linux/scripts/tools-support-relr.sh
Nick Desaulniers 27f2a4db76 Makefile: fix GDB warning with CONFIG_RELR
GDB produces the following warning when debugging kernels built with
CONFIG_RELR:

BFD: /android0/linux-next/vmlinux: unknown type [0x13] section `.relr.dyn'

when loading a kernel built with CONFIG_RELR into GDB. It can also
prevent debugging symbols using such relocations.

Peter sugguests:
  [That flag] means that lld will use dynamic tags and section type
  numbers in the OS-specific range rather than the generic range. The
  kernel itself doesn't care about these numbers; it determines the
  location of the RELR section using symbols defined by a linker script.

Link: https://github.com/ClangBuiltLinux/linux/issues/1057
Suggested-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20210522012626.2811297-1-ndesaulniers@google.com
Signed-off-by: Will Deacon <will@kernel.org>
2021-06-08 13:09:34 +01:00

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#!/bin/sh -eu
# SPDX-License-Identifier: GPL-2.0
tmp_file=$(mktemp)
trap "rm -f $tmp_file.o $tmp_file $tmp_file.bin" EXIT
cat << "END" | $CC -c -x c - -o $tmp_file.o >/dev/null 2>&1
void *p = &p;
END
$LD $tmp_file.o -shared -Bsymbolic --pack-dyn-relocs=relr \
--use-android-relr-tags -o $tmp_file
# Despite printing an error message, GNU nm still exits with exit code 0 if it
# sees a relr section. So we need to check that nothing is printed to stderr.
test -z "$($NM $tmp_file 2>&1 >/dev/null)"
$OBJCOPY -O binary $tmp_file $tmp_file.bin