From 3cf4fdf8d17423dea4e5913ab14fb6305f3c2571 Mon Sep 17 00:00:00 2001
From: Michael Chang <[email protected]>
Date: Fri, 18 Feb 2022 21:43:38 +0800
Subject: [PATCH 4/5] Introduce prep_load_env command

This command will accept grub disk device and perform load_env for
environment block located at end of PReP partition which belongs to that
input disk device. All variables read from that environment block are
exported to grub as environment variables.

Please note there's no support for whitelist variables and also
--skip-sig option compared to ordinary load_env command.

v2:
To avoid disrupting the boot process with errors, it's important to log
any errors that may occur and always return GRUB_ERR_NONE.

v3:
Making the new module powerpc_ieee1275 specific.

Signed-off-by: Michael Chang <[email protected]>
---
 grub-core/Makefile.core.def       |   5 +
 grub-core/commands/prep_loadenv.c | 227 ++++++++++++++++++++++++++++++
 2 files changed, 232 insertions(+)
 create mode 100644 grub-core/commands/prep_loadenv.c

--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -2679,3 +2679,9 @@
   common = lib/libtasn1_wrap/tests/Test_strings.c;
   common = lib/libtasn1_wrap/wrap_tests.c;
 };
+
+module = {
+  name = prep_loadenv;
+  common = commands/prep_loadenv.c;
+  enable = powerpc_ieee1275;
+};
--- /dev/null
+++ b/grub-core/commands/prep_loadenv.c
@@ -0,0 +1,237 @@
+#include <grub/dl.h>
+#include <grub/mm.h>
+#include <grub/file.h>
+#include <grub/disk.h>
+#include <grub/misc.h>
+#include <grub/err.h>
+#include <grub/env.h>
+#include <grub/partition.h>
+#include <grub/lib/envblk.h>
+#include <grub/extcmd.h>
+#include <grub/i18n.h>
+#include <grub/gpt_partition.h>
+
+GRUB_MOD_LICENSE ("GPLv3+");
+
+static char *
+match_substr (regmatch_t *match, const char *str)
+{
+  if (match->rm_so != -1)
+    {
+      char *substr;
+      regoff_t sz = match->rm_eo - match->rm_so;
+
+      if (!sz)
+	return NULL;
+      substr = grub_malloc (1 + sz);
+      if (!substr)
+	{
+	  grub_print_error ();
+	  return NULL;
+	}
+      grub_memcpy (substr, str + match->rm_so, sz);
+      substr[sz] = '\0';
+      return substr;
+    }
+
+  return NULL;
+}
+
+static int
+is_prep_partition (grub_device_t dev)
+{
+  if (!dev->disk)
+    return 0;
+  if (!dev->disk->partition)
+    return 0;
+  if (grub_strcmp (dev->disk->partition->partmap->name, "msdos") == 0)
+    return (dev->disk->partition->msdostype == 0x41);
+
+  if (grub_strcmp (dev->disk->partition->partmap->name, "gpt") == 0)
+    {
+      struct grub_gpt_partentry gptdata;
+      grub_partition_t p = dev->disk->partition;
+      int ret = 0;
+      dev->disk->partition = dev->disk->partition->parent;
+
+      if (grub_disk_read (dev->disk, p->offset, p->index,
+			  sizeof (gptdata), &gptdata) == 0)
+	{
+	  const grub_guid_t template = {
+	    grub_cpu_to_le32_compile_time (0x9e1a2d38),
+	    grub_cpu_to_le16_compile_time (0xc612),
+	    grub_cpu_to_le16_compile_time (0x4316),
+	    { 0xaa, 0x26, 0x8b, 0x49, 0x52, 0x1e, 0x5a, 0x8b }
+	  };
+
+	  ret = grub_memcmp (&template, &gptdata.type,
+			     sizeof (template)) == 0;
+	}
+      dev->disk->partition = p;
+      return ret;
+    }
+
+  return 0;
+}
+
+static int
+part_hook (grub_disk_t disk, const grub_partition_t partition, void *data)
+{
+  char **ret = data;
+  char *partition_name, *devname;
+  grub_device_t dev;
+
+  partition_name = grub_partition_get_name (partition);
+  if (! partition_name)
+    return 2;
+
+  devname = grub_xasprintf ("%s,%s", disk->name, partition_name);
+  grub_free (partition_name);
+  if (!devname)
+    return 2;
+
+  dev = grub_device_open (devname);
+  if (!dev)
+    {
+      grub_free (devname);
+      return 2;
+    }
+  if (is_prep_partition (dev))
+    {
+      *ret = devname;
+      return 1;
+    }
+  grub_free (devname);
+  grub_device_close (dev);
+  return 0;
+}
+
+static int
+set_var (const char *name, const char *value,
+	 void *hook_data __attribute__ ((unused)))
+{
+  grub_env_set (name, value);
+  grub_env_export (name);
+  return 0;
+}
+
+static grub_err_t
+prep_read_envblk (const char *devname)
+{
+  char *buf = NULL;
+  grub_device_t dev = NULL;
+  grub_envblk_t envblk = NULL;
+
+  dev = grub_device_open (devname);
+  if (!dev)
+    return grub_errno;
+
+  if (!dev->disk || !dev->disk->partition)
+    {
+      grub_error (GRUB_ERR_BAD_DEVICE, "disk device required");
+      goto fail;
+    }
+
+  buf = grub_malloc (GRUB_ENVBLK_PREP_SIZE);
+  if (!buf)
+    goto fail;
+
+  if (grub_disk_read (dev->disk, dev->disk->partition->len - (GRUB_ENVBLK_PREP_SIZE >> GRUB_DISK_SECTOR_BITS), 0, GRUB_ENVBLK_PREP_SIZE, buf))
+    goto fail;
+
+  envblk = grub_envblk_open (buf, GRUB_ENVBLK_PREP_SIZE);
+  if (!envblk)
+    {
+      grub_error (GRUB_ERR_BAD_FILE_TYPE, "invalid environment block");
+      goto fail;
+    }
+  grub_envblk_iterate (envblk, NULL, set_var);
+
+ fail:
+  if (envblk)
+    grub_envblk_close (envblk);
+  else
+    grub_free (buf);
+  if (dev)
+    grub_device_close (dev);
+  return grub_errno;
+}
+
+static grub_err_t
+prep_partname (const char *devname, char **prep)
+{
+  grub_device_t dev = NULL;
+  grub_err_t err;
+  int ret;
+
+  dev = grub_device_open (devname);
+  if (!dev)
+    return grub_errno;
+
+  /* Only needed for disk device */
+  if (!dev->disk)
+    {
+      err = GRUB_ERR_NONE;
+      goto out;
+    }
+
+  ret = grub_partition_iterate (dev->disk, part_hook, prep);
+  if (ret == 1 && *prep)
+    {
+      err = GRUB_ERR_NONE;
+      goto out;
+    }
+  else if (ret == 0 && grub_errno == GRUB_ERR_NONE)
+    err = grub_error (GRUB_ERR_FILE_NOT_FOUND, "no prep partition");
+  else
+    err = grub_errno;
+
+ out:
+  grub_device_close (dev);
+  return err;
+}
+
+static grub_err_t
+grub_cmd_prep_loadenv (grub_command_t cmd __attribute__ ((unused)),
+		       int argc,
+		       char **argv)
+{
+  char *devname, *prep = NULL;
+  grub_err_t err;
+
+  if (argc < 1)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name required");
+
+  devname = grub_file_get_device_name(argv[0]);
+  if (!devname)
+    return grub_errno;
+
+  err = prep_partname (devname, &prep);
+  if (prep == NULL || err != GRUB_ERR_NONE)
+    goto out;
+
+  err = prep_read_envblk (prep);
+
+ out:
+  grub_free (devname);
+  grub_free (prep);
+  
+  if (err)
+    grub_print_error ();
+  return GRUB_ERR_NONE;
+}
+
+static grub_command_t cmd_prep_load;
+
+GRUB_MOD_INIT(prep_loadenv)
+{
+  cmd_prep_load =
+    grub_register_command("prep_load_env", grub_cmd_prep_loadenv,
+			  "DEVICE",
+			  N_("Load variables from environment block file."));
+}
+
+GRUB_MOD_FINI(prep_loadenv)
+{
+  grub_unregister_command (cmd_prep_load);
+}