[glibc] malloc: Correct the documentation of the top_pad default

[Florian Weimer <fw@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=6c93af6b458031ebba5484bdc0029ad92720d51d

commit 6c93af6b458031ebba5484bdc0029ad92720d51d
Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu Aug 4 10:24:47 2022 +0200

    malloc: Correct the documentation of the top_pad default
    
    DEFAULT_TOP_PAD is defined as 131072 in
    sysdeps/generic/malloc-machine.h.

Diff:
---
 elf/dl-tunables.list           | 1 +
 elf/tst-rtld-list-tunables.exp | 2 +-
 manual/tunables.texi           | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list
index e6a56b3070..e925590c36 100644
--- a/elf/dl-tunables.list
+++ b/elf/dl-tunables.list
@@ -42,6 +42,7 @@ glibc {
       type: SIZE_T
       env_alias: MALLOC_TOP_PAD_
       security_level: SXID_IGNORE
+      default: 131072
     }
     perturb {
       type: INT_32
diff --git a/elf/tst-rtld-list-tunables.exp b/elf/tst-rtld-list-tunables.exp
index cdfdb56a94..2233ea9c7c 100644
--- a/elf/tst-rtld-list-tunables.exp
+++ b/elf/tst-rtld-list-tunables.exp
@@ -9,7 +9,7 @@ glibc.malloc.perturb: 0 (min: 0, max: 255)
 glibc.malloc.tcache_count: 0x0 (min: 0x0, max: 0x[f]+)
 glibc.malloc.tcache_max: 0x0 (min: 0x0, max: 0x[f]+)
 glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0x[f]+)
-glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0x[f]+)
+glibc.malloc.top_pad: 0x20000 (min: 0x0, max: 0x[f]+)
 glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0x[f]+)
 glibc.rtld.dynamic_sort: 2 (min: 1, max: 2)
 glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
diff --git a/manual/tunables.texi b/manual/tunables.texi
index 83cdcdac6d..ffd50a3fe2 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -143,7 +143,7 @@ number of bytes to retain when shrinking any of the arenas.  This provides the
 necessary hysteresis in heap size such that excessive amounts of system calls
 can be avoided.
 
-The default value of this tunable is @samp{0}.
+The default value of this tunable is @samp{131072} (128 KB).
 @end deftp
 
 @deftp Tunable glibc.malloc.perturb