[PATCH] LoongArch: Adapt R_LARCH_{PCALA,GOT,TLS_IE,TLS_DESC}64_* handling per psABI v2.30

[Xi Ruoyao]

On Tue, 2024-01-16 at 14:38 +0800, mengqinggang wrote:
> 
> 在 2024/1/15 下午8:44, Xi Ruoyao 写道:
> > In LoongArch psABI v2.30, an offset (-8 for LO20 and -12 for HI12)
> > should be applied on PC for these reloc types to avoid wrong relocation
> > when the instruction sequence crosses a page boundary.
> > 
> > The lld linker has already adapted the change.  Make it for the bfd
> > linker too.
> > 
> > Link: https://github.com/loongson/la-abi-specs/releases/v2.30
> > Link: https://github.com/loongson-community/discussions/issues/17
> > Link: https://github.com/llvm/llvm-project/pull/73387
> > Signed-off-by: Xi Ruoyao <xry111@xry111.site>
> > ---
> >   bfd/elfnn-loongarch.c                         | 29 +++++++++++--------
> >   .../ld-loongarch-elf/ld-loongarch-elf.exp     |  1 +
> >   ld/testsuite/ld-loongarch-elf/pcala64.d       | 15 ++++++++++
> >   ld/testsuite/ld-loongarch-elf/pcala64.s       |  8 +++++
> >   4 files changed, 41 insertions(+), 12 deletions(-)
> >   create mode 100644 ld/testsuite/ld-loongarch-elf/pcala64.d
> >   create mode 100644 ld/testsuite/ld-loongarch-elf/pcala64.s
> > 
> > diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
> > index 3858a3179fd..e4f4da7a0dc 100644
> > --- a/bfd/elfnn-loongarch.c
> > +++ b/bfd/elfnn-loongarch.c
> > @@ -3544,14 +3544,16 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
> >   	    }
> >   	  break;
> >   
> > -	case R_LARCH_PCALA64_LO20:
> >   	case R_LARCH_PCALA64_HI12:
> > +	  pc -= 4;
> > +	  /* Fall through.  */
> > +	case R_LARCH_PCALA64_LO20:
> >   	  if (h && h->plt.offset != MINUS_ONE)
> >   	    relocation = sec_addr (plt) + h->plt.offset;
> >   	  else
> >   	    relocation += rel->r_addend;
> >   
> > -	  RELOCATE_CALC_PC64_HI32 (relocation, pc);
> > +	  RELOCATE_CALC_PC64_HI32 (relocation, pc - 8);
> 
> 
> The 'pc - 8' triggered an error because the pc parameter is not enclosed 
> in parentheses in macro definition.
> 
> /home/mengqinggang/toolchains/src/binutils-gdb/bfd/elfnn-loongarch.c:3546:51: 
> error: suggest parentheses around '-' in operand of '&' 
> [-Werror=parentheses]
>   3546 |           RELOCATE_CALC_PC64_HI32 (relocation, pc - 8);
>        |                                                ~~~^~~
> /home/mengqinggang/toolchains/src/binutils-gdb/bfd/elfnn-loongarch.c:2532:22: 
> note: in definition of macro 'RELOCATE_CALC_PC64_HI32'
>   2532 |                   - (pc & ~(bfd_vma)0xfff);             \
>        |                      ^~

Interesting, why didn't I see this error...  And in this case it happens
to work because - has a higher precedence.  But I'll add parentheses in
V2 anyway.

/* snip */

> > diff --git a/ld/testsuite/ld-loongarch-elf/pcala64.d b/ld/testsuite/ld-loongarch-elf/pcala64.d
> > new file mode 100644
> > index 00000000000..6b1411577db
> > --- /dev/null
> > +++ b/ld/testsuite/ld-loongarch-elf/pcala64.d
> > @@ -0,0 +1,15 @@
> > +#ld: -Ttext=0x180000ff8 -Tdata=0x1000000000 -shared
> 
> 
> The test need to be disabled on loongarch*-elf target because -shared 
> option is not supported on loongarch*-elf target.
> 
> It can be disabled by  adding a line "#skip: loongarch*-elf" after 
> "#objdump -d".

I'll just remove the -shared option.  I changed the function name to
"_start" so it should work without -shared, but I forgot to actually
remove -shared.


-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University