Re: [PATCH v1 04/10] asm-generic: Use HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR to define associated stubs

[Christophe Leroy]

Le 12/10/2021 à 08:02, Helge Deller a écrit :
> On 10/11/21 17:25, Christophe Leroy wrote:
> > Use HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR instead of 'dereference_function_descriptor'
> > to know whether arch has function descriptors.
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> > ---
> >   arch/ia64/include/asm/sections.h    | 4 ++--
> >   arch/parisc/include/asm/sections.h  | 6 ++++--
> >   arch/powerpc/include/asm/sections.h | 6 ++++--
> >   include/asm-generic/sections.h      | 3 ++-
> >   4 files changed, 12 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> > index 35f24e52149a..80f5868afb06 100644
> > --- a/arch/ia64/include/asm/sections.h
> > +++ b/arch/ia64/include/asm/sections.h
> > @@ -7,6 +7,8 @@
> >    *	David Mosberger-Tang <davidm@xxxxxxxxxx>
> >    */
> >
> > +#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> > +
> >   #include <linux/elf.h>
> >   #include <linux/uaccess.h>
> >   #include <asm-generic/sections.h>
> > @@ -27,8 +29,6 @@ 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..2e781ee19b66 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_DEREFERENCE_FUNCTION_DESCRIPTOR 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..b7f1ba04e756 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_DEREFERENCE_FUNCTION_DESCRIPTOR 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..1db5cfd69817 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_DEREFERENCE_FUNCTION_DESCRIPTOR
> > +#else
>
> why not
> #ifndef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
> instead of #if/#else ?

To avoid changing it again in patch 6, or getting an ugly #ifndef/#else 
at the end.

> >   #define dereference_function_descriptor(p) ((void *)(p))
> >   #define dereference_kernel_function_descriptor(p) ((void *)(p))
> >   #endif