linux-kernel - Re: [PATCH 1/6] efistub: pass uefi secureboot flag via fdt params

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Message-ID: <CAMj1kXEXvmO5mrTcKpqYUASBAQB-1=xLa0vg7KwmvOHMjaQ34w@mail.gmail.com>
Date:   Fri, 11 Sep 2020 18:01:09 +0300
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Chester Lin <clin@...e.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, zohar@...ux.ibm.com,
        dmitry.kasatkin@...il.com, Jonathan Corbet <corbet@....net>,
        Mark Rutland <mark.rutland@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        "Lee, Chun-Yi" <jlee@...e.com>
Subject: Re: [PATCH 1/6] efistub: pass uefi secureboot flag via fdt params

On Fri, 4 Sep 2020 at 10:29, Chester Lin <clin@...e.com> wrote:
>
> Add a new UEFI parameter: "linux,uefi-secure-boot" in fdt boot params
> as other architectures have done in their own boot data. For example,
> the boot_params->secure_boot in x86.
>
> Signed-off-by: Chester Lin <clin@...e.com>

Why do we need this flag? Can't the OS simply check the variable directly?

> ---
>  drivers/firmware/efi/libstub/fdt.c | 39 +++++++++++++++++++++++++++++-
>  1 file changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
> index 11ecf3c4640e..c9a341e4715f 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -136,6 +136,10 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
>         if (status)
>                 goto fdt_set_fail;
>
> +       status = fdt_setprop_var(fdt, node, "linux,uefi-secure-boot", fdt_val32);
> +       if (status)
> +               goto fdt_set_fail;
> +
>         if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
>                 efi_status_t efi_status;
>
> @@ -199,6 +203,24 @@ static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map)
>         return EFI_SUCCESS;
>  }
>
> +static efi_status_t update_fdt_secboot(void *fdt, u32 secboot)
> +{
> +       int node = fdt_path_offset(fdt, "/chosen");
> +       u32 fdt_val32;
> +       int err;
> +
> +       if (node < 0)
> +               return EFI_LOAD_ERROR;
> +
> +       fdt_val32 = cpu_to_fdt32(secboot);
> +
> +       err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-secure-boot", fdt_val32);
> +       if (err)
> +               return EFI_LOAD_ERROR;
> +
> +       return EFI_SUCCESS;
> +}
> +
>  struct exit_boot_struct {
>         efi_memory_desc_t       *runtime_map;
>         int                     *runtime_entry_count;
> @@ -208,6 +230,9 @@ struct exit_boot_struct {
>  static efi_status_t exit_boot_func(struct efi_boot_memmap *map,
>                                    void *priv)
>  {
> +       efi_status_t status;
> +       enum efi_secureboot_mode secboot_status;
> +       u32 secboot_var = 0;
>         struct exit_boot_struct *p = priv;
>         /*
>          * Update the memory map with virtual addresses. The function will also
> @@ -217,7 +242,19 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map,
>         efi_get_virtmap(*map->map, *map->map_size, *map->desc_size,
>                         p->runtime_map, p->runtime_entry_count);
>
> -       return update_fdt_memmap(p->new_fdt_addr, map);
> +       status = update_fdt_memmap(p->new_fdt_addr, map);
> +
> +       if (status != EFI_SUCCESS)
> +               return status;
> +
> +       secboot_status = efi_get_secureboot();
> +
> +       if (secboot_status == efi_secureboot_mode_enabled)
> +               secboot_var = 1;
> +
> +       status = update_fdt_secboot(p->new_fdt_addr, secboot_var);
> +
> +       return status;
>  }
>
>  #ifndef MAX_FDT_SIZE
> --
> 2.26.1
>