[PATCH v2] fdt: automatically add /chosen/kaslr-seed if DM_RNG is enabled
Ilias Apalodimas
ilias.apalodimas at linaro.org
Tue May 21 14:04:29 CEST 2024
Hi Tim
On Wed, 15 May 2024 at 23:50, Tim Harvey <tharvey at gateworks.com> wrote:
>
> If RANDOMIZE_BASE is enabled in the Linux kernel instructing it to
> randomize the virtual address at which the kernel image is loaded, it
> expects entropy to be provided by the bootloader by populating
> /chosen/kaslr-seed with a 64-bit value from source of entropy at boot.
Since you'll send a v2, mind adding some description for UEFI on the
commit message?
efi_try_purge_kaslr_seed() has a comment of the behaviour
Thanks
/Ilias
>
> If we have DM_RNG enabled populate this value automatically when
> fdt_chosen is called unless ARMV8_SEC_FIRMWARE_SUPPORT is enabled as
> it's implementation uses a different source of entropy.
>
> As this fdt node is added elsewhere create a library function and
> use it to deduplicate code.
>
> Note that the kalsrseed command (CMD_KASLRSEED) is likely pointless now
> but left in place in case boot scripts exist that rely on this command
> existing and returning success. An informational message is printed to
> alert users of this command that it is likely no longer needed.
>
> Signed-off-by: Tim Harvey <tharvey at gateworks.com>
> ---
> v2:
> - fix typo in commit msg
> - use stack for seed to avoid unecessary malloc/free
> - move to a library function and deduplicate code by using it elsewhere
> ---
> board/xilinx/common/board.c | 35 -----------------------------
> boot/fdt_support.c | 10 +++++++++
> boot/pxe_utils.c | 35 +++--------------------------
> cmd/kaslrseed.c | 45 ++++++-------------------------------
> include/kaslrseed.h | 17 ++++++++++++++
> lib/Makefile | 1 +
> lib/kaslrseed.c | 34 ++++++++++++++++++++++++++++
> 7 files changed, 72 insertions(+), 105 deletions(-)
> create mode 100644 include/kaslrseed.h
> create mode 100644 lib/kaslrseed.c
>
> diff --git a/board/xilinx/common/board.c b/board/xilinx/common/board.c
> index 30a81376ac41..f741e8957818 100644
> --- a/board/xilinx/common/board.c
> +++ b/board/xilinx/common/board.c
> @@ -713,41 +713,6 @@ int ft_board_setup(void *blob, struct bd_info *bd)
> if (IS_ENABLED(CONFIG_FDT_FIXUP_PARTITIONS) && IS_ENABLED(CONFIG_NAND_ZYNQ))
> fdt_fixup_mtdparts(blob, nodes, ARRAY_SIZE(nodes));
>
> - if (uclass_get_device(UCLASS_RNG, 0, &dev) || !dev) {
> - debug("No RNG device\n");
> - return 0;
> - }
> -
> - if (dm_rng_read(dev, buf, n)) {
> - debug("Reading RNG failed\n");
> - return 0;
> - }
> -
> - if (!blob) {
> - debug("No FDT memory address configured. Please configure\n"
> - "the FDT address via \"fdt addr <address>\" command.\n"
> - "Aborting!\n");
> - return 0;
> - }
> -
> - ret = fdt_check_header(blob);
> - if (ret < 0) {
> - debug("fdt_chosen: %s\n", fdt_strerror(ret));
> - return ret;
> - }
> -
> - nodeoffset = fdt_find_or_add_subnode(blob, 0, "chosen");
> - if (nodeoffset < 0) {
> - debug("Reading chosen node failed\n");
> - return nodeoffset;
> - }
> -
> - ret = fdt_setprop(blob, nodeoffset, "kaslr-seed", buf, sizeof(buf));
> - if (ret < 0) {
> - debug("Unable to set kaslr-seed on chosen node: %s\n", fdt_strerror(ret));
> - return ret;
> - }
> -
> return 0;
> }
> #endif
> diff --git a/boot/fdt_support.c b/boot/fdt_support.c
> index 874ca4d6f5af..3455d60d69dc 100644
> --- a/boot/fdt_support.c
> +++ b/boot/fdt_support.c
> @@ -8,6 +8,7 @@
>
> #include <abuf.h>
> #include <env.h>
> +#include <kaslrseed.h>
> #include <log.h>
> #include <mapmem.h>
> #include <net.h>
> @@ -300,6 +301,15 @@ int fdt_chosen(void *fdt)
> if (nodeoffset < 0)
> return nodeoffset;
>
> + if (IS_ENABLED(CONFIG_DM_RNG) && !IS_ENABLED(ARMV8_SEC_FIRMWARE_SUPPORT)) {
> + err = fdt_kaslrseed(fdt);
> + if (err) {
> + printf("WARNING: could not set kaslr-seed %s.\n",
> + fdt_strerror(err));
> + return err;
> + }
> + }
> +
> if (IS_ENABLED(CONFIG_BOARD_RNG_SEED) && !board_rng_seed(&buf)) {
> err = fdt_setprop(fdt, nodeoffset, "rng-seed",
> abuf_data(&buf), abuf_size(&buf));
> diff --git a/boot/pxe_utils.c b/boot/pxe_utils.c
> index 4b22bb6f525a..8d70233fc08d 100644
> --- a/boot/pxe_utils.c
> +++ b/boot/pxe_utils.c
> @@ -8,6 +8,7 @@
> #include <dm.h>
> #include <env.h>
> #include <image.h>
> +#include <kaslrseed.h>
> #include <log.h>
> #include <malloc.h>
> #include <mapmem.h>
> @@ -323,10 +324,6 @@ static void label_boot_kaslrseed(void)
> #if CONFIG_IS_ENABLED(DM_RNG)
> ulong fdt_addr;
> struct fdt_header *working_fdt;
> - size_t n = 0x8;
> - struct udevice *dev;
> - u64 *buf;
> - int nodeoffset;
> int err;
>
> /* Get the main fdt and map it */
> @@ -342,35 +339,9 @@ static void label_boot_kaslrseed(void)
> if (err <= 0)
> return;
>
> - if (uclass_get_device(UCLASS_RNG, 0, &dev) || !dev) {
> - printf("No RNG device\n");
> - return;
> - }
> -
> - nodeoffset = fdt_find_or_add_subnode(working_fdt, 0, "chosen");
> - if (nodeoffset < 0) {
> - printf("Reading chosen node failed\n");
> - return;
> - }
> -
> - buf = malloc(n);
> - if (!buf) {
> - printf("Out of memory\n");
> - return;
> - }
> -
> - if (dm_rng_read(dev, buf, n)) {
> - printf("Reading RNG failed\n");
> - goto err;
> - }
> -
> - err = fdt_setprop(working_fdt, nodeoffset, "kaslr-seed", buf, sizeof(buf));
> - if (err < 0) {
> + err = fdt_kaslrseed(working_fdt);
> + if (err < 0)
> printf("Unable to set kaslr-seed on chosen node: %s\n", fdt_strerror(err));
> - goto err;
> - }
> -err:
> - free(buf);
> #endif
> return;
> }
> diff --git a/cmd/kaslrseed.c b/cmd/kaslrseed.c
> index e0d3c7fe7489..ea5c07d729cf 100644
> --- a/cmd/kaslrseed.c
> +++ b/cmd/kaslrseed.c
> @@ -9,33 +9,16 @@
> #include <command.h>
> #include <dm.h>
> #include <hexdump.h>
> +#include <kaslrseed.h>
> #include <malloc.h>
> #include <rng.h>
> #include <fdt_support.h>
>
> static int do_kaslr_seed(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
> {
> - size_t n = 0x8;
> - struct udevice *dev;
> - u64 *buf;
> - int nodeoffset;
> - int ret = CMD_RET_SUCCESS;
> + int err;
>
> - if (uclass_get_device(UCLASS_RNG, 0, &dev) || !dev) {
> - printf("No RNG device\n");
> - return CMD_RET_FAILURE;
> - }
> -
> - buf = malloc(n);
> - if (!buf) {
> - printf("Out of memory\n");
> - return CMD_RET_FAILURE;
> - }
> -
> - if (dm_rng_read(dev, buf, n)) {
> - printf("Reading RNG failed\n");
> - return CMD_RET_FAILURE;
> - }
> + printf("Notice: a /chosen/kaslr-seed is automatically added to the device-tree when booted via booti/bootm/bootz therefore using this command is likely no longer needed");
>
> if (!working_fdt) {
> printf("No FDT memory address configured. Please configure\n"
> @@ -44,27 +27,13 @@ static int do_kaslr_seed(struct cmd_tbl *cmdtp, int flag, int argc, char *const
> return CMD_RET_FAILURE;
> }
>
> - ret = fdt_check_header(working_fdt);
> - if (ret < 0) {
> - printf("fdt_chosen: %s\n", fdt_strerror(ret));
> + err = fdt_kaslrseed(working_fdt);
> + if (err < 0) {
> + printf("Unable to set kaslr-seed on chosen node: %s\n", fdt_strerror(err));
> return CMD_RET_FAILURE;
> }
>
> - nodeoffset = fdt_find_or_add_subnode(working_fdt, 0, "chosen");
> - if (nodeoffset < 0) {
> - printf("Reading chosen node failed\n");
> - return CMD_RET_FAILURE;
> - }
> -
> - ret = fdt_setprop(working_fdt, nodeoffset, "kaslr-seed", buf, sizeof(buf));
> - if (ret < 0) {
> - printf("Unable to set kaslr-seed on chosen node: %s\n", fdt_strerror(ret));
> - return CMD_RET_FAILURE;
> - }
> -
> - free(buf);
> -
> - return ret;
> + return CMD_RET_SUCCESS;
> }
>
> U_BOOT_LONGHELP(kaslrseed,
> diff --git a/include/kaslrseed.h b/include/kaslrseed.h
> new file mode 100644
> index 000000000000..3fe82f418acf
> --- /dev/null
> +++ b/include/kaslrseed.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Copyright 2024 Tim Harvey <tharvey at gateworks.com>
> + */
> +
> +#if !defined _KASLRSEED_H_
> +#define _KASLRSEED_H_
> +
> +/**
> + * fdt_kaslrseed() - create a 'kaslr-seed' node in chosen
> + *
> + * @blob: fdt blob
> + * Return: 0 if OK, -ve on error
> + */
> +int fdt_kaslrseed(void *blob);
> +
> +#endif /* _KASLRSEED_H_ */
> diff --git a/lib/Makefile b/lib/Makefile
> index 2a76acf100d0..20a0242055fa 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -149,6 +149,7 @@ obj-y += date.o
> obj-y += rtc-lib.o
> obj-$(CONFIG_LIB_ELF) += elf.o
>
> +obj-$(CONFIG_DM_RNG) += kaslrseed.o
> obj-$(CONFIG_$(SPL_TPL_)SEMIHOSTING) += semihosting.o
>
> #
> diff --git a/lib/kaslrseed.c b/lib/kaslrseed.c
> new file mode 100644
> index 000000000000..ad06bee2b88d
> --- /dev/null
> +++ b/lib/kaslrseed.c
> @@ -0,0 +1,34 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2024 Tim Harvey <tharvey at gateworks.com>
> + */
> +#include <dm.h>
> +#include <rng.h>
> +#include <fdt_support.h>
> +
> +int fdt_kaslrseed(void *fdt)
> +{
> + struct udevice *dev;
> + int nodeoffset;
> + u64 data;
> + int err;
> +
> + err = fdt_check_header(fdt);
> + if (err < 0)
> + return err;
> +
> + /* find or create "/chosen" node. */
> + nodeoffset = fdt_find_or_add_subnode(fdt, 0, "chosen");
> + if (nodeoffset < 0)
> + return nodeoffset;
> +
> + err = uclass_get_device(UCLASS_RNG, 0, &dev);
> + if (!err)
> + err = dm_rng_read(dev, &data, sizeof(data));
> + if (!err)
> + err = fdt_setprop(fdt, nodeoffset, "kaslr-seed", &data, sizeof(data));
> + if (err < 0)
> + printf("WARNING: could not set kaslr-seed %s.\n", fdt_strerror(err));
> +
> + return err;
> +}
> --
> 2.25.1
>
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