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; + + /* find or create "/chosen" node. */ + nodeoffset = fdt_find_or_add_subnode(fdt, 0, "chosen"); + if (nodeoffset < 0) + return nodeoffset; + + /* 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 */