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x86-64: Fix memset() to support sizes of 4Gb and above

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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: Jan 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jan Beulich 2012-01-05 16:10:42 +00:00 committed by Ingo Molnar
parent 4269329090
commit 5d7244e7c9
1 changed files with 15 additions and 18 deletions
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33
arch/x86/lib/memset_64.S
View File

@ -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