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Add fdt_kaslrseed function to add kaslr-seed to chosen node

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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>
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
This commit is contained in:
Tim Harvey 2024-06-18 14:06:06 -07:00 • committed by Tom Rini
parent 9e9f78f7aa
commit 00afd1ec82
2 changed files with 54 additions and 0 deletions
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44
boot/fdt_support.c
View file

@ -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

10
include/fdt_support.h
View file

@ -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 */