powerpc: Support CMDLINE_EXTEND

Bring powerpc in line with other architectures that support extending or
overriding the bootloader provided command line.

The current behaviour is most like CMDLINE_FROM_BOOTLOADER where the
bootloader command line is preferred but the kernel config can provide a
fallback so CMDLINE_FROM_BOOTLOADER is the default. CMDLINE_EXTEND can
be used to append the CMDLINE from the kernel config to the one provided
by the bootloader.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190801225006.21952-1-chris.packham@alliedtelesis.co.nz

1 files changed, 24 insertions, 12 deletions

diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index 100f1b57ec2f..90987db10974 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -303,16 +303,24 @@ static char __init *prom_strstr(const char *s1, const char *s2)
 	return NULL;
 }
 
-static size_t __init prom_strlcpy(char *dest, const char *src, size_t size)
-{
-	size_t ret = prom_strlen(src);
+static size_t __init prom_strlcat(char *dest, const char *src, size_t count)
+{
+	size_t dsize = prom_strlen(dest);
+	size_t len = prom_strlen(src);
+	size_t res = dsize + len;
+
+	/* This would be a bug */
+	if (dsize >= count)
+		return count;
+
+	dest += dsize;
+	count -= dsize;
+	if (len >= count)
+		len = count-1;
+	memcpy(dest, src, len);
+	dest[len] = 0;
+	return res;
 
-	if (size) {
-		size_t len = (ret >= size) ? size - 1 : ret;
-		memcpy(dest, src, len);
-		dest[len] = '\0';
-	}
-	return ret;
 }
 
 #ifdef CONFIG_PPC_PSERIES
@@ -764,10 +772,14 @@ static void __init early_cmdline_parse(void)
 
 	prom_cmd_line[0] = 0;
 	p = prom_cmd_line;
-	if ((long)prom.chosen > 0)
+
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && (long)prom.chosen > 0)
 		l = prom_getprop(prom.chosen, "bootargs", p, COMMAND_LINE_SIZE-1);
-	if (IS_ENABLED(CONFIG_CMDLINE_BOOL) && (l <= 0 || p[0] == '\0')) /* dbl check */
-		prom_strlcpy(prom_cmd_line, CONFIG_CMDLINE, sizeof(prom_cmd_line));
+
+	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) || l <= 0 || p[0] == '\0')
+		prom_strlcat(prom_cmd_line, " " CONFIG_CMDLINE,
+			     sizeof(prom_cmd_line));
+
 	prom_printf("command line: %s\n", prom_cmd_line);
 
 #ifdef CONFIG_PPC64