[glibc] sysdeps: tst-bz21269: handle ENOSYS & skip appropriately

[Sam James]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=652b9fdb77d9fd056d4dd26dad2c14142768ab49

commit 652b9fdb77d9fd056d4dd26dad2c14142768ab49
Author: Sam James <sam@gentoo.org>
Date:   Sat Aug 5 00:04:33 2023 +0100

    sysdeps: tst-bz21269: handle ENOSYS & skip appropriately
    
    SYS_modify_ldt requires CONFIG_MODIFY_LDT_SYSCALL to be set in the kernel, which
    some distributions may disable for hardening. Check if that's the case (unset)
    and mark the test as UNSUPPORTED if so.
    
    Reviewed-by: DJ Delorie <dj@redhat.com>
    Signed-off-by: Sam James <sam@gentoo.org>

Diff:
---
 sysdeps/unix/sysv/linux/i386/tst-bz21269.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/sysdeps/unix/sysv/linux/i386/tst-bz21269.c b/sysdeps/unix/sysv/linux/i386/tst-bz21269.c
index f508ef8f16..28f5359bea 100644
--- a/sysdeps/unix/sysv/linux/i386/tst-bz21269.c
+++ b/sysdeps/unix/sysv/linux/i386/tst-bz21269.c
@@ -52,7 +52,16 @@ xset_thread_area (struct user_desc *u_info)
 static void
 xmodify_ldt (int func, const void *ptr, unsigned long bytecount)
 {
-  TEST_VERIFY_EXIT (syscall (SYS_modify_ldt, func, ptr, bytecount) == 0);
+  long ret = syscall (SYS_modify_ldt, func, ptr, bytecount);
+
+  if (ret == -1)
+    {
+      if (errno == ENOSYS)
+	FAIL_UNSUPPORTED ("modify_ldt not supported");
+      FAIL_EXIT1 ("modify_ldt failed (errno=%d)", errno);
+    }
+
+  return 0;
 }
 
 static int