From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Peter Jones <pjones@redhat.com>
Date: Wed, 12 Sep 2018 16:12:27 -0400
Subject: [PATCH] x86-efi: Allow initrd+params+cmdline allocations above 4GB.

This enables everything except the kernel itself to be above 4GB.
Putting the kernel up there still doesn't work, because of the way
params->code32_start is used.

Signed-off-by: Peter Jones <pjones@redhat.com>
(cherry picked from commit 2b636967018431b046b625ad4753c8de51f7f6b2)
---
 grub-core/loader/i386/efi/linux.c | 67 +++++++++++++++++++++++++++++++++++----
 include/grub/i386/linux.h         |  6 +++-
 2 files changed, 65 insertions(+), 8 deletions(-)

diff --git a/grub-core/loader/i386/efi/linux.c b/grub-core/loader/i386/efi/linux.c
index 5eed2014c..e9d2c85b3 100644
--- a/grub-core/loader/i386/efi/linux.c
+++ b/grub-core/loader/i386/efi/linux.c
@@ -54,13 +54,22 @@ struct allocation_choice {
     grub_efi_allocate_type_t alloc_type;
 };
 
-static struct allocation_choice max_addresses[] =
+static struct allocation_choice max_addresses[4] =
   {
+    /* the kernel overrides this one with pref_address and
+     * GRUB_EFI_ALLOCATE_ADDRESS */
     { GRUB_EFI_MAX_ALLOCATION_ADDRESS, GRUB_EFI_ALLOCATE_MAX_ADDRESS },
+    /* this one is always below 4GB, which we still *prefer* even if the flag
+     * is set. */
     { GRUB_EFI_MAX_ALLOCATION_ADDRESS, GRUB_EFI_ALLOCATE_MAX_ADDRESS },
+    /* If the flag in params is set, this one gets changed to be above 4GB. */
     { GRUB_EFI_MAX_ALLOCATION_ADDRESS, GRUB_EFI_ALLOCATE_MAX_ADDRESS },
     { 0, 0 }
   };
+static struct allocation_choice saved_addresses[4];
+
+#define save_addresses() grub_memcpy(saved_addresses, max_addresses, sizeof(max_addresses))
+#define restore_addresses() grub_memcpy(max_addresses, saved_addresses, sizeof(max_addresses))
 
 static inline void
 kernel_free(void *addr, grub_efi_uintn_t size)
@@ -82,6 +91,11 @@ kernel_alloc(grub_efi_uintn_t size, const char * const errmsg)
       grub_uint64_t max = max_addresses[i].addr;
       grub_efi_uintn_t pages;
 
+      /*
+       * When we're *not* loading the kernel, or >4GB allocations aren't
+       * supported, these entries are basically all the same, so don't re-try
+       * the same parameters.
+       */
       if (max == prev_max)
 	continue;
 
@@ -170,6 +184,9 @@ read(grub_file_t file, grub_uint8_t *bufp, grub_size_t len)
   return bufpos;
 }
 
+#define LOW_U32(val) ((grub_uint32_t)(((grub_addr_t)(val)) & 0xffffffffull))
+#define HIGH_U32(val) ((grub_uint32_t)(((grub_addr_t)(val) >> 32) & 0xffffffffull))
+
 static grub_err_t
 grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
                  int argc, char *argv[])
@@ -214,8 +231,12 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
     goto fail;
   grub_dprintf ("linux", "initrd_mem = %p\n", initrd_mem);
 
-  params->ramdisk_size = size;
-  params->ramdisk_image = initrd_mem;
+  params->ramdisk_size = LOW_U32(size);
+  params->ramdisk_image = LOW_U32(initrd_mem);
+#if defined(__x86_64__)
+  params->ext_ramdisk_size = HIGH_U32(size);
+  params->ext_ramdisk_image = HIGH_U32(initrd_mem);
+#endif
 
   ptr = initrd_mem;
 
@@ -353,6 +374,18 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
     }
 #endif
 
+#if defined(__x86_64__)
+  if (lh->xloadflags & LINUX_XLF_CAN_BE_LOADED_ABOVE_4G)
+    {
+      grub_dprintf ("linux", "Loading kernel above 4GB is supported; enabling.\n");
+      max_addresses[2].addr = GRUB_EFI_MAX_USABLE_ADDRESS;
+    }
+  else
+    {
+      grub_dprintf ("linux", "Loading kernel above 4GB is not supported\n");
+    }
+#endif
+
   params = kernel_alloc (sizeof(*params), "cannot allocate kernel parameters");
   if (!params)
     goto fail;
@@ -387,21 +420,40 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
 
   grub_dprintf ("linux", "cmdline:%s\n", linux_cmdline);
   grub_dprintf ("linux", "setting lh->cmd_line_ptr to 0x%08x\n",
-		linux_cmdline);
-  lh->cmd_line_ptr = linux_cmdline;
+		LOW_U32(linux_cmdline));
+  lh->cmd_line_ptr = LOW_U32(linux_cmdline);
+#if defined(__x86_64__)
+  if ((grub_efi_uintn_t)linux_cmdline > 0xffffffffull)
+    {
+      grub_dprintf ("linux", "setting params->ext_cmd_line_ptr to 0x%08x\n",
+		    HIGH_U32(linux_cmdline));
+      params->ext_cmd_line_ptr = HIGH_U32(linux_cmdline);
+    }
+#endif
 
   handover_offset = lh->handover_offset;
   grub_dprintf("linux", "handover_offset: 0x%08x\n", handover_offset);
 
   start = (lh->setup_sects + 1) * 512;
 
+  /*
+   * AFAICS >4GB for kernel *cannot* work because of params->code32_start being
+   * 32-bit and getting called unconditionally in head_64.S from either entry
+   * point.
+   *
+   * so nerf that out here...
+   */
+  save_addresses();
   grub_dprintf ("linux", "lh->pref_address: %p\n", (void *)(grub_addr_t)lh->pref_address);
   if (lh->pref_address < (grub_uint64_t)GRUB_EFI_MAX_ALLOCATION_ADDRESS)
     {
       max_addresses[0].addr = lh->pref_address;
       max_addresses[0].alloc_type = GRUB_EFI_ALLOCATE_ADDRESS;
     }
+  max_addresses[1].addr = GRUB_EFI_MAX_ALLOCATION_ADDRESS;
+  max_addresses[2].addr = GRUB_EFI_MAX_ALLOCATION_ADDRESS;
   kernel_mem = kernel_alloc (lh->init_size, N_("can't allocate kernel"));
+  restore_addresses();
   if (!kernel_mem)
     goto fail;
   grub_dprintf("linux", "kernel_mem = %p\n", kernel_mem);
@@ -410,8 +462,9 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
 
   loaded = 1;
 
-  grub_dprintf ("linux", "setting lh->code32_start to %p\n", kernel_mem);
-  lh->code32_start = (grub_uint32_t)(grub_addr_t) kernel_mem;
+  grub_dprintf ("linux", "setting lh->code32_start to 0x%08x\n",
+		LOW_U32(kernel_mem));
+  lh->code32_start = LOW_U32(kernel_mem);
 
   grub_memcpy (kernel_mem, (char *)kernel + start, filelen - start);
 
diff --git a/include/grub/i386/linux.h b/include/grub/i386/linux.h
index 8474a857e..a4b37dcce 100644
--- a/include/grub/i386/linux.h
+++ b/include/grub/i386/linux.h
@@ -230,7 +230,11 @@ struct linux_kernel_params
   grub_uint32_t ofw_cif_handler;	/* b8 */
   grub_uint32_t ofw_idt;		/* bc */
 
-  grub_uint8_t padding7[0x1b8 - 0xc0];
+  grub_uint32_t ext_ramdisk_image;	/* 0xc0 */
+  grub_uint32_t ext_ramdisk_size;	/* 0xc4 */
+  grub_uint32_t ext_cmd_line_ptr;	/* 0xc8 */
+
+  grub_uint8_t padding7[0x1b8 - 0xcc];
 
   union
     {
