[PATCH 4/5] 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.senozhat...@gmail.com>
---
 arch/parisc/boot/compressed/vmlinux.lds.S |  2 ++
 arch/parisc/include/asm/sections.h        |  3 +++
 arch/parisc/kernel/module.c               | 14 ++++++++++++++
 arch/parisc/kernel/process.c              | 10 ++++++++++
 arch/parisc/kernel/vmlinux.lds.S          |  2 ++
 5 files changed, 31 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 9d13c3507ad6..e3cde650b2f9 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -6,7 +6,10 @@
 
 #ifdef CONFIG_64BIT
 #undef dereference_function_descriptor
+#undef dereference_kernel_function_descriptor
+
 void *dereference_function_descriptor(void *);
+void *dereference_kernel_function_descriptor(void *);
 #endif
 
 #endif
diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c
index f1a76935a314..bc2eae8634fd 100644
--- a/arch/parisc/kernel/module.c
+++ b/arch/parisc/kernel/module.c
@@ -954,3 +954,17 @@ 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)
+{
+       void *opd_sz = mod->arch.fdesc_offset +
+                      mod->arch.fdesc_max * sizeof(Elf64_Fdesc);
+
+       if (addr < mod->arch.fdesc_offset || opd_sz < addr)
+               return addr;
+
+       return dereference_function_descriptor(addr);
+}
+#endif
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 30f92391a93e..f30776bdaa79 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -267,6 +267,8 @@ get_wchan(struct task_struct *p)
 }
 
 #ifdef CONFIG_64BIT
+extern char __start_opd[], __end_opd[];
+
 void *dereference_function_descriptor(void *ptr)
 {
        Elf64_Fdesc *desc = ptr;
@@ -276,6 +278,14 @@ void *dereference_function_descriptor(void *ptr)
                ptr = p;
        return ptr;
 }
+
+void *dereference_kernel_function_descriptor(void *ptr)
+{
+       if (ptr < (void *)__start_opd || (void *)__end_opd < ptr)
+               return ptr;
+
+       return dereference_function_descriptor(ptr);
+}
 #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