Commit 5d7244e7 authored by Jan Beulich's avatar Jan Beulich Committed by Ingo Molnar
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x86-64: Fix memset() to support sizes of 4Gb and above 



While currently there doesn't appear to be any reachable in-tree
case where such large memory blocks may be passed to memset()
(alloc_bootmem() being the primary non-reachable one, as it gets
called with suitably large sizes in FLATMEM configurations), we
have recently hit the problem a second time in our Xen kernels.

Rather than working around it a second time, prevent others from
falling into the same trap by fixing this long standing
limitation.

Signed-off-by: default avatarJan Beulich <jbeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/4F05D992020000780006AA09@nat28.tlf.novell.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 42693290

arch/x86/lib/memset_64.S

+15 −18
Original line number Diff line number Diff line
@@ -19,16 +19,15 @@ 
	.section .altinstr_replacement, "ax", @progbits

.Lmemset_c:

	movq %rdi,%r9

	movl %edx,%r8d

	andl $7,%r8d

	movl %edx,%ecx

	shrl $3,%ecx

	movq %rdx,%rcx

	andl $7,%edx

	shrq $3,%rcx

	/* expand byte value  */

	movzbl %sil,%esi

	movabs $0x0101010101010101,%rax

	mulq %rsi		/* with rax, clobbers rdx */

	imulq %rsi,%rax

	rep stosq

	movl %r8d,%ecx

	movl %edx,%ecx

	rep stosb

	movq %r9,%rax

	ret
@@ -50,7 +49,7 @@ 
.Lmemset_c_e:

	movq %rdi,%r9

	movb %sil,%al

	movl %edx,%ecx

	movq %rdx,%rcx

	rep stosb

	movq %r9,%rax

	ret
@@ -61,12 +60,11 @@ ENTRY(memset) 
ENTRY(__memset)

	CFI_STARTPROC

	movq %rdi,%r10

	movq %rdx,%r11



	/* expand byte value  */

	movzbl %sil,%ecx

	movabs $0x0101010101010101,%rax

	mul    %rcx		/* with rax, clobbers rdx */

	imulq  %rcx,%rax



	/* align dst */

	movl  %edi,%r9d
@@ -75,13 +73,13 @@ ENTRY(__memset) 
	CFI_REMEMBER_STATE

.Lafter_bad_alignment:



	movl %r11d,%ecx

	shrl $6,%ecx

	movq  %rdx,%rcx

	shrq  $6,%rcx

	jz	 .Lhandle_tail



	.p2align 4

.Lloop_64:

	decl   %ecx

	decq  %rcx

	movq  %rax,(%rdi)

	movq  %rax,8(%rdi)

	movq  %rax,16(%rdi)
@@ -97,7 +95,7 @@ ENTRY(__memset) 
	   to predict jump tables. */

	.p2align 4

.Lhandle_tail:

	movl	%r11d,%ecx

	movl	%edx,%ecx

	andl    $63&(~7),%ecx

	jz 		.Lhandle_7

	shrl	$3,%ecx
@@ -109,12 +107,11 @@ ENTRY(__memset) 
	jnz    .Lloop_8



.Lhandle_7:

	movl	%r11d,%ecx

	andl	$7,%ecx

	andl	$7,%edx

	jz      .Lende

	.p2align 4

.Lloop_1:

	decl    %ecx

	decl    %edx

	movb 	%al,(%rdi)

	leaq	1(%rdi),%rdi

	jnz     .Lloop_1
@@ -125,13 +122,13 @@ ENTRY(__memset) 


	CFI_RESTORE_STATE

.Lbad_alignment:

	cmpq $7,%r11

	cmpq $7,%rdx

	jbe	.Lhandle_7

	movq %rax,(%rdi)	/* unaligned store */

	movq $8,%r8

	subq %r9,%r8

	addq %r8,%rdi

	subq %r8,%r11

	subq %r8,%rdx

	jmp .Lafter_bad_alignment

.Lfinal:

	CFI_ENDPROC

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