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authorAndi Kleen <ak@suse.de>2006-01-11 22:44:45 +0100
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-11 19:04:55 -0800
commit2cbc9ee35c992f88fb2558a4f13920e3df4ef3bb (patch)
tree51bed27fe9050cae3e7de2d24f55874455316ab2 /arch/x86_64/lib
parent17a941d854a3f7b0bb916fdeee4c9ffdcc19d8d3 (diff)
downloadlinux-linaro-stable-2cbc9ee35c992f88fb2558a4f13920e3df4ef3bb.tar.gz
[PATCH] x86_64: Clean up copy_*_user
- Remove optimization for old B stepping Opteron - Make the fast path for copies with a multiple of eight length faster. - Minor instruction rearrangement to hopefully avoid a pipeline stall or two. - Add comment about errata to consider. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/x86_64/lib')
-rw-r--r--arch/x86_64/lib/copy_user.S244
1 files changed, 23 insertions, 221 deletions
diff --git a/arch/x86_64/lib/copy_user.S b/arch/x86_64/lib/copy_user.S
index dfa358b05c89..79422b6559c3 100644
--- a/arch/x86_64/lib/copy_user.S
+++ b/arch/x86_64/lib/copy_user.S
@@ -4,12 +4,9 @@
* Functions to copy from and to user space.
*/
-#define FIX_ALIGNMENT 1
-
#include <asm/current.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
- #include <asm/cpufeature.h>
/* Standard copy_to_user with segment limit checking */
.globl copy_to_user
@@ -21,23 +18,7 @@ copy_to_user:
jc bad_to_user
cmpq threadinfo_addr_limit(%rax),%rcx
jae bad_to_user
-2:
- .byte 0xe9 /* 32bit jump */
- .long .Lcug-1f
-1:
-
- .section .altinstr_replacement,"ax"
-3: .byte 0xe9 /* replacement jmp with 8 bit immediate */
- .long copy_user_generic_c-1b /* offset */
- .previous
- .section .altinstructions,"a"
- .align 8
- .quad 2b
- .quad 3b
- .byte X86_FEATURE_K8_C
- .byte 5
- .byte 5
- .previous
+ jmp copy_user_generic
/* Standard copy_from_user with segment limit checking */
.globl copy_from_user
@@ -72,223 +53,44 @@ bad_to_user:
* rsi source
* rdx count
*
+ * Only 4GB of copy is supported. This shouldn't be a problem
+ * because the kernel normally only writes from/to page sized chunks
+ * even if user space passed a longer buffer.
+ * And more would be dangerous because both Intel and AMD have
+ * errata with rep movsq > 4GB. If someone feels the need to fix
+ * this please consider this.
+ *
* Output:
* eax uncopied bytes or 0 if successful.
*/
- .globl copy_user_generic
- .p2align 4
-copy_user_generic:
- .byte 0x66,0x66,0x90 /* 5 byte nop for replacement jump */
- .byte 0x66,0x90
-1:
- .section .altinstr_replacement,"ax"
-2: .byte 0xe9 /* near jump with 32bit immediate */
- .long copy_user_generic_c-1b /* offset */
- .previous
- .section .altinstructions,"a"
- .align 8
- .quad copy_user_generic
- .quad 2b
- .byte X86_FEATURE_K8_C
- .byte 5
- .byte 5
- .previous
-.Lcug:
- pushq %rbx
- xorl %eax,%eax /*zero for the exception handler */
-
-#ifdef FIX_ALIGNMENT
- /* check for bad alignment of destination */
- movl %edi,%ecx
- andl $7,%ecx
- jnz .Lbad_alignment
-.Lafter_bad_alignment:
-#endif
- movq %rdx,%rcx
-
- movl $64,%ebx
- shrq $6,%rdx
- decq %rdx
- js .Lhandle_tail
-
- .p2align 4
-.Lloop:
-.Ls1: movq (%rsi),%r11
-.Ls2: movq 1*8(%rsi),%r8
-.Ls3: movq 2*8(%rsi),%r9
-.Ls4: movq 3*8(%rsi),%r10
-.Ld1: movq %r11,(%rdi)
-.Ld2: movq %r8,1*8(%rdi)
-.Ld3: movq %r9,2*8(%rdi)
-.Ld4: movq %r10,3*8(%rdi)
-
-.Ls5: movq 4*8(%rsi),%r11
-.Ls6: movq 5*8(%rsi),%r8
-.Ls7: movq 6*8(%rsi),%r9
-.Ls8: movq 7*8(%rsi),%r10
-.Ld5: movq %r11,4*8(%rdi)
-.Ld6: movq %r8,5*8(%rdi)
-.Ld7: movq %r9,6*8(%rdi)
-.Ld8: movq %r10,7*8(%rdi)
-
- decq %rdx
-
- leaq 64(%rsi),%rsi
- leaq 64(%rdi),%rdi
-
- jns .Lloop
-
- .p2align 4
-.Lhandle_tail:
- movl %ecx,%edx
- andl $63,%ecx
- shrl $3,%ecx
- jz .Lhandle_7
- movl $8,%ebx
- .p2align 4
-.Lloop_8:
-.Ls9: movq (%rsi),%r8
-.Ld9: movq %r8,(%rdi)
- decl %ecx
- leaq 8(%rdi),%rdi
- leaq 8(%rsi),%rsi
- jnz .Lloop_8
-
-.Lhandle_7:
- movl %edx,%ecx
- andl $7,%ecx
- jz .Lende
- .p2align 4
-.Lloop_1:
-.Ls10: movb (%rsi),%bl
-.Ld10: movb %bl,(%rdi)
- incq %rdi
- incq %rsi
- decl %ecx
- jnz .Lloop_1
-
-.Lende:
- popq %rbx
- ret
-
-#ifdef FIX_ALIGNMENT
- /* align destination */
- .p2align 4
-.Lbad_alignment:
- movl $8,%r9d
- subl %ecx,%r9d
- movl %r9d,%ecx
- cmpq %r9,%rdx
- jz .Lhandle_7
- js .Lhandle_7
-.Lalign_1:
-.Ls11: movb (%rsi),%bl
-.Ld11: movb %bl,(%rdi)
- incq %rsi
- incq %rdi
- decl %ecx
- jnz .Lalign_1
- subq %r9,%rdx
- jmp .Lafter_bad_alignment
-#endif
-
- /* table sorted by exception address */
- .section __ex_table,"a"
- .align 8
- .quad .Ls1,.Ls1e
- .quad .Ls2,.Ls2e
- .quad .Ls3,.Ls3e
- .quad .Ls4,.Ls4e
- .quad .Ld1,.Ls1e
- .quad .Ld2,.Ls2e
- .quad .Ld3,.Ls3e
- .quad .Ld4,.Ls4e
- .quad .Ls5,.Ls5e
- .quad .Ls6,.Ls6e
- .quad .Ls7,.Ls7e
- .quad .Ls8,.Ls8e
- .quad .Ld5,.Ls5e
- .quad .Ld6,.Ls6e
- .quad .Ld7,.Ls7e
- .quad .Ld8,.Ls8e
- .quad .Ls9,.Le_quad
- .quad .Ld9,.Le_quad
- .quad .Ls10,.Le_byte
- .quad .Ld10,.Le_byte
-#ifdef FIX_ALIGNMENT
- .quad .Ls11,.Lzero_rest
- .quad .Ld11,.Lzero_rest
-#endif
- .quad .Le5,.Le_zero
- .previous
-
- /* compute 64-offset for main loop. 8 bytes accuracy with error on the
- pessimistic side. this is gross. it would be better to fix the
- interface. */
- /* eax: zero, ebx: 64 */
-.Ls1e: addl $8,%eax
-.Ls2e: addl $8,%eax
-.Ls3e: addl $8,%eax
-.Ls4e: addl $8,%eax
-.Ls5e: addl $8,%eax
-.Ls6e: addl $8,%eax
-.Ls7e: addl $8,%eax
-.Ls8e: addl $8,%eax
- addq %rbx,%rdi /* +64 */
- subq %rax,%rdi /* correct destination with computed offset */
-
- shlq $6,%rdx /* loop counter * 64 (stride length) */
- addq %rax,%rdx /* add offset to loopcnt */
- andl $63,%ecx /* remaining bytes */
- addq %rcx,%rdx /* add them */
- jmp .Lzero_rest
-
- /* exception on quad word loop in tail handling */
- /* ecx: loopcnt/8, %edx: length, rdi: correct */
-.Le_quad:
- shll $3,%ecx
- andl $7,%edx
- addl %ecx,%edx
- /* edx: bytes to zero, rdi: dest, eax:zero */
-.Lzero_rest:
- movq %rdx,%rcx
-.Le_byte:
- xorl %eax,%eax
-.Le5: rep
- stosb
- /* when there is another exception while zeroing the rest just return */
-.Le_zero:
- movq %rdx,%rax
- jmp .Lende
-
- /* C stepping K8 run faster using the string copy instructions.
- This is also a lot simpler. Use them when possible.
- Patch in jmps to this code instead of copying it fully
- to avoid unwanted aliasing in the exception tables. */
-
- /* rdi destination
- * rsi source
- * rdx count
- *
- * Output:
- * eax uncopied bytes or 0 if successfull.
- */
-copy_user_generic_c:
+ .globl copy_user_generic
+copy_user_generic:
movl %edx,%ecx
shrl $3,%ecx
andl $7,%edx
+ jz 5f
1: rep
movsq
movl %edx,%ecx
+ xor %eax,%eax
2: rep
movsb
-4: movl %ecx,%eax
ret
+ /* align here? */
+5: xorl %eax,%eax
+6: rep movsq
+ ret
+
+ .section .fixup,"ax"
3: lea (%rdx,%rcx,8),%rax
ret
-
+4: movl %ecx,%eax
+ ret
+ .previous
+
.section __ex_table,"a"
.quad 1b,3b
.quad 2b,4b
+ .quad 6b,4b
.previous