parisc64: Add .opd based function descriptor dereference

We are moving towards separate kernel and module function descriptor
dereference callbacks. This patch enables it for parisc64.

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/20171109234830.5067-5-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: 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
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Helge Deller <deller@gmx.de> #parisc64
Signed-off-by: Petr Mladek <pmladek@suse.com>

arch/parisc/boot/compressed/vmlinux.lds.S

@@ -29,7 +29,9 @@ SECTIONS
 	. = ALIGN(16);
 	/* Linkage tables */
 	.opd : {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	} PROVIDE (__gp = .);
 	.plt : {
 		*(.plt)

arch/parisc/include/asm/sections.h

@@ -6,8 +6,14 @@
 #include <asm-generic/sections.h>
 
 #ifdef CONFIG_64BIT
+
+#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
+
 #undef dereference_function_descriptor
 void *dereference_function_descriptor(void *);
+
+#undef dereference_kernel_function_descriptor
+void *dereference_kernel_function_descriptor(void *);
 #endif
 
 #endif

arch/parisc/kernel/module.c

@@ -66,6 +66,7 @@
 
 #include <asm/pgtable.h>
 #include <asm/unwind.h>
+#include <asm/sections.h>
 
 #if 0
 #define DEBUGP printk
@@ -954,3 +955,18 @@ void module_arch_cleanup(struct module *mod)
 {
 	deregister_unwind_table(mod);
 }
+
+#ifdef CONFIG_64BIT
+void *dereference_module_function_descriptor(struct module *mod, void *ptr)
+{
+	unsigned long start_opd = (Elf64_Addr)mod->core_layout.base +
+				   mod->arch.fdesc_offset;
+	unsigned long end_opd = start_opd +
+				mod->arch.fdesc_count * sizeof(Elf64_Fdesc);
+
+	if (ptr < (void *)start_opd || ptr >= (void *)end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
+#endif

arch/parisc/kernel/process.c

@@ -276,6 +276,15 @@ void *dereference_function_descriptor(void *ptr)
 		ptr = p;
 	return ptr;
 }
+
+void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd ||
+			ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
 #endif
 
 static inline unsigned long brk_rnd(void)

arch/parisc/kernel/vmlinux.lds.S

@@ -100,7 +100,9 @@ SECTIONS
 	. = ALIGN(16);
 	/* Linkage tables */
 	.opd : {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	} PROVIDE (__gp = .);
 	.plt : {
 		*(.plt)