linux-kernel - Re: [PATCH v2 09/12] powerpc: extend execmem

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Message-ID: <CAPhsuW6TmwsBmP4NQroE5OEFsaHh+S9zweXa4Fs_ZeJURguqAg@mail.gmail.com>
Date:   Fri, 16 Jun 2023 13:09:45 -0700
From:   Song Liu <song@...nel.org>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "David S. Miller" <davem@...emloft.net>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Helge Deller <deller@....de>,
        Huacai Chen <chenhuacai@...nel.org>,
        Kent Overstreet <kent.overstreet@...ux.dev>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nadav Amit <nadav.amit@...il.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Puranjay Mohan <puranjay12@...il.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Russell King <linux@...linux.org.uk>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, bpf@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-mm@...ck.org, linux-modules@...r.kernel.org,
        linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev,
        netdev@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v2 09/12] powerpc: extend execmem_params for kprobes allocations

On Fri, Jun 16, 2023 at 1:52 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> From: "Mike Rapoport (IBM)" <rppt@...nel.org>
>
> powerpc overrides kprobes::alloc_insn_page() to remove writable
> permissions when STRICT_MODULE_RWX is on.
>
> Add definition of jit area to execmem_params to allow using the generic
> kprobes::alloc_insn_page() with the desired permissions.
>
> As powerpc uses breakpoint instructions to inject kprobes, it does not
> need to constrain kprobe allocations to the modules area and can use the
> entire vmalloc address space.
>
> Signed-off-by: Mike Rapoport (IBM) <rppt@...nel.org>

Acked-by: Song Liu <song@...nel.org>


> ---
>  arch/powerpc/kernel/kprobes.c | 14 --------------
>  arch/powerpc/kernel/module.c  | 13 +++++++++++++
>  2 files changed, 13 insertions(+), 14 deletions(-)
>
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index 5db8df5e3657..14c5ddec3056 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -126,20 +126,6 @@ kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offse
>         return (kprobe_opcode_t *)(addr + offset);
>  }
>
> -void *alloc_insn_page(void)
> -{
> -       void *page;
> -
> -       page = jit_text_alloc(PAGE_SIZE);
> -       if (!page)
> -               return NULL;
> -
> -       if (strict_module_rwx_enabled())
> -               set_memory_rox((unsigned long)page, 1);
> -
> -       return page;
> -}
> -
>  int arch_prepare_kprobe(struct kprobe *p)
>  {
>         int ret = 0;
> diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
> index 4c6c15bf3947..8e5b379d6da1 100644
> --- a/arch/powerpc/kernel/module.c
> +++ b/arch/powerpc/kernel/module.c
> @@ -96,6 +96,11 @@ static struct execmem_params execmem_params = {
>                         .alignment = 1,
>                 },
>         },
> +       .jit = {
> +               .text = {
> +                       .alignment = 1,
> +               },
> +       },
>  };
>
>
> @@ -131,5 +136,13 @@ struct execmem_params __init *execmem_arch_params(void)
>
>         execmem_params.modules.text.pgprot = prot;
>
> +       execmem_params.jit.text.start = VMALLOC_START;
> +       execmem_params.jit.text.end = VMALLOC_END;
> +
> +       if (strict_module_rwx_enabled())
> +               execmem_params.jit.text.pgprot = PAGE_KERNEL_ROX;
> +       else
> +               execmem_params.jit.text.pgprot = PAGE_KERNEL_EXEC;
> +
>         return &execmem_params;
>  }
> --
> 2.35.1
>