From bce5a1e8a34006a5e80213ede5e5c465d53f1dce Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Tue, 18 Oct 2022 10:21:55 -0700 Subject: x86/mem: Move memmove to out of line assembler When building ARCH=i386 with CONFIG_LTO_CLANG_FULL=y, 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 Signed-off-by: Nick Desaulniers Signed-off-by: Dave Hansen Reviewed-by: Kees Cook Tested-by: Kees Cook Tested-by: Nathan Chancellor Link: https://lore.kernel.org/all/20221018172155.287409-1-ndesaulniers%40google.com --- 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 7ba5f61d7273..4f1a40a86534 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -60,6 +60,7 @@ ifeq ($(CONFIG_X86_32),y) lib-y += checksum_32.o lib-y += strstr_32.o lib-y += string_32.o + lib-y += memmove_32.o ifneq ($(CONFIG_X86_CMPXCHG64),y) lib-y += 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 = 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:" - : "=&c" (d0), "=&S" (d1), "=&D" (d2), - "=r" (d3),"=r" (d4), "=r"(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=3 passes these in registers: + * dest_in: %eax + * src_in: %edx + * n: %ecx + * See also: arch/x86/entry/calling.h for description of the calling convention. + * + * 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 clobber + * 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 2b5cc70ac53f..7513e6d5dc90 100644 --- a/lib/memcpy_kunit.c +++ b/lib/memcpy_kunit.c @@ -105,6 +105,8 @@ static void memcpy_test(struct kunit *test) #undef TEST_OP } +static unsigned char larger_array [2048]; + static void memmove_test(struct kunit *test) { #define TEST_OP "memmove" @@ -179,6 +181,26 @@ static void memmove_test(struct kunit *test) ptr = &overlap.data[2]; memmove(ptr, overlap.data, 5); compare("overlapping write", overlap, overlap_expected); + + /* Verify larger overlapping moves. */ + larger_array[256] = 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] = 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 } -- cgit v1.2.3