[Skiboot] [PATCH v2 1/2] Add infrastructure for pointer validation.

[Balbir Singh]

From: Balbir Singh <bsingharora at gmail.com>

If the kernel called an OPAL API with vmalloc'd address
or any other address range in real mode, we would hit
a problem with aliasing. Since the top 4 bits are ignored
in real mode, pointers from 0xc.. and 0xd.. (and other ranges)
could collide and lead to hard to solve bugs. This patch
adds the infrastructure for pointer validation and a simple
test case for testing the API

Signed-off-by: Balbir Singh <bsingharora at gmail.com>
---

Changelog v2:
	- No functional changes
	- Update copyright to 2016
	- Add reference to the power ISA section 5.7

 core/test/Makefile.check |  1 +
 core/test/run-api-test.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/opal-api.h       | 25 ++++++++++++++++++++++++
 3 files changed, 77 insertions(+)
 create mode 100644 core/test/run-api-test.c

diff --git a/core/test/Makefile.check b/core/test/Makefile.check
index b24bc21..cc3b47a 100644
--- a/core/test/Makefile.check
+++ b/core/test/Makefile.check
@@ -20,6 +20,7 @@ CORE_TEST := core/test/run-device \
 CORE_TEST_NOSTUB := core/test/run-console-log
 CORE_TEST_NOSTUB += core/test/run-console-log-buf-overrun
 CORE_TEST_NOSTUB += core/test/run-console-log-pr_fmt
+CORE_TEST_NOSTUB += core/test/run-api-test
 
 LCOV_EXCLUDE += $(CORE_TEST:%=%.c) core/test/stubs.c
 LCOV_EXCLUDE += $(CORE_TEST_NOSTUB:%=%.c) /usr/include/*
diff --git a/core/test/run-api-test.c b/core/test/run-api-test.c
new file mode 100644
index 0000000..58e9735
--- /dev/null
+++ b/core/test/run-api-test.c
@@ -0,0 +1,51 @@
+/* Copyright 2014-2016 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * For now it just validates that addresses passed are sane and test the
+ * wrapper that validates addresses
+ */
+
+#include <config.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <stdarg.h>
+#include <compiler.h>
+#include <opal-api.h>
+
+#define __TEST__
+unsigned long top_of_ram;	/* Fake it here */
+int main(void)
+{
+	unsigned long addr = 0xd000000000000000;
+
+	top_of_ram = 16ULL * 1024 * 1024 * 1024; /* 16 GB */
+	assert(opal_addr_valid((void *)addr) == false);
+
+	addr = 0xc000000000000000;
+	assert(opal_addr_valid((void *)addr) == true);
+
+	addr = 0x0;
+	assert(opal_addr_valid((void *)addr) == true);
+
+	addr = ~0;
+	assert(opal_addr_valid((void *)addr) == false);
+
+	addr = top_of_ram + 1;
+	assert(opal_addr_valid((void *)addr) == false);
+	return 0;
+}
diff --git a/include/opal-api.h b/include/opal-api.h
index c86244b..a937709 100644
--- a/include/opal-api.h
+++ b/include/opal-api.h
@@ -213,6 +213,9 @@
 
 #ifndef __ASSEMBLY__
 
+#include <stdbool.h>
+#include <types.h>
+
 /* Other enums */
 enum OpalVendorApiTokens {
 	OPAL_START_VENDOR_API_RANGE = 1000, OPAL_END_VENDOR_API_RANGE = 1999
@@ -1043,6 +1046,28 @@ enum {
 	OPAL_PCI_TCE_KILL_ALL,
 };
 
+extern unsigned long top_of_ram;
+
+/*
+ * Returns true if the address is valid, false otherwise
+ *
+ * Checks if the passed address belongs to real address space
+ * or 0xc000... kernel address space. It also checks that
+ * addr <= total physical memory. The magic value 60 comes
+ * from 60 bit real address mentioned in section 5.7 of the
+ * Power ISA (Book 3S).
+ */
+static inline bool opal_addr_valid(const void *addr)
+{
+	unsigned long val = (unsigned long)addr;
+	if ((val >> 60) != 0xc && (val >> 60) != 0x0)
+		return false;
+	val &= ~0xf000000000000000;
+	if (val > top_of_ram)
+		return false;
+	return true;
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __OPAL_API_H */
-- 
2.5.5