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

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.

NOTE:
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: stable@vger.kernel.org
Tested-by: default avatarCorentin LABBE <clabbe@baylibre.com>
Signed-off-by: default avatarEugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent e494239a

arch/arc/kernel/head.S

+2 −2
Original line number Diff line number Diff line
@@ -103,9 +103,9 @@ ENTRY(stext) 
#ifdef CONFIG_ARC_UBOOT_SUPPORT

	; 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]

#endif

arch/arc/kernel/setup.c

+62 −25
Original line number Diff line number Diff line
@@ -462,44 +462,81 @@ void setup_processor(void) 
	arc_chk_core_config();

}



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_CMDLINE	1

#define UBOOT_TAG_DTB		2



void __init handle_uboot_args(void)

{

	bool use_embedded_dtb = true;

	bool append_cmdline = false;



#ifdef CONFIG_ARC_UBOOT_SUPPORT

	/* 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;

	}



	/* See if u-boot passed an external Device Tree blob */

	machine_desc = setup_machine_fdt(uboot_arg);	/* uboot_tag == 2 */

	if (!machine_desc)

	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);



		/* external Device Tree blob is invalid - use embedded one */

		use_embedded_dtb = !machine_desc;

	}



	if (uboot_tag == UBOOT_TAG_CMDLINE)

		append_cmdline = true;



ignore_uboot_args:

#endif

	{

		/* 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

	 * NOTE: @boot_command_line is populated by setup_machine_fdt() so this

	 * append processing can only happen after.

	 */

		if (uboot_tag == 1) {

	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);

		strlcat(boot_command_line, uboot_arg, COMMAND_LINE_SIZE);

	}

}



void __init setup_arch(char **cmdline_p)

{

	handle_uboot_args();



	/* Save unparsed command line copy for /proc/cmdline */

	*cmdline_p = boot_command_line;

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