target/linux/generic/pending-4.19/332-arc-add-OWRTDTB-section.patch

   1 From 34ef04f3845ed2b47d57dd9d3b795b16e1f8185a Mon Sep 17 00:00:00 2001
   2 From: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
   3 Date: Fri, 15 Mar 2019 18:53:38 +0300
   4 Subject: [PATCH] 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: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
  16 Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
  17 Signed-off-by: Evgeniy Didin <Evgeniy.Didin@synopsys.com>
  18 ---
  19  arch/arc/kernel/head.S        | 10 ++++++++++
  20  arch/arc/kernel/setup.c       |  4 +++-
  21  arch/arc/kernel/vmlinux.lds.S | 13 +++++++++++++
  22  3 files changed, 26 insertions(+), 1 deletion(-)
  23
  24 --- a/arch/arc/kernel/head.S
  25 +++ b/arch/arc/kernel/head.S
  26 @@ -59,6 +59,16 @@
  27  #endif
  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 --- a/arch/arc/kernel/setup.c
  44 +++ b/arch/arc/kernel/setup.c
  45 @@ -528,7 +528,7 @@ ignore_uboot_args:
  46  #endif
  47
  48         if (use_embedded_dtb) {
  49 -               machine_desc = setup_machine_fdt(__dtb_start);
  50 +               machine_desc = setup_machine_fdt(&__image_dtb);
  51                 if (!machine_desc)
  52                         panic("Embedded DT invalid\n");
  53         }
  54 @@ -544,6 +544,8 @@ ignore_uboot_args:
  55         }
  56  }
  57
  58 +extern struct boot_param_header __image_dtb;
  59 +
  60  void __init setup_arch(char **cmdline_p)
  61  {
  62         handle_uboot_args();
  63 --- a/arch/arc/kernel/vmlinux.lds.S
  64 +++ b/arch/arc/kernel/vmlinux.lds.S
  65 @@ -30,6 +30,19 @@ SECTIONS
  66
  67         . = CONFIG_LINUX_LINK_BASE;
  68
  69 +       /*
  70 +       * In OpenWRT we want to patch built binary embedding .dtb of choice.
  71 +       * This is implemented with "patch-dtb" utility which searches for
  72 +       * "OWRTDTB:" string in first 16k of image and if it is found
  73 +       * copies .dtb right after mentioned string.
  74 +       *
  75 +       * Note: "OWRTDTB:" won't be overwritten with .dtb, .dtb will follow it.
  76 +       */
  77 +       .owrt : {
  78 +               *(.owrt)
  79 +       . = ALIGN(PAGE_SIZE);
  80 +       }
  81 +
  82         _int_vec_base_lds = .;
  83         .vector : {
  84                 *(.vector)