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

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Message-Id: <20170920162910.32053-6-sergey.senozhatsky@gmail.com>
Date:   Thu, 21 Sep 2017 01:29:07 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        James Bottomley <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jessica Yu <jeyu@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        linux-ia64@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [RFC][PATCH v2 5/7] 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].

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Signed-off-by: Helge Deller <deller@....de>
---
 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