queue-3.18/x86-build-mark-per-cpu-symbols-as-absolute-explicitl.patch

   1 From 7baf64c75458df5078a9a0ada893f009c328b6ed Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Rafael=20=C3=81vila=20de=20Esp=C3=ADndola?=
   3  <rafael@espindo.la>
   4 Date: Wed, 19 Dec 2018 11:01:43 -0800
   5 Subject: x86/build: Mark per-CPU symbols as absolute explicitly for LLD
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   9
  10 [ Upstream commit d071ae09a4a1414c1433d5ae9908959a7325b0ad ]
  11
  12 Accessing per-CPU variables is done by finding the offset of the
  13 variable in the per-CPU block and adding it to the address of the
  14 respective CPU's block.
  15
  16 Section 3.10.8 of ld.bfd's documentation states:
  17
  18   For expressions involving numbers, relative addresses and absolute
  19   addresses, ld follows these rules to evaluate terms:
  20
  21   Other binary operations, that is, between two relative addresses
  22   not in the same section, or between a relative address and an
  23   absolute address, first convert any non-absolute term to an
  24   absolute address before applying the operator."
  25
  26 Note that LLVM's linker does not adhere to the GNU ld's implementation
  27 and as such requires implicitly-absolute terms to be explicitly marked
  28 as absolute in the linker script. If not, it fails currently with:
  29
  30   ld.lld: error: ./arch/x86/kernel/vmlinux.lds:153: at least one side of the expression must be absolute
  31   ld.lld: error: ./arch/x86/kernel/vmlinux.lds:154: at least one side of the expression must be absolute
  32   Makefile:1040: recipe for target 'vmlinux' failed
  33
  34 This is not a functional change for ld.bfd which converts the term to an
  35 absolute symbol anyways as specified above.
  36
  37 Based on a previous submission by Tri Vo <trong@android.com>.
  38
  39 Reported-by: Dmitry Golovin <dima@golovin.in>
  40 Signed-off-by: Rafael Ávila de Espíndola <rafael@espindo.la>
  41 [ Update commit message per Boris' and Michael's suggestions. ]
  42 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
  43 [ Massage commit message more, fix typos. ]
  44 Signed-off-by: Borislav Petkov <bp@suse.de>
  45 Tested-by: Dmitry Golovin <dima@golovin.in>
  46 Cc: "H. Peter Anvin" <hpa@zytor.com>
  47 Cc: Andy Lutomirski <luto@kernel.org>
  48 Cc: Brijesh Singh <brijesh.singh@amd.com>
  49 Cc: Cao Jin <caoj.fnst@cn.fujitsu.com>
  50 Cc: Ingo Molnar <mingo@redhat.com>
  51 Cc: Joerg Roedel <jroedel@suse.de>
  52 Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
  53 Cc: Masami Hiramatsu <mhiramat@kernel.org>
  54 Cc: Thomas Gleixner <tglx@linutronix.de>
  55 Cc: Tri Vo <trong@android.com>
  56 Cc: dima@golovin.in
  57 Cc: morbo@google.com
  58 Cc: x86-ml <x86@kernel.org>
  59 Link: https://lkml.kernel.org/r/20181219190145.252035-1-ndesaulniers@google.com
  60 Signed-off-by: Sasha Levin <sashal@kernel.org>
  61 ---
  62  arch/x86/kernel/vmlinux.lds.S | 2 +-
  63  1 file changed, 1 insertion(+), 1 deletion(-)
  64
  65 diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
  66 index 49edf2dd3613..1bd47a144db1 100644
  67 --- a/arch/x86/kernel/vmlinux.lds.S
  68 +++ b/arch/x86/kernel/vmlinux.lds.S
  69 @@ -345,7 +345,7 @@ SECTIONS
  70   * Per-cpu symbols which need to be offset from __per_cpu_load
  71   * for the boot processor.
  72   */
  73 -#define INIT_PER_CPU(x) init_per_cpu__##x = x + __per_cpu_load
  74 +#define INIT_PER_CPU(x) init_per_cpu__##x = ABSOLUTE(x) + __per_cpu_load
  75  INIT_PER_CPU(gdt_page);
  76  INIT_PER_CPU(irq_stack_union);
  77
  78 --
  79 2.19.1
  80