Re: [PATCH v11 3/9] powerpc: Always define MODULES_{VADDR,END}

[Jordan Niethe <jniethe5@gmail.com>]

On Thu, Apr 29, 2021 at 3:04 PM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 29/04/2021 à 05:15, 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@gmail.com>
> > ---
> > v10: New to series
> > v11: - Consider more places MODULES_VADDR was being used
> > ---
> >   arch/powerpc/include/asm/pgtable.h    | 11 +++++++++++
> >   arch/powerpc/kernel/module.c          |  5 +----
> >   arch/powerpc/mm/kasan/kasan_init_32.c | 10 +++++-----
> >   arch/powerpc/mm/ptdump/ptdump.c       |  4 ++--
> >   4 files changed, 19 insertions(+), 11 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> > index c6a676714f04..882fda779648 100644
> > --- a/arch/powerpc/include/asm/pgtable.h
> > +++ b/arch/powerpc/include/asm/pgtable.h
> > @@ -39,6 +39,17 @@ struct mm_struct;
> >   #define __S110      PAGE_SHARED_X
> >   #define __S111      PAGE_SHARED_X
> >
> > +#ifndef MODULES_VADDR
> > +#define MODULES_VADDR VMALLOC_START
> > +#define MODULES_END VMALLOC_END
> > +#endif
> > +
> > +#if defined(CONFIG_PPC_BOOK3S_32) && defined(CONFIG_STRICT_KERNEL_RWX)
>
> No no.
>
> TASK_SIZE > MODULES_VADDR is ALWAYS wrong, for any target, in any configuration.
>
> Why is it a problem to leave the test as a BUILD_BUG_ON() in module_alloc() ?
On ppc64s, MODULES_VADDR is __vmalloc_start (a variable)  and
TASK_SIZE depends on current.
Also for nohash like 44x, MODULES_VADDR is defined based on high_memory.
If I put it back in module_alloc() and wrap it with #ifdef
CONFIG_PPC_BOOK3S_32 will that be fine?

>
> > +#if TASK_SIZE > MODULES_VADDR
> > +#error TASK_SIZE > MODULES_VADDR
> > +#endif
> > +#endif
> > +
> >   #ifndef __ASSEMBLY__
> >
> >   /* Keep these as a macros to avoid include dependency mess */
> > diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
> > index fab84024650c..c60c7457ff47 100644
> > --- a/arch/powerpc/kernel/module.c
> > +++ b/arch/powerpc/kernel/module.c
> > @@ -15,6 +15,7 @@
> >   #include <linux/sort.h>
> >   #include <asm/setup.h>
> >   #include <asm/sections.h>
> > +#include <linux/mm.h>
> >
> >   static LIST_HEAD(module_bug_list);
> >
> > @@ -88,7 +89,6 @@ int module_finalize(const Elf_Ehdr *hdr,
> >       return 0;
> >   }
> >
> > -#ifdef MODULES_VADDR
> >   static __always_inline void *
> >   __module_alloc(unsigned long size, unsigned long start, unsigned long end)
> >   {
> > @@ -102,8 +102,6 @@ void *module_alloc(unsigned long size)
> >       unsigned long limit = (unsigned long)_etext - SZ_32M;
> >       void *ptr = NULL;
> >
> > -     BUILD_BUG_ON(TASK_SIZE > MODULES_VADDR);
> > -
> >       /* First try within 32M limit from _etext to avoid branch trampolines */
> >       if (MODULES_VADDR < PAGE_OFFSET && MODULES_END > limit)
> >               ptr = __module_alloc(size, limit, MODULES_END);
> > @@ -113,4 +111,3 @@ void *module_alloc(unsigned long size)
> >
> >       return ptr;
> >   }
> > -#endif
> > diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
> > index cf8770b1a692..42c057366ac7 100644
> > --- a/arch/powerpc/mm/kasan/kasan_init_32.c
> > +++ b/arch/powerpc/mm/kasan/kasan_init_32.c
> > @@ -116,11 +116,11 @@ static void __init kasan_unmap_early_shadow_vmalloc(void)
> >
> >       kasan_update_early_region(k_start, k_end, __pte(0));
> >
> > -#ifdef MODULES_VADDR
> > -     k_start = (unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR);
> > -     k_end = (unsigned long)kasan_mem_to_shadow((void *)MODULES_END);
> > -     kasan_update_early_region(k_start, k_end, __pte(0));
> > -#endif
> > +     if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
>
> Shouldn't it be an || ?
Yeah
>
> As soon as either MODULES_VADDR or MODULES_END differs from the vmalloc boundaries, it needs to be
> done I think.
>
> > +             k_start = (unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR);
> > +             k_end = (unsigned long)kasan_mem_to_shadow((void *)MODULES_END);
> > +             kasan_update_early_region(k_start, k_end, __pte(0));
> > +     }
> >   }
> >
> >   void __init kasan_mmu_init(void)
> > diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
> > index aca354fb670b..0431457f668f 100644
> > --- a/arch/powerpc/mm/ptdump/ptdump.c
> > +++ b/arch/powerpc/mm/ptdump/ptdump.c
> > @@ -73,7 +73,7 @@ struct addr_marker {
> >
> >   static struct addr_marker address_markers[] = {
> >       { 0,    "Start of kernel VM" },
> > -#ifdef MODULES_VADDR
> > +#if defined(CONFIG_BOOK32_32) && defined(CONFIG_STRICT_KERNEL_RWX)
>
> Not valid anymore, see https://github.com/linuxppc/linux/commit/80edc68e0479 and
> https://github.com/linuxppc/linux/commit/9132a2e82adc
>
> The best would be to be able to do something like:
>
> #if MODULES_VADDR != VMALLOC_START
I tried to do it like that originally but with stuff like
#define VMALLOC_START ((((long)high_memory + VMALLOC_OFFSET) &
~(VMALLOC_OFFSET-1)))
it doesn't work.
>
> If it doesn't work, then it has to be
>
> #if defined(CONFIG_BOOK32_32) || defined(CONFIG_PPC_8xx)
Ok, thanks.
>
> >       { 0,    "modules start" },
> >       { 0,    "modules end" },
> >   #endif
> > @@ -359,7 +359,7 @@ static void populate_markers(void)
> >   #else
> >       address_markers[i++].start_address = TASK_SIZE;
> >   #endif
> > -#ifdef MODULES_VADDR
> > +#if defined(CONFIG_BOOK32_32) && defined(CONFIG_STRICT_KERNEL_RWX)
>
> Same.
>
> >       address_markers[i++].start_address = MODULES_VADDR;
> >       address_markers[i++].start_address = MODULES_END;
> >   #endif
> >