linux-hardening - [PATCH] pstore/ram: Add support for dynamically allocated ramoops memory regions

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Message-ID: <20230622005213.458236-1-isaacmanjarres@google.com>
Date:   Wed, 21 Jun 2023 17:52:13 -0700
From:   "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
To:     Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     "Isaac J. Manjarres" <isaacm@...eaurora.org>,
        Mukesh Ojha <mojha@...eaurora.org>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        "Isaac J . Manjarres" <isaacmanjarres@...gle.com>,
        kernel-team@...roid.com, linux-hardening@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] pstore/ram: Add support for dynamically allocated ramoops
 memory regions

From: "Isaac J. Manjarres" <isaacm@...eaurora.org>

The reserved memory region for ramoops is assumed to be at a fixed
and known location when read from the devicetree. This is not desirable
in environments where it is preferred for the region to be dynamically
allocated early during boot (i.e. the memory region is defined with
the "alloc-ranges" property instead of the "reg" property).

If the location of the ramoops region is not fixed via the "reg"
devicetree property, the call to platform_get_resource() will fail
because resources of type IORESOURCE_MEM must be described with the
"reg" property.

Since ramoops regions are part of the reserved-memory devicetree
node, they exist in the reserved_mem array. This means that the
of_reserved_mem_lookup() function can be used to retrieve the
reserved_mem structure for the ramoops region, and that structure
contains the base and size of the region, even if it has been
dynamically allocated.

Thus invoke of_reserved_mem_lookup() in case the call to
platform_get_resource() fails in order to support dynamically
allocated ramoops memory regions.

Signed-off-by: Isaac J. Manjarres <isaacm@...eaurora.org>
Signed-off-by: Mukesh Ojha <mojha@...eaurora.org>
Signed-off-by: Prasad Sodagudi <psodagud@...eaurora.org>
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
---
 fs/pstore/ram.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index ade66dbe5f39..e4bbba187011 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -20,6 +20,7 @@
 #include <linux/compiler.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/of_reserved_mem.h>

 #include "internal.h"
 #include "ram_internal.h"
@@ -643,6 +644,7 @@ static int ramoops_parse_dt(struct platform_device *pdev,
 {
 	struct device_node *of_node = pdev->dev.of_node;
 	struct device_node *parent_node;
+	struct reserved_mem *rmem;
 	struct resource *res;
 	u32 value;
 	int ret;
@@ -651,13 +653,20 @@ static int ramoops_parse_dt(struct platform_device *pdev,

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res) {
-		dev_err(&pdev->dev,
-			"failed to locate DT /reserved-memory resource\n");
-		return -EINVAL;
+		rmem = of_reserved_mem_lookup(of_node);
+		if (rmem) {
+			pdata->mem_size = rmem->size;
+			pdata->mem_address = rmem->base;
+		} else {
+			dev_err(&pdev->dev,
+				"failed to locate DT /reserved-memory resource\n");
+			return -EINVAL;
+		}
+	} else {
+		pdata->mem_size = resource_size(res);
+		pdata->mem_address = res->start;
 	}

-	pdata->mem_size = resource_size(res);
-	pdata->mem_address = res->start;
 	/*
 	 * Setting "unbuffered" is deprecated and will be ignored if
 	 * "mem_type" is also specified.
-- 
2.41.0.178.g377b9f9a00-goog