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From:   Song Liu <song@kernel.org>
Date:   Fri, 16 Jun 2023 13:01:08 -0700
Message-ID: <CAPhsuW4J+rFvh9WJVWLZxFHtcYxahYk=NoKYdU9FMibZU8986w@mail.gmail.com>
Subject: Re: [PATCH v2 06/12] mm/execmem: introduce execmem_data_alloc()
To:     Mike Rapoport <rppt@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        "David S. Miller" <davem@davemloft.net>,
        Dinh Nguyen <dinguyen@kernel.org>,
        Heiko Carstens <hca@linux.ibm.com>,
        Helge Deller <deller@gmx.de>,
        Huacai Chen <chenhuacai@kernel.org>,
        Kent Overstreet <kent.overstreet@linux.dev>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nadav Amit <nadav.amit@gmail.com>,
        "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Puranjay Mohan <puranjay12@gmail.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Russell King <linux@armlinux.org.uk>,
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On Fri, Jun 16, 2023 at 1:51=E2=80=AFAM Mike Rapoport <rppt@kernel.org> wro=
te:
>
> From: "Mike Rapoport (IBM)" <rppt@kernel.org>
>
> Data related to code allocations, such as module data section, need to
> comply with architecture constraints for its placement and its
> allocation right now was done using execmem_text_alloc().
>
> Create a dedicated API for allocating data related to code allocations
> and allow architectures to define address ranges for data allocations.
>
> Since currently this is only relevant for powerpc variants that use the
> VMALLOC address space for module data allocations, automatically reuse
> address ranges defined for text unless address range for data is
> explicitly defined by an architecture.
>
> With separation of code and data allocations, data sections of the
> modules are now mapped as PAGE_KERNEL rather than PAGE_KERNEL_EXEC which
> was a default on many architectures.
>
> Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
[...]
>  static void free_mod_mem(struct module *mod)
> diff --git a/mm/execmem.c b/mm/execmem.c
> index a67acd75ffef..f7bf496ad4c3 100644
> --- a/mm/execmem.c
> +++ b/mm/execmem.c
> @@ -63,6 +63,20 @@ void *execmem_text_alloc(size_t size)
>                              fallback_start, fallback_end, kasan);
>  }
>
> +void *execmem_data_alloc(size_t size)
> +{
> +       unsigned long start =3D execmem_params.modules.data.start;
> +       unsigned long end =3D execmem_params.modules.data.end;
> +       pgprot_t pgprot =3D execmem_params.modules.data.pgprot;
> +       unsigned int align =3D execmem_params.modules.data.alignment;
> +       unsigned long fallback_start =3D execmem_params.modules.data.fall=
back_start;
> +       unsigned long fallback_end =3D execmem_params.modules.data.fallba=
ck_end;
> +       bool kasan =3D execmem_params.modules.flags & EXECMEM_KASAN_SHADO=
W;
> +
> +       return execmem_alloc(size, start, end, align, pgprot,
> +                            fallback_start, fallback_end, kasan);
> +}
> +
>  void execmem_free(void *ptr)
>  {
>         /*
> @@ -101,6 +115,28 @@ static bool execmem_validate_params(struct execmem_p=
arams *p)
>         return true;
>  }
>
> +static void execmem_init_missing(struct execmem_params *p)

Shall we call this execmem_default_init_data?

> +{
> +       struct execmem_modules_range *m =3D &p->modules;
> +
> +       if (!pgprot_val(execmem_params.modules.data.pgprot))
> +               execmem_params.modules.data.pgprot =3D PAGE_KERNEL;

Do we really need to check each of these? IOW, can we do:

if (!pgprot_val(execmem_params.modules.data.pgprot)) {
       execmem_params.modules.data.pgprot =3D PAGE_KERNEL;
       execmem_params.modules.data.alignment =3D m->text.alignment;
       execmem_params.modules.data.start =3D m->text.start;
       execmem_params.modules.data.end =3D m->text.end;
       execmem_params.modules.data.fallback_start =3D m->text.fallback_star=
t;
      execmem_params.modules.data.fallback_end =3D m->text.fallback_end;
}

Thanks,
Song

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