + nand_chip->ecc.write_subpage = omap_write_subpage_bch;
>>>> mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
>>>> oobbytes_per_step = nand_chip->ecc.bytes;
>>>>
>>>> @@ -2087,7 +2197,7 @@ static int omap_nand_probe(struct platform_device *pdev)
>>>> nand_chip->ecc.strength = 8;
>>>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>>>> nand_chip->ecc.correct = nand_bch_correct_data;
>>>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>>>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_sw;
>>>> mtd_set_ooblayout(mtd, &omap_sw_ooblayout_ops);
>>>> /* Reserve one byte for the OMAP marker */
>>>> oobbytes_per_step = nand_chip->ecc.bytes + 1;
>>>> @@ -2109,9 +2219,10 @@ static int omap_nand_probe(struct platform_device *pdev)
>>>> nand_chip->ecc.strength = 8;
>>>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>>>> nand_chip->ecc.correct = omap_elm_correct_data;
>>>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>>>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_multi;
>>>
>>> Hm, it still looks wrong. omap_calculate_ecc_bch_multi() will generate
>>> the same overflow when called by the core, or am I missing something?
>>>
>> In the current setup core will never call ecc.calculate as we're overriding every op
>> that can be used.
>
> Do you have a custom ->read_subpage()? If you don't, the core will use
> nand_read_subpage(), and it's calling ->calculate() internally.
read_subpage() will only be used if NAND_SUBPAGE_READ is set. We don't set it for omap2-nand.
>
>>
>> The thing is that omap driver code uses these hooks as is so I wasn't sure
>> if I should change the caller code to call the multi versions directly and fix these
>> hooks to single sector versions.
>
> I'd prefer this solution.
>
>>
>> Alternatively, is it OK to set them to NULL?
>
> Hm, I'm pretty sure it's not, see my comment about ->read_subpage().
>
Now is it?
>>
>>
>>>> nand_chip->ecc.read_page = omap_read_page_bch;
>>>> nand_chip->ecc.write_page = omap_write_page_bch;
>>>> + nand_chip->ecc.write_subpage = omap_write_subpage_bch;
>>>> mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
>>>> oobbytes_per_step = nand_chip->ecc.bytes;
>>>>
>>>> @@ -2131,9 +2242,10 @@ static int omap_nand_probe(struct platform_device *pdev)
>>>> nand_chip->ecc.strength = 16;
>>>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>>>> nand_chip->ecc.correct = omap_elm_correct_data;
>>>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>>>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_multi;
>>>> nand_chip->ecc.read_page = omap_read_page_bch;
>>>> nand_chip->ecc.write_page = omap_write_page_bch;
>>>> + nand_chip->ecc.write_subpage = omap_write_subpage_bch;
>>>> mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
>>>> oobbytes_per_step = nand_chip->ecc.bytes;
>>>>
>>>
>>
>
--
cheers,
-roger
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