[RFC][PATCH v2 5/7] parisc64: Add .opd based function descriptor dereference

[Sergey Senozhatsky]

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].

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
---
 arch/parisc/boot/compressed/vmlinux.lds.S |  2 ++
 arch/parisc/include/asm/sections.h        |  2 ++
 arch/parisc/kernel/module.c               | 17 +++++++++++++++++
 arch/parisc/kernel/process.c              |  9 +++++++++
 arch/parisc/kernel/vmlinux.lds.S          |  2 ++
 5 files changed, 32 insertions(+)

diff --git a/arch/parisc/boot/compressed/vmlinux.lds.S b/arch/parisc/boot/compressed/vmlinux.lds.S
index a4ce3314e78e..4ebd4e65524c 100644
--- a/arch/parisc/boot/compressed/vmlinux.lds.S
+++ b/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)
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 59fbe0067112..845ddc9a3421 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -7,6 +7,8 @@
 #ifdef CONFIG_64BIT
 #undef dereference_function_descriptor
 unsigned long dereference_function_descriptor(unsigned long);
+#undef dereference_kernel_function_descriptor
+unsigned long dereference_kernel_function_descriptor(unsigned long);
 #endif
 
 #endif
diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c
index f1a76935a314..28f89b3dcc11 100644
--- a/arch/parisc/kernel/module.c
+++ b/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 +955,19 @@ void module_arch_cleanup(struct module *mod)
 {
 	deregister_unwind_table(mod);
 }
+
+#ifdef CONFIG_64BIT
+unsigned long dereference_module_function_descriptor(struct module *mod,
+						     unsigned long addr)
+{
+	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 (addr < start_opd || addr >= end_opd)
+		return addr;
+
+	return dereference_function_descriptor(addr);
+}
+#endif
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index f00a5f93492a..ff13726b2d2d 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -276,6 +276,15 @@ unsigned long dereference_function_descriptor(unsigned long ptr)
 		ptr = (unsigned long)p;
 	return ptr;
 }
+
+unsigned long dereference_kernel_function_descriptor(unsigned long addr)
+{
+	if (addr < (unsigned long)__start_opd ||
+			addr >= (unsigned long)__end_opd)
+		return addr;
+
+	return dereference_function_descriptor(addr);
+}
 #endif
 
 static inline unsigned long brk_rnd(void)
diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S
index ffe2cbf52d1a..ab030895dd1e 100644
--- a/arch/parisc/kernel/vmlinux.lds.S
+++ b/arch/parisc/kernel/vmlinux.lds.S
@@ -99,7 +99,9 @@ SECTIONS
 	. = ALIGN(16);
 	/* Linkage tables */
 	.opd : {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	} PROVIDE (__gp = .);
 	.plt : {
 		*(.plt)
-- 
2.14.1