linux-kernel - Re: [PATCH v3 06/60] arm64: ptdump: Allow VMALLOC

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Date:   Tue, 7 Mar 2023 18:01:22 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Ryan Roberts <ryan.roberts@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v3 06/60] arm64: ptdump: Allow VMALLOC_END to be defined
 at boot

On Tue, 7 Mar 2023 at 17:58, Ryan Roberts <ryan.roberts@....com> wrote:
>
> On 07/03/2023 14:04, Ard Biesheuvel wrote:
> > Extend the existing pattern for populating ptdump marker entries at
> > boot, and add handling of VMALLOC_END, which will cease to be a compile
> > time constant for configurations that support 52-bit virtual addressing.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> > ---
> >  arch/arm64/mm/ptdump.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
> > index 76d28056bd14920a..910b35f02280cbdb 100644
> > --- a/arch/arm64/mm/ptdump.c
> > +++ b/arch/arm64/mm/ptdump.c
> > @@ -31,7 +31,12 @@ enum address_markers_idx {
> >       PAGE_END_NR,
> >  #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
> >       KASAN_START_NR,
> > +     KASAN_END_NR,
> >  #endif
> > +     MODULES_NR,
> > +     MODULES_END_NR,
> > +     VMALLOC_START_NR,
> > +     VMALLOC_END_NR,
> >  };
> >
> >  static struct addr_marker address_markers[] = {
> > @@ -44,7 +49,7 @@ static struct addr_marker address_markers[] = {
> >       { MODULES_VADDR,                "Modules start" },
> >       { MODULES_END,                  "Modules end" },
> >       { VMALLOC_START,                "vmalloc() area" },
> > -     { VMALLOC_END,                  "vmalloc() end" },
> > +     { 0,                            "vmalloc() end" },
> >       { VMEMMAP_START,                "vmemmap start" },
> >       { VMEMMAP_START + VMEMMAP_SIZE, "vmemmap end" },
> >       { PCI_IO_START,                 "PCI I/O start" },
>
> With all the VA layout changes, and the addition of 52-bit PA/VA for 4KB and
> 16KB pages, Documentation/arm64/memory.rst now looks very wrong. Suggest
> updating it to reflect reality?
>

Yeah good point. And I don't think we necessarily have to describe
every imaginable combo exhaustively.