On Fri, Jun 08, 2018 at 03:33:36PM -0700, Palmer Dabbelt wrote:
> On Thu, 07 Jun 2018 09:51:33 PDT (-0700), [email protected] wrote:
> > On Thu, Jun 07, 2018 at 09:30:19AM -0700, Palmer Dabbelt wrote:
> > > diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
> > > index 58fb2877c865..bd51e47ebd44 100644
> > > --- a/arch/riscv/lib/uaccess.S
> > > +++ b/arch/riscv/lib/uaccess.S
> > > @@ -13,7 +13,15 @@ _epc:
> > > .previous
> > > .endm
> > >
> > > -ENTRY(__copy_user)
> > > +/* __asm_copy_to_user and __asm_copy_from_user are actually the same
> > > function,
> > > + * they're just provided as two different symbols to C code so sparse
> > > doesn't
> > > + * yell about casting between two different address spaces. */
> > > +.global __asm_copy_to_user
> > > +.set __asm_copy_to_user,__asm_copy_tofrom_user
> > > +.global __asm_copy_from_user
> > > +.set __asm_copy_from_user,__asm_copy_tofrom_user
> > > +
> > > +ENTRY(__asm_copy_tofrom_user)
> >
> > I don't think that the size (as reported by objdump, for example) will
> > be correct or even present for __asm_copy_to_user & __asm_copy_to_user.
> >
> > What can be done is:
> > ENTRY(__asm_copy_to_user)
> > ENTRY(__asm_copy_from_user)
> >
> > <function definition>
> >
> > ENDPROC(__asm_copy_to_user)
> > ENDPROC(__asm_copy_from_user)
> >
> Thanks. Do you mind checking to make sure this works and submitting a patch?
Not at all.
I should have done it already when I sent the previous email.
I tried it and ... the preprocessed asm is as expected:
.globl __asm_copy_to_user ; .balign 4 ; __asm_copy_to_user:
.globl __asm_copy_from_user ; .balign 4 ; __asm_copy_from_user:
li t6, 0x00040000
csrs sstatus, t6
...
But the nm -S returns different sizes for them:
0000000000000004 000000000000006c T __asm_copy_from_user
0000000000000002 000000000000006e T __asm_copy_to_user
and the object code is:
0000000000000000 <__asm_copy_to_user-0x2>:
0: 0001 nop
0000000000000002 <__asm_copy_to_user>:
2: 0001 nop
0000000000000004 <__asm_copy_from_user>:
4: 00040fb7 lui t6,0x40
8: 100fa073 csrs sstatus,t6
...
Why these unnneded nops?
Is this a known problem of my toolchain (I use a plain gcc 7.3 +
binutils 2.29, both configured as riscv64-none-elf)?
If I remove the two ENTRY() and use instead:
.globl __asm_copy_to_user ; __asm_copy_to_user:
.globl __asm_copy_from_user ; __asm_copy_from_user:
(IOW, I drop the .balign) then I get the expected result.
But well, this seems unrelated to the double ENTRY.
I can't test it more for now because I've some link errors (which,
I understand are probably solved in the riscv tree of binutils).
I'll send you the patch anyway since, as far as I understand the changes
specific to this copy_to/from_user is OK.
Regards,
-- Luc
