Hi Heinrich,
On Tue, 17 Sept 2024 at 11:49, Heinrich Schuchardt
<heinrich.schucha...@canonical.com> wrote:
>
> For measured be boot we must avoid any volatile values in the device-tree.
> We already delete /chosen/kaslr-seed if we provide and EFI RNG protocol.
>
> Additionally remove /chosen/rng-seed provided by QEMU or U-Boot.
>
> Signed-off-by: Heinrich Schuchardt <heinrich.schucha...@canonical.com>
> ---
> v2:
> Use an index instead of a position pointer for better readability
> ---
> include/efi_loader.h | 2 +-
> lib/efi_loader/efi_dt_fixup.c | 15 ++++++++++-----
> lib/efi_loader/efi_helper.c | 2 +-
> 3 files changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index f84852e384f..511281e150e 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -567,7 +567,7 @@ efi_status_t EFIAPI efi_convert_pointer(efi_uintn_t
> debug_disposition,
> /* Carve out DT reserved memory ranges */
> void efi_carve_out_dt_rsv(void *fdt);
> /* Purge unused kaslr-seed */
> -void efi_try_purge_kaslr_seed(void *fdt);
> +void efi_try_purge_rng_seed(void *fdt);
> /* Called by bootefi to make console interface available */
> efi_status_t efi_console_register(void);
> /* Called by efi_init_obj_list() to proble all block devices */
> diff --git a/lib/efi_loader/efi_dt_fixup.c b/lib/efi_loader/efi_dt_fixup.c
> index 9d017804eea..0dac94b0c6c 100644
> --- a/lib/efi_loader/efi_dt_fixup.c
> +++ b/lib/efi_loader/efi_dt_fixup.c
> @@ -41,7 +41,7 @@ static void efi_reserve_memory(u64 addr, u64 size, bool
> nomap)
> }
>
> /**
> - * efi_try_purge_kaslr_seed() - Remove unused kaslr-seed
> + * efi_try_purge_rng_seed() - Remove unused kaslr-seed, rng-seed
> *
> * Kernel's EFI STUB only relies on EFI_RNG_PROTOCOL for randomization
> * and completely ignores the kaslr-seed for its own randomness needs
> @@ -51,8 +51,9 @@ static void efi_reserve_memory(u64 addr, u64 size, bool
> nomap)
> *
> * @fdt: Pointer to device tree
> */
> -void efi_try_purge_kaslr_seed(void *fdt)
> +void efi_try_purge_rng_seed(void *fdt)
> {
> + const char * const prop[] = {"kaslr-seed", "rng-seed"};
> const efi_guid_t efi_guid_rng_protocol = EFI_RNG_PROTOCOL_GUID;
> struct efi_handler *handler;
> efi_status_t ret;
> @@ -67,9 +68,13 @@ void efi_try_purge_kaslr_seed(void *fdt)
> if (nodeoff < 0)
> return;
>
> - err = fdt_delprop(fdt, nodeoff, "kaslr-seed");
> - if (err < 0 && err != -FDT_ERR_NOTFOUND)
> - log_err("Error deleting kaslr-seed\n");
> + for (size_t i = 0; i < ARRAY_SIZE(prop); ++i) {
> + err = fdt_delprop(fdt, nodeoff, prop[i]);
> + if (err < 0 && err != -FDT_ERR_NOTFOUND)
> + log_err("Error deleting %s\n", prop[i]);
> + else
> + log_debug("Deleted /chosen/%s\n", prop[i]);
> + }
> }
>
> /**
> diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
> index 96f847652ec..a481eb4b7e3 100644
> --- a/lib/efi_loader/efi_helper.c
> +++ b/lib/efi_loader/efi_helper.c
> @@ -522,7 +522,7 @@ efi_status_t efi_install_fdt(void *fdt)
> /* Create memory reservations as indicated by the device tree */
> efi_carve_out_dt_rsv(fdt);
>
> - efi_try_purge_kaslr_seed(fdt);
> + efi_try_purge_rng_seed(fdt);
>
> if (CONFIG_IS_ENABLED(EFI_TCG2_PROTOCOL_MEASURE_DTB)) {
> ret = efi_tcg2_measure_dtb(fdt);
> --
> 2.45.2
>
I saw the comment on RISC-V. If there's size issues you are concerned,
I am fine with v2 as well -- just add a comment on why if you decide
to merge that
For v2 & v3
Reviewed-by: Ilias Apalodimas <ilias.apalodi...@linaro.org>
