[PATCH v10 03/10] powerpc: Always define MODULES_{VADDR,END}

[Jordan Niethe]

On Wed, Apr 21, 2021 at 3:14 PM Christophe Leroy
<christophe.leroy at csgroup.eu> wrote:
>
>
>
> Le 21/04/2021 à 04:46, Jordan Niethe a écrit :
> > On Fri, Apr 2, 2021 at 12:36 AM Christophe Leroy
> > <christophe.leroy at csgroup.eu> wrote:
> >>
> >>
> >>
> >> Le 30/03/2021 à 06:51, Jordan Niethe a écrit :
> >>> If MODULES_{VADDR,END} are not defined set them to VMALLOC_START and
> >>> VMALLOC_END respectively. This reduces the need for special cases. For
> >>> example, powerpc's module_alloc() was previously predicated on
> >>> MODULES_VADDR being defined but now is unconditionally defined.
> >>>
> >>> This will be useful reducing conditional code in other places that need
> >>> to allocate from the module region (i.e., kprobes).
> >>>
> >>> Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
> >>> ---
> >>> v10: New to series
> >>> ---
> >>>    arch/powerpc/include/asm/pgtable.h | 5 +++++
> >>>    arch/powerpc/kernel/module.c       | 5 +----
> >>
> >> You probably also have changes to do in kernel/ptdump.c
> >>
> >> In mm/book3s32/mmu.c and mm/kasan/kasan_init_32.c as well allthough that's harmless here.
> >>
> >>>    2 files changed, 6 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> >>> index 4eed82172e33..014c2921f26a 100644
> >>> --- a/arch/powerpc/include/asm/pgtable.h
> >>> +++ b/arch/powerpc/include/asm/pgtable.h
> >>> @@ -167,6 +167,11 @@ struct seq_file;
> >>>    void arch_report_meminfo(struct seq_file *m);
> >>>    #endif /* CONFIG_PPC64 */
> >>>
> >>> +#ifndef MODULES_VADDR
> >>> +#define MODULES_VADDR VMALLOC_START
> >>> +#define MODULES_END VMALLOC_END
> >>> +#endif
> >>> +
> >>>    #endif /* __ASSEMBLY__ */
> >>>
> >>>    #endif /* _ASM_POWERPC_PGTABLE_H */
> >>> diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
> >>> index a211b0253cdb..f1fb58389d58 100644
> >>> --- a/arch/powerpc/kernel/module.c
> >>> +++ b/arch/powerpc/kernel/module.c
> >>> @@ -14,6 +14,7 @@
> >>>    #include <asm/firmware.h>
> >>>    #include <linux/sort.h>
> >>>    #include <asm/setup.h>
> >>> +#include <linux/mm.h>
> >>>
> >>>    static LIST_HEAD(module_bug_list);
> >>>
> >>> @@ -87,13 +88,9 @@ int module_finalize(const Elf_Ehdr *hdr,
> >>>        return 0;
> >>>    }
> >>>
> >>> -#ifdef MODULES_VADDR
> >>>    void *module_alloc(unsigned long size)
> >>>    {
> >>> -     BUILD_BUG_ON(TASK_SIZE > MODULES_VADDR);
> >>> -
> >>
> >> The above check is needed somewhere, if you remove it from here you have to perform the check
> >> somewhere else.
> >
> > This also introduces this warning:
> > fs/proc/kcore.c:626:52: warning: self-comparison always evaluates to
> > false [-Wtautological-compare]
> >    626 |  if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
> > I might leave this patch out of this series and use an #ifdef for now
> > and make this change separately as a follow up.
>
> x86/32 at least does the same (see
> https://elixir.bootlin.com/linux/v5.12-rc8/source/arch/x86/include/asm/pgtable_32_areas.h#L47)
>
> They probably also get the warning, so I think would shouldn't bother.
> One day someone will fix fs/proc/kcore.c , that's not a powerpc problem.
Yeah you are right. I'll add the BUILD_BUG_ON() check to
asm/task_size_32.h and keep the patch.
>
> >
> >>
> >>>        return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END, GFP_KERNEL,
> >>>                                    PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
> >>>                                    __builtin_return_address(0));
> >>>    }
> >>> -#endif
> >>>