Commit a66f2e57 authored by Eugeniy Paltsev's avatar Eugeniy Paltsev Committed by Vineet Gupta

ARC: U-boot: check arguments paranoidly

Handle U-boot arguments paranoidly:
 * don't allow to pass unknown tag.
 * try to use external device tree blob only if corresponding tag
   (TAG_DTB) is set.
 * don't check uboot_tag if kernel build with no ARC_UBOOT_SUPPORT.

If U-boot args are invalid we skip them and try to use embedded device
tree blob. We can't panic on invalid U-boot args as we really pass
invalid args due to bug in U-boot code.
This happens if we don't provide external DTB to U-boot and
don't set 'bootargs' U-boot environment variable (which is default
case at least for HSDK board) In that case we will pass
{r0 = 1 (bootargs in r2); r1 = 0; r2 = 0;} to linux which is invalid.

While I'm at it refactor U-boot arguments handling code.

Cc: [email protected]
Tested-by: Corentin Labbe's avatarCorentin LABBE <[email protected]>
Signed-off-by: default avatarEugeniy Paltsev <[email protected]>
Signed-off-by: default avatarVineet Gupta <[email protected]>
parent e494239a
......@@ -103,9 +103,9 @@ ENTRY(stext)
; Uboot - kernel ABI
; r0 = [0] No uboot interaction, [1] cmdline in r2, [2] DTB in r2
; r1 = magic number (board identity, unused as of now
; r1 = magic number (always zero as of now)
; r2 = pointer to uboot provided cmdline or external DTB in mem
; These are handled later in setup_arch()
; These are handled later in handle_uboot_args()
st r0, [@uboot_tag]
st r2, [@uboot_arg]
......@@ -462,43 +462,80 @@ void setup_processor(void)
static inline int is_kernel(unsigned long addr)
static inline bool uboot_arg_invalid(unsigned long addr)
if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
return 1;
return 0;
* Check that it is a untranslated address (although MMU is not enabled
* yet, it being a high address ensures this is not by fluke)
if (addr < PAGE_OFFSET)
return true;
/* Check that address doesn't clobber resident kernel image */
return addr >= (unsigned long)_stext && addr <= (unsigned long)_end;
void __init setup_arch(char **cmdline_p)
#define IGNORE_ARGS "Ignore U-boot args: "
/* uboot_tag values for U-boot - kernel ABI revision 0; see head.S */
#define UBOOT_TAG_NONE 0
#define UBOOT_TAG_DTB 2
void __init handle_uboot_args(void)
bool use_embedded_dtb = true;
bool append_cmdline = false;
/* make sure that uboot passed pointer to cmdline/dtb is valid */
if (uboot_tag && is_kernel((unsigned long)uboot_arg))
panic("Invalid uboot arg\n");
/* check that we know this tag */
if (uboot_tag != UBOOT_TAG_NONE &&
uboot_tag != UBOOT_TAG_CMDLINE &&
uboot_tag != UBOOT_TAG_DTB) {
pr_warn(IGNORE_ARGS "invalid uboot tag: '%08x'\n", uboot_tag);
goto ignore_uboot_args;
if (uboot_tag != UBOOT_TAG_NONE &&
uboot_arg_invalid((unsigned long)uboot_arg)) {
pr_warn(IGNORE_ARGS "invalid uboot arg: '%px'\n", uboot_arg);
goto ignore_uboot_args;
/* see if U-boot passed an external Device Tree blob */
if (uboot_tag == UBOOT_TAG_DTB) {
machine_desc = setup_machine_fdt((void *)uboot_arg);
/* See if u-boot passed an external Device Tree blob */
machine_desc = setup_machine_fdt(uboot_arg); /* uboot_tag == 2 */
if (!machine_desc)
/* external Device Tree blob is invalid - use embedded one */
use_embedded_dtb = !machine_desc;
if (uboot_tag == UBOOT_TAG_CMDLINE)
append_cmdline = true;
/* No, so try the embedded one */
if (use_embedded_dtb) {
machine_desc = setup_machine_fdt(__dtb_start);
if (!machine_desc)
panic("Embedded DT invalid\n");
* If we are here, it is established that @uboot_arg didn't
* point to DT blob. Instead if u-boot says it is cmdline,
* append to embedded DT cmdline.
* setup_machine_fdt() would have populated @boot_command_line
if (uboot_tag == 1) {
/* Ensure a whitespace between the 2 cmdlines */
strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
strlcat(boot_command_line, uboot_arg,
* NOTE: @boot_command_line is populated by setup_machine_fdt() so this
* append processing can only happen after.
if (append_cmdline) {
/* Ensure a whitespace between the 2 cmdlines */
strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
strlcat(boot_command_line, uboot_arg, COMMAND_LINE_SIZE);
void __init setup_arch(char **cmdline_p)
/* Save unparsed command line copy for /proc/cmdline */
*cmdline_p = boot_command_line;
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