[RFC][PATCH] pstore: use DT reserved-memory bindings

[Kees Cook]

Instead of a ramoops-specific node, use a child node of /reserved-memory.
This requires that of_platform_populate() be called for the node, though,
since it does not have its own "compatible" property.

Suggested-by: Rob Herring <ro...@kernel.org>
Signed-off-by: Kees Cook <kees...@chromium.org>
---
Here's what I've got for moving ramoops under /reserved-memory... still
feels like a bit of a hack.
---
Documentation/devicetree/bindings/misc/ramoops.txt | 48 ----------------------
.../bindings/reserved-memory/ramoops.txt | 48 ++++++++++++++++++++++
Documentation/ramoops.txt | 2 +-
drivers/of/platform.c | 5 +++
fs/pstore/ram.c | 12 +-----
5 files changed, 56 insertions(+), 59 deletions(-)
delete mode 100644 Documentation/devicetree/bindings/misc/ramoops.txt
create mode 100644 Documentation/devicetree/bindings/reserved-memory/ramoops.txt

diff --git a/Documentation/devicetree/bindings/misc/ramoops.txt b/Documentation/devicetree/bindings/misc/ramoops.txt
deleted file mode 100644
index cd02cec67d38..000000000000
--- 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/devicetree/bindings/reserved-memory/ramoops.txt b/Documentation/devicetree/bindings/reserved-memory/ramoops.txt
new file mode 100644
index 000000000000..e81f821a2135
--- /dev/null
+++ b/Documentation/devicetree/bindings/reserved-memory/ramoops.txt
@@ -0,0 +1,48 @@
+Ramoops oops/panic logger
+=========================
+
+ramoops provides persistent RAM storage for oops and panics, so they can be
+recovered after a reboot. This is a child-node of "/reserved-memory", and
+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"
+
+- reg: 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 9264bcab4099..deaf07cbf484 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -55,7 +55,7 @@ Setting the ramoops parameters can be done in 3 different manners:
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.
+ Documentation/device-tree/bindings/reserved-memory/ramoops.txt.
3. 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:

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 16e8daffac06..c07adf72bb8e 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -356,6 +356,11 @@ static int of_platform_bus_create(struct device_node *bus,
void *platform_data = NULL;
int rc = 0;

+ /* Always populate reserved-memory nodes. */
+ if (strict && strcmp(bus->full_name, "/reserved-memory") == 0) {
+ return of_platform_populate(bus, matches, lookup, parent);
+ }
+
/* Make sure it has a compatible property */
if (strict && (!of_get_property(bus, "compatible", NULL))) {
pr_debug("%s() - skipping %s, no compatible prop\n",
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 47516a794011..af5cee0c2156 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -486,24 +486,16 @@ 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);
+ ret = of_address_to_resource(of_node, 0, &res);
if (ret) {
dev_err(&pdev->dev,
- "failed to translate memory-region to resource: %d\n",
+ "failed to translate reserved-memory to resource: %d\n",
ret);
return ret;
}
--
2.7.4


--
Kees Cook
Brillo & Chrome OS Security

[Rob Herring]

On Fri, Jul 29, 2016 at 8:16 PM, Kees Cook <kees...@chromium.org> wrote:
> Instead of a ramoops-specific node, use a child node of /reserved-memory.
> This requires that of_platform_populate() be called for the node, though,
> since it does not have its own "compatible" property.
>
> Suggested-by: Rob Herring <ro...@kernel.org>
> Signed-off-by: Kees Cook <kees...@chromium.org>
> ---
> Here's what I've got for moving ramoops under /reserved-memory... still
> feels like a bit of a hack.
> ---
> Documentation/devicetree/bindings/misc/ramoops.txt | 48 ----------------------
> .../bindings/reserved-memory/ramoops.txt | 48 ++++++++++++++++++++++

Use -M option or so you don't forget you can set in your git config:

[diff]
renames = true

> Documentation/ramoops.txt | 2 +-
> drivers/of/platform.c | 5 +++
> fs/pstore/ram.c | 12 +-----
> 5 files changed, 56 insertions(+), 59 deletions(-)

[...]

> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 16e8daffac06..c07adf72bb8e 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -356,6 +356,11 @@ static int of_platform_bus_create(struct device_node *bus,
> void *platform_data = NULL;
> int rc = 0;
>
> + /* Always populate reserved-memory nodes. */
> + if (strict && strcmp(bus->full_name, "/reserved-memory") == 0) {
> + return of_platform_populate(bus, matches, lookup, parent);
> + }
> +

This can be a lot cleaner now with the DT changes in 4.8. We could
make this more generic and call of_platform_populate with the
/reserved-memory node as the root, but that would :

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 765390e..4c36e06 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -499,8 +499,15 @@ EXPORT_SYMBOL_GPL(of_platform_default_populate);

static int __init of_platform_default_populate_init(void)
{
- if (of_have_populated_dt())
- of_platform_default_populate(NULL, NULL, NULL);
+ struct device_node *node;
+
+ if (!of_have_populated_dt())
+ return -ENODEV;
+
+ node = of_find_compatible_node(NULL, NULL, "ramoops");
+ of_platform_device_create(node, NULL, NULL);
+
+ of_platform_default_populate(NULL, NULL, NULL);

return 0;

}


> /* Make sure it has a compatible property */
> if (strict && (!of_get_property(bus, "compatible", NULL))) {
> pr_debug("%s() - skipping %s, no compatible prop\n",
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 47516a794011..af5cee0c2156 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -486,24 +486,16 @@ 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);
> + ret = of_address_to_resource(of_node, 0, &res);

You can use the standard platform device resource functions now.

[Kees Cook]

Instead of a ramoops-specific node, use a child node of /reserved-memory.

This requires that of_platform_device_create() be explicitly called
for the node, though, since "/reserved-memory" does not have its own

"compatible" property.

Suggested-by: Rob Herring <ro...@kernel.org>
Signed-off-by: Kees Cook <kees...@chromium.org>
---

v2:
- rebase to 4.8, use of_platform_default_populate_init(), robh
- use platform device resources instead of node directly, robh
---
.../bindings/{misc => reserved-memory}/ramoops.txt | 8 ++---
Documentation/ramoops.txt | 38 +++++++++++++++-------
drivers/of/platform.c | 20 ++++++++++--
fs/pstore/ram.c | 23 ++++---------
4 files changed, 56 insertions(+), 33 deletions(-)
rename Documentation/devicetree/bindings/{misc => reserved-memory}/ramoops.txt (86%)

diff --git a/Documentation/devicetree/bindings/misc/ramoops.txt b/Documentation/devicetree/bindings/reserved-memory/ramoops.txt
similarity index 86%
rename from Documentation/devicetree/bindings/misc/ramoops.txt
rename to Documentation/devicetree/bindings/reserved-memory/ramoops.txt
index cd02cec67d38..e81f821a2135 100644
--- a/Documentation/devicetree/bindings/misc/ramoops.txt
+++ b/Documentation/devicetree/bindings/reserved-memory/ramoops.txt
@@ -2,8 +2,9 @@ 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.

+recovered after a reboot. This is a child-node of "/reserved-memory", and
+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

@@ -21,8 +22,7 @@ Required properties:

- compatible: must be "ramoops"

-- memory-region: phandle to a region of memory that is preserved between
- reboots

+- reg: region of memory that is preserved between reboots

Optional properties:
diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
index 9264bcab4099..26b9f31cf65a 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -45,18 +45,34 @@ corrupt, but usually it is restorable.

2. Setting the parameters

-Setting the ramoops parameters can be done in 3 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
- and then use the reserved memory for ramoops. For example, assuming a machine
- with > 128 MB of memory, the following kernel command line will tell the
- kernel to use only the first 128 MB of memory, and place ECC-protected ramoops
- region at 128 MB boundary:
+Setting the ramoops parameters can be done in several different manners:
+
+ A. 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 and then use the reserved memory for ramoops. For example, assuming a
+ machine with > 128 MB of memory, the following kernel command line will tell
+ the 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
+
+ B. Use Device Tree bindings, as described in
+ Documentation/device-tree/bindings/reserved-memory/ramoops.txt.
+ For example:
+
+ reserved-memory {
+ #address-cells = <2>;
+ #size-cells = <2>;
+ ranges;
+
+ ramoops@8f000000 {
+ compatible = "ramoops";
+ reg = <0 0x8f000000 0 0x100000>;
+ record-size = <0x4000>;
+ console-size = <0x4000>;
+ };
+ };
+
+ C. 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/drivers/of/platform.c b/drivers/of/platform.c
index 765390e3ed8d..8aa197691074 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -499,8 +499,24 @@ EXPORT_SYMBOL_GPL(of_platform_default_populate);

static int __init of_platform_default_populate_init(void)
{
- if (of_have_populated_dt())
- of_platform_default_populate(NULL, NULL, NULL);
+ struct device_node *node;
+
+ if (!of_have_populated_dt())
+ return -ENODEV;
+

+ /*
+ * Handle ramoops explicitly, since it is inside /reserved-memory,
+ * which lacks a "compatible" property.
+ */
+ node = of_find_node_by_path("/reserved-memory");
+ if (node) {
+ node = of_find_compatible_node(node, NULL, "ramoops");
+ if (node)

+ of_platform_device_create(node, NULL, NULL);
+ }
+

+ /* Populate everything else. */

+ of_platform_default_populate(NULL, NULL, NULL);

return 0;
}

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 47516a794011..427eee7570bb 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -486,30 +486,21 @@ 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;
+ 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) {
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!res) {

dev_err(&pdev->dev,
- "failed to translate memory-region to resource: %d\n",

- ret);
- return ret;
+ "failed to locate DT /reserved-memory resource\n");
+ return -EINVAL;
}

- pdata->mem_size = resource_size(&res);
- pdata->mem_address = res.start;
+ 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");

[Kees Cook]

On Mon, Aug 1, 2016 at 8:54 AM, Rob Herring <rob...@kernel.org> wrote:
> On Fri, Jul 29, 2016 at 8:16 PM, Kees Cook <kees...@chromium.org> wrote:
>> Instead of a ramoops-specific node, use a child node of /reserved-memory.
>> This requires that of_platform_populate() be called for the node, though,
>> since it does not have its own "compatible" property.
>>
>> Suggested-by: Rob Herring <ro...@kernel.org>
>> Signed-off-by: Kees Cook <kees...@chromium.org>
>> ---
>> Here's what I've got for moving ramoops under /reserved-memory... still
>> feels like a bit of a hack.
>> ---
>> Documentation/devicetree/bindings/misc/ramoops.txt | 48 ----------------------
>> .../bindings/reserved-memory/ramoops.txt | 48 ++++++++++++++++++++++
>
> Use -M option or so you don't forget you can set in your git config:
>
> [diff]
> renames = true

Added, thanks.

>
>> Documentation/ramoops.txt | 2 +-
>> drivers/of/platform.c | 5 +++
>> fs/pstore/ram.c | 12 +-----
>> 5 files changed, 56 insertions(+), 59 deletions(-)
>
> [...]
>
>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>> index 16e8daffac06..c07adf72bb8e 100644
>> --- a/drivers/of/platform.c
>> +++ b/drivers/of/platform.c
>> @@ -356,6 +356,11 @@ static int of_platform_bus_create(struct device_node *bus,
>> void *platform_data = NULL;
>> int rc = 0;
>>
>> + /* Always populate reserved-memory nodes. */
>> + if (strict && strcmp(bus->full_name, "/reserved-memory") == 0) {
>> + return of_platform_populate(bus, matches, lookup, parent);
>> + }
>> +
>
> This can be a lot cleaner now with the DT changes in 4.8. We could
> make this more generic and call of_platform_populate with the
> /reserved-memory node as the root, but that would :

Is there a word missing above? "...but that would [need]:" ?

> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 765390e..4c36e06 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -499,8 +499,15 @@ EXPORT_SYMBOL_GPL(of_platform_default_populate);
>
> static int __init of_platform_default_populate_init(void)
> {
> - if (of_have_populated_dt())
> - of_platform_default_populate(NULL, NULL, NULL);
> + struct device_node *node;
> +
> + if (!of_have_populated_dt())
> + return -ENODEV;
> +
> + node = of_find_compatible_node(NULL, NULL, "ramoops");
> + of_platform_device_create(node, NULL, NULL);

Does of_platform_device_create() DTRT if node is NULL here? (Looks
like "yes", but goes through a spin lock first: I think it'd be nicer
to check for a NULL node here.) Should this first look for
/reserved-memory, then ramoops?

Testing this as-is seems to work, though I'll send a version that
looks up /reserved-memory first before ramoops.

Okay, sounds good. I still have to parse the ramoops-specific stuff
off the of_node, so it doesn't really change things too much here, but
does look a little cleaner.

Thanks!

-Kees

>
>> if (ret) {
>> dev_err(&pdev->dev,
>> - "failed to translate memory-region to resource: %d\n",
>> + "failed to translate reserved-memory to resource: %d\n",
>> ret);
>> return ret;
>> }
>> --
>> 2.7.4
>>
>>
>> --
>> Kees Cook
>> Brillo & Chrome OS Security

--
Kees Cook
Chrome OS & Brillo Security

[Rob Herring]

Uh, didn't finish that. ...would create devices for other nodes with
compatible strings. That's not really a problem, but not necessary
either presently.

>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>> index 765390e..4c36e06 100644
>> --- a/drivers/of/platform.c
>> +++ b/drivers/of/platform.c
>> @@ -499,8 +499,15 @@ EXPORT_SYMBOL_GPL(of_platform_default_populate);
>>
>> static int __init of_platform_default_populate_init(void)
>> {
>> - if (of_have_populated_dt())
>> - of_platform_default_populate(NULL, NULL, NULL);
>> + struct device_node *node;
>> +
>> + if (!of_have_populated_dt())
>> + return -ENODEV;
>> +
>> + node = of_find_compatible_node(NULL, NULL, "ramoops");
>> + of_platform_device_create(node, NULL, NULL);
>
> Does of_platform_device_create() DTRT if node is NULL here? (Looks
> like "yes", but goes through a spin lock first: I think it'd be nicer
> to check for a NULL node here.)

It does, but either way is fine with me.

> Should this first look for
> /reserved-memory, then ramoops?

No, that's not necessary. It could match if located in other places,
but it's not really the kernel's job to be a DT validator beyond what
it requires.

Rob

[Rob Herring]

On Mon, Aug 1, 2016 at 2:05 PM, Kees Cook <kees...@chromium.org> wrote:
> Instead of a ramoops-specific node, use a child node of /reserved-memory.
> This requires that of_platform_device_create() be explicitly called
> for the node, though, since "/reserved-memory" does not have its own
> "compatible" property.

As I mentioned in my other reply, not strictly needed to find
/reserved-memory node first, but it's fine either way.

Acked-by: Rob Herring <ro...@kernel.org>

[Kees Cook]

On Mon, Aug 1, 2016 at 12:58 PM, Rob Herring <rob...@kernel.org> wrote:
> On Mon, Aug 1, 2016 at 2:05 PM, Kees Cook <kees...@chromium.org> wrote:
>> Instead of a ramoops-specific node, use a child node of /reserved-memory.
>> This requires that of_platform_device_create() be explicitly called
>> for the node, though, since "/reserved-memory" does not have its own
>> "compatible" property.
>
> As I mentioned in my other reply, not strictly needed to find
> /reserved-memory node first, but it's fine either way.
>
> Acked-by: Rob Herring <ro...@kernel.org>

Great! Thanks for helping aim me to the right place. :)

-Kees

>
>>
>> Suggested-by: Rob Herring <ro...@kernel.org>
>> Signed-off-by: Kees Cook <kees...@chromium.org>
>> ---
>> v2:
>> - rebase to 4.8, use of_platform_default_populate_init(), robh
>> - use platform device resources instead of node directly, robh
>> ---
>> .../bindings/{misc => reserved-memory}/ramoops.txt | 8 ++---
>> Documentation/ramoops.txt | 38 +++++++++++++++-------
>> drivers/of/platform.c | 20 ++++++++++--
>> fs/pstore/ram.c | 23 ++++---------
>> 4 files changed, 56 insertions(+), 33 deletions(-)
>> rename Documentation/devicetree/bindings/{misc => reserved-memory}/ramoops.txt (86%)