On Sat, Jun 09, 2018 at 01:00:08PM -0700, Palmer Dabbelt wrote:
On Fri, 08 Jun 2018 17:13:12 PDT (-0700), luc.vanoostenryck@xxxxxxxxx wrote:
> 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.
I think it's probably a bug in binutils-2.29 that should be fixed by
2.30 -- IIRC we had some bugs that looked like this and they got
fixed, though it might be just in master (so 2.31).
I've tried binutils-2.30 and riscv-binutils-gdb, both still have
the problem and master binutils-gdb doesn't compile for me.
OTOH, everything is fine if I disabled CONFIG_RISCV_ISA_C.
Either way it looks innocuous WRT the patch.
With this, the RISC-V arch should be sparse clean.
I'll recheck after -rc1.