On Sun, May 24, 2020 at 2:26 PM Alexandre Ghiti wrote:
>
> Relocating kernel at runtime is done very early in the boot process, so
> it is not convenient to check for relocations there and react in case a
> relocation was not expected.
>
> Powerpc architecture has a script that allows to check at compile time
> for such unexpected relocations: extract the common logic to scripts/
> and add arch specific scripts triggered at postlink.
>
> At the moment, powerpc and riscv architectures take advantage of this
> compile-time check.
>
> Signed-off-by: Alexandre Ghiti
> ---
> arch/powerpc/tools/relocs_check.sh | 18 ++-
> arch/riscv/Makefile.postlink | 36 ++
> arch/riscv/tools/relocs_check.sh | 26 +
> scripts/relocs_check.sh| 20 +
> 4 files changed, 84 insertions(+), 16 deletions(-)
> create mode 100644 arch/riscv/Makefile.postlink
> create mode 100755 arch/riscv/tools/relocs_check.sh
> create mode 100755 scripts/relocs_check.sh
Maybe you should send the change arch/powerpc/tools/relocs_check.sh
as a separate patch so that it can be picked up by arch/powerpc maintainers.
>
> diff --git a/arch/powerpc/tools/relocs_check.sh
> b/arch/powerpc/tools/relocs_check.sh
> index 014e00e74d2b..e367895941ae 100755
> --- a/arch/powerpc/tools/relocs_check.sh
> +++ b/arch/powerpc/tools/relocs_check.sh
> @@ -15,21 +15,8 @@ if [ $# -lt 3 ]; then
> exit 1
> fi
>
> -# Have Kbuild supply the path to objdump and nm so we handle cross
> compilation.
> -objdump="$1"
> -nm="$2"
> -vmlinux="$3"
> -
> -# Remove from the bad relocations those that match an undefined weak symbol
> -# which will result in an absolute relocation to 0.
> -# Weak unresolved symbols are of that form in nm output:
> -# " w _binary__btf_vmlinux_bin_end"
> -undef_weak_symbols=$($nm "$vmlinux" | awk '$1 ~ /w/ { print $2 }')
> -
> bad_relocs=$(
> -$objdump -R "$vmlinux" |
> - # Only look at relocation lines.
> - grep -E '\ +${srctree}/scripts/relocs_check.sh "$@" |
> # These relocations are okay
> # On PPC64:
> # R_PPC64_RELATIVE, R_PPC64_NONE
> @@ -43,8 +30,7 @@ R_PPC_ADDR16_LO
> R_PPC_ADDR16_HI
> R_PPC_ADDR16_HA
> R_PPC_RELATIVE
> -R_PPC_NONE' |
> - ([ "$undef_weak_symbols" ] && grep -F -w -v "$undef_weak_symbols" ||
> cat)
> +R_PPC_NONE'
> )
>
> if [ -z "$bad_relocs" ]; then
> diff --git a/arch/riscv/Makefile.postlink b/arch/riscv/Makefile.postlink
> new file mode 100644
> index ..bf2b2bca1845
> --- /dev/null
> +++ b/arch/riscv/Makefile.postlink
> @@ -0,0 +1,36 @@
> +# SPDX-License-Identifier: GPL-2.0
> +# ===
> +# Post-link riscv pass
> +# ===
> +#
> +# Check that vmlinux relocations look sane
> +
> +PHONY := __archpost
> +__archpost:
> +
> +-include include/config/auto.conf
> +include scripts/Kbuild.include
> +
> +quiet_cmd_relocs_check = CHKREL $@
> +cmd_relocs_check = \
> + $(CONFIG_SHELL) $(srctree)/arch/riscv/tools/relocs_check.sh
> "$(OBJDUMP)" "$(NM)" "$@"
> +
> +# `@true` prevents complaint when there is nothing to be done
> +
> +vmlinux: FORCE
> + @true
> +ifdef CONFIG_RELOCATABLE
> + $(call if_changed,relocs_check)
> +endif
> +
> +%.ko: FORCE
> + @true
> +
> +clean:
> + @true
> +
> +PHONY += FORCE clean
> +
> +FORCE:
> +
> +.PHONY: $(PHONY)
> diff --git a/arch/riscv/tools/relocs_check.sh
> b/arch/riscv/tools/relocs_check.sh
> new file mode 100755
> index ..baeb2e7b2290
> --- /dev/null
> +++ b/arch/riscv/tools/relocs_check.sh
> @@ -0,0 +1,26 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +# Based on powerpc relocs_check.sh
> +
> +# This script checks the relocations of a vmlinux for "suspicious"
> +# relocations.
> +
> +if [ $# -lt 3 ]; then
> +echo "$0 [path to objdump] [path to nm] [path to vmlinux]" 1>&2
> +exit 1
> +fi
> +
> +bad_relocs=$(
> +${srctree}/scripts/relocs_check.sh "$@" |
> + # These relocations are okay
> + # R_RISCV_RELATIVE
> + grep -F -w -v 'R_RISCV_RELATIVE'
> +)
> +
> +if [ -z "$bad_relocs" ]; then
> + exit 0
> +fi
> +
> +num_bad=$(echo "$bad_relocs" | wc -l)
> +echo "WARNING: $num_bad bad relocations"
> +echo "$bad_relocs"
> diff --git a/scripts/relocs_check.sh b/scripts/relocs_check.sh
> new file mode 100755
> index ..137c660499f3
> --- /dev/null
> +++ b/scripts/relocs_check.sh
> @@ -0,0 +1,20 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +
> +# Get a list of all the relocations, remove from it the relocations
> +# that are known to be legitimate and return this list to arch specific
> +# script that will look for suspicious relocations.
> +
> +objdump="$1"
> +nm="$2"
> +vmlinux="$3"
> +
> +# Remove fro
