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

Sergey Senozhatsky
2017-09-16T03:53:44Z

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@gmail.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