target/linux/generic/patches-4.4/332-arc-add-OWRTDTB-section.patch

   1 From 690e7f2cad271595ff68cace1c45fb10779bde41 Mon Sep 17 00:00:00 2001
   2 From: Alexey Brodkin <abrodkin@synopsys.com>
   3 Date: Fri, 15 Jan 2016 00:34:01 +0300
   4 Subject: [PATCH 2/2] openwrt: arc - add OWRTDTB section
   5
   6 This change allows OpenWRT to patch resulting kernel binary with
   7 external .dtb.
   8
   9 That allows us to re-use exactky the same vmlinux on different boards
  10 given its ARC core configurations match (at least cache line sizes etc).
  11
  12 ""patch-dtb" searches for ASCII "OWRTDTB:" strign and copies external
  13 .dtb right after it, keeping the string in place.
  14
  15 Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
  16 ---
  17  arch/arc/kernel/head.S        | 10 ++++++++++
  18  arch/arc/kernel/setup.c       |  4 +++-
  19  arch/arc/kernel/vmlinux.lds.S | 13 +++++++++++++
  20  3 files changed, 26 insertions(+), 1 deletion(-)
  21
  22 diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
  23 index 689dd86..51154ae 100644
  24 --- a/arch/arc/kernel/head.S
  25 +++ b/arch/arc/kernel/head.S
  26 @@ -49,6 +49,16 @@
  27  1:
  28  .endm
  29
  30 +; Here "patch-dtb" will embed external .dtb
  31 +; Note "patch-dtb" searches for ASCII "OWRTDTB:" string
  32 +; and pastes .dtb right after it, hense the string precedes
  33 +; __image_dtb symbol.
  34 +       .section .owrt, "aw",@progbits
  35 +       .ascii  "OWRTDTB:"
  36 +ENTRY(__image_dtb)
  37 +       .fill   0x4000
  38 +END(__image_dtb)
  39 +
  40         .section .init.text, "ax",@progbits
  41
  42  ;----------------------------------------------------------------
  43 diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
  44 index e1b8744..9481c9d 100644
  45 --- a/arch/arc/kernel/setup.c
  46 +++ b/arch/arc/kernel/setup.c
  47 @@ -370,6 +370,8 @@ static inline int is_kernel(unsigned long addr)
  48         return 0;
  49  }
  50
  51 +extern struct boot_param_header __image_dtb;
  52 +
  53  void __init setup_arch(char **cmdline_p)
  54  {
  55  #ifdef CONFIG_ARC_UBOOT_SUPPORT
  56 @@ -383,7 +385,7 @@ void __init setup_arch(char **cmdline_p)
  57  #endif
  58         {
  59                 /* No, so try the embedded one */
  60 -               machine_desc = setup_machine_fdt(__dtb_start);
  61 +               machine_desc = setup_machine_fdt(&__image_dtb);
  62                 if (!machine_desc)
  63                         panic("Embedded DT invalid\n");
  64
  65 diff --git a/arch/arc/kernel/vmlinux.lds.S b/arch/arc/kernel/vmlinux.lds.S
  66 index 894e696..ecfc284 100644
  67 --- a/arch/arc/kernel/vmlinux.lds.S
  68 +++ b/arch/arc/kernel/vmlinux.lds.S
  69 @@ -30,6 +30,19 @@ SECTIONS
  70
  71         . = CONFIG_LINUX_LINK_BASE;
  72
  73 +       /*
  74 +        * In OpenWRT we want to patch built binary embedding .dtb of choice.
  75 +        * This is implemented with "patch-dtb" utility which searches for
  76 +        * "OWRTDTB:" string in first 16k of image and if it is found
  77 +        * copies .dtb right after mentioned string.
  78 +        *
  79 +        * Note: "OWRTDTB:" won't be overwritten with .dtb, .dtb will follow it.
  80 +        */
  81 +       .owrt : {
  82 +               *(.owrt)
  83 +               . = ALIGN(PAGE_SIZE);
  84 +       }
  85 +
  86         _int_vec_base_lds = .;
  87         .vector : {
  88                 *(.vector)
  89 --
  90 2.4.3
  91