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

From: Kees Cook
Date: Thu Jul 28 2016 - 18:44:58 EST

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