x86: Define MINIMUM_X86_ISA_LEVEL in config.h [BZ #31676]

Define MINIMUM_X86_ISA_LEVEL at configure time to avoid

/usr/bin/ld: …/build/elf/librtld.os: in function `init_cpu_features':
…/git/elf/../sysdeps/x86/cpu-features.c:1202: undefined reference to `_dl_runtime_resolve_fxsave'
/usr/bin/ld: …/build/elf/librtld.os: relocation R_X86_64_PC32 against undefined hidden symbol `_dl_runtime_resolve_fxsave' can not be used when making a shared object
/usr/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status

when glibc is built with -march=x86-64-v3 and configured with
--with-rtld-early-cflags=-march=x86-64, which is used to allow ld.so to
print an error message on unsupported CPUs:

Fatal glibc error: CPU does not support x86-64-v3

This fixes BZ #31676.
Reviewed-by: Sunil K Pandey <skpgkp2@gmail.com>

config.h.in

@@ -285,6 +285,9 @@
 /* Define if x86 ISA level should be included in shared libraries.  */
 #undef INCLUDE_X86_ISA_LEVEL
 
+/* The x86 ISA level.  1 for baseline.  Undefined on non-x86.  */
+#undef MINIMUM_X86_ISA_LEVEL
+
 /* Define if -msahf is enabled by default on x86.  */
 #undef HAVE_X86_LAHF_SAHF
 

sysdeps/x86/configure

@@ -151,6 +151,13 @@ printf "%s\n" "$libc_cv_have_x86_isa_level" >&6; }
 else
   libc_cv_have_x86_isa_level=baseline
 fi
+if test $libc_cv_have_x86_isa_level = baseline; then
+  printf "%s\n" "#define MINIMUM_X86_ISA_LEVEL 1" >>confdefs.h
+
+else
+  printf "%s\n" "#define MINIMUM_X86_ISA_LEVEL $libc_cv_have_x86_isa_level" >>confdefs.h
+
+fi
 config_vars="$config_vars
 have-x86-isa-level = $libc_cv_have_x86_isa_level"
 config_vars="$config_vars

sysdeps/x86/configure.ac

@@ -105,6 +105,11 @@ EOF
 else
   libc_cv_have_x86_isa_level=baseline
 fi
+if test $libc_cv_have_x86_isa_level = baseline; then
+  AC_DEFINE_UNQUOTED(MINIMUM_X86_ISA_LEVEL, 1)
+else
+  AC_DEFINE_UNQUOTED(MINIMUM_X86_ISA_LEVEL, $libc_cv_have_x86_isa_level)
+fi
 LIBC_CONFIG_VAR([have-x86-isa-level], [$libc_cv_have_x86_isa_level])
 LIBC_CONFIG_VAR([x86-isa-level-3-or-above], [3 4])
 LIBC_CONFIG_VAR([enable-x86-isa-level], [$libc_cv_include_x86_isa_level])

sysdeps/x86/isa-level.h

@@ -61,8 +61,10 @@
 # define __X86_ISA_V4 0
 #endif
 
+#ifndef MINIMUM_X86_ISA_LEVEL
 # define MINIMUM_X86_ISA_LEVEL                                                 \
   (__X86_ISA_V1 + __X86_ISA_V2 + __X86_ISA_V3 + __X86_ISA_V4)
+#endif
 
 /* Depending on the minimum ISA level, a feature check result can be a
    compile-time constant.. */