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[PATCH 0/8] Remove alloca usage from glob
From: |
Adhemerval Zanella |
Subject: |
[PATCH 0/8] Remove alloca usage from glob |
Date: |
Tue, 5 Jan 2021 15:58:12 -0300 |
This is a respin on an old patchset [1] which is no longer on patchwork.
The main change is just a rebase against master since glibc version is
now on sync with gnulib.
I am sending it also to gnulib to get feedback from the project,
specifically for the part not specific for the system support by glibc
and extra requirements.
The idea of removing the alloca allows a slight better code generation,
simplifies the boilerplate code to avoid the unbounded alloca usage,
and it plays better with security compiler mitigation tools (such as the
ones for stack clash).
On x86_64 with gcc 9.2.1 build glob for shared object, the total stack
usage went from:
glob.c:261:1:next_brace_sub 8 static
glob.c:1205:1:prefix_array 96 static
glob.c:1185:1:collated_compare 8 static
glob.c:250:1:is_dir.isra.0 160 static
glob.c:1259:1:glob_in_dir 864 dynamic
glob.c:297:1:__glob 1360 dynamic
to
glob.c:231:1:next_brace_sub 8 static
dynarray-skeleton.c:203:1:globnames_array_free 32 static
glob.c:1131:1:prefix_array 96 static
glob.c:1111:1:collated_compare 8 static
dynarray-skeleton.c:275:1:globnames_array_add__ 48 static
dynarray-skeleton.c:373:1:char_array_resize.part.0 48 static
char_array-skeleton.c:274:1:char_array_replace_str_pos 48 static
char_array-skeleton.c:204:1:char_array_crop 32 static
char_array-skeleton.c:240:1:char_array_append_str 48 static
char_array-skeleton.c:118:1:char_array_set_str_size 32 static
char_array-skeleton.c:161:1:char_array_init_str 32 static
glob.c:220:1:is_dir.isra.0 160 static
glob.c:1200:1:glob_in_dir 1088 static
glob.c:267:1:__glob 1824 static
(it was obtained with -fstack-usage gcc option).
It is a slight increase and due GNU extension where glob might be called
recursivelly internally the total stack usage might be still slight
larger than current implementation. But I still think it is a worth
tradeoff.
[1] https://sourceware.org/pipermail/libc-alpha/2018-February/091326.html
Adhemerval Zanella (8):
malloc: Add specialized dynarray for C strings
posix: Use char_array for internal glob dirname
posix: Remove alloca usage for GLOB_BRACE on glob
posix: Remove alloca usage on glob dirname
posix: Use dynarray for globname in glob
posix: Remove alloca usage on glob user_name
posix: Use char_array for home_dir in glob
posix: Remove all alloca usage in glob
malloc/Makefile | 4 +-
malloc/Versions | 7 +
malloc/char_array-impl.c | 57 +++
malloc/char_array-skeleton.c | 288 +++++++++++++
malloc/char_array.h | 53 +++
malloc/dynarray.h | 9 +
malloc/dynarray_overflow_failure.c | 31 ++
malloc/malloc-internal.h | 14 +
malloc/tst-char_array.c | 112 ++++++
posix/glob.c | 622 +++++++++++------------------
10 files changed, 817 insertions(+), 380 deletions(-)
create mode 100644 malloc/char_array-impl.c
create mode 100644 malloc/char_array-skeleton.c
create mode 100644 malloc/char_array.h
create mode 100644 malloc/dynarray_overflow_failure.c
create mode 100644 malloc/tst-char_array.c
--
2.25.1
- [PATCH 0/8] Remove alloca usage from glob,
Adhemerval Zanella <=
- [PATCH 1/8] malloc: Add specialized dynarray for C strings, Adhemerval Zanella, 2021/01/05
- [PATCH 3/8] posix: Remove alloca usage for GLOB_BRACE on glob, Adhemerval Zanella, 2021/01/05
- [PATCH 4/8] posix: Remove alloca usage on glob dirname, Adhemerval Zanella, 2021/01/05
- [PATCH 2/8] posix: Use char_array for internal glob dirname, Adhemerval Zanella, 2021/01/05
- [PATCH 6/8] posix: Remove alloca usage on glob user_name, Adhemerval Zanella, 2021/01/05
- [PATCH 5/8] posix: Use dynarray for globname in glob, Adhemerval Zanella, 2021/01/05
- [PATCH 7/8] posix: Use char_array for home_dir in glob, Adhemerval Zanella, 2021/01/05
- [PATCH 8/8] posix: Remove all alloca usage in glob, Adhemerval Zanella, 2021/01/05
- Re: [PATCH 0/8] Remove alloca usage from glob, Paul Eggert, 2021/01/13