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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Date: Mon, 2 Aug 2021 23:10:01 +1000
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Subject: [PATCH] arm64: Fix EFI loader kernel image allocation
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We are currently allocating just enough memory for the file size,
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which means that the kernel BSS is in limbo (and not even zeroed).
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We are also not honoring the alignment specified in the image
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PE header.
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This makes us use the PE optional header in which the kernel puts the
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actual size it needs, including BSS, and make sure we clear it, and
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honors the specified alignment for the image.
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Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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[pjones: arm: check for the PE magic for the compiled arch]
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Signed-off-by: Peter Jones <pjones@redhat.com>
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Signed-off-by: Robbie Harwood <rharwood@redhat.com>
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---
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 grub-core/loader/arm64/linux.c | 100 +++++++++++++++++++++++++++--------------
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 include/grub/arm/linux.h       |   1 +
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 include/grub/arm64/linux.h     |   1 +
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 3 files changed, 68 insertions(+), 34 deletions(-)
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diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c
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index 47f8cf0d84..f18d90bd74 100644
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--- a/grub-core/loader/arm64/linux.c
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+++ b/grub-core/loader/arm64/linux.c
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@@ -41,6 +41,8 @@ GRUB_MOD_LICENSE ("GPLv3+");
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 static grub_dl_t my_mod;
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 static int loaded;
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+static void *kernel_alloc_addr;
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+static grub_uint32_t kernel_alloc_pages;
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 static void *kernel_addr;
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 static grub_uint64_t kernel_size;
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 static grub_uint32_t handover_offset;
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@@ -204,9 +206,8 @@ grub_linux_unload (void)
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 			 GRUB_EFI_BYTES_TO_PAGES (initrd_end - initrd_start));
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   initrd_start = initrd_end = 0;
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   grub_free (linux_args);
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-  if (kernel_addr)
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-    grub_efi_free_pages ((grub_addr_t) kernel_addr,
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-			 GRUB_EFI_BYTES_TO_PAGES (kernel_size));
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+  if (kernel_alloc_addr)
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+    grub_efi_free_pages ((grub_addr_t) kernel_alloc_addr, kernel_alloc_pages);
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   grub_fdt_unload ();
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   return GRUB_ERR_NONE;
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 }
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@@ -311,14 +312,35 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
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   return grub_errno;
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 }
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+static grub_err_t
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+parse_pe_header (void *kernel, grub_uint64_t *total_size,
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+		 grub_uint32_t *entry_offset,
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+		 grub_uint32_t *alignment)
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+{
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+  struct linux_arch_kernel_header *lh = kernel;
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+  struct grub_armxx_linux_pe_header *pe;
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+
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+  pe = (void *)((unsigned long)kernel + lh->hdr_offset);
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+
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+  if (pe->opt.magic != GRUB_PE32_PEXX_MAGIC)
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+    return grub_error(GRUB_ERR_BAD_OS, "Invalid PE optional header magic");
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+
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+  *total_size   = pe->opt.image_size;
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+  *entry_offset = pe->opt.entry_addr;
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+  *alignment    = pe->opt.section_alignment;
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+
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+  return GRUB_ERR_NONE;
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+}
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+
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 static grub_err_t
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 grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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 		int argc, char *argv[])
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 {
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   grub_file_t file = 0;
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-  struct linux_arch_kernel_header lh;
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-  struct grub_armxx_linux_pe_header *pe;
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   grub_err_t err;
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+  grub_off_t filelen;
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+  grub_uint32_t align;
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+  void *kernel = NULL;
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   int rc;
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   grub_dl_ref (my_mod);
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@@ -333,40 +355,24 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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   if (!file)
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     goto fail;
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-  kernel_size = grub_file_size (file);
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-
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-  if (grub_file_read (file, &lh, sizeof (lh)) < (long) sizeof (lh))
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-    return grub_errno;
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-
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-  if (grub_arch_efi_linux_check_image (&lh) != GRUB_ERR_NONE)
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-    goto fail;
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-
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-  grub_loader_unset();
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-
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-  grub_dprintf ("linux", "kernel file size: %lld\n", (long long) kernel_size);
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-  kernel_addr = grub_efi_allocate_any_pages (GRUB_EFI_BYTES_TO_PAGES (kernel_size));
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-  grub_dprintf ("linux", "kernel numpages: %lld\n",
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-		(long long) GRUB_EFI_BYTES_TO_PAGES (kernel_size));
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-  if (!kernel_addr)
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+  filelen = grub_file_size (file);
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+  kernel = grub_malloc(filelen);
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+  if (!kernel)
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     {
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-      grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
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+      grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("cannot allocate kernel load buffer"));
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       goto fail;
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     }
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-  grub_file_seek (file, 0);
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-  if (grub_file_read (file, kernel_addr, kernel_size)
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-      < (grub_int64_t) kernel_size)
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+  if (grub_file_read (file, kernel, filelen) < (grub_ssize_t)filelen)
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     {
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-      if (!grub_errno)
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-	grub_error (GRUB_ERR_BAD_OS, N_("premature end of file %s"), argv[0]);
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+      grub_error (GRUB_ERR_FILE_READ_ERROR, N_("Can't read kernel %s"),
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+		  argv[0]);
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       goto fail;
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     }
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-  grub_dprintf ("linux", "kernel @ %p\n", kernel_addr);
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-
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   if (grub_efi_get_secureboot () == GRUB_EFI_SECUREBOOT_MODE_ENABLED)
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     {
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-      rc = grub_linuxefi_secure_validate (kernel_addr, kernel_size);
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+      rc = grub_linuxefi_secure_validate (kernel, filelen);
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       if (rc <= 0)
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 	{
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 	  grub_error (GRUB_ERR_INVALID_COMMAND,
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@@ -375,8 +381,32 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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 	}
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     }
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-  pe = (void *)((unsigned long)kernel_addr + lh.hdr_offset);
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-  handover_offset = pe->opt.entry_addr;
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+  if (grub_arch_efi_linux_check_image (kernel) != GRUB_ERR_NONE)
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+    goto fail;
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+  if (parse_pe_header (kernel, &kernel_size, &handover_offset, &align) != GRUB_ERR_NONE)
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+    goto fail;
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+  grub_dprintf ("linux", "kernel mem size     : %lld\n", (long long) kernel_size);
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+  grub_dprintf ("linux", "kernel entry offset : %d\n", handover_offset);
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+  grub_dprintf ("linux", "kernel alignment    : 0x%x\n", align);
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+
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+  grub_loader_unset();
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+
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+  kernel_alloc_pages = GRUB_EFI_BYTES_TO_PAGES (kernel_size + align - 1);
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+  kernel_alloc_addr = grub_efi_allocate_any_pages (kernel_alloc_pages);
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+  grub_dprintf ("linux", "kernel numpages: %d\n", kernel_alloc_pages);
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+  if (!kernel_alloc_addr)
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+    {
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+      grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
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+      goto fail;
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+    }
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+  kernel_addr = (void *)ALIGN_UP((grub_uint64_t)kernel_alloc_addr, align);
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+
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+  grub_dprintf ("linux", "kernel @ %p\n", kernel_addr);
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+  grub_memcpy (kernel_addr, kernel, grub_min(filelen, kernel_size));
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+  if (kernel_size > filelen)
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+    grub_memset ((char *)kernel_addr + filelen, 0, kernel_size - filelen);
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+  grub_free(kernel);
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+  kernel = NULL;
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   cmdline_size = grub_loader_cmdline_size (argc, argv) + sizeof (LINUX_IMAGE);
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   linux_args = grub_malloc (cmdline_size);
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@@ -400,6 +430,9 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
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     }
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 fail:
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+  if (kernel)
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+    grub_free (kernel);
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+
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   if (file)
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     grub_file_close (file);
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@@ -412,9 +445,8 @@ fail:
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   if (linux_args && !loaded)
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     grub_free (linux_args);
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-  if (kernel_addr && !loaded)
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-    grub_efi_free_pages ((grub_addr_t) kernel_addr,
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-			 GRUB_EFI_BYTES_TO_PAGES (kernel_size));
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+  if (kernel_alloc_addr && !loaded)
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+    grub_efi_free_pages ((grub_addr_t) kernel_alloc_addr, kernel_alloc_pages);
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   return grub_errno;
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 }
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diff --git a/include/grub/arm/linux.h b/include/grub/arm/linux.h
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index b582f67f66..966a5074f5 100644
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--- a/include/grub/arm/linux.h
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+++ b/include/grub/arm/linux.h
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@@ -44,6 +44,7 @@ struct grub_arm_linux_pe_header
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 #if defined(__arm__)
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 # define GRUB_LINUX_ARMXX_MAGIC_SIGNATURE GRUB_LINUX_ARM_MAGIC_SIGNATURE
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+# define GRUB_PE32_PEXX_MAGIC GRUB_PE32_PE32_MAGIC
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 # define linux_arch_kernel_header linux_arm_kernel_header
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 # define grub_armxx_linux_pe_header grub_arm_linux_pe_header
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 #endif
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diff --git a/include/grub/arm64/linux.h b/include/grub/arm64/linux.h
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index ea030312df..422bf2bf24 100644
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--- a/include/grub/arm64/linux.h
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+++ b/include/grub/arm64/linux.h
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@@ -48,6 +48,7 @@ struct grub_arm64_linux_pe_header
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 #if defined(__aarch64__)
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 # define GRUB_LINUX_ARMXX_MAGIC_SIGNATURE GRUB_LINUX_ARM64_MAGIC_SIGNATURE
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+# define GRUB_PE32_PEXX_MAGIC GRUB_PE32_PE64_MAGIC
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 # define linux_arch_kernel_header linux_arm64_kernel_header
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 # define grub_armxx_linux_pe_header grub_arm64_linux_pe_header
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 #endif