initramfs: fix initramfs size calculation

The size of a built-in initramfs is calculated in init/initramfs.c by
"__initramfs_end - __initramfs_start".  Those symbols are defined in the
linker script include/asm-generic/vmlinux.lds.h:

#define INIT_RAM_FS                                                     \
        . = ALIGN(PAGE_SIZE);                                           \
        VMLINUX_SYMBOL(__initramfs_start) = .;                          \
        *(.init.ramfs)                                                  \
        VMLINUX_SYMBOL(__initramfs_end) = .;

If the initramfs file has an odd number of bytes, the "__initramfs_end"
symbol points to an odd address, for example, the symbols in the
System.map might look like:

    0000000000572000 T __initramfs_start
    00000000005bcd05 T __initramfs_end	  <-- odd address

At least on s390 this causes a problem:

Certain s390 instructions, especially instructions for loading addresses
(larl) or branch addresses must be on even addresses.  The compiler loads
the symbol addresses with the "larl" instruction.  This instruction sets
the last bit to 0 and, therefore, for odd size files, the calculated size
is one byte less than it should be:

    0000000000540a9c <populate_rootfs>:
      540a9c:     eb cf f0 78 00 24       stmg    %r12,%r15,120(%r15),
      540aa2:     c0 10 00 01 8a af       larl    %r1,572000 <__initramfs_start>
      540aa8:     c0 c0 00 03 e1 2e       larl    %r12,5bcd04 <initramfs_end>
                                                  (Instead of  5bcd05)
      ...
      540abe:     1b c1                   sr      %r12,%r1

To fix the problem, this patch introduces the global variable
__initramfs_size, which is calculated in the "usr/initramfs_data.S" file.
The populate_rootfs() function can then use the start marker of the
.init.ramfs section and the value of __initramfs_size for loading the
initramfs.  Because the start marker and size is sufficient, the
__initramfs_end symbol is no longer needed and is removed.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Michal Marek <mmarek@suse.cz>
Acked-by: "H. Peter Anvin" <hpa@zytor.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 030a954ed292a59feae0bbf8437f370127b22bd6..0c6387d6a6aef1e82826de20523e5947ff2f7c46 100644 (file)
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -633,7 +633,8 @@
        . = ALIGN(PAGE_SIZE);                                           \
        VMLINUX_SYMBOL(__initramfs_start) = .;                          \
        *(.init.ramfs)                                                  \
-       VMLINUX_SYMBOL(__initramfs_end) = .;
+       . = ALIGN(8);                                                   \
+       *(.init.ramfs.info)
 #else
 #define INIT_RAM_FS
 #endif

diff --git a/init/initramfs.c b/init/initramfs.c
index 4b9c20205092e1f7de716633c0d51bd8746e74af..371c3da64ad30381f6b9ea09d9c5e8469bd72dcc 100644 (file)
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -483,7 +483,8 @@ static int __init retain_initrd_param(char *str)
 }
 __setup("retain_initrd", retain_initrd_param);
 
-extern char __initramfs_start[], __initramfs_end[];
+extern char __initramfs_start[];
+extern unsigned long __initramfs_size;
 #include <linux/initrd.h>
 #include <linux/kexec.h>
 
@@ -570,8 +571,7 @@ static void __init clean_rootfs(void)
 
 static int __init populate_rootfs(void)
 {
-       char *err = unpack_to_rootfs(__initramfs_start,
-                        __initramfs_end - __initramfs_start);
+       char *err = unpack_to_rootfs(__initramfs_start, __initramfs_size);
        if (err)
                panic(err);     /* Failed to decompress INTERNAL initramfs */
        if (initrd_start) {
@@ -585,8 +585,7 @@ static int __init populate_rootfs(void)
                        return 0;
                } else {
                        clean_rootfs();
-                       unpack_to_rootfs(__initramfs_start,
-                                __initramfs_end - __initramfs_start);
+                       unpack_to_rootfs(__initramfs_start, __initramfs_size);
                }
                printk(KERN_INFO "rootfs image is not initramfs (%s)"
                                "; looks like an initrd\n", err);

diff --git a/usr/initramfs_data.S b/usr/initramfs_data.S
index 49a545fea12019616cd1476cd8fa7c4eb0e5e279..b9efed5e35cc222f3e7b34d922bbc1b90b29987b 100644 (file)
--- a/usr/initramfs_data.S
+++ b/usr/initramfs_data.S
@@ -11,11 +11,7 @@
   -T initramfs_data.scr initramfs_data.cpio.gz -o initramfs_data.o
    ld -m elf_i386  -r -o built-in.o initramfs_data.o
 
-  initramfs_data.scr looks like this:
-SECTIONS
-{
-       .init.ramfs : { *(.data) }
-}
+  For including the .init.ramfs sections, see include/asm-generic/vmlinux.lds.
 
   The above example is for i386 - the parameters vary from architectures.
   Eventually look up LDFLAGS_BLOB in an older version of the
@@ -28,4 +24,14 @@ SECTIONS
 #include <linux/stringify.h>
 
 .section .init.ramfs,"a"
+__irf_start:
 .incbin __stringify(INITRAMFS_IMAGE)
+__irf_end:
+.section .init.ramfs.info,"a"
+.globl __initramfs_size
+__initramfs_size:
+#ifdef CONFIG_32BIT
+       .long __irf_end - __irf_start
+#else
+       .quad __irf_end - __irf_start
+#endif