25 files changed, 155 insertions, 144 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 678a80713b21..fe24174cb63c 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -205,6 +205,9 @@ config HAVE_FUNCTION_ERROR_INJECTION
 config HAVE_NMI
 	bool
 
+config HAVE_FUNCTION_DESCRIPTORS
+	bool
+
 config TRACE_IRQFLAGS_SUPPORT
 	bool
 
diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index a7e01573abd8..da85c3b23b16 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -35,6 +35,7 @@ config IA64
 	select HAVE_SETUP_PER_CPU_AREA
 	select TTY
 	select HAVE_ARCH_TRACEHOOK
+	select HAVE_FUNCTION_DESCRIPTORS
 	select HAVE_VIRT_CPU_ACCOUNTING
 	select HUGETLB_PAGE_SIZE_VARIABLE if HUGETLB_PAGE
 	select VIRT_TO_BUS
diff --git a/arch/ia64/include/asm/elf.h b/arch/ia64/include/asm/elf.h
index 6629301a2620..2ef5f9966ad1 100644
--- a/arch/ia64/include/asm/elf.h
+++ b/arch/ia64/include/asm/elf.h
@@ -226,7 +226,7 @@ struct got_entry {
  * Layout of the Function Descriptor
  */
 struct fdesc {
-	uint64_t ip;
+	uint64_t addr;
 	uint64_t gp;
 };
 
diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 3a033d2008b3..8e0875cf6071 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -9,6 +9,9 @@
 
 #include <linux/elf.h>
 #include <linux/uaccess.h>
+
+typedef struct fdesc func_desc_t;
+
 #include <asm-generic/sections.h>
 
 extern char __phys_per_cpu_start[];
@@ -27,25 +30,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->ip))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		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 360f36b0eb3f..8f62cf97f691 100644
--- a/arch/ia64/kernel/module.c
+++ b/arch/ia64/kernel/module.c
@@ -602,15 +602,15 @@ get_fdesc (struct module *mod, uint64_t value, int *okp)
 		return value;
 
 	/* Look for existing function descriptor. */
-	while (fdesc->ip) {
-		if (fdesc->ip == value)
+	while (fdesc->addr) {
+		if (fdesc->addr == value)
 			return (uint64_t)fdesc;
 		if ((uint64_t) ++fdesc >= mod->arch.opd->sh_addr + mod->arch.opd->sh_size)
 			BUG();
 	}
 
 	/* Create new one */
-	fdesc->ip = value;
+	fdesc->addr = value;
 	fdesc->gp = mod->arch.gp;
 	return (uint64_t) fdesc;
 }
diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 43c1c880def6..82e7ab1a9764 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -69,6 +69,7 @@ config PARISC
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS
 	select HAVE_SOFTIRQ_ON_OWN_STACK if IRQSTACKS
 	select TRACE_IRQFLAGS_SUPPORT
+	select HAVE_FUNCTION_DESCRIPTORS if 64BIT
 
 	help
 	  The PA-RISC microprocessor is designed by Hewlett-Packard and used
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index bb52aea0cb21..33df42b5cc6d 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -2,20 +2,14 @@
 #ifndef _PARISC_SECTIONS_H
 #define _PARISC_SECTIONS_H
 
+#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
+#include <asm/elf.h>
+typedef Elf64_Fdesc func_desc_t;
+#endif
+
 /* nothing to see, move along */
 #include <asm-generic/sections.h>
 
 extern char __alt_instructions[], __alt_instructions_end[];
 
-#ifdef CONFIG_64BIT
-
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
-#undef dereference_function_descriptor
-void *dereference_function_descriptor(void *);
-
-#undef dereference_kernel_function_descriptor
-void *dereference_kernel_function_descriptor(void *);
-#endif
-
 #endif
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index ea3d83b6fb62..2030c77592d3 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -263,27 +263,6 @@ __get_wchan(struct task_struct *p)
 	return 0;
 }
 
-#ifdef CONFIG_64BIT
-void *dereference_function_descriptor(void *ptr)
-{
-	Elf64_Fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd ||
-			ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif
-
 static inline unsigned long brk_rnd(void)
 {
 	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 28e4047e99e8..23ce71367467 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -207,6 +207,7 @@ config PPC
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS	if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
 	select HAVE_FAST_GUP
 	select HAVE_FTRACE_MCOUNT_RECORD
+	select HAVE_FUNCTION_DESCRIPTORS	if PPC64 && !CPU_LITTLE_ENDIAN
 	select HAVE_FUNCTION_ERROR_INJECTION
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 1e1ef4352f62..eb541e730d3c 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -213,7 +213,7 @@ CHECKFLAGS	+= -m$(BITS) -D__powerpc__ -D__powerpc$(BITS)__
 ifdef CONFIG_CPU_BIG_ENDIAN
 CHECKFLAGS	+= -D__BIG_ENDIAN__
 else
-CHECKFLAGS	+= -D__LITTLE_ENDIAN__
+CHECKFLAGS	+= -D__LITTLE_ENDIAN__ -D_CALL_ELF=2
 endif
 
 ifdef CONFIG_476FPE_ERR46
diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index e26080539c31..409483b2d0ce 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -118,7 +118,7 @@ static inline unsigned long ppc_function_entry(void *func)
 	 * function's descriptor. The first entry in the descriptor is the
 	 * address of the function text.
 	 */
-	return ((func_descr_t *)func)->entry;
+	return ((struct func_desc *)func)->addr;
 #else
 	return (unsigned long)func;
 #endif
diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index b8425e3cfd81..971589a21bc0 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -176,4 +176,10 @@ do {									\
 /* Relocate the kernel image to @final_address */
 void relocate(unsigned long final_address);
 
+struct func_desc {
+	unsigned long addr;
+	unsigned long toc;
+	unsigned long env;
+};
+
 #endif /* _ASM_POWERPC_ELF_H */
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 38f79e42bf3c..8be2c491c733 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -6,6 +6,10 @@
 #include <linux/elf.h>
 #include <linux/uaccess.h>
 
+#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
+typedef struct func_desc func_desc_t;
+#endif
+
 #include <asm-generic/sections.h>
 
 extern char __head_end[];
@@ -54,31 +58,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 		(unsigned long)_stext < end;
 }
 
-#ifdef PPC64_ELF_ABI_v1
-
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct ppc64_opd_entry *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif /* PPC64_ELF_ABI_v1 */
-
 #endif
 
 #endif /* __KERNEL__ */
diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
index f1630c553efe..97da77bc48c9 100644
--- a/arch/powerpc/include/asm/types.h
+++ b/arch/powerpc/include/asm/types.h
@@ -23,12 +23,6 @@
 
 typedef __vector128 vector128;
 
-typedef struct {
-	unsigned long entry;
-	unsigned long toc;
-	unsigned long env;
-} func_descr_t;
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_TYPES_H */
diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
index 860c59291bfc..308857123a08 100644
--- a/arch/powerpc/include/uapi/asm/elf.h
+++ b/arch/powerpc/include/uapi/asm/elf.h
@@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
 /* Keep this the last entry.  */
 #define R_PPC64_NUM		253
 
-/* There's actually a third entry here, but it's unused */
-struct ppc64_opd_entry
-{
-	unsigned long funcaddr;
-	unsigned long r2;
-};
-
-
 #endif /* _UAPI_ASM_POWERPC_ELF_H */
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 94d14cf99bca..794720530442 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -33,20 +33,13 @@
 
 #ifdef PPC64_ELF_ABI_v2
 
-/* An address is simply the address of the function. */
-typedef unsigned long func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
-	return addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func;
+	func_desc_t desc = {
+		.addr = addr,
+	};
+
+	return desc;
 }
 
 /* PowerPC64 specific values for the Elf64_Sym st_other field.  */
@@ -64,20 +57,9 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
 }
 #else
 
-/* An address is address of the OPD entry, which contains address of fn. */
-typedef struct ppc64_opd_entry func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
-	return *(struct ppc64_opd_entry *)addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return func_desc(addr).funcaddr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func.funcaddr;
+	return *(struct func_desc *)addr;
 }
 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
@@ -94,6 +76,16 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
 }
 #endif
 
+static unsigned long func_addr(unsigned long addr)
+{
+	return func_desc(addr).addr;
+}
+
+static unsigned long stub_func_addr(func_desc_t func)
+{
+	return func.addr;
+}
+
 #define STUB_MAGIC 0x73747562 /* stub */
 
 /* Like PPC32, we need little trampolines to do > 24-bit jumps (into
@@ -188,7 +180,7 @@ static int relacmp(const void *_x, const void *_y)
 static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 				    const Elf64_Shdr *sechdrs)
 {
-	/* One extra reloc so it's always 0-funcaddr terminated */
+	/* One extra reloc so it's always 0-addr terminated */
 	unsigned long relocs = 1;
 	unsigned i;
 
diff --git a/arch/powerpc/kernel/ptrace/ptrace.c b/arch/powerpc/kernel/ptrace/ptrace.c
index c43f77e2ac31..1212a812a7ab 100644
--- a/arch/powerpc/kernel/ptrace/ptrace.c
+++ b/arch/powerpc/kernel/ptrace/ptrace.c
@@ -445,4 +445,10 @@ void __init pt_regs_check(void)
 	 * real registers.
 	 */
 	BUILD_BUG_ON(PT_DSCR < sizeof(struct user_pt_regs) / sizeof(unsigned long));
+
+#ifdef PPC64_ELF_ABI_v1
+	BUILD_BUG_ON(!IS_ENABLED(CONFIG_HAVE_FUNCTION_DESCRIPTORS));
+#else
+	BUILD_BUG_ON(IS_ENABLED(CONFIG_HAVE_FUNCTION_DESCRIPTORS));
+#endif
 }
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index d1e1fc0acbea..73d483b07ff3 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -936,11 +936,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 		 * descriptor is the entry address of signal and the second
 		 * entry is the TOC value we need to use.
 		 */
-		func_descr_t __user *funct_desc_ptr =
-			(func_descr_t __user *) ksig->ka.sa.sa_handler;
+		struct func_desc __user *ptr =
+			(struct func_desc __user *)ksig->ka.sa.sa_handler;
 
-		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
-		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
+		err |= get_user(regs->ctr, &ptr->addr);
+		err |= get_user(regs->gpr[2], &ptr->toc);
 	}
 
 	/* enter the signal handler in native-endian mode */
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index f69b964b9952..e2228b6fc09b 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -149,6 +149,7 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(WRITE_RO),
 	CRASHTYPE(WRITE_RO_AFTER_INIT),
 	CRASHTYPE(WRITE_KERN),
+	CRASHTYPE(WRITE_OPD),
 	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
 	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
 	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index d6137c70ebbe..305fc2ec3f25 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -106,6 +106,7 @@ void __init lkdtm_perms_init(void);
 void lkdtm_WRITE_RO(void);
 void lkdtm_WRITE_RO_AFTER_INIT(void);
 void lkdtm_WRITE_KERN(void);
+void lkdtm_WRITE_OPD(void);
 void lkdtm_EXEC_DATA(void);
 void lkdtm_EXEC_STACK(void);
 void lkdtm_EXEC_KMALLOC(void);
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 2dede2ef658f..2c6aba3ff32b 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -10,6 +10,7 @@
 #include <linux/mman.h>
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
+#include <asm/sections.h>
 
 /* Whether or not to fill the target memory area with do_nothing(). */
 #define CODE_WRITE	true
@@ -21,7 +22,7 @@
 /* This is non-const, so it will end up in the .data section. */
 static u8 data_area[EXEC_SIZE];
 
-/* This is cost, so it will end up in the .rodata section. */
+/* This is const, so it will end up in the .rodata section. */
 static const unsigned long rodata = 0xAA55AA55;
 
 /* This is marked __ro_after_init, so it should ultimately be .rodata. */
@@ -31,31 +32,51 @@ static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
  * This just returns to the caller. It is designed to be copied into
  * non-executable memory regions.
  */
-static void do_nothing(void)
+static noinline void do_nothing(void)
 {
 	return;
 }
 
 /* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
+static noinline void do_overwritten(void)
 {
 	pr_info("do_overwritten wasn't overwritten!\n");
 	return;
 }
 
+static noinline void do_almost_nothing(void)
+{
+	pr_info("do_nothing was hijacked!\n");
+}
+
+static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
+{
+	if (!have_function_descriptors())
+		return dst;
+
+	memcpy(fdesc, do_nothing, sizeof(*fdesc));
+	fdesc->addr = (unsigned long)dst;
+	barrier();
+
+	return fdesc;
+}
+
 static noinline void execute_location(void *dst, bool write)
 {
-	void (*func)(void) = dst;
+	void (*func)(void);
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
 	if (write == CODE_WRITE) {
-		memcpy(dst, do_nothing, EXEC_SIZE);
+		memcpy(dst, do_nothing_text, EXEC_SIZE);
 		flush_icache_range((unsigned long)dst,
 				   (unsigned long)dst + EXEC_SIZE);
 	}
-	pr_info("attempting bad execution at %px\n", func);
+	pr_info("attempting bad execution at %px\n", dst);
+	func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
@@ -65,16 +86,19 @@ static void execute_user_location(void *dst)
 	int copied;
 
 	/* Intentionally crossing kernel/user memory boundary. */
-	void (*func)(void) = dst;
+	void (*func)(void);
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
-	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
+	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
 				   EXEC_SIZE, FOLL_WRITE);
 	if (copied < EXEC_SIZE)
 		return;
-	pr_info("attempting bad execution at %px\n", func);
+	pr_info("attempting bad execution at %px\n", dst);
+	func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
@@ -113,8 +137,9 @@ void lkdtm_WRITE_KERN(void)
 	size_t size;
 	volatile unsigned char *ptr;
 
-	size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
-	ptr = (unsigned char *)do_overwritten;
+	size = (unsigned long)dereference_function_descriptor(do_overwritten) -
+	       (unsigned long)dereference_function_descriptor(do_nothing);
+	ptr = dereference_function_descriptor(do_overwritten);
 
 	pr_info("attempting bad %zu byte write at %px\n", size, ptr);
 	memcpy((void *)ptr, (unsigned char *)do_nothing, size);
@@ -124,6 +149,23 @@ void lkdtm_WRITE_KERN(void)
 	do_overwritten();
 }
 
+void lkdtm_WRITE_OPD(void)
+{
+	size_t size = sizeof(func_desc_t);
+	void (*func)(void) = do_nothing;
+
+	if (!have_function_descriptors()) {
+		pr_info("XFAIL: Platform doesn't use function descriptors.\n");
+		return;
+	}
+	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
+	memcpy(do_nothing, do_almost_nothing, size);
+	pr_err("FAIL: survived bad write\n");
+
+	asm("" : "=m"(func));
+	func();
+}
+
 void lkdtm_EXEC_DATA(void)
 {
 	execute_location(data_area, CODE_WRITE);
@@ -151,7 +193,8 @@ void lkdtm_EXEC_VMALLOC(void)
 
 void lkdtm_EXEC_RODATA(void)
 {
-	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+	execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing),
+			 CODE_AS_IS);
 }
 
 void lkdtm_EXEC_USERSPACE(void)
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index 690f741764e1..d0f7bdd2fdf2 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -59,11 +59,24 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
 extern __visible const void __nosave_begin, __nosave_end;
 
 /* Function descriptor handling (if any).  Override in asm/sections.h */
-#ifndef dereference_function_descriptor
+#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr);
+void *dereference_kernel_function_descriptor(void *ptr);
+#else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
+
+/* An address is simply the address of the function. */
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
 #endif
 
+static inline bool have_function_descriptors(void)
+{
+	return IS_ENABLED(CONFIG_HAVE_FUNCTION_DESCRIPTORS);
+}
+
 /**
  * memory_contains - checks if an object is contained within a memory region
  * @begin: virtual address of the beginning of the memory region
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index 4176c7eca7b5..ce1bd2fbf23e 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -48,7 +48,7 @@ static inline int is_ksym_addr(unsigned long addr)
 
 static inline void *dereference_symbol_descriptor(void *ptr)
 {
-#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
+#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
 	struct module *mod;
 
 	ptr = dereference_kernel_function_descriptor(ptr);
diff --git a/kernel/extable.c b/kernel/extable.c
index b6f330f0fe74..bda5e9761541 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -3,6 +3,7 @@
    Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
 
 */
+#include <linux/elf.h>
 #include <linux/ftrace.h>
 #include <linux/memory.h>
 #include <linux/extable.h>
@@ -132,12 +133,33 @@ out:
 }
 
 /*
- * On some architectures (PPC64, IA64) function pointers
+ * On some architectures (PPC64, IA64, PARISC) function pointers
  * are actually only tokens to some data that then holds the
  * real function address. As a result, to find if a function
  * pointer is part of the kernel text, we need to do some
  * special dereferencing first.
  */
+#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr)
+{
+	func_desc_t *desc = ptr;
+	void *p;
+
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
+		ptr = p;
+	return ptr;
+}
+EXPORT_SYMBOL_GPL(dereference_function_descriptor);
+
+void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
+#endif
+
 int func_ptr_is_kernel_text(void *ptr)
 {
 	unsigned long addr;
diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt
index 6b36b7f5dcf9..243c781f0780 100644
--- a/tools/testing/selftests/lkdtm/tests.txt
+++ b/tools/testing/selftests/lkdtm/tests.txt
@@ -44,6 +44,7 @@ ACCESS_NULL
 WRITE_RO
 WRITE_RO_AFTER_INIT
 WRITE_KERN
+WRITE_OPD
 REFCOUNT_INC_OVERFLOW
 REFCOUNT_ADD_OVERFLOW
 REFCOUNT_INC_NOT_ZERO_OVERFLOW