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

Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:

quoted

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

Is it worth putting this into Kconfig if you're going to
change it? In any case

That was what I wanted to do in the begining but how can I do that in 
Kconfig ?

#ifdef __powerpc64__
#if defined(_CALL_ELF) && _CALL_ELF == 2
#define PPC64_ELF_ABI_v2
#else
#define PPC64_ELF_ABI_v1
#endif
#endif /* __powerpc64__ */

#ifdef PPC64_ELF_ABI_v1
#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

Christophe

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

quoted

Reviewed-by: Kees Cook <redacted>
Signed-off-by: Christophe Leroy <redacted>
---
  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