linux-kernel - [PATCH 2/5] ia64: Add .opd based function descriptor dereference

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Message-Id: <20170916035347.19705-3-sergey.senozhatsky@gmail.com>
Date:   Sat, 16 Sep 2017 12:53:44 +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 E . J . 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: [PATCH 2/5] ia64: Add .opd based function descriptor dereference

We are moving towards separate kernel and module function descriptor
dereference callbacks. This patch enables it for IA64.

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>
---
 arch/ia64/include/asm/sections.h | 14 +++++++++++++-
 arch/ia64/kernel/module.c        | 13 +++++++++++++
 arch/ia64/kernel/vmlinux.lds.S   |  2 ++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 2ab2003698ef..bff3f3535609 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -25,8 +25,11 @@ extern char __start_gate_fsyscall_patchlist[], __end_gate_fsyscall_patchlist[];
 extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_bubble_down_patchlist[];
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
+extern char __start_opd[], __end_opd[];
 
 #undef dereference_function_descriptor
+#undef dereference_kernel_function_descriptor
+
 static inline void *dereference_function_descriptor(void *ptr)
 {
 	struct fdesc *desc = ptr;
@@ -37,6 +40,15 @@ static inline void *dereference_function_descriptor(void *ptr)
 	return ptr;
 }
 
+static inline void *dereference_kernel_function_descriptor(void *ptr)
+{
+	/*
+	 * Check if the ptr is a function descriptor and thus needs to
+	 * be dereferenced.
+	 */
+	if (ptr < (void *)__start_opd || (void *)__end_opd < ptr)
+		return ptr;
+	return dereference_function_descriptor(ptr);
+}
 
 #endif /* _ASM_IA64_SECTIONS_H */
-
diff --git a/arch/ia64/kernel/module.c b/arch/ia64/kernel/module.c
index d1d945c6bd05..d42f1e19d75d 100644
--- a/arch/ia64/kernel/module.c
+++ b/arch/ia64/kernel/module.c
@@ -35,6 +35,7 @@
 
 #include <asm/patch.h>
 #include <asm/unaligned.h>
+#include <asm/sections.h>
 
 #define ARCH_MODULE_DEBUG 0
 
@@ -917,3 +918,15 @@ module_arch_cleanup (struct module *mod)
 	if (mod->arch.core_unw_table)
 		unw_remove_unwind_table(mod->arch.core_unw_table);
 }
+
+unsigned long dereference_module_function_descriptor(struct module *mod,
+					     unsigned long addr)
+{
+	Elf64_Shdr *opd = mod->arch.opd;
+
+	if (addr < opd->sh_addr ||
+			(opd->sh_addr + opd->sh_size) < addr)
+		return addr;
+
+	return dereference_function_descriptor(addr);
+}
diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
index 798026dde52e..f872ba5ff82a 100644
--- a/arch/ia64/kernel/vmlinux.lds.S
+++ b/arch/ia64/kernel/vmlinux.lds.S
@@ -107,7 +107,9 @@ SECTIONS {
 	RODATA
 
 	.opd : AT(ADDR(.opd) - LOAD_OFFSET) {
+		__start_opd = .;
 		*(.opd)
+		__end_opd = .;
 	}
 
 	/*
-- 
2.14.1