[PATCH] [v2] add kaslr-seed generation to extlinux.conf

[Zhang Ning]

just test today, I find the code doesn't work as expect.

add kaslr-seed to fdt returns -ERR_FDT_NOSPACE, after review code for
dtb_overlay, I guess I need to resize main fdt to hold the new property.

I will resend patch after I comfirm it work.



On Sun, Jan 30, 2022 at 01:10:09PM +0800, Zhang Ning wrote:
> add kaslrseed key word to extlinux.conf,
> which means generate kaslr-seed for linux
> 
> with this patch exlinux.conf boot item looks like
> 
> label l0
>         menu testing
>         linux /boot/vmlinuz-5.15.16-arm
>         initrd /boot/initramfs-5.15.16-arm.img
>         fdtdir /boot/dtbs/5.15.16-arm/
>         kaslrseed
>         append root=UUID=92ae1e50-eeeb-4c5b-8939-7e1cd6cfb059 ro
> 
> Signed-off-by: Zhang Ning <zhangn1985 at qq.com>
> ---
>  boot/pxe_utils.c    | 69 +++++++++++++++++++++++++++++++++++++++++++++
>  include/pxe_utils.h |  2 ++
>  2 files changed, 71 insertions(+)
> 
> diff --git a/boot/pxe_utils.c b/boot/pxe_utils.c
> index bb231b11a2..e76e77b738 100644
> --- a/boot/pxe_utils.c
> +++ b/boot/pxe_utils.c
> @@ -20,6 +20,11 @@
>  #include <errno.h>
>  #include <linux/list.h>
>  
> +#ifdef CONFIG_DM_RNG
> +#include <dm.h>
> +#include <rng.h>
> +#endif
> +
>  #include <splash.h>
>  #include <asm/io.h>
>  
> @@ -311,6 +316,61 @@ static int label_localboot(struct pxe_label *label)
>  	return run_command_list(localcmd, strlen(localcmd), 0);
>  }
>  
> +/*
> + * label_boot_kaslrseed generate kaslrseed from hw rng
> + */
> +
> +static void label_boot_kaslrseed(void)
> +{
> +#ifdef CONFIG_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 */
> +	fdt_addr = hextoul(env_get("fdt_addr_r"), NULL);
> +	working_fdt = map_sysmem(fdt_addr, 0);
> +	err = fdt_check_header(working_fdt);
> +	if (err)
> +		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);
> +#endif
> +	return;
> +}
> +
>  /**
>   * label_boot_fdtoverlay() - Loads fdt overlays specified in 'fdtoverlays'
>   *
> @@ -631,6 +691,9 @@ static int label_boot(struct pxe_context *ctx, struct pxe_label *label)
>  				}
>  			}
>  
> +		if (label->kaslrseed)
> +			label_boot_kaslrseed();
> +
>  #ifdef CONFIG_OF_LIBFDT_OVERLAY
>  			if (label->fdtoverlays)
>  				label_boot_fdtoverlay(ctx, label);
> @@ -710,6 +773,7 @@ enum token_type {
>  	T_ONTIMEOUT,
>  	T_IPAPPEND,
>  	T_BACKGROUND,
> +	T_KASLRSEED,
>  	T_INVALID
>  };
>  
> @@ -741,6 +805,7 @@ static const struct token keywords[] = {
>  	{"ontimeout", T_ONTIMEOUT,},
>  	{"ipappend", T_IPAPPEND,},
>  	{"background", T_BACKGROUND,},
> +	{"kaslrseed", T_KASLRSEED,},
>  	{NULL, T_INVALID}
>  };
>  
> @@ -1194,6 +1259,10 @@ static int parse_label(char **c, struct pxe_menu *cfg)
>  			err = parse_integer(c, &label->ipappend);
>  			break;
>  
> +		case T_KASLRSEED:
> +			label->kaslrseed = 1;
> +			break;
> +
>  		case T_EOL:
>  			break;
>  
> diff --git a/include/pxe_utils.h b/include/pxe_utils.h
> index dad2668818..4a73b2aace 100644
> --- a/include/pxe_utils.h
> +++ b/include/pxe_utils.h
> @@ -33,6 +33,7 @@
>   * initrd - path to the initrd to use for this label.
>   * attempted - 0 if we haven't tried to boot this label, 1 if we have.
>   * localboot - 1 if this label specified 'localboot', 0 otherwise.
> + * kaslrseed - 1 if generate kaslrseed from hw_rng
>   * list - lets these form a list, which a pxe_menu struct will hold.
>   */
>  struct pxe_label {
> @@ -50,6 +51,7 @@ struct pxe_label {
>  	int attempted;
>  	int localboot;
>  	int localboot_val;
> +	int kaslrseed;
>  	struct list_head list;
>  };
>  
> -- 
> 2.34.1
>