On Mon, Jun 11, 2018 at 12:01:37PM -0700, Palmer Dabbelt wrote: > On Sat, 09 Jun 2018 14:42:12 PDT (-0700), luc.vanoostenr...@gmail.com wrote: > > On Sat, Jun 09, 2018 at 01:00:08PM -0700, Palmer Dabbelt wrote: > > > On Fri, 08 Jun 2018 17:13:12 PDT (-0700), luc.vanoostenr...@gmail.com > > > 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. > > OK, I'll try and figure out what's going on. We've had a handful of > headaches trying to get things like '.align 2; .align 2' to actually produce > no NOPs for the second alignment directive, which is surprisingly > complicated due to the aggressive linker relaxation we do.
OK. I imagine indeed but note that no linker is involved here so, if the problem is still present, it must already be in the assembler. > > With this, the RISC-V arch should be sparse clean. > > I'll recheck after -rc1. > > This will be part of the PR that I tag today, so I anticipate it'll be in. Cool! -- Luc
