elf: Add glibc-hwcaps support for LD_LIBRARY_PATH

This hacks non-power-set processing into _dl_important_hwcaps.
Once the legacy hwcaps handling goes away, the subdirectory
handling needs to be reworked, but it is premature to do this
while both approaches are still supported.

ld.so supports two new arguments, --glibc-hwcaps-prepend and
--glibc-hwcaps-mask.  Each accepts a colon-separated list of
glibc-hwcaps subdirectory names.  The prepend option adds additional
subdirectories that are searched first, in the specified order.  The
mask option restricts the automatically selected subdirectories to
those listed in the option argument.  For example, on systems where
/usr/lib64 is on the library search path,
--glibc-hwcaps-prepend=valgrind:debug causes the dynamic loader to
search the directories /usr/lib64/glibc-hwcaps/valgrind and
/usr/lib64/glibc-hwcaps/debug just before /usr/lib64 is searched.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

1 files changed, 66 insertions, 5 deletions

diff --git a/elf/Makefile b/elf/Makefile
index a494b14519..db10541829 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -61,7 +61,8 @@ elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \
 # ld.so uses those routines, plus some special stuff for being the program
 # interpreter and operating independent of libc.
 rtld-routines	= rtld $(all-dl-routines) dl-sysdep dl-environ dl-minimal \
-  dl-error-minimal dl-conflict dl-hwcaps dl-usage
+  dl-error-minimal dl-conflict dl-hwcaps dl-hwcaps_split dl-hwcaps-subdirs \
+  dl-usage
 all-rtld-routines = $(rtld-routines) $(sysdep-rtld-routines)
 
 CFLAGS-dl-runtime.c += -fexceptions -fasynchronous-unwind-tables
@@ -212,14 +213,14 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-filterobj tst-filterobj-dlopen tst-auxobj tst-auxobj-dlopen \
 	 tst-audit14 tst-audit15 tst-audit16 \
 	 tst-single_threaded tst-single_threaded-pthread \
-	 tst-tls-ie tst-tls-ie-dlmopen \
-	 argv0test
+	 tst-tls-ie tst-tls-ie-dlmopen argv0test \
+	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask
 #	 reldep9
 tests-internal += loadtest unload unload2 circleload1 \
 	 neededtest neededtest2 neededtest3 neededtest4 \
 	 tst-tls3 tst-tls6 tst-tls7 tst-tls8 tst-dlmopen2 \
 	 tst-ptrguard1 tst-stackguard1 tst-libc_dlvsym \
-	 tst-create_format1 tst-tls-surplus
+	 tst-create_format1 tst-tls-surplus tst-dl-hwcaps_split
 tests-container += tst-pldd tst-dlopen-tlsmodid-container \
   tst-dlopen-self-container
 test-srcs = tst-pathopt
@@ -331,7 +332,10 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-single_threaded-mod3 tst-single_threaded-mod4 \
 		tst-tls-ie-mod0 tst-tls-ie-mod1 tst-tls-ie-mod2 \
 		tst-tls-ie-mod3 tst-tls-ie-mod4 tst-tls-ie-mod5 \
-		tst-tls-ie-mod6
+		tst-tls-ie-mod6 libmarkermod1-1 libmarkermod1-2 libmarkermod1-3 \
+		libmarkermod2-1 libmarkermod2-2 \
+		libmarkermod3-1 libmarkermod3-2 libmarkermod3-3 \
+		libmarkermod4-1 libmarkermod4-2 libmarkermod4-3 libmarkermod4-4 \
 
 # Most modules build with _ISOMAC defined, but those filtered out
 # depend on internal headers.
@@ -1814,3 +1818,60 @@ $(objpfx)argv0test.out: tst-rtld-argv0.sh $(objpfx)ld.so \
             '$(test-wrapper-env)' '$(run_program_env)' \
             '$(rpath-link)' 'test-argv0' > $@; \
     $(evaluate-test)
+
+# A list containing the name of the most likely searched subdirectory
+# of the glibc-hwcaps directory, for each supported architecture (in
+# other words, the oldest hardware level recognized by the
+# glibc-hwcaps mechanism for this architecture).  Used to obtain test
+# coverage for some glibc-hwcaps tests for the widest possible range
+# of systems.
+glibc-hwcaps-first-subdirs-for-tests =
+
+# The test modules are parameterized by preprocessor macros.
+LDFLAGS-libmarkermod1-1.so += -Wl,-soname,libmarkermod1.so
+LDFLAGS-libmarkermod2-1.so += -Wl,-soname,libmarkermod2.so
+LDFLAGS-libmarkermod3-1.so += -Wl,-soname,libmarkermod3.so
+LDFLAGS-libmarkermod4-1.so += -Wl,-soname,libmarkermod4.so
+$(objpfx)libmarkermod%.os : markermodMARKER-VALUE.c
+	$(compile-command.c) \
+	  -DMARKER=marker$(firstword $(subst -, ,$*)) \
+	  -DVALUE=$(lastword $(subst -, ,$*))
+$(objpfx)libmarkermod1.so: $(objpfx)libmarkermod1-1.so
+	cp $< $@
+$(objpfx)libmarkermod2.so: $(objpfx)libmarkermod2-1.so
+	cp $< $@
+$(objpfx)libmarkermod3.so: $(objpfx)libmarkermod3-1.so
+	cp $< $@
+$(objpfx)libmarkermod4.so: $(objpfx)libmarkermod4-1.so
+	cp $< $@
+
+# tst-glibc-hwcaps-prepend checks that --glibc-hwcaps-prepend is
+# preferred over auto-detected subdirectories.
+$(objpfx)tst-glibc-hwcaps-prepend: $(objpfx)libmarkermod1-1.so
+$(objpfx)glibc-hwcaps/prepend-markermod1/libmarkermod1.so: \
+  $(objpfx)libmarkermod1-2.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)glibc-hwcaps/%/libmarkermod1.so: $(objpfx)libmarkermod1-3.so
+	$(make-target-directory)
+	cp $< $@
+$(objpfx)tst-glibc-hwcaps-prepend.out: \
+  $(objpfx)tst-glibc-hwcaps-prepend $(objpfx)libmarkermod1.so \
+  $(patsubst %,$(objpfx)glibc-hwcaps/%/libmarkermod1.so,prepend-markermod1 \
+    $(glibc-hwcaps-first-subdirs-for-tests))
+	$(test-wrapper) $(rtld-prefix) \
+	  --glibc-hwcaps-prepend prepend-markermod1 \
+	  $< > $@; \
+	$(evaluate-test)
+
+# tst-glibc-hwcaps-mask checks that --glibc-hwcaps-mask can be used to
+# suppress all auto-detected subdirectories.
+$(objpfx)tst-glibc-hwcaps-mask: $(objpfx)libmarkermod1-1.so
+$(objpfx)tst-glibc-hwcaps-mask.out: \
+  $(objpfx)tst-glibc-hwcaps-mask $(objpfx)libmarkermod1.so \
+  $(patsubst %,$(objpfx)glibc-hwcaps/%/libmarkermod1.so,\
+    $(glibc-hwcaps-first-subdirs-for-tests))
+	$(test-wrapper) $(rtld-prefix) \
+	  --glibc-hwcaps-mask does-not-exist \
+	  $< > $@; \
+	$(evaluate-test)