[PATCH v6 2/2] efi: Free malloc regions on exit

[Alexander Graf]

When we exit grub, we don't free all the memory that we allocated earlier
for our heap region. This can cause problems with setups where you try
to descend the boot order using "exit" entries, such as PXE -> HD boot
scenarios.

Signed-off-by: Alexander Graf <address@hidden>

---

v2 -> v3:

  - add comment explaining the number of regions
  - move nr of regions into a define
  - add warning if we exceed the number of freeable regions
  - reset region counter to 0 on fini

v3 -> v4:

  - use dynamic list instead of static array at runtime
  - use allocate_pool for list, so we are not bound by heap or random numbers
  - remember all allocations, not just the heap

v4 -> v5:

  - free dynamic list entries on allocation removal

v5 -> v6:

  - move next ptr to last field
  - s/start_addr/address/
  - s/grub_efi_unremember_pages()/grub_efi_drop_alloc()/
  - s/grub_efi_remember_pages()/grub_efi_store_alloc()/
  - move grub_efi_drop_alloc after grub_efi_store_alloc
  - s/grub2/GRUB/
  - Make grub_efi_memory_fini comment more verbose
  - Drop useless efi_allocated_memory = NULL; line
---
 grub-core/kern/efi/init.c |  1 +
 grub-core/kern/efi/mm.c   | 90 +++++++++++++++++++++++++++++++++++++++++++++++
 include/grub/efi/efi.h    |  1 +
 3 files changed, 92 insertions(+)

diff --git a/grub-core/kern/efi/init.c b/grub-core/kern/efi/init.c
index 2c31847bf..3dfdf2d22 100644
--- a/grub-core/kern/efi/init.c
+++ b/grub-core/kern/efi/init.c
@@ -80,4 +80,5 @@ grub_efi_fini (void)
 {
   grub_efidisk_fini ();
   grub_console_fini ();
+  grub_efi_memory_fini ();
 }
diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
index ac2a4c556..92579a3b4 100644
--- a/grub-core/kern/efi/mm.c
+++ b/grub-core/kern/efi/mm.c
@@ -49,6 +49,80 @@ static grub_efi_uintn_t finish_desc_size;
 static grub_efi_uint32_t finish_desc_version;
 int grub_efi_is_finished = 0;
 
+/*
+ * We need to roll back EFI allocations on exit. Remember allocations that
+ * we'll free on exit.
+ */
+struct efi_allocation;
+struct efi_allocation {
+       grub_efi_physical_address_t address;
+       grub_efi_uint64_t pages;
+       struct efi_allocation *next;
+};
+static struct efi_allocation *efi_allocated_memory;
+
+static void
+grub_efi_store_alloc (grub_efi_physical_address_t address,
+                         grub_efi_uintn_t pages)
+{
+  grub_efi_boot_services_t *b;
+  struct efi_allocation *alloc;
+  grub_efi_status_t status;
+
+  b = grub_efi_system_table->boot_services;
+  status = efi_call_3 (b->allocate_pool, GRUB_EFI_LOADER_DATA,
+                           sizeof(*alloc), (void**)&alloc);
+  if (status == GRUB_EFI_SUCCESS)
+    {
+      alloc->next = efi_allocated_memory;
+      alloc->address = address;
+      alloc->pages = pages;
+      efi_allocated_memory = alloc;
+    }
+  else
+      grub_printf ("Could not malloc memory to remember EFI allocation. "
+                   "Exiting GRUB won't free all memory.\n");
+}
+
+static void
+grub_efi_drop_alloc (grub_efi_physical_address_t address,
+                           grub_efi_uintn_t pages)
+{
+  struct efi_allocation **allocp;
+  grub_efi_boot_services_t *b;
+
+  b = grub_efi_system_table->boot_services;
+
+  for (allocp = &efi_allocated_memory; *allocp;)
+    {
+      struct efi_allocation *alloc;
+      struct efi_allocation *next;
+
+      alloc = *allocp;
+
+      if (alloc->address != address ||
+          alloc->pages != pages)
+        {
+          /* Move on to the next entry */
+          allocp = &alloc->next;
+
+          continue;
+        }
+
+      /* Remember the next entry */
+      next = alloc->next;
+
+      /* Free the current list entry */
+      efi_call_1 (b->free_pool, alloc);
+
+      /* Remove from list */
+      *allocp = next;
+
+      /* Done */
+      break;
+    }
+}
+
 /* Allocate pages. Return the pointer to the first of allocated pages.  */
 void *
 grub_efi_allocate_pages_real (grub_efi_physical_address_t address,
@@ -79,6 +153,7 @@ grub_efi_allocate_pages_real (grub_efi_physical_address_t 
address,
        return 0;
     }
 
+  grub_efi_store_alloc (address, pages);
   return (void *) ((grub_addr_t) address);
 }
 
@@ -108,6 +183,7 @@ grub_efi_free_pages (grub_efi_physical_address_t address,
 
   b = grub_efi_system_table->boot_services;
   efi_call_2 (b->free_pages, address, pages);
+  grub_efi_drop_alloc (address, pages);
 }
 
 #if defined (__i386__) || defined (__x86_64__)
@@ -422,6 +498,20 @@ add_memory_regions (grub_efi_memory_descriptor_t 
*memory_map,
     grub_fatal ("too little memory");
 }
 
+void
+grub_efi_memory_fini (void)
+{
+  /*
+   * Free all stale allocations. grub_efi_free_pages() will remove
+   * the found entry from the list and it will always find the first
+   * list entry (efi_allocated_memory is the list start). Hence we
+   * remove all entries from the list until none is left altogether.
+   */
+  while (efi_allocated_memory)
+      grub_efi_free_pages (efi_allocated_memory->address,
+                           efi_allocated_memory->pages);
+}
+
 #if 0
 /* Print the memory map.  */
 static void
diff --git a/include/grub/efi/efi.h b/include/grub/efi/efi.h
index 3fa082816..c996913e5 100644
--- a/include/grub/efi/efi.h
+++ b/include/grub/efi/efi.h
@@ -55,6 +55,7 @@ EXPORT_FUNC(grub_efi_get_memory_map) (grub_efi_uintn_t 
*memory_map_size,
                                      grub_efi_uintn_t *map_key,
                                      grub_efi_uintn_t *descriptor_size,
                                      grub_efi_uint32_t *descriptor_version);
+void grub_efi_memory_fini (void);
 grub_efi_loaded_image_t *EXPORT_FUNC(grub_efi_get_loaded_image) 
(grub_efi_handle_t image_handle);
 void EXPORT_FUNC(grub_efi_print_device_path) (grub_efi_device_path_t *dp);
 char *EXPORT_FUNC(grub_efi_get_filename) (grub_efi_device_path_t *dp);
-- 
2.12.3