2 files changed, 64 insertions, 27 deletions

diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
index 26e33a8b2d18..1f945d0f40da 100644
--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -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
diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index def19b0ef8c6..8bb156164556 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -462,43 +462,80 @@ 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;
+        }
+
+        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;
+
+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
-                 */
-                if (uboot_tag == 1) {
-                        /* Ensure a whitespace between the 2 cmdlines */
-                        strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
-                        strlcat(boot_command_line, uboot_arg,
-                                COMMAND_LINE_SIZE);
-                }
+        /*
+         * 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)
+{
+        handle_uboot_args();
 
         /* Save unparsed command line copy for /proc/cmdline */
         *cmdline_p = boot_command_line;