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

[Christophe Leroy <christophe.leroy@xxxxxxxxxx>]

Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> > 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@xxxxxxxxx>
>
> > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> >   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