[RFC][PATCH v2 3/7] ia64: Add .opd based function descriptor dereference

From: Sergey Senozhatsky
Date: Wed Sep 20 2017 - 12:29:54 EST


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@xxxxxxxxx>
---
arch/ia64/include/asm/sections.h | 10 +++++++++-
arch/ia64/kernel/module.c | 13 +++++++++++++
arch/ia64/kernel/vmlinux.lds.S | 2 ++
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index de6bfa1ef8fb..3ba7ce9d8bc8 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -37,6 +37,14 @@ static inline unsigned long dereference_function_descriptor(unsigned long ptr)
return ptr;
}

+#undef dereference_kernel_function_descriptor
+static inline 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 /* _ASM_IA64_SECTIONS_H */
-
diff --git a/arch/ia64/kernel/module.c b/arch/ia64/kernel/module.c
index d1d945c6bd05..0741ae6fa957 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 ||
+ addr >= (opd->sh_addr + opd->sh_size))
+ 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