[PATCH v3 5/9] RISC-V: Initial ld.bfd support for TLSDESC.
Nelson Chu
nelson@rivosinc.com
Mon Feb 19 04:33:41 GMT 2024
On Tue, Nov 28, 2023 at 4:51 PM Tatsuyuki Ishi <ishitatsuyuki@gmail.com>
wrote:
> Only relocation handling for now; relaxation is not implemented yet.
>
> bfd/
> * elfnn-riscv.c (riscv_elf_check_relocs): Record GOT reference and
> paired relocation for TLSDESC_HI20.
> (riscv_elf_adjust_dynamic_symbol): Allocate GOT and reloc slots for
> TLSDESC symbols.
> (riscv_elf_size_dynamic_sections): Likewise but for local symbols.
> (tlsdescoff): New helper to determine static addend for R_TLSDESC.
> (riscv_elf_relocate_section): Ignore TLSDESC_CALL reloc for now (it is
> relaxation only).
> Handle TLSDESC_{LOAD,ADD}_LO12 as paired pcrel relocs.
> For TLS GOT slot generation, generalize the logic to handle any
> combination of (GD, IE, TLSDESC).
> Add TLSDESC Rela generation.
> * ld/testsuite/ld-riscv-elf/tls*: Add TLSDESC instruction sequences
> next to the existing GD and IE sequences. Update expectations.
> ---
> bfd/elfnn-riscv.c | 91 +++++++++++++++++++++++++++---
> ld/testsuite/ld-riscv-elf/tls.d | 4 +-
> ld/testsuite/ld-riscv-elf/tls.s | 14 +++++
> ld/testsuite/ld-riscv-elf/tlsbin.d | 5 ++
> 4 files changed, 104 insertions(+), 10 deletions(-)
>
> diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
> index d5190538503..8f63998aa5a 100644
> --- a/bfd/elfnn-riscv.c
> +++ b/bfd/elfnn-riscv.c
> @@ -163,6 +163,7 @@ struct riscv_elf_link_hash_entry
> #define GOT_TLS_GD 2
> #define GOT_TLS_IE 4
> #define GOT_TLS_LE 8
> +#define GOT_TLSDESC 16
> char tls_type;
> };
>
> @@ -300,6 +301,7 @@ riscv_is_insn_reloc (const reloc_howto_type *howto)
> #define GOT_ENTRY_SIZE RISCV_ELF_WORD_BYTES
> #define TLS_GD_GOT_ENTRY_SIZE (RISCV_ELF_WORD_BYTES * 2)
> #define TLS_IE_GOT_ENTRY_SIZE RISCV_ELF_WORD_BYTES
> +#define TLSDESC_GOT_ENTRY_SIZE (RISCV_ELF_WORD_BYTES * 2)
> /* Reserve two entries of GOTPLT for ld.so, one is used for PLT resolver,
> the other is used for link map. Other targets also reserve one more
> entry used for runtime profile? */
> @@ -855,6 +857,12 @@ riscv_elf_check_relocs (bfd *abfd, struct
> bfd_link_info *info,
> return false;
> break;
>
> + case R_RISCV_TLSDESC_HI20:
> + if (!riscv_elf_record_got_reference (abfd, info, h, r_symndx)
> + || !riscv_elf_record_tls_type (abfd, h, r_symndx,
> GOT_TLSDESC))
> + return false;
> + break;
> +
> case R_RISCV_CALL:
> case R_RISCV_CALL_PLT:
> /* These symbol requires a procedure linkage table entry.
> @@ -1313,7 +1321,7 @@ allocate_dynrelocs (struct elf_link_hash_entry *h,
> void *inf)
> s = htab->elf.sgot;
> h->got.offset = s->size;
> dyn = htab->elf.dynamic_sections_created;
> - if (tls_type & (GOT_TLS_GD | GOT_TLS_IE))
> + if (tls_type & (GOT_TLS_GD | GOT_TLS_IE | GOT_TLSDESC))
> {
> int indx = 0;
> bool need_reloc = false;
> @@ -1334,6 +1342,14 @@ allocate_dynrelocs (struct elf_link_hash_entry *h,
> void *inf)
> if (need_reloc)
> htab->elf.srelgot->size += sizeof (ElfNN_External_Rela);
> }
> +
> + /* TLSDESC needs one dynamic reloc and two GOT slots. */
> + if (tls_type & GOT_TLSDESC)
> + {
> + s->size += TLSDESC_GOT_ENTRY_SIZE;
> + /* TLSDESC always use dynamic relocs. */
> + htab->elf.srelgot->size += sizeof (ElfNN_External_Rela);
> + }
}
> else
> {
> @@ -1561,7 +1577,7 @@ riscv_elf_size_dynamic_sections (bfd *output_bfd,
> struct bfd_link_info *info)
> if (*local_got > 0)
> {
> *local_got = s->size;
> - if (*local_tls_type & (GOT_TLS_GD | GOT_TLS_IE))
> + if (*local_tls_type & (GOT_TLS_GD | GOT_TLS_IE |
> GOT_TLSDESC))
> {
> if (*local_tls_type & GOT_TLS_GD)
> {
> @@ -1575,6 +1591,11 @@ riscv_elf_size_dynamic_sections (bfd *output_bfd,
> struct bfd_link_info *info)
> if (bfd_link_dll (info))
> srel->size += sizeof (ElfNN_External_Rela);
> }
> + if (*local_tls_type & GOT_TLSDESC)
> + {
> + s->size += TLSDESC_GOT_ENTRY_SIZE;
> + srel->size += sizeof (ElfNN_External_Rela);
> + }
>
The code base seems different from the upstream code.
> }
> else
> {
> @@ -1725,6 +1746,17 @@ tpoff (struct bfd_link_info *info, bfd_vma address)
> return address - elf_hash_table (info)->tls_sec->vma - TP_OFFSET;
> }
>
> +/* Return the relocation value for a static TLSDESC relocation. */
> +
> +static bfd_vma
> +tlsdescoff (struct bfd_link_info *info, bfd_vma address)
> +{
> + /* If tls_sec is NULL, we should have signalled an error already. */
> + if (elf_hash_table (info)->tls_sec == NULL)
> + return 0;
> + return address - elf_hash_table (info)->tls_sec->vma;
> +}
> +
> /* Return the global pointer's value, or 0 if it is not in use. */
>
> static bfd_vma
> @@ -1774,6 +1806,7 @@ perform_relocation (const reloc_howto_type *howto,
> case R_RISCV_GOT_HI20:
> case R_RISCV_TLS_GOT_HI20:
> case R_RISCV_TLS_GD_HI20:
> + case R_RISCV_TLSDESC_HI20:
> if (ARCH_SIZE > 32 && !VALID_UTYPE_IMM (RISCV_CONST_HIGH_PART
> (value)))
> return bfd_reloc_overflow;
> value = ENCODE_UTYPE_IMM (RISCV_CONST_HIGH_PART (value));
> @@ -1784,6 +1817,8 @@ perform_relocation (const reloc_howto_type *howto,
> case R_RISCV_TPREL_LO12_I:
> case R_RISCV_TPREL_I:
> case R_RISCV_PCREL_LO12_I:
> + case R_RISCV_TLSDESC_LOAD_LO12:
> + case R_RISCV_TLSDESC_ADD_LO12:
> value = ENCODE_ITYPE_IMM (value);
> break;
>
> @@ -2202,8 +2237,8 @@ riscv_elf_relocate_section (bfd *output_bfd,
> bfd_vma relocation;
> bfd_reloc_status_type r = bfd_reloc_ok;
> const char *name = NULL;
> - bfd_vma off, ie_off;
> - bool unresolved_reloc, is_ie = false;
> + bfd_vma off, ie_off, desc_off;
> + bool unresolved_reloc, is_ie = false, is_desc = false;
> bfd_vma pc = sec_addr (input_section) + rel->r_offset;
> int r_type = ELFNN_R_TYPE (rel->r_info), tls_type;
> reloc_howto_type *howto = riscv_elf_rtype_to_howto (input_bfd,
> r_type);
> @@ -2506,6 +2541,7 @@ riscv_elf_relocate_section (bfd *output_bfd,
> case R_RISCV_NONE:
> case R_RISCV_RELAX:
> case R_RISCV_TPREL_ADD:
> + case R_RISCV_TLSDESC_CALL:
> case R_RISCV_COPY:
> case R_RISCV_JUMP_SLOT:
> case R_RISCV_RELATIVE:
> @@ -2827,6 +2863,15 @@ riscv_elf_relocate_section (bfd *output_bfd,
> relocation = dtpoff (info, relocation);
> break;
>
> + case R_RISCV_TLSDESC_LOAD_LO12:
> + case R_RISCV_TLSDESC_ADD_LO12:
> + if (riscv_record_pcrel_lo_reloc (&pcrel_relocs, relocation, rel,
> + input_section, info, howto,
> + contents))
> + continue;
> + r = bfd_reloc_overflow;
> + break;
> +
>
According to the spec, we probably can add a check here to make sure the
addend must be zero, otherwise report dangerous relocation, just similar to
what pcrel_lo did.
> case R_RISCV_32:
> /* Non ABS symbol should be blocked in check_relocs. */
> if (ARCH_SIZE > 32)
> @@ -2892,11 +2937,16 @@ riscv_elf_relocate_section (bfd *output_bfd,
> }
> break;
>
> + case R_RISCV_TLSDESC_HI20:
> + is_desc = true;
> + goto tls;
> +
> case R_RISCV_TLS_GOT_HI20:
> is_ie = true;
> - /* Fall through. */
> + goto tls;
>
> case R_RISCV_TLS_GD_HI20:
> + tls:
> if (h != NULL)
> {
> off = h->got.offset;
> @@ -2909,12 +2959,16 @@ riscv_elf_relocate_section (bfd *output_bfd,
> }
>
> tls_type = _bfd_riscv_elf_tls_type (input_bfd, h, r_symndx);
> - BFD_ASSERT (tls_type & (GOT_TLS_IE | GOT_TLS_GD));
> + BFD_ASSERT (tls_type & (GOT_TLS_IE | GOT_TLS_GD | GOT_TLSDESC));
> /* If this symbol is referenced by both GD and IE TLS, the IE
> reference's GOT slot follows the GD reference's slots. */
> ie_off = 0;
> if ((tls_type & GOT_TLS_GD) && (tls_type & GOT_TLS_IE))
> - ie_off = TLS_GD_GOT_ENTRY_SIZE;
> + ie_off += TLS_GD_GOT_ENTRY_SIZE;
> +
> + desc_off = ie_off;
> + if (tls_type & GOT_TLS_IE)
> + desc_off += TLS_IE_GOT_ENTRY_SIZE;
Is it possible that we only link GD and DESC, but without IE?
> if ((off & 1) != 0)
> off &= ~1;
> @@ -2996,10 +3050,29 @@ riscv_elf_relocate_section (bfd *output_bfd,
> htab->elf.sgot->contents + off + ie_off);
> }
> }
> +
> + if (tls_type & GOT_TLSDESC)
> + {
> + /* TLSDESC is always handled by the dynamic linker and
> always need
> + * a relocation. */
> + bfd_put_NN (output_bfd, 0,
> + htab->elf.sgot->contents + off + desc_off);
> + outrel.r_offset = sec_addr (htab->elf.sgot)
> + + off + desc_off;
> + outrel.r_addend = 0;
> + if (indx == 0)
> + outrel.r_addend = tlsdescoff (info, relocation);
> + outrel.r_info = ELFNN_R_INFO (indx, R_RISCV_TLSDESC);
> + riscv_elf_append_rela (output_bfd, htab->elf.srelgot,
> &outrel);
> + }
> }
>
> BFD_ASSERT (off < (bfd_vma) -2);
> - relocation = sec_addr (htab->elf.sgot) + off + (is_ie ? ie_off :
> 0);
> + relocation = sec_addr (htab->elf.sgot) + off;
> + if (is_ie)
> + relocation += ie_off;
> + else if (is_desc)
> + relocation += desc_off;
> if (!riscv_record_pcrel_hi_reloc (&pcrel_relocs, pc,
> relocation, r_type,
> false))
> @@ -3219,7 +3292,7 @@ riscv_elf_finish_dynamic_symbol (bfd *output_bfd,
> }
>
> if (h->got.offset != (bfd_vma) -1
> - && !(riscv_elf_hash_entry (h)->tls_type & (GOT_TLS_GD | GOT_TLS_IE))
> + && !(riscv_elf_hash_entry (h)->tls_type & (GOT_TLS_GD | GOT_TLS_IE
> | GOT_TLSDESC))
> && !UNDEFWEAK_NO_DYNAMIC_RELOC (info, h))
> {
> asection *sgot;
> diff --git a/ld/testsuite/ld-riscv-elf/tls.d
> b/ld/testsuite/ld-riscv-elf/tls.d
> index e7f20309bf1..6cf008ac7a0 100644
> --- a/ld/testsuite/ld-riscv-elf/tls.d
> +++ b/ld/testsuite/ld-riscv-elf/tls.d
> @@ -2,13 +2,15 @@
> #ld: --shared tmpdir/tlslib.so
> #readelf: -Wr
>
> -Relocation section '.rela.dyn' at offset 0x[0-9a-f]+ contains 5 entries:
> +Relocation section '.rela.dyn' at offset 0x[0-9a-f]+ contains 7 entries:
> +Offset +Info +Type +Symbol's Value +Symbol's Name \+ Addend
> [0-9a-f]+ +[0-9a-f]+ R_RISCV_TLS_DTPMOD64 +0
> [0-9a-f]+ +[0-9a-f]+ R_RISCV_TLS_TPREL64 +4
> +[0-9a-f]+ +[0-9a-f]+ R_RISCV_TLSDESC +4
> [0-9a-f]+ +[0-9a-f]+ R_RISCV_TLS_DTPMOD64 +0+ sg1 \+ 0
> [0-9a-f]+ +[0-9a-f]+ R_RISCV_TLS_DTPREL64 +0+ sg1 \+ 0
> [0-9a-f]+ +[0-9a-f]+ R_RISCV_TLS_TPREL64 +0+ sg1 \+ 0
> +[0-9a-f]+ +[0-9a-f]+ R_RISCV_TLSDESC +0+ sg1 \+ 0
>
> Relocation section '.rela.plt' at offset 0x[0-9a-f]+ contains 1 entry:
> +Offset +Info +Type +Symbol's Value +Symbol's Name \+ Addend
> diff --git a/ld/testsuite/ld-riscv-elf/tls.s
> b/ld/testsuite/ld-riscv-elf/tls.s
> index 79e9bc20374..7cbf5ea6c72 100644
> --- a/ld/testsuite/ld-riscv-elf/tls.s
> +++ b/ld/testsuite/ld-riscv-elf/tls.s
> @@ -17,6 +17,13 @@ _start:
> la.tls.ie a0,sg1
> add a0,a0,tp
>
> + /* GD (TLSDESC), global var */
> +.desc1:
> + auipc a0, %tlsdesc_hi(sg1)
> + lw t0, %tlsdesc_load_lo(.desc1)(a0)
> + addi a0, a0, %tlsdesc_add_lo(.desc1)
> + jalr t0, t0, %tlsdesc_call(.desc1)
> +
> /* GD, local var */
> la.tls.gd a0,sl1
> call __tls_get_addr
> @@ -25,4 +32,11 @@ _start:
> la.tls.ie a0,sl1
> add a0,a0,tp
>
> + /* GD (TLSDESC), local var */
> +.desc2:
> + auipc a0, %tlsdesc_hi(sl1)
> + lw t0, %tlsdesc_load_lo(.desc2)(a0)
> + addi a0, a0, %tlsdesc_add_lo(.desc2)
> + jalr t0, t0, %tlsdesc_call(.desc2)
> +
> ret
> diff --git a/ld/testsuite/ld-riscv-elf/tlsbin.d
> b/ld/testsuite/ld-riscv-elf/tlsbin.d
> index cdcd51a9199..79b7ade405e 100644
> --- a/ld/testsuite/ld-riscv-elf/tlsbin.d
> +++ b/ld/testsuite/ld-riscv-elf/tlsbin.d
> @@ -2,6 +2,11 @@
> #ld: -no-pie tmpdir/tlslib.so
> #readelf: -Wr
>
> +Relocation section '.rela.dyn' at offset 0x[0-9a-f]+ contains 2 entries:
> + +Offset +Info +Type +Symbol's Value +Symbol's Name \+ Addend
> +[0-9a-f]+ +[0-9a-f]+ R_RISCV_TLSDESC +4
> +[0-9a-f]+ +[0-9a-f]+ R_RISCV_TLSDESC +0
> +
> Relocation section '.rela.plt' at offset 0x[0-9a-f]+ contains 1 entry:
> +Offset +Info +Type +Symbol's Value +Symbol's Name \+ Addend
> [0-9a-f]+ +[0-9a-f]+ R_RISCV_JUMP_SLOT +[0-9a-f]+ __tls_get_addr \+ 0
> --
> 2.43.0
>
>
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