[glibc/maskray/grte] Add a --with-lld option to choose LLVMs lld linker

[glibc/maskray/grte] Add a --with-lld option to choose LLVMs lld linker

[Fangrui Song]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=6302c3ccf839007f8632964e99a3e5d038a5e9e2

commit 6302c3ccf839007f8632964e99a3e5d038a5e9e2
Author: Stan Shebs <stanshebs@google.com>
Date:   Wed Feb 14 09:15:44 2018 -0800

    Add a --with-lld option to choose LLVMs lld linker

Diff:
---
 Makeconfig   | 11 +++++++++++
 configure    | 16 ++++++++++++++++
 configure.ac | 11 +++++++++++
 elf/Makefile |  3 ++-
 elf/rtld.c   |  6 ++++++
 5 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/Makeconfig b/Makeconfig
index 695c3f81f1..dce9b3548d 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -521,8 +521,13 @@ CFLAGS-printers-tests := -O0 -ggdb3 -DIS_IN_build
 
 ifeq (yes,$(build-shared))
 # These indicate whether to link using the built ld.so or the installed one.
+ifeq ($(with-lld),no)
 installed-rtld-LDFLAGS = -Wl,-dynamic-linker=$(rtlddir)/$(rtld-installed-name)
 built-rtld-LDFLAGS = -Wl,-dynamic-linker=$(elf-objpfx)ld.so
+else
+installed-rtld-LDFLAGS = -Wl,-dynamic-linker,$(rtlddir)/$(rtld-installed-name)
+built-rtld-LDFLAGS = -Wl,-dynamic-linker,$(elf-objpfx)ld.so
+endif
 
 ifndef rtld-LDFLAGS
 rtld-LDFLAGS = $(installed-rtld-LDFLAGS)
@@ -907,6 +912,12 @@ ifeq ($(with-clang),yes)
 # Non-string format arguments come from debugging prints in ld.so.
 +cflags += -Wno-format-security
 
+ifeq ($(with-lld),yes)
+LDFLAGS.so += -fuse-ld=lld
+LDFLAGS-rtld += -fuse-ld=lld
+LDFLAGS += -fuse-ld=lld
+endif
+
 endif	# with-clang == yes
 
 +cflags += $(cflags-cpu) $(+gccwarn) $(+merge-constants) $(+math-flags) \
diff --git a/configure b/configure
index 8bdc71adf4..0c64f96693 100755
--- a/configure
+++ b/configure
@@ -762,6 +762,7 @@ with_gd_lib
 with_binutils
 with_selinux
 with_clang
+with_lld
 with_headers
 with_default_link
 enable_sanity_checks
@@ -1489,6 +1490,7 @@ Optional Packages:
   --with-binutils=PATH    specify location of binutils (as and ld)
   --with-selinux          if building with SELinux support
   --with-clang            if building with clang (temporary)
+  --with-lld              if building/linking with lld (temporary)
   --with-headers=PATH     location of system headers to use (for example
                           /usr/src/linux/include) [default=compiler default]
   --with-default-link     do not use explicit linker scripts
@@ -3339,6 +3341,16 @@ fi
 config_vars="$config_vars
 with-clang = $with_clang"
 
+# Check whether --with-lld was given.
+if test "${with_lld+set}" = set; then :
+  withval=$with_lld; with_lld=$withval
+else
+  with_lld=no
+fi
+
+config_vars="$config_vars
+with-lld = $with_lld"
+
 
 # Check whether --with-headers was given.
 if test "${with_headers+set}" = set; then :
@@ -4478,6 +4490,7 @@ $as_echo "$libc_cv_prog_ld_gnu" >&6; }
 gnu_ld=$libc_cv_prog_ld_gnu
 
 
+if test "$with_clang" = no; then
 # Accept binutils 2.25 or newer.
 for ac_prog in $AS
 do
@@ -4542,7 +4555,9 @@ if test $ac_verc_fail = yes; then
   AS=: critic_missing="$critic_missing as"
 fi
 
+fi
 
+if test "$with_lld" = no; then
 if test -n "`$LD --version | sed -n 's/^GNU \(gold\).*$/\1/p'`"; then
   # Accept gold 1.14 or higher
   for ac_prog in $LD
@@ -4672,6 +4687,7 @@ if test $ac_verc_fail = yes; then
   LD=: critic_missing="$critic_missing GNU ld"
 fi
 
+fi
 fi
 
 # These programs are version sensitive.
diff --git a/configure.ac b/configure.ac
index 34b905be98..9899b3d848 100644
--- a/configure.ac
+++ b/configure.ac
@@ -144,6 +144,13 @@ AC_ARG_WITH([clang],
 	    [with_clang=$withval],
 	    [with_clang=no])
 LIBC_CONFIG_VAR([with-clang], [$with_clang])
+dnl This is a temporary hack, to help with BFD LD vs LLD debugging.
+AC_ARG_WITH([lld],
+	    AC_HELP_STRING([--with-lld],
+			   [if building/linking with lld (temporary)]),
+	    [with_lld=$withval],
+	    [with_lld=no])
+LIBC_CONFIG_VAR([with-lld], [$with_lld])
 
 AC_ARG_WITH([headers],
 	    AC_HELP_STRING([--with-headers=PATH],
@@ -928,12 +935,15 @@ AC_PROG_LN_S
 
 LIBC_PROG_BINUTILS
 
+if test "$with_clang" = no; then
 # Accept binutils 2.25 or newer.
 AC_CHECK_PROG_VER(AS, $AS, --version,
 		  [GNU assembler.* \([0-9]*\.[0-9.]*\)],
 		  [2.1[0-9][0-9]*|2.2[5-9]*|2.[3-9][0-9]*|[3-9].*|[1-9][0-9]*],
 		  AS=: critic_missing="$critic_missing as")
+fi
 
+if test "$with_lld" = no; then
 if test -n "`$LD --version | sed -n 's/^GNU \(gold\).*$/\1/p'`"; then
   # Accept gold 1.14 or higher
   AC_CHECK_PROG_VER(LD, $LD, --version,
@@ -946,6 +956,7 @@ else
 		    [2.1[0-9][0-9]*|2.2[5-9]*|2.[3-9][0-9]*|[3-9].*|[1-9][0-9]*],
 		    LD=: critic_missing="$critic_missing GNU ld")
 fi
+fi
 
 # These programs are version sensitive.
 AC_CHECK_TOOL_PREFIX
diff --git a/elf/Makefile b/elf/Makefile
index e4605877a3..6aefe50ca7 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -444,9 +444,10 @@ $(objpfx)librtld.map: $(objpfx)dl-allobjs.os $(common-objpfx)libc_pic.a
 	rm -f $@.o
 	mv -f $@T $@
 
+# For lld, add to regexp below for optional address and size to be at front of line.
 $(objpfx)librtld.mk: $(objpfx)librtld.map Makefile
 	LC_ALL=C \
-	sed -n 's@^$(common-objpfx)\([^(]*\)(\([^)]*\.os\)) *.*$$@\1 \2@p' \
+	sed -n 's@^[0-9a-f ]*$(common-objpfx)\([^(]*\)(\([^)]*\.os\)) *.*$$@\1 \2@p' \
 	    $< | \
 	while read lib file; do \
 	  case $$lib in \
diff --git a/elf/rtld.c b/elf/rtld.c
index aaf8c32595..5d4f013784 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -392,7 +392,13 @@ _dl_start_final (void *arg, struct dl_start_final_info *info)
 #endif
   _dl_setup_hash (&GL(dl_rtld_map));
   GL(dl_rtld_map).l_real = &GL(dl_rtld_map);
+#if defined(__clang__)
+  /* Work around an lld complaint that _begin cannot have a reloc and
+     also be absolute because of _begin=0 on linker line.  */
+  GL(dl_rtld_map).l_map_start = (ElfW(Addr)) 0;
+#else
   GL(dl_rtld_map).l_map_start = (ElfW(Addr)) _begin;
+#endif
   GL(dl_rtld_map).l_map_end = (ElfW(Addr)) _end;
   GL(dl_rtld_map).l_text_end = (ElfW(Addr)) _etext;
   /* Copy the TLS related data if necessary.  */