From 7aa4117dabbd62d49f5b19ce36edd959d7bb260d Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Tue, 2 Feb 2021 13:45:58 -0800
Subject: [PATCH v2] x86: Require full ISA support for x86-64 level marker [BZ
 #27318]

Since -march=sandybridge enables ISAs in x86-64 ISA level v3, the v3
marker is set on libc.so.  We couldn't set the needed ISA marker to v2
since this libc won't run on all v2 machines.  Technically, the v3 marker
is correct.  But the resulting libc.so won't run on Sandy Brigde, which
is a v2 machine, even when libc is compiled with -march=sandybridge:

$ ./elf/ld.so ./libc.so
./libc.so: (p) CPU ISA level is lower than required: needed: 7; got: 3

Instead, we require full ISA support for x86-64 level marker and disable
x86-64 level marker for -march=sandybridge which enables ISAs between v2
and v3.
---
 sysdeps/x86/configure    |  7 ++++++-
 sysdeps/x86/configure.ac |  2 +-
 sysdeps/x86/isa-level.c  | 21 ++++++++++++++++++++-
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/sysdeps/x86/configure b/sysdeps/x86/configure
index 5e32dc62b3..5b20646843 100644
--- a/sysdeps/x86/configure
+++ b/sysdeps/x86/configure
@@ -133,7 +133,12 @@ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -nostartfiles -nostdlib -r -o conftest c
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; }; then
   count=`LC_ALL=C $READELF -n conftest | grep NT_GNU_PROPERTY_TYPE_0 | wc -l`
-  if test "$count" = 1; then
+  if test "$count" = 1 && { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -DINCLUDE_X86_ISA_LEVEL -S -o conftest.s $srcdir/sysdeps/x86/isa-level.c'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }; then
     libc_cv_include_x86_isa_level=yes
   fi
 fi
diff --git a/sysdeps/x86/configure.ac b/sysdeps/x86/configure.ac
index f94088f377..54ecd33d2c 100644
--- a/sysdeps/x86/configure.ac
+++ b/sysdeps/x86/configure.ac
@@ -100,7 +100,7 @@ EOF
 libc_cv_include_x86_isa_level=no
 if AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS -nostartfiles -nostdlib -r -o conftest conftest1.S conftest2.S); then
   count=`LC_ALL=C $READELF -n conftest | grep NT_GNU_PROPERTY_TYPE_0 | wc -l`
-  if test "$count" = 1; then
+  if test "$count" = 1 && AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS -DINCLUDE_X86_ISA_LEVEL -S -o conftest.s $srcdir/sysdeps/x86/isa-level.c); then
     libc_cv_include_x86_isa_level=yes
   fi
 fi
diff --git a/sysdeps/x86/isa-level.c b/sysdeps/x86/isa-level.c
index aaf524cb56..7f83449061 100644
--- a/sysdeps/x86/isa-level.c
+++ b/sysdeps/x86/isa-level.c
@@ -25,12 +25,17 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <elf.h>
+#ifdef _LIBC
+# include <elf.h>
+#endif
 
 /* ELF program property for x86 ISA level.  */
 #ifdef INCLUDE_X86_ISA_LEVEL
 # if defined __x86_64__ || defined __FXSR__ || !defined _SOFT_FLOAT \
      || defined  __MMX__ || defined __SSE__ || defined __SSE2__
+#  if !defined __SSE__ || !defined __SSE2__
+#   error "Missing ISAs for x86-64 ISA level baseline"
+#  endif
 #  define ISA_BASELINE	GNU_PROPERTY_X86_ISA_1_BASELINE
 # else
 #  define ISA_BASELINE	0
@@ -40,6 +45,11 @@
      || (defined __x86_64__ && defined __LAHF_SAHF__) \
      || defined __POPCNT__ || defined __SSE3__ \
      || defined __SSSE3__ || defined __SSE4_1__ || defined __SSE4_2__
+#  if !defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 \
+     || !defined __POPCNT__ || !defined __SSE3__ \
+     || !defined __SSSE3__ || !defined __SSE4_1__ || !defined __SSE4_2__
+#   error "Missing ISAs for x86-64 ISA level v2"
+#  endif
 #  define ISA_V2	GNU_PROPERTY_X86_ISA_1_V2
 # else
 #  define ISA_V2	0
@@ -48,6 +58,10 @@
 # if defined __AVX__ || defined __AVX2__ || defined __F16C__ \
      || defined __FMA__ || defined __LZCNT__ || defined __MOVBE__ \
      || defined __XSAVE__
+# if !defined __AVX__ || !defined __AVX2__ || !defined __F16C__ \
+     || !defined __FMA__ || !defined __LZCNT__
+#   error "Missing ISAs for x86-64 ISA level v3"
+#  endif
 #  define ISA_V3	GNU_PROPERTY_X86_ISA_1_V3
 # else
 #  define ISA_V3	0
@@ -55,6 +69,11 @@
 
 # if defined __AVX512F__ || defined __AVX512BW__ || defined __AVX512CD__ \
      || defined __AVX512DQ__ || defined __AVX512VL__
+#  if !defined __AVX512F__ || !defined __AVX512BW__ \
+      || !defined __AVX512CD__ || !defined __AVX512DQ__ \
+      || !defined __AVX512VL__
+#   error "Missing ISAs for x86-64 ISA level v4"
+#  endif
 #  define ISA_V4	GNU_PROPERTY_X86_ISA_1_V4
 # else
 #  define ISA_V4	0
-- 
2.29.2

