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mips: Force RWX stack for hard-float builds that can run on pre-4.8 kernels

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Linux/Mips kernels prior to 4.8 could potentially crash the user
process when doing FPU emulation while running on non-executable
user stack.

Currently, gcc doesn't emit .note.GNU-stack for mips, but that will
change in the future. To ensure that glibc can be used with such
future gcc, without silently resulting in binaries that might crash
in runtime, this patch forces RWX stack for all built objects if
configured to run against minimum kernel version less than 4.8.

	* sysdeps/unix/sysv/linux/mips/Makefile
	(test-xfail-check-execstack):
	Move under mips-has-gnustack != yes.
	(CFLAGS-.o*, ASFLAGS-.o*): New rules.
	Apply -Wa,-execstack if mips-force-execstack == yes.
	* sysdeps/unix/sysv/linux/mips/configure: Regenerated.
	* sysdeps/unix/sysv/linux/mips/configure.ac
	(mips-force-execstack): New var.
	Set to yes for hard-float builds with minimum_kernel < 4.8.0
	or minimum_kernel not set at all.
	(mips-has-gnustack): New var.
	Use value of libc_cv_as_noexecstack
	if mips-force-execstack != yes, otherwise set to no.

(cherry picked from commit 33bc9efd91)
This commit is contained in:
Dragan Mladjenovic 2019-08-23 16:38:04 +00:00 committed by Adhemerval Zanella
parent 52a6381659
commit a7646651f8
3 changed files with 89 additions and 5 deletions
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21
sysdeps/unix/sysv/linux/mips/Makefile
View File

@ -63,14 +63,25 @@ sysdep-dl-routines += dl-static
sysdep_routines += dl-vdso
endif
# Supporting non-executable stacks on MIPS requires changes to both
# the Linux kernel and glibc. See
# <https://sourceware.org/ml/libc-alpha/2016-01/msg00567.html> and
# <https://sourceware.org/ml/libc-alpha/2016-01/msg00719.html>.
# If the compiler doesn't use GNU.stack note,
# this test is expected to fail.
ifneq ($(mips-has-gnustack),yes)
test-xfail-check-execstack = yes
endif
endif
ifeq ($(subdir),stdlib)
gen-as-const-headers += ucontext_i.sym
endif
ifeq ($(mips-force-execstack),yes)
CFLAGS-.o += -Wa,-execstack
CFLAGS-.os += -Wa,-execstack
CFLAGS-.op += -Wa,-execstack
CFLAGS-.oS += -Wa,-execstack
ASFLAGS-.o += -Wa,-execstack
ASFLAGS-.os += -Wa,-execstack
ASFLAGS-.op += -Wa,-execstack
ASFLAGS-.oS += -Wa,-execstack
endif

41
sysdeps/unix/sysv/linux/mips/configure vendored
View File

@ -475,3 +475,44 @@ if test -z "$arch_minimum_kernel"; then
arch_minimum_kernel=4.5.0
fi
fi
# Check if we are supposed to run on kernels older than 4.8.0. If so,
# force executable stack to avoid potential runtime problems with fpu
# emulation.
# NOTE: The check below assumes that in absence of user-provided minumum_kernel
# we will default to arch_minimum_kernel which is currently less than 4.8.0 for
# all known configurations. If this changes, the check must be updated.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the compiler must use executable stack" >&5
$as_echo_n "checking whether the compiler must use executable stack... " >&6; }
if ${libc_cv_mips_force_execstack+:} false; then :
$as_echo_n "(cached) " >&6
else
libc_cv_mips_force_execstack=no
if test $libc_mips_float = hard; then
if test -n "$minimum_kernel"; then
min_version=$((`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1 \* 65536 + \2 \* 256 + \3/'`))
if test $min_version -lt 264192; then
libc_cv_mips_force_execstack=yes
fi
else
libc_cv_mips_force_execstack=yes
fi
fi
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_mips_force_execstack" >&5
$as_echo "$libc_cv_mips_force_execstack" >&6; }
libc_mips_has_gnustack=$libc_cv_as_noexecstack
if test $libc_cv_mips_force_execstack = yes; then
libc_mips_has_gnustack=no
{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: forcing executable stack for pre-4.8.0 Linux kernels" >&5
$as_echo "$as_me: WARNING: forcing executable stack for pre-4.8.0 Linux kernels" >&2;}
fi
config_vars="$config_vars
mips-force-execstack = ${libc_cv_mips_force_execstack}"
config_vars="$config_vars
mips-has-gnustack = ${libc_mips_has_gnustack}"

32
sysdeps/unix/sysv/linux/mips/configure.ac
View File

@ -134,3 +134,35 @@ if test -z "$arch_minimum_kernel"; then
arch_minimum_kernel=4.5.0
fi
fi
# Check if we are supposed to run on kernels older than 4.8.0. If so,
# force executable stack to avoid potential runtime problems with fpu
# emulation.
# NOTE: The check below assumes that in absence of user-provided minumum_kernel
# we will default to arch_minimum_kernel which is currently less than 4.8.0 for
# all known configurations. If this changes, the check must be updated.
AC_CACHE_CHECK([whether the compiler must use executable stack],
libc_cv_mips_force_execstack, [dnl
libc_cv_mips_force_execstack=no
if test $libc_mips_float = hard; then
if test -n "$minimum_kernel"; then
changequote(,)
min_version=$((`echo "$minimum_kernel.0.0.0" | sed 's/\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*/\1 \* 65536 + \2 \* 256 + \3/'`))
changequote([,])
if test $min_version -lt 264192; then
libc_cv_mips_force_execstack=yes
fi
else
libc_cv_mips_force_execstack=yes
fi
fi])
libc_mips_has_gnustack=$libc_cv_as_noexecstack
if test $libc_cv_mips_force_execstack = yes; then
libc_mips_has_gnustack=no
AC_MSG_WARN([forcing executable stack for pre-4.8.0 Linux kernels])
fi
LIBC_CONFIG_VAR([mips-force-execstack],[${libc_cv_mips_force_execstack}])
LIBC_CONFIG_VAR([mips-has-gnustack],[${libc_mips_has_gnustack}])