Re: [PATCH] Revert "pstore/ram: add Device Tree bindings"

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On Thu, Jul 28, 2016 at 2:10 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
> On Thu, Jul 28, 2016 at 3:50 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> On Thu, Jul 28, 2016 at 1:25 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
>>> This reverts commit 35da60941e44dbf57868e67686dd24cc1a33125a.
>>> ---
>>> WTF!
>>>
>>> I don't recall acking this nor have my comments (Arnd's really) been
>>> addressed[1]. This should not have been merged yet.
>>
>> The conversation seemed to me to describe an alternative that could be
>> moved to, but that it was going to need more work. In the meantime,
>> these are the DT bindings used in real devices already. It seemed
>> clear to me that reducing the delta now and improving the
>> implementation in the future was the right thing to do in this case. I
>> didn't think your comments were a hard NAK, but rather a "we should do
>> this in the future", and I added it as a TODO for the pstore tree.
>>
>> Is a revert really justified here? This doesn't break anything (quite
>> the opposite, actually).
>
> Yes. Bindings are an ABI, so they can't evolve other than get
> additional properties.

Okay. I still think that from a pragmatic perspective, this isn't
different from reality: Android carries a version of this, so that ABI
already "exists", but, regardless, I misunderstood the intensity of
your concerns. :)

> I'm keen to have this in too because I know there are lots of users
> (extract a DT from a Calxeda system ;)). It's not really that far off
> (drop memory-region and define the location in /reserved-memory) I
> think. So send a follow-up for 4.8 and then it doesn't need a revert.

Okay, I'll see what I can figure out.

-Kees

>
> Rob
>
>>
>> -Kees
>>
>>>
>>> Rob
>>>
>>> [1] https://lkml.org/lkml/2016/6/21/969
>>>
>>>  Documentation/devicetree/bindings/misc/ramoops.txt | 48 -----------
>>>  Documentation/ramoops.txt                          |  6 +-
>>>  fs/pstore/ram.c                                    | 95 +---------------------
>>>  3 files changed, 4 insertions(+), 145 deletions(-)
>>>  delete mode 100644 Documentation/devicetree/bindings/misc/ramoops.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/misc/ramoops.txt b/Documentation/devicetree/bindings/misc/ramoops.txt
>>> deleted file mode 100644
>>> index cd02cec..0000000
>>> --- a/Documentation/devicetree/bindings/misc/ramoops.txt
>>> +++ /dev/null
>>> @@ -1,48 +0,0 @@
>>> -Ramoops oops/panic logger
>>> -=========================
>>> -
>>> -ramoops provides persistent RAM storage for oops and panics, so they can be
>>> -recovered after a reboot. It is a backend to pstore, so this node is named
>>> -"ramoops" after the backend, rather than "pstore" which is the subsystem.
>>> -
>>> -Parts of this storage may be set aside for other persistent log buffers, such
>>> -as kernel log messages, or for optional ECC error-correction data.  The total
>>> -size of these optional buffers must fit in the reserved region.
>>> -
>>> -Any remaining space will be used for a circular buffer of oops and panic
>>> -records.  These records have a configurable size, with a size of 0 indicating
>>> -that they should be disabled.
>>> -
>>> -At least one of "record-size", "console-size", "ftrace-size", or "pmsg-size"
>>> -must be set non-zero, but are otherwise optional as listed below.
>>> -
>>> -
>>> -Required properties:
>>> -
>>> -- compatible: must be "ramoops"
>>> -
>>> -- memory-region: phandle to a region of memory that is preserved between
>>> -  reboots
>>> -
>>> -
>>> -Optional properties:
>>> -
>>> -- ecc-size: enables ECC support and specifies ECC buffer size in bytes
>>> -  (defaults to 0: no ECC)
>>> -
>>> -- record-size: maximum size in bytes of each dump done on oops/panic
>>> -  (defaults to 0: disabled)
>>> -
>>> -- console-size: size in bytes of log buffer reserved for kernel messages
>>> -  (defaults to 0: disabled)
>>> -
>>> -- ftrace-size: size in bytes of log buffer reserved for function tracing and
>>> -  profiling (defaults to 0: disabled)
>>> -
>>> -- pmsg-size: size in bytes of log buffer reserved for userspace messages
>>> -  (defaults to 0: disabled)
>>> -
>>> -- unbuffered: if present, use unbuffered mappings to map the reserved region
>>> -  (defaults to buffered mappings)
>>> -
>>> -- no-dump-oops: if present, only dump panics (defaults to panics and oops)
>>> diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
>>> index 9264bca..5d86756 100644
>>> --- a/Documentation/ramoops.txt
>>> +++ b/Documentation/ramoops.txt
>>> @@ -45,7 +45,7 @@ corrupt, but usually it is restorable.
>>>
>>>  2. Setting the parameters
>>>
>>> -Setting the ramoops parameters can be done in 3 different manners:
>>> +Setting the ramoops parameters can be done in 2 different manners:
>>>   1. Use the module parameters (which have the names of the variables described
>>>   as before).
>>>   For quick debugging, you can also reserve parts of memory during boot
>>> @@ -54,9 +54,7 @@ Setting the ramoops parameters can be done in 3 different manners:
>>>   kernel to use only the first 128 MB of memory, and place ECC-protected ramoops
>>>   region at 128 MB boundary:
>>>   "mem=128M ramoops.mem_address=0x8000000 ramoops.ecc=1"
>>> - 2. Use Device Tree bindings, as described in
>>> - Documentation/device-tree/bindings/misc/ramoops.txt.
>>> - 3. Use a platform device and set the platform data. The parameters can then
>>> + 2. Use a platform device and set the platform data. The parameters can then
>>>   be set through that platform data. An example of doing that is:
>>>
>>>  #include <linux/pstore_ram.h>
>>> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
>>> index 47516a7..d9668c2 100644
>>> --- a/fs/pstore/ram.c
>>> +++ b/fs/pstore/ram.c
>>> @@ -34,8 +34,6 @@
>>>  #include <linux/slab.h>
>>>  #include <linux/compiler.h>
>>>  #include <linux/pstore_ram.h>
>>> -#include <linux/of.h>
>>> -#include <linux/of_address.h>
>>>
>>>  #define RAMOOPS_KERNMSG_HDR "===="
>>>  #define MIN_MEM_SIZE 4096UL
>>> @@ -460,98 +458,15 @@ static int ramoops_init_prz(struct device *dev, struct ramoops_context *cxt,
>>>         return 0;
>>>  }
>>>
>>> -static int ramoops_parse_dt_size(struct platform_device *pdev,
>>> -                                const char *propname, u32 *value)
>>> -{
>>> -       u32 val32 = 0;
>>> -       int ret;
>>> -
>>> -       ret = of_property_read_u32(pdev->dev.of_node, propname, &val32);
>>> -       if (ret < 0 && ret != -EINVAL) {
>>> -               dev_err(&pdev->dev, "failed to parse property %s: %d\n",
>>> -                       propname, ret);
>>> -               return ret;
>>> -       }
>>> -
>>> -       if (val32 > INT_MAX) {
>>> -               dev_err(&pdev->dev, "%s %u > INT_MAX\n", propname, val32);
>>> -               return -EOVERFLOW;
>>> -       }
>>> -
>>> -       *value = val32;
>>> -       return 0;
>>> -}
>>> -
>>> -static int ramoops_parse_dt(struct platform_device *pdev,
>>> -                           struct ramoops_platform_data *pdata)
>>> -{
>>> -       struct device_node *of_node = pdev->dev.of_node;
>>> -       struct device_node *mem_region;
>>> -       struct resource res;
>>> -       u32 value;
>>> -       int ret;
>>> -
>>> -       dev_dbg(&pdev->dev, "using Device Tree\n");
>>> -
>>> -       mem_region = of_parse_phandle(of_node, "memory-region", 0);
>>> -       if (!mem_region) {
>>> -               dev_err(&pdev->dev, "no memory-region phandle\n");
>>> -               return -ENODEV;
>>> -       }
>>> -
>>> -       ret = of_address_to_resource(mem_region, 0, &res);
>>> -       of_node_put(mem_region);
>>> -       if (ret) {
>>> -               dev_err(&pdev->dev,
>>> -                       "failed to translate memory-region to resource: %d\n",
>>> -                       ret);
>>> -               return ret;
>>> -       }
>>> -
>>> -       pdata->mem_size = resource_size(&res);
>>> -       pdata->mem_address = res.start;
>>> -       pdata->mem_type = of_property_read_bool(of_node, "unbuffered");
>>> -       pdata->dump_oops = !of_property_read_bool(of_node, "no-dump-oops");
>>> -
>>> -#define parse_size(name, field) {                                      \
>>> -               ret = ramoops_parse_dt_size(pdev, name, &value);        \
>>> -               if (ret < 0)                                            \
>>> -                       return ret;                                     \
>>> -               field = value;                                          \
>>> -       }
>>> -
>>> -       parse_size("record-size", pdata->record_size);
>>> -       parse_size("console-size", pdata->console_size);
>>> -       parse_size("ftrace-size", pdata->ftrace_size);
>>> -       parse_size("pmsg-size", pdata->pmsg_size);
>>> -       parse_size("ecc-size", pdata->ecc_info.ecc_size);
>>> -
>>> -#undef parse_size
>>> -
>>> -       return 0;
>>> -}
>>> -
>>>  static int ramoops_probe(struct platform_device *pdev)
>>>  {
>>>         struct device *dev = &pdev->dev;
>>> -       struct ramoops_platform_data *pdata = dev->platform_data;
>>> +       struct ramoops_platform_data *pdata = pdev->dev.platform_data;
>>>         struct ramoops_context *cxt = &oops_cxt;
>>>         size_t dump_mem_sz;
>>>         phys_addr_t paddr;
>>>         int err = -EINVAL;
>>>
>>> -       if (dev_of_node(dev) && !pdata) {
>>> -               pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
>>> -               if (!pdata) {
>>> -                       err = -ENOMEM;
>>> -                       goto fail_out;
>>> -               }
>>> -
>>> -               err = ramoops_parse_dt(pdev, pdata);
>>> -               if (err < 0)
>>> -                       goto fail_out;
>>> -       }
>>> -
>>>         /* Only a single ramoops area allowed at a time, so fail extra
>>>          * probes.
>>>          */
>>> @@ -681,17 +596,11 @@ static int ramoops_remove(struct platform_device *pdev)
>>>         return 0;
>>>  }
>>>
>>> -static const struct of_device_id dt_match[] = {
>>> -       { .compatible = "ramoops" },
>>> -       {}
>>> -};
>>> -
>>>  static struct platform_driver ramoops_driver = {
>>>         .probe          = ramoops_probe,
>>>         .remove         = ramoops_remove,
>>>         .driver         = {
>>> -               .name           = "ramoops",
>>> -               .of_match_table = dt_match,
>>> +               .name   = "ramoops",
>>>         },
>>>  };
>>>
>>> --
>>> 2.9.2
>>>
>>
>>
>>
>> --
>> Kees Cook
>> Chrome OS & Brillo Security



-- 
Kees Cook
Chrome OS & Brillo Security
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