[PATCH v5 0/5] Add support for TLS Descriptors (TLSDESC)

[Fangrui Song]

On Fri, Dec 22, 2023 at 3:42 AM Lulu Cai <cailulu@loongson.cn> wrote:
>
> v5 mainly changes the relocation name and adds relocation
> for immediate value field of ld.w/d.
>
> 1. R_LARCH_TLS_DESC_ADD_PC_LO12 -> R_LARCH_TLS_DESC_PC_LO12.
>    R_LARCH_TLS_DESC_LD(113)     -> R_LARCH_TLS_DESC_LD(119)
>
> 2. Added 32 abs test case.
>
> 3. Added R_LARCH_TLS_DESC_LD relocation to the immediate field of
>    the ld.w/d instruction.
>
>    Such as:
>    pcalau12i $r4,%desc_pc_hi20(var)
>    addi.d $r4,$r4,%desc_pc_lo12(var)
>    ld.d $r1,$r4,0                    -> ld.d $r1,$r4,%desc_ld(var)
>    jirl $r1,$r1,%desc_call(var)
>    addi.d $a0,$a0,$tp
>
> Lulu Cai (4):
>   LoongArch: Add new relocs and macro for TLSDESC.
>   LoongArch: Add support for TLSDESC in ld.
>   LoongArch: Add tls transition support.
>   LoongArch: Add testsuit for DESC and tls transition and tls
>     relaxation.
>
> mengqinggang (1):
>   LoongArch: Add support for TLS LD/GD/DESC relaxation
>
>  bfd/bfd-in2.h                                 |  15 +
>  bfd/elfnn-loongarch.c                         | 552 +++++++++++++++++-
>  bfd/elfxx-loongarch.c                         | 270 ++++++++-
>  bfd/libbfd.h                                  |  15 +
>  bfd/reloc.c                                   |  36 ++
>  gas/config/tc-loongarch.c                     |  20 +-
>  gas/testsuite/gas/loongarch/macro_op.d        | 128 ++--
>  gas/testsuite/gas/loongarch/macro_op_32.d     | 120 ++--
>  .../gas/loongarch/macro_op_large_abs.d        | 160 ++---
>  .../gas/loongarch/macro_op_large_pc.d         | 160 ++---
>  gas/testsuite/gas/loongarch/tlsdesc_32.d      |  28 +
>  gas/testsuite/gas/loongarch/tlsdesc_32.s      |  12 +
>  gas/testsuite/gas/loongarch/tlsdesc_32_abs.d  |  26 +
>  gas/testsuite/gas/loongarch/tlsdesc_32_abs.s  |   8 +
>  gas/testsuite/gas/loongarch/tlsdesc_64.d      |  28 +
>  gas/testsuite/gas/loongarch/tlsdesc_64.s      |  12 +
>  .../gas/loongarch/tlsdesc_large_abs.d         |  34 ++
>  .../gas/loongarch/tlsdesc_large_abs.s         |  12 +
>  .../gas/loongarch/tlsdesc_large_pc.d          |  38 ++
>  .../gas/loongarch/tlsdesc_large_pc.s          |  17 +
>  include/elf/loongarch.h                       |  26 +-
>  include/opcode/loongarch.h                    |   6 +
>  ld/testsuite/ld-loongarch-elf/desc-ie.d       |  16 +
>  ld/testsuite/ld-loongarch-elf/desc-ie.s       |  18 +
>  ld/testsuite/ld-loongarch-elf/desc-le.d       |  15 +
>  ld/testsuite/ld-loongarch-elf/desc-le.s       |  14 +
>  ld/testsuite/ld-loongarch-elf/desc-norelax.d  |  16 +
>  ld/testsuite/ld-loongarch-elf/desc-norelax.s  |   5 +
>  ld/testsuite/ld-loongarch-elf/desc-relax.d    |  15 +
>  ld/testsuite/ld-loongarch-elf/desc-relax.s    |   5 +
>  ld/testsuite/ld-loongarch-elf/ie-le.d         |  13 +
>  ld/testsuite/ld-loongarch-elf/ie-le.s         |  11 +
>  .../ld-loongarch-elf/ld-loongarch-elf.exp     |   9 +
>  ld/testsuite/ld-loongarch-elf/macro_op.d      | 391 +++++++------
>  ld/testsuite/ld-loongarch-elf/macro_op_32.d   | 120 ++--
>  ld/testsuite/ld-loongarch-elf/tlsdesc-dso.d   |  56 ++
>  ld/testsuite/ld-loongarch-elf/tlsdesc-dso.s   |  65 +++
>  opcodes/loongarch-opc.c                       |  54 ++
>  38 files changed, 1980 insertions(+), 566 deletions(-)
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_32.d
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_32.s
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_32_abs.d
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_32_abs.s
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_64.d
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_64.s
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_large_abs.d
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_large_abs.s
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_large_pc.d
>  create mode 100644 gas/testsuite/gas/loongarch/tlsdesc_large_pc.s
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-ie.d
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-ie.s
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-le.d
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-le.s
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-norelax.d
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-norelax.s
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-relax.d
>  create mode 100644 ld/testsuite/ld-loongarch-elf/desc-relax.s
>  create mode 100644 ld/testsuite/ld-loongarch-elf/ie-le.d
>  create mode 100644 ld/testsuite/ld-loongarch-elf/ie-le.s
>  create mode 100644 ld/testsuite/ld-loongarch-elf/tlsdesc-dso.d
>  create mode 100644 ld/testsuite/ld-loongarch-elf/tlsdesc-dso.s
>
> --
> 2.43.0
>

Technically you could define R_LARCH_TLS_DESC to be shared by 32-bit
and 64-bit arches, like RELATIVE/IRELATIVE/JUMP_SLOT.
That said, I see that the change has been made.

It seems that la.tls.desc expands to 4 instructions with 2
R_LARCH_RELAX relocations?
I think one R_LARCH_RELAX is sufficient to implement relaxation.

RISC-V has a similar problem and I have suggested
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/421