In case of devboards we really often disable bootloader and load
Linux image in memory via JTAG. In case of using kernel with
CONFIG_ARC_UBOOT_SUPPORT enabled we may crash as we will try to
interpret some junk in a registers as a pointers to bootargs/etc
which aren't set by anyone in case of JTAG using.
Try to make it much less possible by check magic number and
'U-boot - kernel' ABI revision number passed from U-boot.
Ignore U-boot arguments if we got wrong magic number or unknown
ABI revision.
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@xxxxxxxxxxxx>
---
arch/arc/kernel/head.S | 5 ++++-
arch/arc/kernel/setup.c | 26 ++++++++++++++++++++++++++
2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
index 7095055bb874..3fb88ec62bc7 100644
--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -92,10 +92,13 @@ ENTRY(stext)
#ifdef CONFIG_ARC_UBOOT_SUPPORT
; Uboot - kernel ABI
+ ; r1 = bits [31:8] magic number, bits [7:0] uboot-kernel ABI revision
+ ; ABI revision 0:
; r0 = [0] No uboot interaction, [1] cmdline in r2, [2] DTB in r2
- ; r1 = magic number (board identity, unused as of now
; r2 = pointer to uboot provided cmdline or external DTB in mem
; These are handled later in handle_uboot_args()
+ st r1, [@uboot_rev_magic]
+ mov r1, 0 ; errase magic from the register
st r0, [@uboot_tag]
st r2, [@uboot_arg]
#endif
diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index 7edb35c26322..868dda3d4b43 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -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_rev_magic;
char __initdata *uboot_arg;
const struct machine_desc *machine_desc;
@@ -467,6 +468,10 @@ static inline bool is_kernel(unsigned long addr)
return addr >= (unsigned long)_stext && addr <= (unsigned long)_end;
}
+#define UBOOT_MAGIC_VALUE 0x567890
+#define UBOOT_MAGIC_GET(x) (((x) & GENMASK(31, 8)) >> 8)
+#define UBOOT_REVISION_GET(x) ((x) & GENMASK(7, 0))
+
/* uboot_tag values for U-boot - kernel ABI revisions 0+; see head.S */
#define UBOOT_REV0P_TAG_NONE 0
#define UBOOT_REV0P_TAG_CMDLINE 1
@@ -478,6 +483,25 @@ void __init handle_uboot_args(void)
bool use_embedded_dtb = true;
#ifdef CONFIG_ARC_UBOOT_SUPPORT
+ /* check that we got correct magic */
+ if (UBOOT_MAGIC_GET(uboot_rev_magic) != UBOOT_MAGIC_VALUE) {
+ pr_warn("Invalid magic '%06lx' is passed from uboot, uboot args ingnored\n",
+ UBOOT_MAGIC_GET(uboot_rev_magic));
+
+ goto ignore_uboot_args;
+ }
+
+ /*
+ * check that we know this U-boot args ABI revision.
+ * as for today we only have one revision - '0'.
+ */
+ if (UBOOT_REVISION_GET(uboot_rev_magic) != 0) {
+ pr_warn("Unknown args revision '%02lx' is passed from uboot, uboot args ingnored\n",
+ UBOOT_REVISION_GET(uboot_rev_magic));
+
+ goto ignore_uboot_args;
+ }
+
/* check that we know this tag */
if (uboot_tag != UBOOT_REV0P_TAG_NONE &&
uboot_tag != UBOOT_REV0P_TAG_CMDLINE &&
@@ -498,6 +522,8 @@ void __init handle_uboot_args(void)
if (uboot_tag == UBOOT_REV0P_TAG_CMDLINE)
append_boot_cmdline = true;
+
+ignore_uboot_args:
#endif
if (use_embedded_dtb) {
--
2.14.5
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