x86: Add x86_64 to x86-64 HWCAP [BZ #22093]

Before glibc 2.26, ld.so set dl_platform to "x86_64" and searched the
"x86_64" subdirectory when loading a shared library.  ld.so in glibc
2.26 was changed to set dl_platform to "haswell" or "xeon_phi", based
on supported ISAs.  This led to shared library loading failure for
shared libraries placed under the "x86_64" subdirectory.

This patch adds "x86_64" to x86-64 dl_hwcap so that ld.so will always
search the "x86_64" subdirectory when loading a shared library.

NB: We can't set x86-64 dl_platform to "x86-64" since ld.so will skip
the "haswell" and "xeon_phi" subdirectories on "haswell" and "xeon_phi"
machines.

Tested on i686 and x86-64.

	[BZ #22093]
	* sysdeps/x86/cpu-features.c (init_cpu_features): Initialize
	GLRO(dl_hwcap) to HWCAP_X86_64 for x86-64.
	* sysdeps/x86/dl-hwcap.h (HWCAP_COUNT): Updated.
	(HWCAP_IMPORTANT): Likewise.
	(HWCAP_X86_64): New enum.
	(HWCAP_X86_AVX512_1): Updated.
	* sysdeps/x86/dl-procinfo.c (_dl_x86_hwcap_flags): Add "x86_64".
	* sysdeps/x86_64/Makefile (tests): Add tst-x86_64-1.
	(modules-names): Add x86_64/tst-x86_64mod-1.
	(LDFLAGS-tst-x86_64mod-1.so): New.
	($(objpfx)tst-x86_64-1): Likewise.
	($(objpfx)x86_64/tst-x86_64mod-1.os): Likewise.
	(tst-x86_64-1-clean): Likewise.
	* sysdeps/x86_64/tst-x86_64-1.c: New file.
	* sysdeps/x86_64/tst-x86_64mod-1.c: Likewise.

3 files changed, 11 insertions, 8 deletions

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 6f900840d4..c267f17b76 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -336,7 +336,6 @@ no_cpuid:
 
   /* Reuse dl_platform, dl_hwcap and dl_hwcap_mask for x86.  */
   GLRO(dl_platform) = NULL;
-  GLRO(dl_hwcap) = 0;
 #if !HAVE_TUNABLES && defined SHARED
   /* The glibc.tune.hwcap_mask tunable is initialized already, so no need to do
      this.  */
@@ -344,6 +343,7 @@ no_cpuid:
 #endif
 
 #ifdef __x86_64__
+  GLRO(dl_hwcap) = HWCAP_X86_64;
   if (cpu_features->kind == arch_kind_intel)
     {
       if (CPU_FEATURES_ARCH_P (cpu_features, AVX512F_Usable)
@@ -374,6 +374,7 @@ no_cpuid:
 	GLRO(dl_platform) = "haswell";
     }
 #else
+  GLRO(dl_hwcap) = 0;
   if (CPU_FEATURES_CPU_P (cpu_features, SSE2))
     GLRO(dl_hwcap) |= HWCAP_X86_SSE2;
 
diff --git a/sysdeps/x86/dl-hwcap.h b/sysdeps/x86/dl-hwcap.h
index c95668415a..38627e9eef 100644
--- a/sysdeps/x86/dl-hwcap.h
+++ b/sysdeps/x86/dl-hwcap.h
@@ -24,15 +24,16 @@
 # define HWCAP_PLATFORMS_START	0
 # define HWCAP_PLATFORMS_COUNT	4
 # define HWCAP_START		0
-# define HWCAP_COUNT		2
-# define HWCAP_IMPORTANT	(HWCAP_X86_SSE2 | HWCAP_X86_AVX512_1)
+# define HWCAP_COUNT		3
+# define HWCAP_IMPORTANT \
+  (HWCAP_X86_SSE2 | HWCAP_X86_64 | HWCAP_X86_AVX512_1)
 #elif defined __x86_64__
 /* For 64 bit, only cover x86-64 platforms and capabilities.  */
 # define HWCAP_PLATFORMS_START	2
 # define HWCAP_PLATFORMS_COUNT	4
 # define HWCAP_START		1
-# define HWCAP_COUNT		2
-# define HWCAP_IMPORTANT	(HWCAP_X86_AVX512_1)
+# define HWCAP_COUNT		3
+# define HWCAP_IMPORTANT	(HWCAP_X86_64 | HWCAP_X86_AVX512_1)
 #else
 /* For 32 bit, only cover i586, i686 and SSE2.  */
 # define HWCAP_PLATFORMS_START	0
@@ -45,7 +46,8 @@
 enum
 {
   HWCAP_X86_SSE2		= 1 << 0,
-  HWCAP_X86_AVX512_1		= 1 << 1
+  HWCAP_X86_64			= 1 << 1,
+  HWCAP_X86_AVX512_1		= 1 << 2
 };
 
 static inline const char *
diff --git a/sysdeps/x86/dl-procinfo.c b/sysdeps/x86/dl-procinfo.c
index 43ab8fe25b..0192feb850 100644
--- a/sysdeps/x86/dl-procinfo.c
+++ b/sysdeps/x86/dl-procinfo.c
@@ -58,11 +58,11 @@ PROCINFO_CLASS struct cpu_features _dl_x86_cpu_features
 #if !defined PROCINFO_DECL && defined SHARED
   ._dl_x86_hwcap_flags
 #else
-PROCINFO_CLASS const char _dl_x86_hwcap_flags[2][9]
+PROCINFO_CLASS const char _dl_x86_hwcap_flags[3][9]
 #endif
 #ifndef PROCINFO_DECL
 = {
-    "sse2", "avx512_1"
+    "sse2", "x86_64", "avx512_1"
   }
 #endif
 #if !defined SHARED || defined PROCINFO_DECL