Make LD_HWCAP_MASK usable for static binaries

The LD_HWCAP_MASK environment variable was ignored in static binaries,
which is inconsistent with the behaviour of dynamically linked
binaries.  This seems to have been because of the inability of
ld_hwcap_mask being read early enough to influence anything but now
that it is in tunables, the mask is usable in static binaries as well.

This feature is important for aarch64, which relies on HWCAP_CPUID
being masked out to disable multiarch.  A sanity test on x86_64 shows
that there are no failures.  Likewise for aarch64.

	* elf/dl-hwcaps.h [HAVE_TUNABLES]: Always read hwcap_mask.
	* sysdeps/sparc/sparc32/dl-machine.h [HAVE_TUNABLES]:
	Likewise.
	* sysdeps/x86/cpu-features.c (init_cpu_features): Always set
	up hwcap and hwcap_mask.

diff --git a/ChangeLog b/ChangeLog
index f0b25e31cc7f3ead61c7400e9a8553deca7d1dbc..99b23b9ef3d293192a0fbc40bdf2dc1b8aa15c5d 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2017-06-07  Siddhesh Poyarekar  <siddhesh@sourceware.org>
 
+       * elf/dl-hwcaps.h [HAVE_TUNABLES]: Always read hwcap_mask.
+       * sysdeps/sparc/sparc32/dl-machine.h [HAVE_TUNABLES]:
+       Likewise.
+       * sysdeps/x86/cpu-features.c (init_cpu_features): Always set
+       up hwcap and hwcap_mask.
+
        * sysdeps/unix/sysv/linux/aarch64/cpu-features.c
        (init_cpu_features): Use glibc.tune.hwcap_mask.
        * sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h: New file.

diff --git a/elf/dl-hwcaps.h b/elf/dl-hwcaps.h
index 9ce33173f1defcd93fd37279addb73e9254679fe..2c4fa3db02410d4ed10a5c41dd5ffe7400b21364 100644 (file)
--- a/elf/dl-hwcaps.h
+++ b/elf/dl-hwcaps.h
@@ -18,14 +18,13 @@
 
 #include <elf/dl-tunables.h>
 
-#ifdef SHARED
-# if HAVE_TUNABLES
-#  define GET_HWCAP_MASK() \
-  TUNABLE_GET (glibc, tune, hwcap_mask, uint64_t, NULL)
+#if HAVE_TUNABLES
+# define GET_HWCAP_MASK() TUNABLE_GET (glibc, tune, hwcap_mask, uint64_t, NULL)
+#else
+# ifdef SHARED
+#   define GET_HWCAP_MASK() GLRO(dl_hwcap_mask)
 # else
-#  define GET_HWCAP_MASK() GLRO(dl_hwcap_mask)
+/* HWCAP_MASK is ignored in static binaries when built without tunables.  */
+#  define GET_HWCAP_MASK() (0)
 # endif
-#else
-/* HWCAP_MASK is ignored in static binaries.  */
-# define GET_HWCAP_MASK() (0)
 #endif

diff --git a/sysdeps/sparc/sparc32/dl-machine.h b/sysdeps/sparc/sparc32/dl-machine.h
index f9ae13300d63569c6c4aea66ec8021871b0371ca..95f673270e79e580ffe9581f05b93a50fe695059 100644 (file)
--- a/sysdeps/sparc/sparc32/dl-machine.h
+++ b/sysdeps/sparc/sparc32/dl-machine.h
@@ -37,7 +37,7 @@ elf_machine_matches_host (const Elf32_Ehdr *ehdr)
     return 1;
   else if (ehdr->e_machine == EM_SPARC32PLUS)
     {
-#ifdef SHARED
+#if HAVE_TUNABLES || defined SHARED
       uint64_t hwcap_mask = GET_HWCAP_MASK();
       return GLRO(dl_hwcap) & hwcap_mask & HWCAP_SPARC_V9;
 #else

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 4fe58bfd5166c6ef2a6baba20c6f856ade31e22d..4288001cdd685d3c012279947fb89252dba4ac0a 100644 (file)
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -312,17 +312,16 @@ no_cpuid:
   cpu_features->model = model;
   cpu_features->kind = kind;
 
-#if IS_IN (rtld)
   /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86.  */
   GLRO(dl_platform) = NULL;
   GLRO(dl_hwcap) = 0;
-#if !HAVE_TUNABLES
+#if !HAVE_TUNABLES && defined SHARED
   /* The glibc.tune.hwcap_mask tunable is initialized already, so no need to do
      this.  */
   GLRO(dl_hwcap_mask) = HWCAP_IMPORTANT;
 #endif
 
-# ifdef __x86_64__
+#ifdef __x86_64__
   if (cpu_features->kind == arch_kind_intel)
     {
       if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable)
@@ -352,7 +351,7 @@ no_cpuid:
          && CPU_FEATURES_CPU_P (cpu_features, POPCNT))
        GLRO(dl_platform) = "haswell";
     }
-# else
+#else
   if (CPU_FEATURES_CPU_P (cpu_features, SSE2))
     GLRO(dl_hwcap) |= HWCAP_X86_SSE2;
 
@@ -360,6 +359,5 @@ no_cpuid:
     GLRO(dl_platform) = "i686";
   else if (CPU_FEATURES_ARCH_P (cpu_features, I586))
     GLRO(dl_platform) = "i586";
-# endif
 #endif
 }