ARC: u-boot args: check that magic number is correct (edb64bca) · Commits · 戴 / test

In case of devboards we really often disable bootloader and load Linux image in memory via JTAG. Even if kernel tries to verify uboot_tag and uboot_arg there is sill a chance that we treat some garbage in registers as valid u-boot arguments in JTAG case. E.g. it is enough to have '1' in r0 to treat any value in r2 as a boot command line. So check that magic number passed from u-boot is correct and drop u-boot arguments otherwise. That helps to reduce the possibility of using garbage as u-boot arguments in JTAG case. We can safely check U-boot magic value (0x0) in linux passed via r1 register as U-boot pass it from the beginning. So there is no backward-compatibility issues. Signed-off-by:

Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com> Signed-off-by:

Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/head.S

+1 −0

Original line number	Diff line number	Diff line
		@@ -111,6 +111,7 @@ ENTRY(stext)
		; r2 = pointer to uboot provided cmdline or external DTB in mem
		; These are handled later in handle_uboot_args()
		st r0, [@uboot_tag]
		st r1, [@uboot_magic]
		st r2, [@uboot_arg]

		; setup "current" tsk and optionally cache it in dedicated r25

arch/arc/kernel/setup.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -36,6 +36,7 @@ unsigned int intr_to_DE_cnt;

		/* Part of U-boot ABI: see head.S */
		int __initdata uboot_tag;
		int __initdata uboot_magic;
		char __initdata *uboot_arg;

		const struct machine_desc *machine_desc;
		@@ -504,6 +505,8 @@ static inline bool uboot_arg_invalid(unsigned long addr)
		#define UBOOT_TAG_NONE 0
		#define UBOOT_TAG_CMDLINE 1
		#define UBOOT_TAG_DTB 2
		/* We always pass 0 as magic from U-boot */
		#define UBOOT_MAGIC_VALUE 0

		void __init handle_uboot_args(void)
		{
		@@ -518,6 +521,11 @@ void __init handle_uboot_args(void)
		goto ignore_uboot_args;
		}

		if (uboot_magic != UBOOT_MAGIC_VALUE) {
		pr_warn(IGNORE_ARGS "non zero uboot magic\n");
		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);

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