[PATCH] efi_loader: remove comparisons to string literals from runtime

[Ilias Apalodimas]

Apologies to both for the noise,

I forgot to mark this as v2 and add a changelog....

On Fri, 14 Feb 2025 at 15:46, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> For EFI runtime services, we manage to preserve string literals
> by placing the .efi_runtime section just before .data and preserving
> it when marking the runtime memory by marking surrounding boottime
> code as runtime. This is ok for now but will break if we update any
> linker scripts and decouple .text and .runtime sections.
>
> So let's define the strings we used to compare in the appropriate
> section for runtime services
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---

Changes since v1:
- Allocate the string literals in an efi runtime section instead of the stack

Sorry!
/Ilias
>  lib/efi_loader/efi_var_mem.c      | 3 ++-
>  lib/efi_loader/efi_variable_tee.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/lib/efi_loader/efi_var_mem.c b/lib/efi_loader/efi_var_mem.c
> index b265d95dd6ba..31180df9e3a0 100644
> --- a/lib/efi_loader/efi_var_mem.c
> +++ b/lib/efi_loader/efi_var_mem.c
> @@ -19,6 +19,7 @@
>   */
>  static struct efi_var_file __efi_runtime_data *efi_var_buf;
>  static struct efi_var_entry __efi_runtime_data *efi_current_var;
> +static const u16 __efi_runtime_rodata vtf[] = u"VarToFile";
>
>  /**
>   * efi_var_mem_compare() - compare GUID and name with a variable
> @@ -331,7 +332,7 @@ efi_get_variable_mem(const u16 *variable_name, const efi_guid_t *vendor,
>         if (timep)
>                 *timep = var->time;
>
> -       if (!u16_strcmp(variable_name, u"VarToFile"))
> +       if (!u16_strcmp(variable_name, vtf))
>                 return efi_var_collect_mem(data, data_size, EFI_VARIABLE_NON_VOLATILE);
>
>         old_size = *data_size;
> diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c
> index 0d090d051dd4..6a1fa39bb6f3 100644
> --- a/lib/efi_loader/efi_variable_tee.c
> +++ b/lib/efi_loader/efi_variable_tee.c
> @@ -41,6 +41,7 @@ static u16 mm_sp_id;
>  extern struct efi_var_file __efi_runtime_data *efi_var_buf;
>  static efi_uintn_t max_buffer_size;    /* comm + var + func + data */
>  static efi_uintn_t max_payload_size;   /* func + data */
> +static const u16 __efi_runtime_rodata pk[] = u"PK";
>
>  struct mm_connection {
>         struct udevice *tee;
> @@ -858,7 +859,7 @@ efi_status_t efi_set_variable_int(const u16 *variable_name,
>         if (alt_ret != EFI_SUCCESS)
>                 goto out;
>
> -       if (!u16_strcmp(variable_name, u"PK"))
> +       if (!u16_strcmp(variable_name, pk))
>                 alt_ret = efi_init_secure_state();
>  out:
>         free(comm_buf);
> --
> 2.47.2
>