[glibc] elf: Remove LD_HWCAP_MASK / tunable glibc.cpu.hwcap_mask

[glibc] elf: Remove LD_HWCAP_MASK / tunable glibc.cpu.hwcap_mask

[Stefan Liebler]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=ad0aa1f54975bd20e30559930ea48a3568441ff4

commit ad0aa1f54975bd20e30559930ea48a3568441ff4
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Fri Jun 7 13:42:43 2024 +0200

    elf: Remove LD_HWCAP_MASK / tunable glibc.cpu.hwcap_mask
    
    Remove the environment variable LD_HWCAP_MASK and the tunable
    glibc.cpu.hwcap_mask as those are not used anymore in common-code
    after removal in elf/dl-cache.c:search_cache().
    
    The only remaining user is sparc32 where it is used in
    elf_machine_matches_host().  If sparc32 does not need it anymore,
    we can get rid of it at all.  Otherwise we could also move
    LD_HWCAP_MASK / tunable glibc.cpu.hwcap_mask to be sparc32 specific.
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 elf/dl-tunables.list               |  7 -------
 elf/tst-env-setuid.c               |  1 -
 manual/README.tunables             | 12 ++++++------
 manual/tunables.texi               | 11 -----------
 sysdeps/generic/unsecvars.h        |  1 -
 sysdeps/sparc/sparc32/dl-machine.h |  6 ------
 6 files changed, 6 insertions(+), 32 deletions(-)

diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
index 1186272c81..40ac5b3776 100644
--- a/elf/dl-tunables.list
+++ b/elf/dl-tunables.list
@@ -83,13 +83,6 @@ glibc {
       minval: 0
     }
   }
-  cpu {
-    hwcap_mask {
-      type: UINT_64
-      env_alias: LD_HWCAP_MASK
-      default: HWCAP_IMPORTANT
-    }
-  }
 
   elision {
     enable {
diff --git a/elf/tst-env-setuid.c b/elf/tst-env-setuid.c
index 43047c48f3..59f2ffeb88 100644
--- a/elf/tst-env-setuid.c
+++ b/elf/tst-env-setuid.c
@@ -52,7 +52,6 @@ static const struct envvar_t filtered_envvars[] =
 {
   { "GLIBC_TUNABLES",          FILTERED_VALUE },
   { "LD_AUDIT",                FILTERED_VALUE },
-  { "LD_HWCAP_MASK",           FILTERED_VALUE },
   { "LD_LIBRARY_PATH",         FILTERED_VALUE },
   { "LD_PRELOAD",              FILTERED_VALUE },
   { "LD_PROFILE",              PROFILE_LIB },
diff --git a/manual/README.tunables b/manual/README.tunables
index 72ae00dc02..594879397b 100644
--- a/manual/README.tunables
+++ b/manual/README.tunables
@@ -96,11 +96,11 @@ where 'check' is the tunable name and 'val' is a value of same type.
 To get and set tunables in a different namespace from that module, use the full
 form of the macros as follows:
 
-  val = TUNABLE_GET_FULL (glibc, cpu, hwcap_mask, uint64_t, NULL)
+  val = TUNABLE_GET_FULL (glibc, malloc, mmap_max, int32_t, NULL)
 
-  TUNABLE_SET_FULL (glibc, cpu, hwcap_mask, val)
+  TUNABLE_SET_FULL (glibc, malloc, mmap_max, val)
 
-where 'glibc' is the top namespace, 'cpu' is the tunable namespace and the
+where 'glibc' is the top namespace, 'malloc' is the tunable namespace and the
 remaining arguments are the same as the short form macros.
 
 The minimum and maximum values can updated together with the tunable value
@@ -114,11 +114,11 @@ where 'check' is the tunable name, 'val' is a value of same type, 'min' and
 To set the minimum and maximum values of tunables in a different namespace
 from that module, use the full form of the macros as follows:
 
-  val = TUNABLE_GET_FULL (glibc, cpu, hwcap_mask, uint64_t, NULL)
+  val = TUNABLE_GET_FULL (glibc, malloc, mmap_max, int32_t, NULL)
 
-  TUNABLE_SET_WITH_BOUNDS_FULL (glibc, cpu, hwcap_mask, val, min, max)
+  TUNABLE_SET_WITH_BOUNDS_FULL (glibc, malloc, mmap_max, val, min, max)
 
-where 'glibc' is the top namespace, 'cpu' is the tunable namespace and the
+where 'glibc' is the top namespace, 'malloc' is the tunable namespace and the
 remaining arguments are the same as the short form macros.
 
 When TUNABLE_NAMESPACE is not defined in a module, TUNABLE_GET is equivalent to
diff --git a/manual/tunables.texi b/manual/tunables.texi
index 8dd02d8149..0b1b2898c0 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -55,7 +55,6 @@ glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x4040, max: 0xfffffffffffff
 glibc.cpu.x86_memset_non_temporal_threshold: 0xc0000 (min: 0x4040, max: 0xfffffffffffffff)
 glibc.cpu.x86_shstk:
 glibc.pthread.stack_cache_size: 0x2800000 (min: 0x0, max: 0xffffffffffffffff)
-glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
 glibc.malloc.mmap_max: 0 (min: 0, max: 2147483647)
 glibc.elision.skip_trylock_internal_abort: 3 (min: 0, max: 2147483647)
 glibc.cpu.plt_rewrite: 0 (min: 0, max: 2)
@@ -504,16 +503,6 @@ Behavior of @theglibc{} can be tuned to assume specific hardware capabilities
 by setting the following tunables in the @code{cpu} namespace:
 @end deftp
 
-@deftp Tunable glibc.cpu.hwcap_mask
-This tunable supersedes the @env{LD_HWCAP_MASK} environment variable and is
-identical in features.
-
-The @code{AT_HWCAP} key in the Auxiliary Vector specifies instruction set
-extensions available in the processor at runtime for some architectures.  The
-@code{glibc.cpu.hwcap_mask} tunable allows the user to mask out those
-capabilities at runtime, thus disabling use of those extensions.
-@end deftp
-
 @deftp Tunable glibc.cpu.hwcaps
 The @code{glibc.cpu.hwcaps=-xxx,yyy,-zzz...} tunable allows the user to
 enable CPU/ARCH feature @code{yyy}, disable CPU/ARCH feature @code{xxx}
diff --git a/sysdeps/generic/unsecvars.h b/sysdeps/generic/unsecvars.h
index f1724efe0f..97857a11aa 100644
--- a/sysdeps/generic/unsecvars.h
+++ b/sysdeps/generic/unsecvars.h
@@ -12,7 +12,6 @@
   "LD_DEBUG\0"								      \
   "LD_DEBUG_OUTPUT\0"							      \
   "LD_DYNAMIC_WEAK\0"							      \
-  "LD_HWCAP_MASK\0"							      \
   "LD_LIBRARY_PATH\0"							      \
   "LD_ORIGIN_PATH\0"							      \
   "LD_PRELOAD\0"							      \
diff --git a/sysdeps/sparc/sparc32/dl-machine.h b/sysdeps/sparc/sparc32/dl-machine.h
index d855c66fe3..2c56d8a80e 100644
--- a/sysdeps/sparc/sparc32/dl-machine.h
+++ b/sysdeps/sparc/sparc32/dl-machine.h
@@ -39,13 +39,7 @@ elf_machine_matches_host (const Elf32_Ehdr *ehdr)
     return 1;
   else if (ehdr->e_machine == EM_SPARC32PLUS)
     {
-#if defined SHARED
-      uint64_t hwcap_mask = TUNABLE_GET (glibc, cpu, hwcap_mask, uint64_t,
-					 NULL);
-      return GLRO(dl_hwcap) & hwcap_mask & HWCAP_SPARC_V9;
-#else
       return GLRO(dl_hwcap) & HWCAP_SPARC_V9;
-#endif
     }
   else
     return 0;