multiboot2: Switch to using SLRT interface

The code makes sure that MBI entry goes first in DRTM, so the payload can measure it first on launch. SLRT table is allocated on the heap first, size for it is reserved inside TXT heap by TXT code and data is later copied into its final place. Signed-off-by: Sergii Dmytruk <[email protected]>
TrenchBoot · Dec 4, 2023 · b293777 · b293777
1 parent ba8dbc9
commit b293777
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Showing 6 changed files with 111 additions and 20 deletions.
diff --git a/grub-core/loader/i386/txt/txt.c b/grub-core/loader/i386/txt/txt.c
@@ -586,6 +586,20 @@ init_txt_heap (struct grub_slaunch_params *slparams, struct grub_txt_acm_header
   size = (grub_uint64_t *) ((grub_addr_t) os_mle_data - sizeof (grub_uint64_t));
   *size = sizeof (*os_mle_data) + sizeof (grub_uint64_t);
 
+  if (slparams->slr_table_base == GRUB_SLAUNCH_STORE_IN_OS2MLE)
+    {
+      /* SLRT needs to be at least 4-byte aligned per specification. */
+      slparams->slr_table_base =
+          ALIGN_UP ((grub_addr_t) os_mle_data + sizeof (*os_mle_data), 4);
+
+      /* Recompute size including SLRT table in it. */
+      *size = (slparams->slr_table_base + slparams->slr_table_size)
+            - ((grub_addr_t) os_mle_data - sizeof (grub_uint64_t));
+
+      /* Size of heap sections should be a multiple of 8. */
+      *size = ALIGN_UP (*size, 8);
+    }
+
   grub_memset (os_mle_data, 0, sizeof (*os_mle_data));
 
   os_mle_data->version = GRUB_SL_OS_MLE_STRUCT_VERSION;

diff --git a/grub-core/loader/multiboot.c b/grub-core/loader/multiboot.c
@@ -165,22 +165,11 @@ efi_boot (struct grub_relocator *rel __attribute__ ((unused)),
 static void
 normal_boot (struct grub_relocator *rel, struct grub_relocator32_state state)
 {
-  grub_err_t err;
   struct grub_slaunch_params *slparams = grub_slaunch_params();
   state.edi = grub_slaunch_platform_type ();
 
   if (state.edi == SLP_INTEL_TXT)
     {
-      err = grub_txt_boot_prepare (slparams);
-
-      if (err != GRUB_ERR_NONE)
-	{
-	  grub_printf ("TXT boot preparation failed");
-	  return;
-	}
-
-      grub_slaunch_finish_slr_table ();
-
       /* Configure relocator GETSEC[SENTER] call. */
       state.eax = GRUB_SMX_LEAF_SENTER;
       state.ebx = slparams->dce_base;
@@ -216,6 +205,16 @@ grub_multiboot_boot (void)
   if (err)
     return err;
 
+#ifdef GRUB_USE_MULTIBOOT2
+  if (grub_slaunch_platform_type () == SLP_INTEL_TXT)
+    {
+      err = grub_multiboot2_prepare_slaunch_txt (state.MULTIBOOT_MBI_REGISTER,
+                                                 mbi_size);
+      if (err)
+        return err;
+    }
+#endif
+
   if (grub_efi_is_finished)
     normal_boot (GRUB_MULTIBOOT (relocator), state);
   else

diff --git a/grub-core/loader/multiboot_mbi2.c b/grub-core/loader/multiboot_mbi2.c
@@ -39,6 +39,7 @@
 #include <grub/i386/memory.h>
 #include <grub/i386/slaunch.h>
 #include <grub/i386/txt.h>
+#include <grub/slr_table.h>
 
 #if defined (GRUB_MACHINE_EFI)
 #include <grub/efi/efi.h>
@@ -1167,3 +1168,62 @@ grub_multiboot2_set_bootdev (void)
 
   bootdev_set = 1;
 }
+
+static void
+add_multiboot2_slrt_policy_entries (void)
+{
+  unsigned i;
+  struct module *cur;
+
+  for (i = 0, cur = modules; i < modcnt; i++, cur = cur->next)
+    {
+      grub_slaunch_add_slrt_policy_entry (17,
+                                          GRUB_SLR_ET_MULTIBOOT_MODULE,
+                                          /*flags=*/0,
+                                          cur->start,
+                                          cur->size,
+                                          "Measured MB2 module");
+    }
+}
+
+grub_err_t
+grub_multiboot2_prepare_slaunch_txt (grub_uint32_t mbi_target,
+                                     grub_uint32_t mbi_size)
+{
+  grub_err_t err;
+  struct grub_slaunch_params *slparams = grub_slaunch_params ();
+
+  slparams->slr_table_base = GRUB_SLAUNCH_STORE_IN_OS2MLE;
+  slparams->slr_table_size = GRUB_PAGE_SIZE;
+
+  slparams->slr_table_mem = grub_zalloc (slparams->slr_table_size);
+  if (slparams->slr_table_mem == NULL)
+    return GRUB_ERR_OUT_OF_MEMORY;
+
+  err = grub_txt_boot_prepare (slparams);
+  if (err != GRUB_ERR_NONE)
+    {
+      grub_printf ("TXT boot preparation failed");
+      return err;
+    }
+
+  grub_slaunch_add_slrt_policy_entry (18,
+                                      GRUB_SLR_ET_MULTIBOOT_INFO,
+                                      /*flags=*/0,
+                                      mbi_target,
+                                      mbi_size,
+                                      "Measured MB2 information");
+  grub_slaunch_add_slrt_policy_entries ();
+  grub_txt_add_slrt_policy_entries ();
+  add_multiboot2_slrt_policy_entries ();
+  grub_slaunch_finish_slr_table ();
+
+  grub_dprintf ("multiboot_loader", "slr_table_base = %lx, slr_table_size = %x\n",
+                (unsigned long) slparams->slr_table_base,
+                (unsigned) slparams->slr_table_size);
+  grub_memcpy ((void *)(grub_addr_t) slparams->slr_table_base,
+               slparams->slr_table_mem,
+               slparams->slr_table_size);
+
+  return GRUB_ERR_NONE;
+}
diff --git a/include/grub/i386/slaunch.h b/include/grub/i386/slaunch.h
@@ -27,6 +27,19 @@
 
 #define GRUB_SLAUNCH_TPM_EVT_LOG_SIZE	(8 * GRUB_PAGE_SIZE)
 
+/*
+ * Special value for slr_table_base of struct grub_slaunch_params that indicates
+ * that the table should be stored near OS2MLE data (right after it).
+ *
+ * In this case:
+ *  1. Platform-specific code (e.g., TXT-code) is responsible for setting
+ *     slr_table_base to its final value
+ *  2. SLRT should be copied from slr_table_mem to slr_table_base after invoking
+ *     grub_slaunch_finish_slr_table () by the code which used this special
+ *     value.
+ */
+#define GRUB_SLAUNCH_STORE_IN_OS2MLE    ((grub_uint64_t) 0xFFFFFFFFFFFFFFFF)
+
 #ifndef ASM_FILE
 
 #include <grub/i386/linux.h>
@@ -36,6 +49,7 @@ struct grub_slaunch_params
 {
   grub_uint32_t boot_params_addr;
   grub_uint64_t slr_table_base;
+  /* This is size of SLRT buffer, so maximum size of the table. */
   grub_uint32_t slr_table_size;
   void *slr_table_mem;
   grub_uint32_t mle_start;

diff --git a/include/grub/multiboot2.h b/include/grub/multiboot2.h
@@ -43,6 +43,8 @@ void grub_multiboot2_set_bootdev (void);
 void
 grub_multiboot2_add_elfsyms (grub_size_t num, grub_size_t entsize,
 			    unsigned shndx, void *data);
+grub_err_t grub_multiboot2_prepare_slaunch_txt (grub_uint32_t mbi_target,
+                                                grub_uint32_t mbi_size);
 
 grub_uint32_t grub_multiboot2_get_mmap_count (void);
 grub_err_t grub_multiboot2_set_video_mode (void);

diff --git a/include/grub/slr_table.h b/include/grub/slr_table.h
@@ -65,15 +65,17 @@
 #define GRUB_SLR_ENTRY_END		0xffff
 
 /* Entity Types */
-#define GRUB_SLR_ET_UNSPECIFIED		0x0000
-#define GRUB_SLR_ET_SLRT		0x0001
-#define GRUB_SLR_ET_BOOT_PARAMS		0x0002
-#define GRUB_SLR_ET_SETUP_DATA		0x0003
-#define GRUB_SLR_ET_CMDLINE		0x0004
-#define GRUB_SLR_ET_UEFI_MEMMAP		0x0005
-#define GRUB_SLR_ET_RAMDISK		0x0006
-#define GRUB_SLR_ET_TXT_OS2MLE		0x0010
-#define GRUB_SLR_ET_UNUSED		0xffff
+#define GRUB_SLR_ET_UNSPECIFIED			0x0000
+#define GRUB_SLR_ET_SLRT			0x0001
+#define GRUB_SLR_ET_BOOT_PARAMS			0x0002
+#define GRUB_SLR_ET_SETUP_DATA			0x0003
+#define GRUB_SLR_ET_CMDLINE			0x0004
+#define GRUB_SLR_ET_UEFI_MEMMAP			0x0005
+#define GRUB_SLR_ET_RAMDISK			0x0006
+#define GRUB_SLR_ET_MULTIBOOT_INFO		0x0007
+#define GRUB_SLR_ET_MULTIBOOT_MODULE		0x0008
+#define GRUB_SLR_ET_TXT_OS2MLE			0x0010
+#define GRUB_SLR_ET_UNUSED			0xffff
 
 /*
  * Primary SLR Table Header