Bump.
On 02/05/2016 10:36 AM, Faraz Shahbazker wrote: > Enable non-executable stack mode if assembler and linker support it. > > Currently the MIPS FPU emulator uses eXecute Out of Line (XOL) on the stack to > handle instructions in the delay slots of FPU branches. Because of this MIPS > cannot have a non-executable stack. While the solution on the kernel side is > not yet finalized, we propose changes required on the tools-side to make them > ready for a seamless transition whenever a fixed kernel becomes available. > > glibc/dynamic linker: > ---- > * When non-executable stack is requested, first check AT_FLAGS in the > auxiliary vector to decide if this kernel supports a non-executable > stack. Persist with the non-executable mode specified on the > PT_GNU_STACK segment only if kernel supports it, else revert to an > executable stack. > > * The 25th bit (1<<24) in AT_FLAGS is reserved for use by the kernel to > indicate that it supports a non-executable stack on MIPS. > > * glibc's ABIVERSION is incremented from 3 to 5, so that applications linked > for this glibc can't be accidentally run against older versions. ABIVERSION > 4 has been skipped over because it was chosen for IFUNC support, which is > still under review. > > Patch under review: https://sourceware.org/ml/libc-alpha/2016-01/msg00567.html > > binutils: > ---- > * Increment the ABIVERSION to 5 for objects with non-executable stacks. > > Patch under review: https://sourceware.org/ml/binutils/2016-02/msg00087.html > > gcc: > ---- > * Check if assembler/dynamic linker support the new behaviour > (ABIVERSION >= 5). If yes, enable non-executable stack by default > for all objects. > > gcc/ChangeLog > * configure.ac: Check if assembler supports the new PT_GNU_STACK > ABI change; if yes, enable non-executable stack mode by default. > * configure: Regenerate. > * config.in: Regenerate. > * config/mips/mips.c: Define TARGET_ASM_FILE_END to indicate > stack mode for each C file if LD_MIPS_GNUSTACK is enabled. > > libgcc/ChangeLog > config/mips/crti.S: Add .note.GNU-stack marker if LD_MIPS_GNUSTACK > support is enabled. > config/mips/crtn.S: Add .note.GNU-stack marker if LD_MIPS_GNUSTACK > support is enabled. > config/mips/mips16.S: Add .note.GNU-stack marker if > LD_MIPS_GNUSTACK support is enabled. > config/mips/vr4120-div.S: Add .note.GNU-stack marker if > LD_MIPS_GNUSTACK support is enabled. > > -- gcc/configure.ac gcc/config/mips/mip.c config/mips/crti.S > config/mips/crtn.S config/mips/mips16.S config/mips/vr4120-div.S > --- > gcc/config/mips/mips.c | 5 +++++ > gcc/configure.ac | 23 +++++++++++++++++++++++ > libgcc/config/mips/crti.S | 6 ++++++ > libgcc/config/mips/crtn.S | 6 ++++++ > libgcc/config/mips/mips16.S | 7 +++++++ > libgcc/config/mips/vr4120-div.S | 7 +++++++ > 6 files changed, 54 insertions(+) > > diff --git a/gcc/config/mips/mips.c b/gcc/config/mips/mips.c > index ea18ad6..c3eefc0 100644 > --- a/gcc/config/mips/mips.c > +++ b/gcc/config/mips/mips.c > @@ -20194,6 +20194,11 @@ mips_promote_function_mode (const_tree type > ATTRIBUTE_UNUSED, > #undef TARGET_HARD_REGNO_SCRATCH_OK > #define TARGET_HARD_REGNO_SCRATCH_OK mips_hard_regno_scratch_ok > > +#if HAVE_LD_MIPS_GNUSTACK > +#undef TARGET_ASM_FILE_END > +#define TARGET_ASM_FILE_END file_end_indicate_exec_stack > +#endif > + > struct gcc_target targetm = TARGET_INITIALIZER; > > #include "gt-mips.h" > diff --git a/gcc/configure.ac b/gcc/configure.ac > index 0a626e9..9b8190e 100644 > --- a/gcc/configure.ac > +++ b/gcc/configure.ac > @@ -4562,6 +4562,29 @@ pointers into PC-relative form.]) > AC_MSG_ERROR( > [Requesting --with-nan= requires assembler support for -mnan=]) > fi > + > + AC_CACHE_CHECK([linker for GNU-stack ABI support], > + [gcc_cv_ld_mips_gnustack], > + [gcc_cv_ld_mips_gnustack=no > + if test x$gcc_cv_as != x \ > + -a x$gcc_cv_ld != x \ > + -a x$gcc_cv_readelf != x ; then > + cat > conftest.s <<EOF > +.section .note.GNU-stack,"",%progbits > +EOF > + if $gcc_cv_as -o conftest.o conftest.s > /dev/null 2>&1 \ > + && $gcc_cv_ld -o conftest conftest.o > /dev/null 2>&1; then > + abi_version=`$gcc_cv_readelf -h conftest 2>&1 | grep "ABI Version:" > | cut -d: -f2 | tr -d '[[:space:]]'` > + if test "$abi_version" -ge 5; then > + gcc_cv_ld_mips_gnustack=yes > + fi > + fi > + fi > + rm -f conftest.s conftest.o conftest]) > + if test x$gcc_cv_ld_mips_gnustack = xyes; then > + AC_DEFINE(HAVE_LD_MIPS_GNUSTACK, 1, > + [Define if your linker can handle PT_GNU_STACK segments correctly.]) > + fi > ;; > s390*-*-*) > gcc_GAS_CHECK_FEATURE([.gnu_attribute support], > diff --git a/libgcc/config/mips/crti.S b/libgcc/config/mips/crti.S > index 8521d3c..aa85d94 100644 > --- a/libgcc/config/mips/crti.S > +++ b/libgcc/config/mips/crti.S > @@ -21,6 +21,12 @@ a copy of the GCC Runtime Library Exception along with > this program; > see the files COPYING3 and COPYING.RUNTIME respectively. If not, see > <http://www.gnu.org/licenses/>. */ > > +#include "config.h" > +#if HAVE_LD_MIPS_GNUSTACK > +/* An executable stack is *not* required for these functions. */ > + .section .note.GNU-stack,"",%progbits > +#endif > + > /* 4 slots for argument spill area. 1 for cpreturn, 1 for stack. > Return spill offset of 40 and 20. Aligned to 16 bytes for n32. */ > > diff --git a/libgcc/config/mips/crtn.S b/libgcc/config/mips/crtn.S > index d80c342..6a13b46 100644 > --- a/libgcc/config/mips/crtn.S > +++ b/libgcc/config/mips/crtn.S > @@ -21,6 +21,12 @@ a copy of the GCC Runtime Library Exception along with > this program; > see the files COPYING3 and COPYING.RUNTIME respectively. If not, see > <http://www.gnu.org/licenses/>. */ > > +#include "config.h" > +#if HAVE_LD_MIPS_GNUSTACK > +/* An executable stack is *not* required for these functions. */ > + .section .note.GNU-stack,"",%progbits > +#endif > + > /* 4 slots for argument spill area. 1 for cpreturn, 1 for stack. > Return spill offset of 40 and 20. Aligned to 16 bytes for n32. */ > > diff --git a/libgcc/config/mips/mips16.S b/libgcc/config/mips/mips16.S > index 5080f86..b8f6df8 100644 > --- a/libgcc/config/mips/mips16.S > +++ b/libgcc/config/mips/mips16.S > @@ -48,6 +48,13 @@ see the files COPYING3 and COPYING.RUNTIME respectively. > If not, see > values using the soft-float calling convention, but do the actual > operation using the hard floating point instructions. */ > > +#include "config.h" > +#if HAVE_LD_MIPS_GNUSTACK > +/* An executable stack is *not* required for these functions. */ > + .section .note.GNU-stack,"",%progbits > + .previous > +#endif > + > #if defined _MIPS_SIM && (_MIPS_SIM == _ABIO32 || _MIPS_SIM == _ABIO64) > > /* This file contains 32-bit assembly code. */ > diff --git a/libgcc/config/mips/vr4120-div.S b/libgcc/config/mips/vr4120-div.S > index 9954bc3..262de67 100644 > --- a/libgcc/config/mips/vr4120-div.S > +++ b/libgcc/config/mips/vr4120-div.S > @@ -26,6 +26,13 @@ see the files COPYING3 and COPYING.RUNTIME respectively. > If not, see > -mfix-vr4120. div and ddiv do not give the correct result when one > of the operands is negative. */ > > +#include "config.h" > +#if HAVE_LD_MIPS_GNUSTACK > +/* An executable stack is *not* required for these functions. */ > + .section .note.GNU-stack,"",%progbits > +#endif > + .previous > + > .set nomips16 > > #define DIV \ >
