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Message-Id: <20180529221625.33541-17-thgarnie@google.com> Date: Tue, 29 May 2018 15:15:17 -0700 From: Thomas Garnier <thgarnie@...gle.com> To: kernel-hardening@...ts.openwall.com Cc: Thomas Garnier <thgarnie@...gle.com>, Skip Frederic Weisbecker <frederic@...nel.org>, Skip Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Skip Kees Cook <keescook@...omium.org>, Skip Michael Forney <forney@...gle.com>, Skip Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Ingo Molnar <mingo@...nel.org>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Thomas Gleixner <tglx@...utronix.de>, Nicolas Pitre <nicolas.pitre@...aro.org>, Andrew Morton <akpm@...ux-foundation.org>, Randy Dunlap <rdunlap@...radead.org>, Nicholas Piggin <npiggin@...il.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, linux-kernel@...r.kernel.org Subject: [PATCH v4 16/27] compiler: Option to add PROVIDE_HIDDEN replacement for weak symbols Provide an option to have a PROVIDE_HIDDEN (linker script) entry for each weak symbol. This option solves an error in x86_64 where the linker optimizes PIE generated code to be non-PIE because --emit-relocs was used instead of -pie (to reduce dynamic relocations). Signed-off-by: Thomas Garnier <thgarnie@...gle.com> --- init/Kconfig | 7 +++++++ scripts/link-vmlinux.sh | 14 ++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index f16247675f84..20e2bf2ae4b4 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1954,6 +1954,13 @@ config ASN1 inform it as to what tags are to be expected in a stream and what functions to call on what tags. +config WEAK_PROVIDE_HIDDEN + bool + help + Generate linker script PROVIDE_HIDDEN entries for all weak symbols. It + allows to prevent non-PIE code being replaced by the linker if the + emit-relocs option is used instead of PIE (useful for x86_64 PIE). + source "kernel/Kconfig.locks" config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index 4bf811c09f59..f5d31119b9d7 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -142,6 +142,17 @@ kallsyms() ${CC} ${aflags} -c -o ${2} ${afile} } +gen_weak_provide_hidden() +{ + if [ -n "${CONFIG_WEAK_PROVIDE_HIDDEN}" ]; then + local pattern="s/^\s\+ w \(\w\+\)$/PROVIDE_HIDDEN(\1 = .);/gp" + echo -e "SECTIONS {\n. = _end;" > .tmp_vmlinux_hiddenld + ${NM} ${1} | sed -n "${pattern}" >> .tmp_vmlinux_hiddenld + echo "}" >> .tmp_vmlinux_hiddenld + LDFLAGS_vmlinux="${LDFLAGS_vmlinux} -T .tmp_vmlinux_hiddenld" + fi +} + # Create map file with all symbols from ${1} # See mksymap for additional details mksysmap() @@ -226,6 +237,9 @@ modpost_link vmlinux.o # modpost vmlinux.o to check for section mismatches ${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o +# Generate weak linker script +gen_weak_provide_hidden vmlinux.o + kallsymso="" kallsyms_vmlinux="" if [ -n "${CONFIG_KALLSYMS}" ]; then -- 2.17.0.921.gf22659ad46-goog
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