powerpc/powernv: Get kernel command line accross OPAL takeover

We stash it in boot_command_line which isn't in BSS and so won't
be overwritten. We then use that as a default cmd_line before
we walk the device-tree.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/prom.c

@@ -712,6 +712,13 @@ void __init early_init_devtree(void *params)
 	of_scan_flat_dt(early_init_dt_scan_phyp_dump, NULL);
 #endif
 
+	/* Pre-initialize the cmd_line with the content of boot_commmand_line,
+	 * which will be empty except when the content of the variable has
+	 * been overriden by a bootloading mechanism. This happens typically
+	 * with HAL takeover
+	 */
+	strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
+
 	/* Retrieve various informations from the /chosen node of the
 	 * device-tree, including the platform type, initrd location and
 	 * size, TCE reserve, and more ...

arch/powerpc/kernel/prom_init.c

@@ -1449,6 +1449,10 @@ static void prom_opal_takeover(void)
 		opal_addr = top_addr;
 	args->hal_addr = opal_addr;
 
+	/* Copy the command line to the kernel image */
+	strlcpy(RELOC(boot_command_line), RELOC(prom_cmd_line),
+		COMMAND_LINE_SIZE);
+
 	prom_debug("  k_image    = 0x%lx\n", args->k_image);
 	prom_debug("  k_size     = 0x%lx\n", args->k_size);
 	prom_debug("  k_entry    = 0x%lx\n", args->k_entry);

arch/powerpc/kernel/prom_init_check.sh

@@ -21,7 +21,8 @@ _end enter_prom memcpy memset reloc_offset __secondary_hold
 __secondary_hold_acknowledge __secondary_hold_spinloop __start
 strcmp strcpy strlcpy strlen strncmp strstr logo_linux_clut224
 reloc_got2 kernstart_addr memstart_addr linux_banner _stext
-opal_query_takeover opal_do_takeover opal_enter_rtas opal_secondary_entry"
+opal_query_takeover opal_do_takeover opal_enter_rtas opal_secondary_entry
+boot_command_line"
 
 NM="$1"
 OBJ="$2"