Re: [PATCH v2 09/12] powerpc: extend execmem_params for kprobes allocations

[Song Liu]

On Fri, Jun 16, 2023 at 1:52 AM Mike Rapoport <rppt@xxxxxxxxxx> wrote:
>
> From: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>

Acked-by: Song Liu <song@xxxxxxxxxx>


> ---
>  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
>