[glibc] Add --with-rtld-early-cflags configure option

[glibc] Add --with-rtld-early-cflags configure option

[Florian Weimer]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9ba202c78f0aa39f49929eee63c367847da72ee4

commit 9ba202c78f0aa39f49929eee63c367847da72ee4
Author: Florian Weimer <fweimer@redhat.com>
Date:   Fri Jan 14 20:16:05 2022 +0100

    Add --with-rtld-early-cflags configure option
    
    Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
    Reviewed-by: Carlos O'Donell <carlos@redhat.com>

Diff:
---
 INSTALL             |  8 ++++++++
 NEWS                |  6 ++++++
 config.make.in      |  1 +
 configure           | 13 +++++++++++++
 configure.ac        |  6 ++++++
 elf/Makefile        |  8 ++++++++
 manual/install.texi |  7 +++++++
 7 files changed, 49 insertions(+)

diff --git a/INSTALL b/INSTALL
index 331d405e56..a9dc12fa31 100644
--- a/INSTALL
+++ b/INSTALL
@@ -106,6 +106,14 @@ if 'CFLAGS' is specified it must enable optimization.  For example:
      particular case and potentially change debugging information and
      metadata only).
 
+'--with-rtld-early-cflags=CFLAGS'
+     Use additional compiler flags CFLAGS to build the early startup
+     code of the dynamic linker.  These flags can be used to enable
+     early dynamic linker diagnostics to run on CPUs which are not
+     compatible with the rest of the GNU C Library, for example, due to
+     compiler flags which target a later instruction set architecture
+     (ISA).
+
 '--with-timeoutfactor=NUM'
      Specify an integer NUM to scale the timeout of test programs.  This
      factor can be changed at run time using 'TIMEOUTFACTOR' environment
diff --git a/NEWS b/NEWS
index a957b19fdc..ddd95a8329 100644
--- a/NEWS
+++ b/NEWS
@@ -120,6 +120,12 @@ Major new features:
   The OpenRISC ABI is 32-bit big-endian and uses 64-bit time (y2038 safe) and
   64-bit file offsets (LFS default).
 
+* A new configure option, --with-rtld-early-cflags, can be used to
+  specify additional compiler flags for building the early startup code
+  of the dynamic linker.  On targets which have CPU compatibility
+  checks, this can help to ensure that proper diagnostics are printed if
+  the dynamic loader runs on an incompatible CPU.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * On x86-64, the LD_PREFER_MAP_32BIT_EXEC environment variable support
diff --git a/config.make.in b/config.make.in
index e8630a8d0c..6d43e691f7 100644
--- a/config.make.in
+++ b/config.make.in
@@ -110,6 +110,7 @@ CFLAGS = @CFLAGS@
 CPPFLAGS-config = @CPPFLAGS@
 CPPUNDEFS = @CPPUNDEFS@
 extra-nonshared-cflags = @extra_nonshared_cflags@
+rtld-early-cflags = @rtld_early_cflags@
 ASFLAGS-config = @ASFLAGS_config@
 AR = @AR@
 NM = @NM@
diff --git a/configure b/configure
index 3f956cf777..6a7e5c6164 100755
--- a/configure
+++ b/configure
@@ -681,6 +681,7 @@ force_install
 bindnow
 hardcoded_path_in_tests
 enable_timezone_tools
+rtld_early_cflags
 extra_nonshared_cflags
 use_default_link
 sysheaders
@@ -761,6 +762,7 @@ with_selinux
 with_headers
 with_default_link
 with_nonshared_cflags
+with_rtld_early_cflags
 with_timeoutfactor
 enable_sanity_checks
 enable_shared
@@ -1480,6 +1482,8 @@ Optional Packages:
   --with-default-link     do not use explicit linker scripts
   --with-nonshared-cflags=CFLAGS
                           build nonshared libraries with additional CFLAGS
+  --with-rtld-early-cflags=CFLAGS
+                          build early initialization with additional CFLAGS
   --with-timeoutfactor=NUM
                           specify an integer to scale the timeout
   --with-cpu=CPU          select code for CPU variant
@@ -3386,6 +3390,15 @@ fi
 
 
 
+# Check whether --with-rtld-early-cflags was given.
+if test "${with_rtld_early_cflags+set}" = set; then :
+  withval=$with_rtld_early_cflags; rtld_early_cflags=$withval
+else
+  rtld_early_cflags=
+fi
+
+
+
 
 # Check whether --with-timeoutfactor was given.
 if test "${with_timeoutfactor+set}" = set; then :
diff --git a/configure.ac b/configure.ac
index 277d3527d2..40f2de1661 100644
--- a/configure.ac
+++ b/configure.ac
@@ -162,6 +162,12 @@ AC_ARG_WITH([nonshared-cflags],
 	    [extra_nonshared_cflags=$withval],
 	    [extra_nonshared_cflags=])
 AC_SUBST(extra_nonshared_cflags)
+AC_ARG_WITH([rtld-early-cflags],
+	    AS_HELP_STRING([--with-rtld-early-cflags=CFLAGS],
+			   [build early initialization with additional CFLAGS]),
+	    [rtld_early_cflags=$withval],
+	    [rtld_early_cflags=])
+AC_SUBST(rtld_early_cflags)
 
 AC_ARG_WITH([timeoutfactor],
 	    AS_HELP_STRING([--with-timeoutfactor=NUM],
diff --git a/elf/Makefile b/elf/Makefile
index 3df49742ff..e6a28b243b 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -167,6 +167,14 @@ CFLAGS-.o += $(call elide-stack-protector,.o,$(elide-routines.os))
 CFLAGS-.op += $(call elide-stack-protector,.op,$(elide-routines.os))
 CFLAGS-.os += $(call elide-stack-protector,.os,$(all-rtld-routines))
 
+# Add the requested compiler flags to the early startup code.
+CFLAGS-dl-printf.os += $(rtld-early-cflags)
+CFLAGS-dl-sysdep.os += $(rtld-early-cflags)
+CFLAGS-dl-tunables.os += $(rtld-early-cflags)
+CFLAGS-dl-write.os += $(rtld-early-cflags)
+CFLAGS-dl-writev.os += $(rtld-early-cflags)
+CFLAGS-rtld.os += $(rtld-early-cflags)
+
 ifeq ($(unwind-find-fde),yes)
 routines += unwind-dw2-fde-glibc
 shared-only-routines += unwind-dw2-fde-glibc
diff --git a/manual/install.texi b/manual/install.texi
index b1afc56f5a..accaef45fa 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -131,6 +131,13 @@ that the objects in @file{libc_nonshared.a} are compiled with this flag
 (although this will not affect the generated code in this particular
 case and potentially change debugging information and metadata only).
 
+@item --with-rtld-early-cflags=@var{cflags}
+Use additional compiler flags @var{cflags} to build the early startup
+code of the dynamic linker.  These flags can be used to enable early
+dynamic linker diagnostics to run on CPUs which are not compatible with
+the rest of @theglibc{}, for example, due to compiler flags which target
+a later instruction set architecture (ISA).
+
 @item --with-timeoutfactor=@var{NUM}
 Specify an integer @var{NUM} to scale the timeout of test programs.
 This factor can be changed at run time using @env{TIMEOUTFACTOR}