Please trim useless content.
Did I missed anything interesting in your mail ?
On Sun, Jul 29, 2018 at 11:57:47PM +0200, Oliver Pinter wrote:
> On 7/29/18, Konstantin Belousov <k...@freebsd.org> wrote:
> > +ENTRY(copyin_smap)
> > + PUSH_FRAME_POINTER
> > + movq PCPU(CURPCB),%rax
> > + movq $copyin_fault,PCB_ONFAULT(%rax)
> > + testq %rdx,%rdx /* anything to do? */
> > + jz done_copyin
> > +
> > + /*
> > + * make sure address is valid
> > + */
> > + movq %rdi,%rax
> > + addq %rdx,%rax
> > + jc copyin_fault
> > + movq $VM_MAXUSER_ADDRESS,%rcx
> > + cmpq %rcx,%rax
> > + ja copyin_fault
> > +
> > + xchgq %rdi,%rsi
> > + movq %rdx,%rcx
> > + movb %cl,%al
> > + shrq $3,%rcx /* copy longword-wise */
>
> missing cld from here
In fact not. It is copyin_nosmap that got unneeded cld.
See r327820, apparently I mis-merged this commit into the SMAP branch.
>
> > + stac
> > + rep
> > + movsq
> > + movb %al,%cl
> > + andb $7,%cl /* copy remaining bytes */
> > je done_copyin
> > rep
> > movsb
> > + clac
> > +ENTRY(copyinstr_smap)
> > + PUSH_FRAME_POINTER
> > + movq %rdx,%r8 /* %r8 = maxlen */
> > + movq %rcx,%r9 /* %r9 = *len */
> > + xchgq %rdi,%rsi /* %rdi = from, %rsi = to */
> > + movq PCPU(CURPCB),%rcx
> > + movq $cpystrflt,PCB_ONFAULT(%rcx)
> > +
> > + movq $VM_MAXUSER_ADDRESS,%rax
> > +
> > + /* make sure 'from' is within bounds */
> > + subq %rsi,%rax
> > + jbe cpystrflt
> > +
> > + /* restrict maxlen to <= VM_MAXUSER_ADDRESS-from */
> > + cmpq %rdx,%rax
> > + jae 1f
> > + movq %rax,%rdx
> > + movq %rax,%r8
> > +1:
> > + incq %rdx
>
> missing cld here
Same.
>
> > +
> > +2:
> > + decq %rdx
> > + jz copyinstr_succ
>
> cpystrflt_x:
> /* set *lencopied and return %eax */
> movq PCPU(CURPCB),%rcx
> movq $0,PCB_ONFAULT(%rcx)
>
> testq %r9,%r9
> jz 1f
> subq %rdx,%r8
> movq %r8,(%r9) << Here you access user-space, with cleared
> RFLAGS.AC from the fault handler.
How does this instruction access userspace ? I do not see.
> 1:
> POP_FRAME_POINTER
> ret
So the patch below removes unneeded (mismerged) cld's left in the support.S.
diff --git a/sys/amd64/amd64/support.S b/sys/amd64/amd64/support.S
index 9b8b2a40461..0aa307e6895 100644
--- a/sys/amd64/amd64/support.S
+++ b/sys/amd64/amd64/support.S
@@ -307,7 +307,6 @@ ENTRY(copyout_smap)
movq %rdx,%rcx
shrq $3,%rcx
- cld
stac
rep
movsq
@@ -358,7 +357,6 @@ ENTRY(copyin_nosmap)
movq %rdx,%rcx
movb %cl,%al
shrq $3,%rcx /* copy longword-wise */
- cld
rep
movsq
movb %al,%cl
@@ -887,7 +885,6 @@ ENTRY(copyinstr_nosmap)
movq %rax,%r8
1:
incq %rdx
- cld
2:
decq %rdx
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