From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Peter Jones <pjones@redhat.com>
Date: Fri, 12 Jul 2019 09:53:32 +0200
Subject: [PATCH] x86-efi: Use bounce buffers for reading to addresses > 4GB

Lots of machines apparently can't DMA correctly above 4GB during UEFI,
so use bounce buffers for the initramfs read.

Signed-off-by: Peter Jones <pjones@redhat.com>
---
 grub-core/loader/i386/efi/linux.c | 52 +++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 7 deletions(-)

diff --git a/grub-core/loader/i386/efi/linux.c b/grub-core/loader/i386/efi/linux.c
index 33e981e76e7..2f0336809e7 100644
--- a/grub-core/loader/i386/efi/linux.c
+++ b/grub-core/loader/i386/efi/linux.c
@@ -35,11 +35,16 @@ static grub_dl_t my_mod;
 static int loaded;
 static void *kernel_mem;
 static grub_uint64_t kernel_size;
-static grub_uint8_t *initrd_mem;
+static void *initrd_mem;
 static grub_uint32_t handover_offset;
 struct linux_kernel_params *params;
 static char *linux_cmdline;
 
+#define MIN(a, b) \
+  ({ typeof (a) _a = (a); \
+     typeof (b) _b = (b); \
+     _a < _b ? _a : _b; })
+
 #define BYTES_TO_PAGES(bytes)   (((bytes) + 0xfff) >> 12)
 
 static grub_err_t
@@ -73,6 +78,44 @@ grub_linuxefi_unload (void)
   return GRUB_ERR_NONE;
 }
 
+#define BOUNCE_BUFFER_MAX 0x10000000ull
+
+static grub_ssize_t
+read(grub_file_t file, grub_uint8_t *bufp, grub_size_t len)
+{
+  grub_ssize_t bufpos = 0;
+  static grub_size_t bbufsz = 0;
+  static char *bbuf = NULL;
+
+  if (bbufsz == 0)
+    bbufsz = MIN(BOUNCE_BUFFER_MAX, len);
+
+  while (!bbuf && bbufsz)
+    {
+      bbuf = grub_malloc(bbufsz);
+      if (!bbuf)
+	bbufsz >>= 1;
+    }
+  if (!bbuf)
+    grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("cannot allocate bounce buffer"));
+
+  while (bufpos < (long long)len)
+    {
+      grub_ssize_t sz;
+
+      sz = grub_file_read (file, bbuf, MIN(bbufsz, len - bufpos));
+      if (sz < 0)
+	return sz;
+      if (sz == 0)
+	break;
+
+      grub_memcpy(bufp + bufpos, bbuf, sz);
+      bufpos += sz;
+    }
+
+  return bufpos;
+}
+
 static grub_err_t
 grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
                  int argc, char *argv[])
@@ -126,7 +169,7 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
   for (i = 0; i < nfiles; i++)
     {
       grub_ssize_t cursize = grub_file_size (files[i]);
-      if (grub_file_read (files[i], ptr, cursize) != cursize)
+      if (read (files[i], ptr, cursize) != cursize)
         {
           if (!grub_errno)
             grub_error (GRUB_ERR_FILE_READ_ERROR, N_("premature end of file %s"),
@@ -152,11 +195,6 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
   return grub_errno;
 }
 
-#define MIN(a, b) \
-  ({ typeof (a) _a = (a);  \
-     typeof (b) _b = (b); \
-     _a < _b ? _a : _b; })
-
 static grub_err_t
 grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
 		int argc, char *argv[])
