[PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Christophe Leroy]

Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
HAVE_FUNCTION_DESCRIPTORS and use it instead of
'dereference_function_descriptor' macro to know
whether an arch has function descriptors.

To limit churn in one of the following patches, use
an #ifdef/#else construct with empty first part
instead of an #ifndef in asm-generic/sections.h

Reviewed-by: Kees Cook <keescook at chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy at csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 5 +++--
 arch/parisc/include/asm/sections.h  | 6 ++++--
 arch/powerpc/include/asm/sections.h | 6 ++++--
 include/asm-generic/sections.h      | 3 ++-
 include/linux/kallsyms.h            | 2 +-
 5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 35f24e52149a..6e55e545bf02 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>
+
+#define HAVE_FUNCTION_DESCRIPTORS 1
+
 #include <asm-generic/sections.h>
 
 extern char __phys_per_cpu_start[];
@@ -27,8 +30,6 @@ 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)
 {
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index bb52aea0cb21..85149a89ff3e 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -2,6 +2,10 @@
 #ifndef _PARISC_SECTIONS_H
 #define _PARISC_SECTIONS_H
 
+#ifdef CONFIG_64BIT
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 /* nothing to see, move along */
 #include <asm-generic/sections.h>
 
@@ -9,8 +13,6 @@ 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 *);
 
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 32e7035863ac..bba97b8c38cf 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -8,6 +8,10 @@
 
 #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
 
+#ifdef PPC64_ELF_ABI_v1
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 #include <asm-generic/sections.h>
 
 extern bool init_mem_is_free;
@@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 
 #ifdef PPC64_ELF_ABI_v1
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index d16302d3eb59..b677e926e6b3 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -59,7 +59,8 @@ 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 HAVE_FUNCTION_DESCRIPTORS
+#else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
 #endif
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index a1d6fc82d7f0..9f277baeb559 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
 
 static inline void *dereference_symbol_descriptor(void *ptr)
 {
-#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
+#ifdef HAVE_FUNCTION_DESCRIPTORS
 	struct module *mod;
 
 	ptr = dereference_kernel_function_descriptor(ptr);
-- 
2.31.1