bzimage: Account for extra room when decompressing kernel

Up until now we've been allocating the space for the kernel *after*
we've done all our other allocations, and it made the error paths
particularly cumbersome where we needed to free those
allocations. This is essentially a hack because of the extra space
required when the kernel decompresses itself. By placing all our other
allocations below the kernel they are not trashed during
decompression.

Linux kernels after v2.6.31 (with setup header version 2.10) include
'pref_address' and 'init_size' fields in their setup header. These
fields indicate where the kernel would prefer to be loaded in memory
and the size of the memory allocation required for the kernel,
including space for decompression. By using these fields we no longer
have to allocate space for the kernel after everything else. For
earlier kernel versions we can just make a conservative estimate of
the amount of space required.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>

2 files changed, 53 insertions, 53 deletions

diff --git a/loaders/bzimage/bzimage.c b/loaders/bzimage/bzimage.c
index af73e77..7f0c631 100644
--- a/loaders/bzimage/bzimage.c
+++ b/loaders/bzimage/bzimage.c
@@ -171,9 +171,11 @@ load_kernel(EFI_HANDLE image, CHAR16 *name, char *cmdline)
 {
 	UINTN map_size, _map_size, map_key;
 	EFI_PHYSICAL_ADDRESS kernel_start, addr;
+	EFI_PHYSICAL_ADDRESS pref_address;
 	struct boot_params *boot_params;
 	EFI_MEMORY_DESCRIPTOR *map_buf;
 	struct e820_entry *e820_map;
+	UINT64 setup_sz, init_size;
 	struct boot_params *buf;
 	struct efi_info *efi;
 	UINT32 desc_version;
@@ -181,7 +183,7 @@ load_kernel(EFI_HANDLE image, CHAR16 *name, char *cmdline)
 	struct file *file;
 	UINTN desc_size;
 	EFI_STATUS err;
-	UINTN size = 0;
+	UINT64 size;
 	int i, j = 0;
 
 	err = file_open(name, &file);
@@ -193,14 +195,14 @@ load_kernel(EFI_HANDLE image, CHAR16 *name, char *cmdline)
 		goto out;
 
 	size = 1;
-	err = file_read(file, &size, &nr_setup_secs);
+	err = file_read(file, (UINTN *)&size, &nr_setup_secs);
 	if (err != EFI_SUCCESS)
 		goto out;
 
 	nr_setup_secs++;	/* Add the boot sector */
-	size = nr_setup_secs * 512;
+	setup_sz = nr_setup_secs * 512;
 
-	buf = malloc(size);
+	buf = malloc(setup_sz);
 	if (!buf)
 		goto out;
 
@@ -208,10 +210,16 @@ load_kernel(EFI_HANDLE image, CHAR16 *name, char *cmdline)
 	if (err != EFI_SUCCESS)
 		goto out;
 
-	err = file_read(file, &size, buf);
+	err = file_read(file, (UINTN *)&setup_sz, buf);
+	if (err != EFI_SUCCESS)
+		goto out;
+
+	err = file_size(file, &size);
 	if (err != EFI_SUCCESS)
 		goto out;
 
+	size -= setup_sz;
+
 	/* Check boot sector signature */
 	if (buf->hdr.signature != 0xAA55) {
 		Print(L"bzImage kernel corrupt");
@@ -237,6 +245,20 @@ load_kernel(EFI_HANDLE image, CHAR16 *name, char *cmdline)
 		goto out;
 	}
 
+	if (buf->hdr.version >= 0x20a) {
+		pref_address = buf->hdr.pref_address;
+		init_size = buf->hdr.init_size;
+	} else {
+		pref_address = 0x100000;
+
+		/*
+		 * We need to account for the fact that the kernel
+		 * needs room for decompression, otherwise we could
+		 * end up trashing other chunks of allocated memory.
+		 */
+		init_size = size * 3;
+	}
+
 	/* Don't need an allocated ID, we're a prototype */
 	buf->hdr.loader_id = 0x1;
 
@@ -246,23 +268,28 @@ load_kernel(EFI_HANDLE image, CHAR16 *name, char *cmdline)
 
 	memset((char *)&buf->screen_info, 0x0, sizeof(buf->screen_info));
 
-	err = setup_graphics(buf);
-	if (err != EFI_SUCCESS)
-		goto out;
+	addr = pref_address;
+	err = allocate_pages(AllocateAddress, EfiLoaderData,
+			     EFI_SIZE_TO_PAGES(init_size), &addr);
+	if (err != EFI_SUCCESS) {
+		/*
+		 * We failed to allocate the preferred address, so
+		 * just allocate some memory and hope for the best.
+		 */
+		err = emalloc(init_size, buf->hdr.kernel_alignment, &addr);
+		if (err != EFI_SUCCESS)
+			goto out;
+	}
+
+	kernel_start = addr;
 
 	/*
-	 * Time to allocate our memory.
-	 *
-	 * Because the kernel needs to decompress itself we first
-	 * allocate boot_params, gdt and space for the memory map
-	 * under the assumption that they'll be allocated at lower
-	 * addresses than the kernel. If we dont't allocate these data
-	 * structures first there is the potential for them to be
-	 * trashed when the kernel is decompressed! Allocating them
-	 * underneath the kernel should be safe.
-	 *
-	 * Max kernel size is 8MB
+	 * Read the rest of the kernel image.
 	 */
+	err = file_read(file, (UINTN *)&size, (void *)(UINTN)kernel_start);
+	if (err != EFI_SUCCESS)
+		goto out;
+
 	err = emalloc(16384, 1, &addr);
 	if (err != EFI_SUCCESS)
 		goto out;
@@ -273,6 +300,11 @@ load_kernel(EFI_HANDLE image, CHAR16 *name, char *cmdline)
 
 	/* Copy first two sectors to boot_params */
 	memcpy((char *)boot_params, (char *)buf, 2 * 512);
+	boot_params->hdr.code32_start = (UINT32)((UINT64)kernel_start);
+
+	err = setup_graphics(buf);
+	if (err != EFI_SUCCESS)
+		goto out;
 
 	err = emalloc(gdt.limit, 8, (EFI_PHYSICAL_ADDRESS *)&gdt.base);
 	if (err != EFI_SUCCESS)
@@ -312,38 +344,6 @@ again:
 		goto out;
 
 	map_buf = (EFI_MEMORY_DESCRIPTOR *)(UINTN)addr;
-	size = 0x800000;
-	err = emalloc(size, buf->hdr.kernel_alignment, &kernel_start);
-	if (err != EFI_SUCCESS)
-		goto out;
-
-	/*
-	 * If the firmware doesn't sort the memory map by increasing
-	 * address it's possible that kernel_start may have been
-	 * allocated below boot_params or gdt.base.
-	 *
-	 * Print a warning and hope for the best.
-	 */
-	if (kernel_start < (UINTN)boot_params ||
-	    kernel_start < (UINTN)map_buf ||
-	    kernel_start < (UINTN)gdt.base)
-	    Print(L"Warning: kernel_start is too low.\n");
-
-	/*
-	 * Read the rest of the kernel image.
-	 */
-	err = file_read(file, &size, (void *)(UINTN)kernel_start);
-	if (err != EFI_SUCCESS)
-		goto out;
-
-	boot_params->hdr.code32_start = (UINT32)((UINT64)kernel_start);
-
-	/*
-	 * Remember! We've already allocated map_buf with emalloc (and
-	 * 'map_size' contains its size) which means that it should be
-	 * positioned below our allocation for the kernel. Use that
-	 * space for the memory map.
-	 */
 	err = get_memory_map(&map_size, map_buf, &map_key,
 			     &desc_size, &desc_version);
 	if (err != EFI_SUCCESS) {
@@ -355,9 +355,7 @@ again:
 			 * larger. 'map_size' has been updated by the
 			 * call to memory_map().
 			 */
-			efree(kernel_start, 0x800000);
 			efree((UINTN)map_buf, _map_size);
-			file_set_position(file, (UINT64)nr_setup_secs * 512);
 			goto again;
 		}
 		goto out;
diff --git a/loaders/bzimage/bzimage.h b/loaders/bzimage/bzimage.h
index 370d126..448fff1 100644
--- a/loaders/bzimage/bzimage.h
+++ b/loaders/bzimage/bzimage.h
@@ -80,6 +80,8 @@ struct setup_header {
 	UINT32 payload_offset;
 	UINT32 payload_length;
 	UINT64 setup_data;
+	UINT64 pref_address;
+	UINT32 init_size;
 } __attribute__((packed));
 
 struct efi_info {