From 89e5cef3817a4caf7dea19c8fe4ec7a7ef13ed10 Mon Sep 17 00:00:00 2001
From: GNU Libc Maintainers <debian-glibc@lists.debian.org>
Date: Sun, 25 Dec 2022 18:42:32 +0000
Subject: [PATCH] local-ldso-disable-hwcap

# DP: Allow hwcap's to be disabled with the existence of a file. This
# DP: makes it easier to do upgrades with optimized (hwcap) library
# DP: packages.
# DP: Author: Rewritten by Daniel Jacobowitz <dan@debian.org>
# DP: Upstream status: Debian-Specific
# DP: Status Details: This isn't going to be acceptable upstream, we
# DP:                 only need it because we support in-place upgrades.
# DP: Date: 2003-10-28, (Updated 2005-01-02 gotom, 2007-05-20 aurel32)

# DP: Allow hwcap's to be disabled with the existence of a file. This
# DP: makes it easier to do upgrades with optimized (hwcap) library
# DP: packages.
# DP: Author: Rewritten by Daniel Jacobowitz <dan@debian.org>
# DP: Upstream status: Debian-Specific
# DP: Status Details: This isn't going to be acceptable upstream, we
# DP:                 only need it because we support in-place upgrades.
# DP: Date: 2003-10-28, (Updated 2005-01-02 gotom, 2007-05-20 aurel32)


Gbp-Pq: Topic any
Gbp-Pq: Name local-ldso-disable-hwcap.diff
---
 elf/dl-cache.c           | 10 ++++++++++
 elf/dl-hwcaps.c          | 20 ++++++++++++++++++++
 sysdeps/alpha/ldsodefs.h |  2 ++
 3 files changed, 32 insertions(+)

diff --git a/elf/dl-cache.c b/elf/dl-cache.c
index b97c17b3a..cb5d4f5d4 100644
--- a/elf/dl-cache.c
+++ b/elf/dl-cache.c
@@ -26,6 +26,9 @@
 #include <_itoa.h>
 #include <dl-hwcaps.h>
 #include <dl-isa-level.h>
+#include <fcntl.h>
+#include <sysdep.h>
+#include <not-errno.h>
 
 #ifndef _DL_PLATFORMS_COUNT
 # define _DL_PLATFORMS_COUNT 0
@@ -216,6 +219,11 @@ search_cache (const char *string_table, uint32_t string_table_size,
 #ifdef SHARED
   uint32_t best_priority = 0;
 #endif
+  int disable_hwcap = 0;
+#ifdef NEED_LD_SO_NOHWCAP
+  if (__access_noerrno ("/etc/ld.so.nohwcap", F_OK) == 0)
+    disable_hwcap = 1;
+#endif
 
   while (left <= right)
     {
@@ -297,6 +305,8 @@ search_cache (const char *string_table, uint32_t string_table_size,
 
 		      if ((libnew->hwcap & hwcap_exclude) && !named_hwcap)
 			continue;
+		      if (disable_hwcap && libnew->hwcap != 0)
+			continue;
 		      if (_DL_PLATFORMS_COUNT
 			  && (libnew->hwcap & _DL_HWCAP_PLATFORM) != 0
 			  && ((libnew->hwcap & _DL_HWCAP_PLATFORM)
diff --git a/elf/dl-hwcaps.c b/elf/dl-hwcaps.c
index 92eb53790..e67637374 100644
--- a/elf/dl-hwcaps.c
+++ b/elf/dl-hwcaps.c
@@ -22,6 +22,9 @@
 #include <libintl.h>
 #include <unistd.h>
 #include <ldsodefs.h>
+#include <fcntl.h>
+#include <sysdep.h>
+#include <not-errno.h>
 
 #include <dl-procinfo.h>
 #include <dl-hwcaps.h>
@@ -204,6 +207,23 @@ _dl_important_hwcaps (const char *glibc_hwcaps_prepend,
   /* For TLS enabled builds always add 'tls'.  */
   ++cnt;
 
+#ifdef NEED_LD_SO_NOHWCAP
+  if (__access_noerrno ("/etc/ld.so.nohwcap", F_OK) == 0)
+    {
+      /* If hwcap is disabled, we only have the base directory to search.  */
+      result = (struct r_strlenpair *) malloc (sizeof (*result));
+      if (result == NULL)
+	_dl_signal_error (ENOMEM, NULL, NULL,
+			 N_("cannot create capability list"));
+
+      result[0].str = (char *) result;  /* Does not really matter.  */
+      result[0].len = 0;
+
+      *sz = 1;
+      return result;
+    }
+#endif
+
   /* Create temporary data structure to generate result table.  */
   struct r_strlenpair temp[cnt];
   m = 0;
diff --git a/sysdeps/alpha/ldsodefs.h b/sysdeps/alpha/ldsodefs.h
index a04f6ddc7..8ea560577 100644
--- a/sysdeps/alpha/ldsodefs.h
+++ b/sysdeps/alpha/ldsodefs.h
@@ -37,6 +37,8 @@ struct La_alpha_retval;
 				      struct La_alpha_retval *,		\
 				      const char *);
 
+#define NEED_LD_SO_NOHWCAP
+
 #include_next <ldsodefs.h>
 
 #endif
-- 
2.30.2