efi: libstub: Enable efi_printk() in zboot decompressor

Split the efi_printk() routine into its own source file, and provide
local implementations of strlen() and strnlen() so that the standalone
zboot app can efi_err and efi_info etc.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 31 insertions, 2 deletions

diff --git a/drivers/firmware/efi/libstub/string.c b/drivers/firmware/efi/libstub/string.c
index 9f5810d86646..5a1519d435bf 100644
--- a/drivers/firmware/efi/libstub/string.c
+++ b/drivers/firmware/efi/libstub/string.c
@@ -11,7 +11,37 @@
 #include <linux/types.h>
 #include <linux/string.h>
 
-#ifndef __HAVE_ARCH_STRSTR
+#ifndef EFI_HAVE_STRLEN
+/**
+ * strlen - Find the length of a string
+ * @s: The string to be sized
+ */
+size_t strlen(const char *s)
+{
+	const char *sc;
+
+	for (sc = s; *sc != '\0'; ++sc)
+		/* nothing */;
+	return sc - s;
+}
+#endif
+
+#ifndef EFI_HAVE_STRNLEN
+/**
+ * strnlen - Find the length of a length-limited string
+ * @s: The string to be sized
+ * @count: The maximum number of bytes to search
+ */
+size_t strnlen(const char *s, size_t count)
+{
+	const char *sc;
+
+	for (sc = s; count-- && *sc != '\0'; ++sc)
+		/* nothing */;
+	return sc - s;
+}
+#endif
+
 /**
  * strstr - Find the first substring in a %NUL terminated string
  * @s1: The string to be searched
@@ -33,7 +63,6 @@ char *strstr(const char *s1, const char *s2)
 	}
 	return NULL;
 }
-#endif
 
 /**
  * strncmp - Compare two length-limited strings