diff options
| -rw-r--r-- | arch/x86_64/lib/copy_user.S | 244 |
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 |