powerpc64: Add .opd based function descriptor dereference

We are moving towards separate kernel and module function descriptor
dereference callbacks. This patch enables it for powerpc64.

For pointers that belong to the kernel
-  Added __start_opd and __end_opd pointers, to track the kernel
   .opd section address range;

-  Added dereference_kernel_function_descriptor(). Now we
   will dereference only function pointers that are within
   [__start_opd, __end_opd);

For pointers that belong to a module
-  Added dereference_module_function_descriptor() to handle module
   function descriptor dereference. Now we will dereference only
   pointers that are within [module->opd.start, module->opd.end).

Link: http://lkml.kernel.org/r/20171109234830.5067-4-sergey.senozhatsky@gmail.com
To: Tony Luck <tony.luck@intel.com>
To: Fenghua Yu <fenghua.yu@intel.com>
To: Helge Deller <deller@gmx.de>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Paul Mackerras <paulus@samba.org>
To: Michael Ellerman <mpe@ellerman.id.au>
To: James Bottomley <jejb@parisc-linux.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-ia64@vger.kernel.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Santosh Sivaraj <santosh@fossix.org> #powerpc
Signed-off-by: Petr Mladek <pmladek@suse.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 82bec63bbd4f..e335a8f846af 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -66,6 +66,9 @@ static inline int overlaps_kvm_tmp(unsigned long start, unsigned long end)
 }
 
 #ifdef PPC64_ELF_ABI_v1
+
+#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
+
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
@@ -76,6 +79,15 @@ static inline void *dereference_function_descriptor(void *ptr)
 		ptr = p;
 	return ptr;
 }
+
+#undef dereference_kernel_function_descriptor
+static inline void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
 #endif /* PPC64_ELF_ABI_v1 */
 
 #endif