[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Mon, 25 Jun 2018 15:39:04 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: kernel-hardening@...ts.openwall.com
Cc: Thomas Garnier <thgarnie@...gle.com>, Ingo Molnar <mingo@...nel.org>,
Masahiro Yamada <yamada.masahiro@...ionext.com>, Thomas Gleixner <tglx@...utronix.de>,
Kees Cook <keescook@...omium.org>, "Peter Zijlstra (Intel)" <peterz@...radead.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Randy Dunlap <rdunlap@...radead.org>,
Nicholas Piggin <npiggin@...il.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v5 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 d4f90cc38ede..2d7431a8b108 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1974,6 +1974,13 @@ 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
--
2.18.0.rc2.346.g013aa6912e-goog
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
