RISC-V: crypto: add a vector-crypto-accelerated SHA256
From: Heiko Stuebner <heiko.stuebner@...> Date: Thu, 2 Feb 2023 18:21:58 +0100
Commit-Message
This adds an accelerated SHA256 algorithm using either the Zvknha or Zvknhb vector crypto extensions. The spec says that Zvknhb supports SHA-256 and SHA-512. Zvknha supports only SHA-256. so the relevant acclerating instructions are included in both. Co-developed-by: Charalampos Mitrodimas <charalampos.mitrodimas@...> Signed-off-by: Charalampos Mitrodimas <charalampos.mitrodimas@...> Signed-off-by: Heiko Stuebner <heiko.stuebner@...>
Patch-Comment
arch/riscv/crypto/Kconfig | 11 + arch/riscv/crypto/Makefile | 7 + arch/riscv/crypto/sha256-riscv64-glue.c | 115 +++++++ .../crypto/sha256-riscv64-zvbb-zvknha.pl | 314 ++++++++++++++++++ 4 files changed, 447 insertions(+) create mode 100644 arch/riscv/crypto/sha256-riscv64-glue.c create mode 100644 arch/riscv/crypto/sha256-riscv64-zvbb-zvknha.pl
Statistics
- 447 lines added
- 0 lines removed
Changes
-------------------------- arch/riscv/crypto/Kconfig ---------------------------
index a1493b556993..860919d230aa 100644
@@ -17,4 +17,15 @@ config CRYPTO_GHASH_RISCV64
- Zvbb vector crypto extension
- Zvkg vector crypto extension
+config CRYPTO_SHA256_RISCV64
+ tristate "Hash functions: SHA-256"
+ depends on 64BIT && RISCV_ISA_V
+ select CRYPTO_HASH
+ select CRYPTO_LIB_SHA256
+ help
+ SHA-256 secure hash algorithm (FIPS 180)
+
+ Architecture: riscv64 using
+ - Zvknha or Zvknhb vector crypto extensions
+
endmenu
-------------------------- arch/riscv/crypto/Makefile --------------------------
index 496e784984cc..cae2f255ceae 100644
@@ -12,6 +12,9 @@ ifdef CONFIG_RISCV_ISA_V
ghash-riscv64-y += ghash-riscv64-zvbb-zvbc.o ghash-riscv64-zvkg.o
endif
+obj-$(CONFIG_CRYPTO_SHA256_RISCV64) += sha256-riscv64.o
+sha256-riscv64-y := sha256-riscv64-glue.o sha256-riscv64-zvbb-zvknha.o
+
quiet_cmd_perlasm = PERLASM $@
cmd_perlasm = $(PERL) $(<) void $(@)
@@ -24,4 +27,8 @@ $(obj)/ghash-riscv64-zvbb-zvbc.S: $(src)/ghash-riscv64-zvbb-zvbc.pl
$(obj)/ghash-riscv64-zvkg.S: $(src)/ghash-riscv64-zvkg.pl
$(call cmd,perlasm)
+$(obj)/sha256-riscv64-zvbb-zvknha.S: $(src)/sha256-riscv64-zvbb-zvknha.pl
+ $(call cmd,perlasm)
+
clean-files += ghash-riscv64-zbc.S ghash-riscv64-zvkb.S ghash-riscv64-zvkg.S
+clean-files += sha256-riscv64-zvknha.S
------------------- arch/riscv/crypto/sha256-riscv64-glue.c --------------------
new file mode 100644
index 000000000000..1c9c88029f60
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Linux/riscv64 port of the OpenSSL SHA256 implementation for RISCV64
+ *
+ * Copyright (C) 2022 VRULL GmbH
+ * Author: Heiko Stuebner <heiko.stuebner@vrull.eu>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <asm/simd.h>
+#include <asm/vector.h>
+#include <crypto/internal/hash.h>
+#include <crypto/internal/simd.h>
+#include <crypto/sha2.h>
+#include <crypto/sha256_base.h>
+
+asmlinkage void sha256_block_data_order_zvbb_zvknha(u32 *digest, const void *data,
+ unsigned int num_blks);
+
+static void __sha256_block_data_order(struct sha256_state *sst, u8 const *src,
+ int blocks)
+{
+ sha256_block_data_order_zvbb_zvknha(sst->state, src, blocks);
+}
+
+static int riscv64_sha256_update(struct shash_desc *desc, const u8 *data,
+ unsigned int len)
+{
+ if (crypto_simd_usable()) {
+ int ret;
+
+ kernel_rvv_begin();
+ ret = sha256_base_do_update(desc, data, len,
+ __sha256_block_data_order);
+ kernel_rvv_end();
+ return ret;
+ } else {
+ sha256_update(shash_desc_ctx(desc), data, len);
+ return 0;
+ }
+}
+
+static int riscv64_sha256_finup(struct shash_desc *desc, const u8 *data,
+ unsigned int len, u8 *out)
+{
+ if (!crypto_simd_usable()) {
+ sha256_update(shash_desc_ctx(desc), data, len);
+ sha256_final(shash_desc_ctx(desc), out);
+ return 0;
+ }
+
+ kernel_rvv_begin();
+ if (len)
+ sha256_base_do_update(desc, data, len,
+ __sha256_block_data_order);
+
+ sha256_base_do_finalize(desc, __sha256_block_data_order);
+ kernel_rvv_end();
+
+ return sha256_base_finish(desc, out);
+}
+
+static int riscv64_sha256_final(struct shash_desc *desc, u8 *out)
+{
+ return riscv64_sha256_finup(desc, NULL, 0, out);
+}
+
+static struct shash_alg sha256_alg = {
+ .digestsize = SHA256_DIGEST_SIZE,
+ .init = sha256_base_init,
+ .update = riscv64_sha256_update,
+ .final = riscv64_sha256_final,
+ .finup = riscv64_sha256_finup,
+ .descsize = sizeof(struct sha256_state),
+ .base.cra_name = "sha256",
+ .base.cra_driver_name = "sha256-riscv64-zvknha",
+ .base.cra_priority = 150,
+ .base.cra_blocksize = SHA256_BLOCK_SIZE,
+ .base.cra_module = THIS_MODULE,
+};
+
+static int __init sha256_mod_init(void)
+{
+ /*
+ * From the spec:
+ * Zvknhb supports SHA-256 and SHA-512. Zvknha supports only SHA-256.
+ */
+ if ((riscv_isa_extension_available(NULL, ZVKNHA) ||
+ riscv_isa_extension_available(NULL, ZVKNHB)) &&
+ riscv_isa_extension_available(NULL, ZVBB) &&
+ riscv_vector_vlen() >= 128)
+
+ return crypto_register_shash(&sha256_alg);
+
+ return 0;
+}
+
+static void __exit sha256_mod_fini(void)
+{
+ if ((riscv_isa_extension_available(NULL, ZVKNHA) ||
+ riscv_isa_extension_available(NULL, ZVKNHB)) &&
+ riscv_isa_extension_available(NULL, ZVBB) &&
+ riscv_vector_vlen() >= 128)
+ crypto_unregister_shash(&sha256_alg);
+}
+
+module_init(sha256_mod_init);
+module_exit(sha256_mod_fini);
+
+MODULE_DESCRIPTION("SHA-256 secure hash for riscv64");
+MODULE_AUTHOR("Andy Polyakov <appro@openssl.org>");
+MODULE_AUTHOR("Heiko Stuebner <heiko.stuebner@vrull.eu>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_CRYPTO("sha256");
--------------- arch/riscv/crypto/sha256-riscv64-zvbb-zvknha.pl ----------------
new file mode 100644
index 000000000000..ab3ac4e373d9
@@ -0,0 +1,314 @@
+#! /usr/bin/env perl
+# SPDX-License-Identifier: Apache-2.0 OR BSD-2-Clause
+#
+# This file is dual-licensed, meaning that you can use it under your
+# choice of either of the following two licenses:
+#
+# Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the Apache License 2.0 (the "License"). You can obtain
+# a copy in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+#
+# or
+#
+# Copyright (c) 2023, Christoph Müllner <christoph.muellner@vrull.eu>
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# The generated code of this file depends on the following RISC-V extensions:
+# - RV64I
+# - RISC-V vector ('V') with VLEN >= 128
+# - Vector Bit-manipulation used in Cryptography ('Zvbb')
+# - Vector SHA-2 Secure Hash ('Zvknha')
+
+use strict;
+use warnings;
+
+use FindBin qw($Bin);
+use lib "$Bin";
+use lib "$Bin/../../perlasm";
+use riscv;
+
+# $output is the last argument if it looks like a file (it has an extension)
+# $flavour is the first argument if it doesn't look like a file
+my $output = $#ARGV >= 0 && $ARGV[$#ARGV] =~ m|\.\w+$| ? pop : undef;
+my $flavour = $#ARGV >= 0 && $ARGV[0] !~ m|\.| ? shift : undef;
+
+$output and open STDOUT,">$output";
+
+my $code=<<___;
+.text
+___
+
+my ($V0, $V10, $V11, $V12, $V13, $V14, $V15, $V16, $V17) = ("v0", "v10", "v11", "v12", "v13", "v14","v15", "v16", "v17");
+my ($V26, $V27) = ("v26", "v27");
+
+my $K256 = "K256";
+
+# Function arguments
+my ($H, $INP, $LEN, $KT, $STRIDE) = ("a0", "a1", "a2", "a3", "t3");
+
+################################################################################
+# void sha256_block_data_order_zvbb_zvknha(void *c, const void *p, size_t len)
+$code .= <<___;
+.p2align 2
+.globl sha256_block_data_order_zvbb_zvknha
+.type sha256_block_data_order_zvbb_zvknha,\@function
+sha256_block_data_order_zvbb_zvknha:
+ @{[vsetivli__x0_4_e32_m1_ta_ma]}
+
+ # H is stored as {a,b,c,d},{e,f,g,h}, but we need {f,e,b,a},{h,g,d,c}
+ # We achieve this by reading with a negative stride followed by
+ # element sliding.
+ li $STRIDE, -4
+ addi $H, $H, 12
+ @{[vlse32_v $V16, $H, $STRIDE]} # {d,c,b,a}
+ addi $H, $H, 16
+ @{[vlse32_v $V17, $H, $STRIDE]} # {h,g,f,e}
+ # Keep H advanced by 12
+ addi $H, $H, -16
+
+ @{[vmv_v_v $V27, $V16]} # {d,c,b,a}
+ @{[vslidedown_vi $V26, $V16, 2]} # {b,a,0,0}
+ @{[vslidedown_vi $V16, $V17, 2]} # {f,e,0,0}
+ @{[vslideup_vi $V16, $V26, 2]} # {f,e,b,a}
+ @{[vslideup_vi $V17, $V27, 2]} # {h,g,d,c}
+
+ # Keep the old state as we need it later: H' = H+{a',b',c',...,h'}.
+ @{[vmv_v_v $V26, $V16]}
+ @{[vmv_v_v $V27, $V17]}
+
+L_round_loop:
+ la $KT, $K256 # Load round constants K256
+
+ # Load the 512-bits of the message block in v10-v13 and perform
+ # an endian swap on each 4 bytes element.
+ @{[vle32_v $V10, $INP]}
+ @{[vrev8_v $V10, $V10]}
+ add $INP, $INP, 16
+ @{[vle32_v $V11, $INP]}
+ @{[vrev8_v $V11, $V11]}
+ add $INP, $INP, 16
+ @{[vle32_v $V12, $INP]}
+ @{[vrev8_v $V12, $V12]}
+ add $INP, $INP, 16
+ @{[vle32_v $V13, $INP]}
+ @{[vrev8_v $V13, $V13]}
+ add $INP, $INP, 16
+
+ # Decrement length by 1
+ add $LEN, $LEN, -1
+
+ # Set v0 up for the vmerge that replaces the first word (idx==0)
+ @{[vid_v $V0]}
+ @{[vmseq_vi $V0, $V0, 0x0]} # v0.mask[i] = (i == 0 ? 1 : 0)
+
+ # Quad-round 0 (+0, Wt from oldest to newest in v10->v11->v12->v13)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V10]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V12, $V11, $V0]}
+ @{[vsha2ms_vv $V10, $V14, $V13]} # Generate W[19:16]
+
+ # Quad-round 1 (+1, v11->v12->v13->v10)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V11]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V13, $V12, $V0]}
+ @{[vsha2ms_vv $V11, $V14, $V10]} # Generate W[23:20]
+
+ # Quad-round 2 (+2, v12->v13->v10->v11)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V12]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V10, $V13, $V0]}
+ @{[vsha2ms_vv $V12, $V14, $V11]} # Generate W[27:24]
+
+ # Quad-round 3 (+3, v13->v10->v11->v12)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V13]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V11, $V10, $V0]}
+ @{[vsha2ms_vv $V13, $V14, $V12]} # Generate W[31:28]
+
+ # Quad-round 4 (+0, v10->v11->v12->v13)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V10]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V12, $V11, $V0]}
+ @{[vsha2ms_vv $V10, $V14, $V13]} # Generate W[35:32]
+
+ # Quad-round 5 (+1, v11->v12->v13->v10)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V11]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V13, $V12, $V0]}
+ @{[vsha2ms_vv $V11, $V14, $V10]} # Generate W[39:36]
+
+ # Quad-round 6 (+2, v12->v13->v10->v11)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V12]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V10, $V13, $V0]}
+ @{[vsha2ms_vv $V12, $V14, $V11]} # Generate W[43:40]
+
+ # Quad-round 7 (+3, v13->v10->v11->v12)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V13]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V11, $V10, $V0]}
+ @{[vsha2ms_vv $V13, $V14, $V12]} # Generate W[47:44]
+
+ # Quad-round 8 (+0, v10->v11->v12->v13)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V10]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V12, $V11, $V0]}
+ @{[vsha2ms_vv $V10, $V14, $V13]} # Generate W[51:48]
+
+ # Quad-round 9 (+1, v11->v12->v13->v10)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V11]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V13, $V12, $V0]}
+ @{[vsha2ms_vv $V11, $V14, $V10]} # Generate W[55:52]
+
+ # Quad-round 10 (+2, v12->v13->v10->v11)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V12]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V10, $V13, $V0]}
+ @{[vsha2ms_vv $V12, $V14, $V11]} # Generate W[59:56]
+
+ # Quad-round 11 (+3, v13->v10->v11->v12)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V13]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+ @{[vmerge_vvm $V14, $V11, $V10, $V0]}
+ @{[vsha2ms_vv $V13, $V14, $V12]} # Generate W[63:60]
+
+ # Quad-round 12 (+0, v10->v11->v12->v13)
+ # Note that we stop generating new message schedule words (Wt, v10-13)
+ # as we already generated all the words we end up consuming (i.e., W[63:60]).
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V10]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+
+ # Quad-round 13 (+1, v11->v12->v13->v10)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V11]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+
+ # Quad-round 14 (+2, v12->v13->v10->v11)
+ @{[vle32_v $V15, $KT]}
+ addi $KT, $KT, 16
+ @{[vadd_vv $V14, $V15, $V12]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+
+ # Quad-round 15 (+3, v13->v10->v11->v12)
+ @{[vle32_v $V15, $KT]}
+ # No kt increment needed.
+ @{[vadd_vv $V14, $V15, $V13]}
+ @{[vsha2cl_vv $V17, $V16, $V14]}
+ @{[vsha2ch_vv $V16, $V17, $V14]}
+
+ # H' = H+{a',b',c',...,h'}
+ @{[vadd_vv $V16, $V26, $V16]}
+ @{[vadd_vv $V17, $V27, $V17]}
+ @{[vmv_v_v $V26, $V16]}
+ @{[vmv_v_v $V27, $V17]}
+ bnez $LEN, L_round_loop
+
+ # v26 = v16 = {f,e,b,a}
+ # v27 = v17 = {h,g,d,c}
+ # Let's do the opposit transformation like on entry.
+
+ @{[vslideup_vi $V17, $V16, 2]} # {h,g,f,e}
+
+ @{[vslidedown_vi $V16, $V27, 2]} # {d,c,0,0}
+ @{[vslidedown_vi $V26, $V26, 2]} # {b,a,0,0}
+ @{[vslideup_vi $V16, $V26, 2]} # {d,c,b,a}
+
+ # H is already advanced by 12
+ @{[vsse32_v $V16, $H, $STRIDE]} # {a,b,c,d}
+ addi $H, $H, 16
+ @{[vsse32_v $V17, $H, $STRIDE]} # {e,f,g,h}
+
+ ret
+.size sha256_block_data_order_zvbb_zvknha,.-sha256_block_data_order_zvbb_zvknha
+
+.p2align 2
+.type $K256,\@object
+$K256:
+ .word 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5
+ .word 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5
+ .word 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3
+ .word 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174
+ .word 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc
+ .word 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da
+ .word 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7
+ .word 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967
+ .word 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13
+ .word 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85
+ .word 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3
+ .word 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070
+ .word 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5
+ .word 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3
+ .word 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208
+ .word 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
+.size $K256,.-$K256
+___
+
+print $code;
+
+close STDOUT or die "error closing STDOUT: $!";