From nobody Fri May 3 00:03:28 2024 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E7746C433FE for ; Fri, 30 Sep 2022 18:55:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232453AbiI3SzP (ORCPT ); Fri, 30 Sep 2022 14:55:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44358 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231281AbiI3SzM (ORCPT ); Fri, 30 Sep 2022 14:55:12 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3507FA61C2 for ; Fri, 30 Sep 2022 11:55:08 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id t6-20020a25b706000000b006b38040b6f7so4519191ybj.6 for ; Fri, 30 Sep 2022 11:55:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date; bh=v2LjyoB4oXn5tsUdqc33HUQg9IqD1qhygtW9mpaC2IY=; b=rMfQcAUSrSKBRgJMIoMFb1XGunkT14ZkpPcoepHFE9Yf351UUNzEn903RROKWMkRsP 3hDysyQZt+Un0rFhAI92p36YiqhrombfqEXygPH3ETxVPcQ9pWDV0fDKmeEJPr5hFV3O pvSas1R9gg6Ed/4b4aOQ7CTY8/r24BM+j8yz2nwrgD2S1Wc26kbGZH8gm1VQ3zJdonkp 7OxWBi3YyfHmTdxbnemMihr4/9v5YT81/QaHYlHiwXRMPrsGV5bIMKSFWx2TWyKQJv5L 0DbfMaiMNrcghQvMI/EUkFJiwfgf7LdH1pj3ogzoXl5YuvipBL+GZJSV+zLzHuHbiH4D rYCQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date; bh=v2LjyoB4oXn5tsUdqc33HUQg9IqD1qhygtW9mpaC2IY=; b=SobBY8OxoMlc1/qgE3qPdWsJOiJhCqEj8aSkCH/CLHDqer8fyNyifA/uHlCwvpRxxc u/OYaFdd8T7QeaqKSxMdYrAd0gq51sSeQxhKNYCaLK6pWH6UbirIUyhhUzji/o+CWhWs rpCchbWp9t85RbQ4l92zK7l58YTWArGRDX4mFDCryfWwLeQfB2PG1KAC1jhS9+Xr+opn 14UIKAmW2nCCYRon5Q64yuHHevkLVyWFn2M1oy2P4NjYe7u7iSVnjoBnYdVVnMdBk3Hc wcH9umm4zXFHVE/4gEAOjnmO67n7C3VdUDLSYtvu/DjAKeqgd5eK5uiBQdiZbwCgnzYx WGDQ== X-Gm-Message-State: ACrzQf1dNl6t9qJRWRbWi1aZnVG/Js0DGI0SLOPivXTlC+vssckOKoIE /A5quHoeiFqKrpdy4box7W6E7ntOLm7MFp9Z/fs= X-Google-Smtp-Source: AMsMyM5bokV9MZRZzKoWMIacJPhD3Hk70qBYrb7llbmZxcJl+qLAvChVDwpOj+dKKDQUTGAjhmA1bsfY488mEzBKQ4s= X-Received: from ndesaulniers-desktop.svl.corp.google.com ([2620:0:100e:712:8142:a086:b6c7:da71]) (user=ndesaulniers job=sendgmr) by 2002:a0d:ea16:0:b0:354:38f0:1992 with SMTP id t22-20020a0dea16000000b0035438f01992mr9833804ywe.229.1664564107476; Fri, 30 Sep 2022 11:55:07 -0700 (PDT) Date: Fri, 30 Sep 2022 11:55:03 -0700 In-Reply-To: Mime-Version: 1.0 References: X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=UIrHvErwpgNbhCkRZAYSX0CFd/XFEwqX3D0xqtqjNug= X-Developer-Signature: v=1; a=ed25519-sha256; t=1664564103; l=14429; i=ndesaulniers@google.com; s=20220923; h=from:subject; bh=kAcwgpfZH1kRqijJsCLcxjTzakWQv/uxI8I2yTNbbWg=; b=bqGGGd1SxuvMnxouYmOziGk7tpL5kaqwZUU14W5VptGx9AI/YYRtv1v6iXW8uOsaAORzO7XDMTwI wWa5zQY5DVExMJmxUWVrgsUksLYkJH8+rO0ELN/Yy1XtV4y1V4ey X-Mailer: git-send-email 2.38.0.rc1.362.ged0d419d3c-goog Message-ID: <20220930185503.66319-1-ndesaulniers@google.com> Subject: [PATCH v5] x86, mem: move memmove to out of line assembler From: Nick Desaulniers To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen Cc: x86@kernel.org, "H . Peter Anvin" , Peter Zijlstra , Kees Cook , linux-kernel@vger.kernel.org, Linus Torvalds , llvm@lists.linux.dev, Andy Lutomirski , Rasmus Villemoes , Nick Desaulniers , Ingo Molnar , David Laight Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" When building ARCH=3Di386 with CONFIG_LTO_CLANG_FULL=3Dy, it's possible (depending on additional configs which I have not been able to isolate) to observe a failure during register allocation: error: inline assembly requires more registers than available when memmove is inlined into tcp_v4_fill_cb() or tcp_v6_fill_cb(). memmove is quite large and probably shouldn't be inlined due to size alone. A noinline function attribute would be the simplest fix, but there's a few things that stand out with the current definition: In addition to having complex constraints that can't always be resolved, the clobber list seems to be missing %bx. By using numbered operands rather than symbolic operands, the constraints are quite obnoxious to refactor. Having a large function be 99% inline asm is a code smell that this function should simply be written in stand-alone out-of-line assembler. Moving this to out of line assembler guarantees that the compiler cannot inline calls to memmove. This has been done previously for 64b: commit 9599ec0471de ("x86-64, mem: Convert memmove() to assembly file and fix return value bug") That gives the opportunity for other cleanups like fixing the inconsistent use of tabs vs spaces and instruction suffixes, and the label 3 appearing twice. Symbolic operands, local labels, and additional comments would provide this code with a fresh coat of paint. Finally, add a test that tickles the `rep movsl` implementation to test it for correctness, since it has implicit operands. Suggested-by: Ingo Molnar Suggested-by: David Laight Reviewed-by: Kees Cook Tested-by: Kees Cook Signed-off-by: Nick Desaulniers --- Changes v4 -> v5: * Reword+reorder commit message, in particular drop the "maybe" language around %dx and %cl clobber, now that I know of arch/x86/entry/calling.h. * Drop most of my previous comments about caller vs. callee saved, as per Ingo, and use Ingo's comments verbatim. * Reference arch/x86/entry/calling.h in comment. * Reorder pushl/popl. NFC * Rename labels as per David. 16_byteswap -> move_16B * Use /* comments */ more consistently, as per Ingo. * Add Ingo's+David's SB tags. * Carry forward Kees' RB/TB tags. Changes v3 -> v4: * Fix bug I introduced in v1 when I changed src and dest to use different scratch registers, which breaks `rep movsl` as pointed out by Rasmus. This requires 2 `movl`s earlier on, changing the tmp registers, then adjusting which registers we save/restore by the calling convention. I intentionally did not carry forward tags from Kees from v3 due to this bug. * Add a Kunit test that hangs on v3, but passes on v4. It uses a few magic constants as well in order to test the `rep movsl` paths. Changes v2 -> v3: * Fix bug I introduced in v1 when I changed one of temp register operands for one of the two instructions performing a mem to mem swap, but not the other instruction's operand, and discovered by Kees. Verified KUnit memcpy tests are passing via: $ ./tools/testing/kunit/kunit.py run --arch=3Di386 --make_options LLVM=3D1 $ ./tools/testing/kunit/kunit.py run --arch=3Di386 Fixed by using symbolic identifiers rather than open coded registers for the less-than-word-size temporary registers. * Expand the comment about callee saved registers on i386 with a reference to the psABI. Changes v1 -> v2: * Add reference to 9599ec0471de in commit message. * Include asm/export.h then make sure to EXPORT_SYMBOL(memmove). arch/x86/lib/Makefile | 1 + arch/x86/lib/memcpy_32.c | 187 ----------------------------------- arch/x86/lib/memmove_32.S | 200 ++++++++++++++++++++++++++++++++++++++ lib/memcpy_kunit.c | 22 +++++ 4 files changed, 223 insertions(+), 187 deletions(-) create mode 100644 arch/x86/lib/memmove_32.S diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index f76747862bd2..9a0b8ed782e2 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -60,6 +60,7 @@ ifeq ($(CONFIG_X86_32),y) lib-y +=3D checksum_32.o lib-y +=3D strstr_32.o lib-y +=3D string_32.o + lib-y +=3D memmove_32.o ifneq ($(CONFIG_X86_CMPXCHG64),y) lib-y +=3D cmpxchg8b_emu.o atomic64_386_32.o endif diff --git a/arch/x86/lib/memcpy_32.c b/arch/x86/lib/memcpy_32.c index ef3af7ff2c8a..a29b64befb93 100644 --- a/arch/x86/lib/memcpy_32.c +++ b/arch/x86/lib/memcpy_32.c @@ -17,190 +17,3 @@ __visible void *memset(void *s, int c, size_t count) return __memset(s, c, count); } EXPORT_SYMBOL(memset); - -__visible void *memmove(void *dest, const void *src, size_t n) -{ - int d0,d1,d2,d3,d4,d5; - char *ret =3D dest; - - __asm__ __volatile__( - /* Handle more 16 bytes in loop */ - "cmp $0x10, %0\n\t" - "jb 1f\n\t" - - /* Decide forward/backward copy mode */ - "cmp %2, %1\n\t" - "jb 2f\n\t" - - /* - * movs instruction have many startup latency - * so we handle small size by general register. - */ - "cmp $680, %0\n\t" - "jb 3f\n\t" - /* - * movs instruction is only good for aligned case. - */ - "mov %1, %3\n\t" - "xor %2, %3\n\t" - "and $0xff, %3\n\t" - "jz 4f\n\t" - "3:\n\t" - "sub $0x10, %0\n\t" - - /* - * We gobble 16 bytes forward in each loop. - */ - "3:\n\t" - "sub $0x10, %0\n\t" - "mov 0*4(%1), %3\n\t" - "mov 1*4(%1), %4\n\t" - "mov %3, 0*4(%2)\n\t" - "mov %4, 1*4(%2)\n\t" - "mov 2*4(%1), %3\n\t" - "mov 3*4(%1), %4\n\t" - "mov %3, 2*4(%2)\n\t" - "mov %4, 3*4(%2)\n\t" - "lea 0x10(%1), %1\n\t" - "lea 0x10(%2), %2\n\t" - "jae 3b\n\t" - "add $0x10, %0\n\t" - "jmp 1f\n\t" - - /* - * Handle data forward by movs. - */ - ".p2align 4\n\t" - "4:\n\t" - "mov -4(%1, %0), %3\n\t" - "lea -4(%2, %0), %4\n\t" - "shr $2, %0\n\t" - "rep movsl\n\t" - "mov %3, (%4)\n\t" - "jmp 11f\n\t" - /* - * Handle data backward by movs. - */ - ".p2align 4\n\t" - "6:\n\t" - "mov (%1), %3\n\t" - "mov %2, %4\n\t" - "lea -4(%1, %0), %1\n\t" - "lea -4(%2, %0), %2\n\t" - "shr $2, %0\n\t" - "std\n\t" - "rep movsl\n\t" - "mov %3,(%4)\n\t" - "cld\n\t" - "jmp 11f\n\t" - - /* - * Start to prepare for backward copy. - */ - ".p2align 4\n\t" - "2:\n\t" - "cmp $680, %0\n\t" - "jb 5f\n\t" - "mov %1, %3\n\t" - "xor %2, %3\n\t" - "and $0xff, %3\n\t" - "jz 6b\n\t" - - /* - * Calculate copy position to tail. - */ - "5:\n\t" - "add %0, %1\n\t" - "add %0, %2\n\t" - "sub $0x10, %0\n\t" - - /* - * We gobble 16 bytes backward in each loop. - */ - "7:\n\t" - "sub $0x10, %0\n\t" - - "mov -1*4(%1), %3\n\t" - "mov -2*4(%1), %4\n\t" - "mov %3, -1*4(%2)\n\t" - "mov %4, -2*4(%2)\n\t" - "mov -3*4(%1), %3\n\t" - "mov -4*4(%1), %4\n\t" - "mov %3, -3*4(%2)\n\t" - "mov %4, -4*4(%2)\n\t" - "lea -0x10(%1), %1\n\t" - "lea -0x10(%2), %2\n\t" - "jae 7b\n\t" - /* - * Calculate copy position to head. - */ - "add $0x10, %0\n\t" - "sub %0, %1\n\t" - "sub %0, %2\n\t" - - /* - * Move data from 8 bytes to 15 bytes. - */ - ".p2align 4\n\t" - "1:\n\t" - "cmp $8, %0\n\t" - "jb 8f\n\t" - "mov 0*4(%1), %3\n\t" - "mov 1*4(%1), %4\n\t" - "mov -2*4(%1, %0), %5\n\t" - "mov -1*4(%1, %0), %1\n\t" - - "mov %3, 0*4(%2)\n\t" - "mov %4, 1*4(%2)\n\t" - "mov %5, -2*4(%2, %0)\n\t" - "mov %1, -1*4(%2, %0)\n\t" - "jmp 11f\n\t" - - /* - * Move data from 4 bytes to 7 bytes. - */ - ".p2align 4\n\t" - "8:\n\t" - "cmp $4, %0\n\t" - "jb 9f\n\t" - "mov 0*4(%1), %3\n\t" - "mov -1*4(%1, %0), %4\n\t" - "mov %3, 0*4(%2)\n\t" - "mov %4, -1*4(%2, %0)\n\t" - "jmp 11f\n\t" - - /* - * Move data from 2 bytes to 3 bytes. - */ - ".p2align 4\n\t" - "9:\n\t" - "cmp $2, %0\n\t" - "jb 10f\n\t" - "movw 0*2(%1), %%dx\n\t" - "movw -1*2(%1, %0), %%bx\n\t" - "movw %%dx, 0*2(%2)\n\t" - "movw %%bx, -1*2(%2, %0)\n\t" - "jmp 11f\n\t" - - /* - * Move data for 1 byte. - */ - ".p2align 4\n\t" - "10:\n\t" - "cmp $1, %0\n\t" - "jb 11f\n\t" - "movb (%1), %%cl\n\t" - "movb %%cl, (%2)\n\t" - ".p2align 4\n\t" - "11:" - : "=3D&c" (d0), "=3D&S" (d1), "=3D&D" (d2), - "=3Dr" (d3),"=3Dr" (d4), "=3Dr"(d5) - :"0" (n), - "1" (src), - "2" (dest) - :"memory"); - - return ret; - -} -EXPORT_SYMBOL(memmove); diff --git a/arch/x86/lib/memmove_32.S b/arch/x86/lib/memmove_32.S new file mode 100644 index 000000000000..0588b2c0fc95 --- /dev/null +++ b/arch/x86/lib/memmove_32.S @@ -0,0 +1,200 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#include +#include + +SYM_FUNC_START(memmove) +/* + * void *memmove(void *dest_in, const void *src_in, size_t n) + * -mregparm=3D3 passes these in registers: + * dest_in: %eax + * src_in: %edx + * n: %ecx + * See also: arch/x86/entry/calling.h for description of the calling conve= ntion. + * + * n can remain in %ecx, but for `rep movsl`, we'll need dest in %edi and = src + * in %esi. + */ +.set dest_in, %eax +.set dest, %edi +.set src_in, %edx +.set src, %esi +.set n, %ecx +.set tmp0, %edx +.set tmp0w, %dx +.set tmp1, %ebx +.set tmp1w, %bx +.set tmp2, %eax +.set tmp3b, %cl + +/* + * Save all callee-saved registers, because this function is going to clob= ber + * all of them: + */ + pushl %ebp + movl %esp, %ebp // set standard frame pointer + + pushl %ebx + pushl %edi + pushl %esi + pushl %eax // save 'dest_in' parameter [eax] as the return value + + movl src_in, src + movl dest_in, dest + + /* Handle more 16 bytes in loop */ + cmpl $0x10, n + jb .Lmove_16B + + /* Decide forward/backward copy mode */ + cmpl dest, src + jb .Lbackwards_header + + /* + * movs instruction have many startup latency + * so we handle small size by general register. + */ + cmpl $680, n + jb .Ltoo_small_forwards + /* movs instruction is only good for aligned case. */ + movl src, tmp0 + xorl dest, tmp0 + andl $0xff, tmp0 + jz .Lforward_movs +.Ltoo_small_forwards: + subl $0x10, n + + /* We gobble 16 bytes forward in each loop. */ +.Lmove_16B_forwards_loop: + subl $0x10, n + movl 0*4(src), tmp0 + movl 1*4(src), tmp1 + movl tmp0, 0*4(dest) + movl tmp1, 1*4(dest) + movl 2*4(src), tmp0 + movl 3*4(src), tmp1 + movl tmp0, 2*4(dest) + movl tmp1, 3*4(dest) + leal 0x10(src), src + leal 0x10(dest), dest + jae .Lmove_16B_forwards_loop + addl $0x10, n + jmp .Lmove_16B + + /* Handle data forward by movs. */ +.p2align 4 +.Lforward_movs: + movl -4(src, n), tmp0 + leal -4(dest, n), tmp1 + shrl $2, n + rep movsl + movl tmp0, (tmp1) + jmp .Ldone + + /* Handle data backward by movs. */ +.p2align 4 +.Lbackwards_movs: + movl (src), tmp0 + movl dest, tmp1 + leal -4(src, n), src + leal -4(dest, n), dest + shrl $2, n + std + rep movsl + movl tmp0,(tmp1) + cld + jmp .Ldone + + /* Start to prepare for backward copy. */ +.p2align 4 +.Lbackwards_header: + cmpl $680, n + jb .Ltoo_small_backwards + movl src, tmp0 + xorl dest, tmp0 + andl $0xff, tmp0 + jz .Lbackwards_movs + + /* Calculate copy position to tail. */ +.Ltoo_small_backwards: + addl n, src + addl n, dest + subl $0x10, n + + /* We gobble 16 bytes backward in each loop. */ +.Lmove_16B_backwards_loop: + subl $0x10, n + + movl -1*4(src), tmp0 + movl -2*4(src), tmp1 + movl tmp0, -1*4(dest) + movl tmp1, -2*4(dest) + movl -3*4(src), tmp0 + movl -4*4(src), tmp1 + movl tmp0, -3*4(dest) + movl tmp1, -4*4(dest) + leal -0x10(src), src + leal -0x10(dest), dest + jae .Lmove_16B_backwards_loop + /* Calculate copy position to head. */ + addl $0x10, n + subl n, src + subl n, dest + + /* Move data from 8 bytes to 15 bytes. */ +.p2align 4 +.Lmove_16B: + cmpl $8, n + jb .Lmove_8B + movl 0*4(src), tmp0 + movl 1*4(src), tmp1 + movl -2*4(src, n), tmp2 + movl -1*4(src, n), src + + movl tmp0, 0*4(dest) + movl tmp1, 1*4(dest) + movl tmp2, -2*4(dest, n) + movl src, -1*4(dest, n) + jmp .Ldone + + /* Move data from 4 bytes to 7 bytes. */ +.p2align 4 +.Lmove_8B: + cmpl $4, n + jb .Lmove_4B + movl 0*4(src), tmp0 + movl -1*4(src, n), tmp1 + movl tmp0, 0*4(dest) + movl tmp1, -1*4(dest, n) + jmp .Ldone + + /* Move data from 2 bytes to 3 bytes. */ +.p2align 4 +.Lmove_4B: + cmpl $2, n + jb .Lmove_1B + movw 0*2(src), tmp0w + movw -1*2(src, n), tmp1w + movw tmp0w, 0*2(dest) + movw tmp1w, -1*2(dest, n) + jmp .Ldone + + /* Move data for 1 byte. */ +.p2align 4 +.Lmove_1B: + cmpl $1, n + jb .Ldone + movb (src), tmp3b + movb tmp3b, (dest) +.p2align 4 +.Ldone: + popl dest_in // restore 'dest_in' [eax] as the return value + /* Restore all callee-saved registers: */ + popl %esi + popl %edi + popl %ebx + popl %ebp + + RET +SYM_FUNC_END(memmove) +EXPORT_SYMBOL(memmove) diff --git a/lib/memcpy_kunit.c b/lib/memcpy_kunit.c index 62f8ffcbbaa3..fc3a5be1d10b 100644 --- a/lib/memcpy_kunit.c +++ b/lib/memcpy_kunit.c @@ -107,6 +107,8 @@ static void memcpy_test(struct kunit *test) #undef TEST_OP } =20 +static unsigned char larger_array [2048]; + static void memmove_test(struct kunit *test) { #define TEST_OP "memmove" @@ -181,6 +183,26 @@ static void memmove_test(struct kunit *test) ptr =3D &overlap.data[2]; memmove(ptr, overlap.data, 5); compare("overlapping write", overlap, overlap_expected); + + /* Verify larger overlapping moves. */ + larger_array[256] =3D 0xAAu; + /* + * Test a backwards overlapping memmove first. 256 and 1024 are + * important for i386 to use rep movsl. + */ + memmove(larger_array, larger_array + 256, 1024); + KUNIT_ASSERT_EQ(test, larger_array[0], 0xAAu); + KUNIT_ASSERT_EQ(test, larger_array[256], 0x00); + KUNIT_ASSERT_NULL(test, + memchr(larger_array + 1, 0xaa, ARRAY_SIZE(larger_array) - 1)); + /* Test a forwards overlapping memmove. */ + larger_array[0] =3D 0xBBu; + memmove(larger_array + 256, larger_array, 1024); + KUNIT_ASSERT_EQ(test, larger_array[0], 0xBBu); + KUNIT_ASSERT_EQ(test, larger_array[256], 0xBBu); + KUNIT_ASSERT_NULL(test, memchr(larger_array + 1, 0xBBu, 256 - 1)); + KUNIT_ASSERT_NULL(test, + memchr(larger_array + 257, 0xBBu, ARRAY_SIZE(larger_array) - 257)); #undef TEST_OP } =20 --=20 2.38.0.rc1.362.ged0d419d3c-goog