On Thu, Jun 20, 2024 at 6:58 AM Caleb Connolly caleb.connolly@linaro.org wrote:

Hi Tim,

On 18/06/2024 23:06, Tim Harvey 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.

Add a fdt_kaslrseed function to accommodate this allowing an existing node to be overwritten if present. For now use the first rng device but it would be good to enhance this in the future to allow some sort of selection or policy in choosing the rng device used.

Signed-off-by: Tim Harvey tharvey@gateworks.com Reviewed-by: Simon Glass sjg@chromium.org Cc: Michal Simek michal.simek@amd.com Cc: Andy Yan andy.yan@rock-chips.com Cc: Akash Gajjar gajjar04akash@gmail.com Cc: Ilias Apalodimas ilias.apalodimas@linaro.org Cc: Simon Glass sjg@chromium.org Cc: Patrick Delaunay patrick.delaunay@foss.st.com Cc: Patrice Chotard patrice.chotard@foss.st.com Cc: Devarsh Thakkar devarsht@ti.com Cc: Heinrich Schuchardt xypron.glpk@gmx.de Cc: Hugo Villeneuve hvilleneuve@dimonoff.com Cc: Marek Vasut marex@denx.de Cc: Tom Rini trini@konsulko.com Cc: Chris Morgan macromorgan@hotmail.com

---

v6:

• collected tags

v5:

• move function to boot/fdt_support.c
• remove ability to select rng index and note in the commit log something like this as a future enhancement.
• fixed typo in commit message s/it's/its/
• use cmd_process_error per Michal's suggestion

v4:

• add missing /n to notice in kaslrseed cmd
• combine ints in declaration
• remove unused vars from board/xilinx/common/board.c ft_board_setup

v3:

• skip if CONFIG_MEASURED_BOOT
• fix skip for CONFIG_ARMV8_SEC_FIRMWARE_SUPPORT
• pass in rng index and bool to specify overwrite
• remove duplicate error strings printed outside of fdt_kaslrseed
• added note to commit log about how EFI STUB weeds out kalsr-seed

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

---

boot/fdt_support.c | 44 +++++++++++++++++++++++++++++++++++++++++++ include/fdt_support.h | 10 ++++++++++ 2 files changed, 54 insertions(+)

diff --git a/boot/fdt_support.c b/boot/fdt_support.c index 2bd80a9dfb18..b1b2679dea0c 100644 --- a/boot/fdt_support.c +++ b/boot/fdt_support.c @@ -7,12 +7,15 @@ */

#include <common.h> +#include <dm.h> #include <abuf.h> #include <env.h> #include <log.h> #include <mapmem.h> #include <net.h> +#include <rng.h> #include <stdio_dev.h> +#include <dm/device_compat.h> #include <dm/ofnode.h> #include <linux/ctype.h> #include <linux/types.h> @@ -274,6 +277,47 @@ int fdt_initrd(void *fdt, ulong initrd_start, ulong initrd_end) return 0; }

+int fdt_kaslrseed(void *fdt, bool overwrite) +{

• int len, err, nodeoffset;
  

• struct udevice *dev;
  

• const u64 *orig;
  

• u64 data = 0;
  

• err = fdt_check_header(fdt);
  

• if (err < 0)
  

•         return err;
  

All the paths that call fdt_kaslrseed() call fdt_check_header() beforehand, I think it's safe to drop this.

Hi Caleb,

The do_kaslr_seed path does not check for this and instead passes working_fdt - perhaps your point is still valid if working_fdt is guaranteed to always be a valid fdt?

...

• /* find or create "/chosen" node. */
  

• nodeoffset = fdt_find_or_add_subnode(fdt, 0, "chosen");
  

• if (nodeoffset < 0)
  

•         return nodeoffset;
  

Arguably, this shouldn't be the responsibility of this function, maybe it would be better to error our here?

I'm not sure what your point is here... it is erroring out.

Best Regards,

Tim

...

• /* return without error if we are not overwriting and existing non-zero node */
  

• orig = fdt_getprop(fdt, nodeoffset, "kaslr-seed", &len);
  

• if (orig && len == sizeof(*orig))
  

•         data = fdt64_to_cpu(*orig);
  

• if (data && !overwrite) {
  

•         debug("not overwriting existing kaslr-seed\n");
  

•         return 0;
  

• }
  

• err = uclass_get_device(UCLASS_RNG, 0, &dev);
  

• if (err) {
  

•         printf("No RNG device\n");
  

•         return err;
  

• }
  

• err = dm_rng_read(dev, &data, sizeof(data));
  

• if (err) {
  

•         dev_err(dev, "dm_rng_read failed: %d\n", err);
  

•         return 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;
  

+}

• /**
  • board_fdt_chosen_bootargs - boards may override this function to use

  •                         alternative kernel command line arguments
    

diff --git a/include/fdt_support.h b/include/fdt_support.h index 4b71b8948d99..741e2360c224 100644 --- a/include/fdt_support.h +++ b/include/fdt_support.h @@ -463,4 +463,14 @@ void fdt_fixup_board_enet(void *blob); #ifdef CONFIG_CMD_PSTORE void fdt_fixup_pstore(void *blob); #endif

+/**

• • fdt_kaslrseed() - create a 'kaslr-seed' node in chosen
• • @blob: fdt blob
• • @overwrite: do not overwrite existing non-zero node unless true
• • Return: 0 if OK, -ve on error
• */

+int fdt_kaslrseed(void *blob, bool overwrite);

• #endif /* ifndef __FDT_SUPPORT_H */

-- // Caleb (they/them)

On 6/18/24 23:06, Tim Harvey wrote:

Use the fdt_kaslrseed function to deduplicate code doing the same thing.

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.

Note that the Kernel's EFI STUB only relies on EFI_RNG_PROTOCOL for randomization and completely ignores the kaslr-seed for its own randomness needs (i.e the randomization of the physical placement of the kernel). It gets weeded out from the DTB that gets handed over via efi_install_fdt() as it would also mess up the measured boot DTB TPM measurements as well.

Signed-off-by: Tim Harvey tharvey@gateworks.com Reviewed-by: Simon Glass sjg@chromium.org Cc: Michal Simek michal.simek@amd.com Cc: Andy Yan andy.yan@rock-chips.com Cc: Akash Gajjar gajjar04akash@gmail.com Cc: Ilias Apalodimas ilias.apalodimas@linaro.org Cc: Simon Glass sjg@chromium.org Cc: Patrick Delaunay patrick.delaunay@foss.st.com Cc: Patrice Chotard patrice.chotard@foss.st.com Cc: Devarsh Thakkar devarsht@ti.com Cc: Heinrich Schuchardt xypron.glpk@gmx.de Cc: Hugo Villeneuve hvilleneuve@dimonoff.com Cc: Marek Vasut marex@denx.de Cc: Tom Rini trini@konsulko.com Cc: Chris Morgan macromorgan@hotmail.com

---

v6:

• collected tags

v5:

• fixed typo in commit message s/it's/its/
• use cmd_process_error per Michal's suggestion

v4:

• add missing /n to notice in kaslrseed cmd
• combine ints in declaration
• remove unused vars from board/xilinx/common/board.c ft_board_setup

v3:

• skip if CONFIG_MEASURED_BOOT
• fix skip for CONFIG_ARMV8_SEC_FIRMWARE_SUPPORT
• pass in rng index and bool to specify overwrite
• remove duplicate error strings printed outside of fdt_kaslrseed
• added note to commit log about how EFI STUB weeds out kalsr-seed

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 | 40 ------------------------------ boot/pxe_utils.c | 34 +------------------------ cmd/kaslrseed.c | 49 ++++++------------------------------- 3 files changed, 8 insertions(+), 115 deletions(-)

diff --git a/board/xilinx/common/board.c b/board/xilinx/common/board.c index b47d2d23f913..098738017bab 100644 --- a/board/xilinx/common/board.c +++ b/board/xilinx/common/board.c @@ -702,11 +702,6 @@ phys_addr_t board_get_usable_ram_top(phys_size_t total_size) #define MAX_RAND_SIZE 8 int ft_board_setup(void *blob, struct bd_info *bd) {

• size_t n = MAX_RAND_SIZE;
• struct udevice *dev;
• u8 buf[MAX_RAND_SIZE];
• int nodeoffset, ret;
• static const struct node_info nodes[] = { { "arm,pl353-nand-r2p1", MTD_DEV_TYPE_NAND, }, };

@@ -714,41 +709,6 @@ 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/pxe_utils.c b/boot/pxe_utils.c index 5c1c962ff4c1..38ca9b81a42d 100644 --- a/boot/pxe_utils.c +++ b/boot/pxe_utils.c @@ -324,10 +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 */

@@ -343,35 +339,7 @@ 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) {

• printf("Unable to set kaslr-seed on chosen node: %s\n", fdt_strerror(err));
  

• goto err;
  

• }

-err:

• free(buf);

• fdt_kaslrseed(working_fdt, true); #endif return; }

diff --git a/cmd/kaslrseed.c b/cmd/kaslrseed.c index 9acb8e163863..645cab2e74fd 100644 --- a/cmd/kaslrseed.c +++ b/cmd/kaslrseed.c @@ -16,56 +16,21 @@

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 = CMD_RET_SUCCESS;

• 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\n");

  if (!working_fdt) { printf("No FDT memory address configured. Please configure\n" "the FDT address via "fdt addr <address>" command.\n" "Aborting!\n");

• return CMD_RET_FAILURE;
  

• }
• ret = fdt_check_header(working_fdt);
• if (ret < 0) {

• printf("fdt_chosen: %s\n", fdt_strerror(ret));
  

• 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;
  

• err = CMD_RET_FAILURE;
  

• } else {

• if (fdt_kaslrseed(working_fdt, true) < 0)
  

• 	err = 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_process_error(cmdtp, err); }

  U_BOOT_LONGHELP(kaslrseed,

Acked-by: Michal Simek michal.simek@amd.com

Thanks, Michal