MIPS: Add support for CONFIG_DEBUG_VIRTUAL

Provide hooks to intercept bad usages of virt_to_phys() and
__pa_symbol() throughout the kernel. To make this possible, we need to
rename the current implement of virt_to_phys() into
__virt_to_phys_nodebug() and wrap it around depending on
CONFIG_DEBUG_VIRTUAL.

A similar thing is needed for __pa_symbol() which is now aliased to
__phys_addr_symbol() whose implementation is either the direct return of
RELOC_HIDE or goes through the debug version.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

2 files changed, 58 insertions, 0 deletions

diff --git a/arch/mips/mm/Makefile b/arch/mips/mm/Makefile
index 865926a37775..fa1f729e0700 100644
--- a/arch/mips/mm/Makefile
+++ b/arch/mips/mm/Makefile
@@ -40,3 +40,5 @@ obj-$(CONFIG_R5000_CPU_SCACHE)	+= sc-r5k.o
 obj-$(CONFIG_RM7000_CPU_SCACHE) += sc-rm7k.o
 obj-$(CONFIG_MIPS_CPU_SCACHE)	+= sc-mips.o
 obj-$(CONFIG_SCACHE_DEBUGFS)	+= sc-debugfs.o
+
+obj-$(CONFIG_DEBUG_VIRTUAL)	+= physaddr.o
diff --git a/arch/mips/mm/physaddr.c b/arch/mips/mm/physaddr.c
new file mode 100644
index 000000000000..a1ced5e44951
--- /dev/null
+++ b/arch/mips/mm/physaddr.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bug.h>
+#include <linux/export.h>
+#include <linux/types.h>
+#include <linux/mmdebug.h>
+#include <linux/mm.h>
+
+#include <asm/sections.h>
+#include <asm/io.h>
+#include <asm/page.h>
+#include <asm/dma.h>
+
+static inline bool __debug_virt_addr_valid(unsigned long x)
+{
+	/* high_memory does not get immediately defined, and there
+	 * are early callers of __pa() against PAGE_OFFSET
+	 */
+	if (!high_memory && x >= PAGE_OFFSET)
+		return true;
+
+	if (high_memory && x >= PAGE_OFFSET && x < (unsigned long)high_memory)
+		return true;
+
+	/*
+	 * MAX_DMA_ADDRESS is a virtual address that may not correspond to an
+	 * actual physical address. Enough code relies on
+	 * virt_to_phys(MAX_DMA_ADDRESS) that we just need to work around it
+	 * and always return true.
+	 */
+	if (x == MAX_DMA_ADDRESS)
+		return true;
+
+	return false;
+}
+
+phys_addr_t __virt_to_phys(volatile const void *x)
+{
+	WARN(!__debug_virt_addr_valid((unsigned long)x),
+	     "virt_to_phys used for non-linear address: %pK (%pS)\n",
+	     x, x);
+
+	return __virt_to_phys_nodebug(x);
+}
+EXPORT_SYMBOL(__virt_to_phys);
+
+phys_addr_t __phys_addr_symbol(unsigned long x)
+{
+	/* This is bounds checking against the kernel image only.
+	 * __pa_symbol should only be used on kernel symbol addresses.
+	 */
+	VIRTUAL_BUG_ON(x < (unsigned long)_text ||
+		       x > (unsigned long)_end);
+
+	return __pa_symbol_nodebug(x);
+}
+EXPORT_SYMBOL(__phys_addr_symbol);