efi: centralize efivarfs_parse_filename

Turning an EFI varfs filename into its components will be useful for the
EFI loader as well, so factor that out.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20211122084732.2597109-15-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2 files changed, 117 insertions, 1 deletions

diff --git a/common/efi/Makefile b/common/efi/Makefile
index ed110f5a68..a7cebde4f1 100644
--- a/common/efi/Makefile
+++ b/common/efi/Makefile
@@ -3,4 +3,4 @@
 obj-$(CONFIG_EFI_BOOTUP)	+= payload/
 obj-$(CONFIG_EFI_GUID)		+= guid.o
 obj-$(CONFIG_EFI_DEVICEPATH)	+= devicepath.o
-obj-y				+= errno.o
+obj-y				+= errno.o efivar-filename.o
diff --git a/common/efi/efivar-filename.c b/common/efi/efivar-filename.c
new file mode 100644
index 0000000000..51d0130fa7
--- /dev/null
+++ b/common/efi/efivar-filename.c
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/ctype.h>
+#include <string.h>
+#include <efi/efi-util.h>
+
+static int char_to_nibble(char c)
+{
+	int ret = tolower(c);
+
+	return ret <= '9' ? ret - '0' : ret - 'a' + 10;
+}
+
+static int read_byte_str(const char *str, u8 *out)
+{
+	if (!isxdigit(*str) || !isxdigit(*(str + 1)))
+		return -EINVAL;
+
+	*out = (char_to_nibble(*str) << 4) | char_to_nibble(*(str + 1));
+
+	return 0;
+}
+
+static int efi_guid_parse(const char *str, efi_guid_t *guid)
+{
+	int i, ret;
+	u8 idx[] = { 3, 2, 1, 0, 5, 4, 7, 6, 8, 9, 10, 11, 12, 13, 14, 15 };
+
+	for (i = 0; i < 16; i++) {
+		ret = read_byte_str(str, &guid->b[idx[i]]);
+		if (ret)
+			return ret;
+		str += 2;
+
+		switch (i) {
+		case 3:
+		case 5:
+		case 7:
+		case 9:
+			if (*str != '-')
+				return -EINVAL;
+			str++;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+
+int __efivarfs_parse_filename(const char *filename, efi_guid_t *vendor,
+			      s16 *name, size_t *namelen)
+{
+	int len, ret;
+	const char *guidstr;
+	int i;
+
+	len = strlen(filename);
+
+	if (len < sizeof("-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"))
+		return -EINVAL;
+
+	guidstr = filename + len - sizeof("xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx");
+	if (*guidstr != '-' || guidstr == filename)
+		return -EINVAL;
+
+	guidstr++;
+
+	ret = efi_guid_parse(guidstr, vendor);
+	if (ret)
+		return ret;
+
+	if (guidstr - filename > *namelen)
+		ret = -EFBIG;
+
+	*namelen = guidstr - filename;
+
+	if (ret)
+		return ret;
+
+	for (i = 0; i < *namelen - 1; i++)
+		name[i] = filename[i];
+
+	name[i] = L'\0';
+
+	return 0;
+}
+
+int efivarfs_parse_filename(const char *filename, efi_guid_t *vendor,
+			    s16 **name)
+{
+	int ret;
+	s16 *varname;
+	size_t namelen = 0;
+	int i;
+
+	if (*filename == '/')
+		filename++;
+
+	ret = __efivarfs_parse_filename(filename, vendor, NULL, &namelen);
+	if (ret != -EFBIG)
+		return ret;
+
+	varname = xzalloc(namelen * sizeof(s16));
+
+	for (i = 0; i < namelen - 1; i++)
+		varname[i] = filename[i];
+
+	varname[i] = L'\0';
+
+	*name = varname;
+
+	return 0;
+}
+
+