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bintools-wrapper: skip dynamic linker for static binaries #106908

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Dec 14, 2020
Merged

bintools-wrapper: skip dynamic linker for static binaries #106908

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5 changes: 5 additions & 0 deletions pkgs/build-support/bintools-wrapper/add-flags.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ var_templates_list=(
NIX_IGNORE_LD_THROUGH_GCC
NIX_LDFLAGS
NIX_LDFLAGS_BEFORE
NIX_DYNAMIC_LINKER
NIX_LDFLAGS_AFTER
NIX_LDFLAGS_HARDEN
NIX_HARDENING_ENABLE
Expand All @@ -25,6 +26,10 @@ if [ -e @out@/nix-support/libc-ldflags ]; then
NIX_LDFLAGS_@suffixSalt@+=" $(< @out@/nix-support/libc-ldflags)"
fi

if [ -z "$NIX_DYNAMIC_LINKER_@suffixSalt@" ] && [ -e @out@/nix-support/dynamic-linker ]; then
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This also allows users to specify their own link loader.

NIX_DYNAMIC_LINKER_@suffixSalt@="$(< @out@/nix-support/dynamic-linker)"
fi

if [ -e @out@/nix-support/libc-ldflags-before ]; then
NIX_LDFLAGS_BEFORE_@suffixSalt@="$(< @out@/nix-support/libc-ldflags-before) $NIX_LDFLAGS_BEFORE_@suffixSalt@"
fi
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8 changes: 1 addition & 7 deletions pkgs/build-support/bintools-wrapper/default.nix
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Expand Up @@ -243,13 +243,7 @@ stdenv.mkDerivation {
if [ -e ${libc_lib}/lib/32/ld-linux.so.2 ]; then
echo ${libc_lib}/lib/32/ld-linux.so.2 > $out/nix-support/dynamic-linker-m32
fi
''
# The dynamic linker is passed in `ldflagsBefore' to allow
# explicit overrides of the dynamic linker by callers to ld
# (the *last* value counts, so ours should come first).
+ ''
echo -dynamic-linker "$dynamicLinker" >> $out/nix-support/libc-ldflags-before
'') + ''
'') + ''
fi
'')

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13 changes: 12 additions & 1 deletion pkgs/build-support/bintools-wrapper/ld-wrapper.sh
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Expand Up @@ -20,6 +20,7 @@ if [ -z "${NIX_BINTOOLS_WRAPPER_FLAGS_SET_@suffixSalt@:-}" ]; then
source @out@/nix-support/add-flags.sh
fi

setDynamicLinker=1

# Optionally filter out paths not refering to the store.
expandResponseParams "$@"
Expand Down Expand Up @@ -47,6 +48,11 @@ if [[ "${NIX_ENFORCE_PURITY:-}" = 1 && -n "${NIX_STORE:-}"
# Our ld is not built with sysroot support (Can we fix that?)
:
else
if [[ "$p" = -static || "$p" = -static-pie ]]; then
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There are a few other flags from the man page like -Bstatic, -dn, and -non_shared may be relevant (I'm not sure if any of them are used in practice though)

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Interesting. Do they have the same semantic.

# Using a dynamic linker for static binaries can lead to crashes.
# This was observed for rust binaries.
setDynamicLinker=0
fi
rest+=("$p")
fi
n+=1
Expand All @@ -63,6 +69,11 @@ extraBefore=(${hardeningLDFlags[@]+"${hardeningLDFlags[@]}"})
if [ -z "${NIX_LDFLAGS_SET_@suffixSalt@:-}" ]; then
extraAfter+=($NIX_LDFLAGS_@suffixSalt@)
extraBefore+=($NIX_LDFLAGS_BEFORE_@suffixSalt@)
# By adding dynamic linker to extraBefore we allow the users set their
# own dynamic linker as NIX_LD_FLAGS will override earlier set flags
if [ "$setDynamicLinker" = 1 ]; then
extraBefore+=("-dynamic-linker" "$NIX_DYNAMIC_LINKER_@suffixSalt@")
fi
fi

extraAfter+=($NIX_LDFLAGS_AFTER_@suffixSalt@)
Expand Down Expand Up @@ -134,7 +145,7 @@ then
done
fi

if [ -e "@out@/nix-support/dynamic-linker-m32" ] && (( "$link32" )); then
if [[ "$link32" = "0" && "$setDynamicLinker" = 1 && -e "@out@/nix-support/dynamic-linker-m32" ]]; then
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As pointed out in #107253, (( "$link32" )) is an arithmetic expansion that returns true (status 0) if $link32 is nonzero, not if it’s zero.

# We have an alternate 32-bit linker and we're producing a 32-bit ELF, let's
# use it.
extraAfter+=(
Expand Down
6 changes: 6 additions & 0 deletions pkgs/build-support/cc-wrapper/cc-wrapper.sh
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Expand Up @@ -28,6 +28,7 @@ cc1=0
[[ "@prog@" = *++ ]] && isCpp=1 || isCpp=0
cppInclude=1
cInclude=1
setDynamicLinker=1

expandResponseParams "$@"
declare -i n=0
Expand Down Expand Up @@ -58,6 +59,8 @@ while (( "$n" < "$nParams" )); do
cppInclude=0
elif [ "$p" = -nostdinc++ ]; then
cppInclude=0
elif [[ "$p" = -static || "$p" = -static-pie ]]; then
setDynamicLinker=0
elif [[ "$p" != -?* ]]; then
# A dash alone signifies standard input; it is not a flag
nonFlagArgs=1
Expand Down Expand Up @@ -152,6 +155,9 @@ if [ "$dontLink" != 1 ]; then
for i in $NIX_LDFLAGS_BEFORE_@suffixSalt@; do
extraBefore+=("-Wl,$i")
done
if [ "$setDynamicLinker" = 1 ]; then
extraBefore+=("-Wl,-dynamic-linker=$NIX_DYNAMIC_LINKER_@suffixSalt@")
fi
for i in $NIX_LDFLAGS_@suffixSalt@; do
if [ "${i:0:3}" = -L/ ]; then
extraAfter+=("$i")
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20 changes: 16 additions & 4 deletions pkgs/test/cc-wrapper/default.nix
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@@ -1,11 +1,13 @@
{ stdenv }:
{ stdenv, glibc }:
with stdenv.lib;
let
# Sanitizers are not supported on Darwin.
# Sanitizer headers aren't available in older libc++ stdenvs due to a bug
sanitizersWorking =
(stdenv.cc.isClang && versionAtLeast (getVersion stdenv.cc.name) "5.0.0")
|| (stdenv.cc.isGNU && stdenv.isLinux);
sanitizersWorking = !stdenv.hostPlatform.isMusl && (
(stdenv.cc.isClang && versionAtLeast (getVersion stdenv.cc.name) "5.0.0")
|| (stdenv.cc.isGNU && stdenv.isLinux)
);
staticLibc = optionalString (stdenv.hostPlatform.libc == "glibc") "-L ${glibc.static}/lib";
in stdenv.mkDerivation {
name = "cc-wrapper-test";

Expand All @@ -28,6 +30,16 @@ in stdenv.mkDerivation {
./core-foundation-check
''}

printf "checking whether compiler builds valid static C binaries... " >&2
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@LnL7 do I need to disable this on darwin?

$CC ${staticLibc} -static -o cc-static ${./cc-main.c}
./cc-static
# our glibc does not have pie enabled yet.
${optionalString (stdenv.hostPlatform.isMusl && stdenv.cc.isGNU) ''
printf "checking whether compiler builds valid static pie C binaries... " >&2
$CC ${staticLibc} -static-pie -o cc-static-pie ${./cc-main.c}
./cc-static-pie
''}

printf "checking whether compiler uses NIX_CFLAGS_COMPILE... " >&2
mkdir -p foo/include
cp ${./foo.c} foo/include/foo.h
Expand Down