git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 466d696117db97802e4c2b2745f7af9c259ac92a Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Fri, 23 Oct 2020 21:50:47 -0700
   4 Subject: RISC-V: Fix the VDSO symbol generaton for binutils-2.35+
   5
   6 From: Palmer Dabbelt <palmerdabbelt@google.com>
   7
   8 [ Upstream commit c2c81bb2f69138f902e1a58d3bef6ad97fb8a92c ]
   9
  10 We were relying on GNU ld's ability to re-link executable files in order
  11 to extract our VDSO symbols.  This behavior was deemed a bug as of
  12 binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have
  13 the linker fail if any attempt to link in an executable is made."), but
  14 as that has been backported to at least Debian's binutils-2.34 in may
  15 manifest in other places.
  16
  17 The previous version of this was a bit of a mess: we were linking a
  18 static executable version of the VDSO, containing only a subset of the
  19 input symbols, which we then linked into the kernel.  This worked, but
  20 certainly wasn't a supported path through the toolchain.  Instead this
  21 new version parses the textual output of nm to produce a symbol table.
  22 Both rely on near-zero addresses being linkable, but as we rely on weak
  23 undefined symbols being linkable elsewhere I don't view this as a major
  24 issue.
  25
  26 Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API")
  27 Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
  28 Signed-off-by: Sasha Levin <sashal@kernel.org>
  29 ---
  30  arch/riscv/kernel/vdso/.gitignore |  1 +
  31  arch/riscv/kernel/vdso/Makefile   | 18 +++++++++---------
  32  arch/riscv/kernel/vdso/so2s.sh    |  6 ++++++
  33  3 files changed, 16 insertions(+), 9 deletions(-)
  34  create mode 100755 arch/riscv/kernel/vdso/so2s.sh
  35
  36 diff --git a/arch/riscv/kernel/vdso/.gitignore b/arch/riscv/kernel/vdso/.gitignore
  37 index 11ebee9e4c1d6..3a19def868ecc 100644
  38 --- a/arch/riscv/kernel/vdso/.gitignore
  39 +++ b/arch/riscv/kernel/vdso/.gitignore
  40 @@ -1,3 +1,4 @@
  41  # SPDX-License-Identifier: GPL-2.0-only
  42  vdso.lds
  43  *.tmp
  44 +vdso-syms.S
  45 diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
  46 index 7d6a94d45ec94..cb8f9e4cfcbf8 100644
  47 --- a/arch/riscv/kernel/vdso/Makefile
  48 +++ b/arch/riscv/kernel/vdso/Makefile
  49 @@ -43,19 +43,14 @@ $(obj)/vdso.o: $(obj)/vdso.so
  50  SYSCFLAGS_vdso.so.dbg = $(c_flags)
  51  $(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE
  52         $(call if_changed,vdsold)
  53 +SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
  54 +       -Wl,--build-id -Wl,--hash-style=both
  55
  56  # We also create a special relocatable object that should mirror the symbol
  57  # table and layout of the linked DSO. With ld --just-symbols we can then
  58  # refer to these symbols in the kernel code rather than hand-coded addresses.
  59 -
  60 -SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
  61 -       -Wl,--build-id=sha1 -Wl,--hash-style=both
  62 -$(obj)/vdso-dummy.o: $(src)/vdso.lds $(obj)/rt_sigreturn.o FORCE
  63 -       $(call if_changed,vdsold)
  64 -
  65 -LDFLAGS_vdso-syms.o := -r --just-symbols
  66 -$(obj)/vdso-syms.o: $(obj)/vdso-dummy.o FORCE
  67 -       $(call if_changed,ld)
  68 +$(obj)/vdso-syms.S: $(obj)/vdso.so FORCE
  69 +       $(call if_changed,so2s)
  70
  71  # strip rule for the .so file
  72  $(obj)/%.so: OBJCOPYFLAGS := -S
  73 @@ -73,6 +68,11 @@ quiet_cmd_vdsold = VDSOLD  $@
  74                             $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
  75                     rm $@.tmp
  76
  77 +# Extracts symbol offsets from the VDSO, converting them into an assembly file
  78 +# that contains the same symbols at the same offsets.
  79 +quiet_cmd_so2s = SO2S    $@
  80 +      cmd_so2s = $(NM) -D $< | $(srctree)/$(src)/so2s.sh > $@
  81 +
  82  # install commands for the unstripped file
  83  quiet_cmd_vdso_install = INSTALL $@
  84        cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
  85 diff --git a/arch/riscv/kernel/vdso/so2s.sh b/arch/riscv/kernel/vdso/so2s.sh
  86 new file mode 100755
  87 index 0000000000000..e64cb6d9440e7
  88 --- /dev/null
  89 +++ b/arch/riscv/kernel/vdso/so2s.sh
  90 @@ -0,0 +1,6 @@
  91 +#!/bin/sh
  92 +# SPDX-License-Identifier: GPL-2.0+
  93 +# Copyright 2020 Palmer Dabbelt <palmerdabbelt@google.com>
  94 +
  95 +sed 's!\([0-9a-f]*\) T \([a-z0-9_]*\)\(@@LINUX_4.15\)*!.global \2\n.set \2,0x\1!' \
  96 +| grep '^\.'
  97 --
  98 2.27.0
  99