From 4042e13fecde52ed782022d5864af32e0b852ff9 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@coreos.com>
Date: Wed, 14 Oct 2015 08:24:00 -0700
Subject: [PATCH] Add fwconfig command
Add a command to read values from the qemu fwcfg store. This allows data
to be passed from the qemu command line to grub.
Example use:
echo '(hd0,1)' >rootdev
qemu -fw_cfg opt/rootdev,file=rootdev
fwconfig opt/rootdev root
---
grub-core/Makefile.core.def | 6 ++
grub-core/commands/fwconfig.c | 121 ++++++++++++++++++++++++++++++++++
2 files changed, 127 insertions(+)
create mode 100644 grub-core/commands/fwconfig.c
diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index 4ec5684ca..3824f0fa2 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -2358,3 +2358,9 @@ module = {
common = loader/i386/xen_file64.c;
extra_dist = loader/i386/xen_fileXX.c;
};
+
+module = {
+ name = fwconfig;
+ common = commands/fwconfig.c;
+ enable = x86;
+};
diff --git a/grub-core/commands/fwconfig.c b/grub-core/commands/fwconfig.c
new file mode 100644
index 000000000..289d167fd
--- /dev/null
+++ b/grub-core/commands/fwconfig.c
@@ -0,0 +1,121 @@
+/* fwconfig.c - command to read config from qemu fwconfig */
+/*
+ * GRUB -- GRand Unified Bootloader
+ * Copyright (C) 2015 CoreOS, Inc.
+ *
+ * GRUB is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GRUB is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/dl.h>
+#include <grub/misc.h>
+#include <grub/extcmd.h>
+#include <grub/env.h>
+#include <grub/cpu/io.h>
+#include <grub/i18n.h>
+#include <grub/mm.h>
+
+GRUB_MOD_LICENSE ("GPLv3+");
+
+#define SELECTOR 0x510
+#define DATA 0x511
+
+#define SIGNATURE_INDEX 0x00
+#define DIRECTORY_INDEX 0x19
+
+static grub_extcmd_t cmd_read_fwconfig;
+
+struct grub_qemu_fwcfgfile {
+ grub_uint32_t size;
+ grub_uint16_t select;
+ grub_uint16_t reserved;
+ char name[56];
+};
+
+static const struct grub_arg_option options[] =
+ {
+ {0, 'v', 0, N_("Save read value into variable VARNAME."),
+ N_("VARNAME"), ARG_TYPE_STRING},
+ {0, 0, 0, 0, 0, 0}
+ };
+
+static grub_err_t
+grub_cmd_fwconfig (grub_extcmd_context_t ctxt, int argc, char **argv)
+{
+ grub_uint32_t i, j, value = 0;
+ struct grub_qemu_fwcfgfile file;
+ char fwsig[4], signature[4] = { 'Q', 'E', 'M', 'U' };
+
+ if (argc != 2)
+ return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("two arguments expected"));
+
+ /* Verify that we have meaningful hardware here */
+ grub_outw(SIGNATURE_INDEX, SELECTOR);
+ for (i=0; i<sizeof(fwsig); i++)
+ fwsig[i] = grub_inb(DATA);
+
+ if (grub_memcmp(fwsig, signature, sizeof(signature)) != 0)
+ return grub_error (GRUB_ERR_BAD_DEVICE, N_("invalid fwconfig hardware signature: got 0x%x%x%x%x"), fwsig[0], fwsig[1], fwsig[2], fwsig[3]);
+
+ /* Find out how many file entries we have */
+ grub_outw(DIRECTORY_INDEX, SELECTOR);
+ value = grub_inb(DATA) | grub_inb(DATA) << 8 | grub_inb(DATA) << 16 | grub_inb(DATA) << 24;
+ value = grub_be_to_cpu32(value);
+ /* Read the file description for each file */
+ for (i=0; i<value; i++)
+ {
+ for (j=0; j<sizeof(file); j++)
+ {
+ ((char *)&file)[j] = grub_inb(DATA);
+ }
+ /* Check whether it matches what we're looking for, and if so read the file */
+ if (grub_strncmp(file.name, argv[0], sizeof(file.name)) == 0)
+ {
+ grub_uint32_t filesize = grub_be_to_cpu32(file.size);
+ grub_uint16_t location = grub_be_to_cpu16(file.select);
+ char *data = grub_malloc(filesize+1);
+
+ if (!data)
+ return grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("can't allocate buffer for data"));
+
+ grub_outw(location, SELECTOR);
+ for (j=0; j<filesize; j++)
+ {
+ data[j] = grub_inb(DATA);
+ }
+
+ data[filesize] = '\0';
+
+ grub_env_set (argv[1], data);
+
+ grub_free(data);
+ return 0;
+ }
+ }
+
+ return grub_error (GRUB_ERR_FILE_NOT_FOUND, N_("couldn't find entry %s"), argv[0]);
+}
+
+GRUB_MOD_INIT(fwconfig)
+{
+ cmd_read_fwconfig =
+ grub_register_extcmd ("fwconfig", grub_cmd_fwconfig, 0,
+ N_("PATH VAR"),
+ N_("Set VAR to the contents of fwconfig PATH"),
+ options);
+}
+
+GRUB_MOD_FINI(fwconfig)
+{
+ grub_unregister_extcmd (cmd_read_fwconfig);
+}