[PATCH v3] aarch64: Add support for %dtprel(var) and R_AARCH64_TLS_DTPREL64
Alice Carlotti
alice.carlotti@arm.com
Thu Apr 9 14:38:14 GMT 2026
On Wed, Apr 08, 2026 at 03:45:38PM +0530, Shivam Gupta wrote:
> This patch allows R_AARCH64_TLS_DTPREL64 relocations in non-allocated
> sections, which is required for DWARF debug information when using
> Thread Local Storage. This matches the behavior in LLD.
>
> Also a new syntax to parse dtprel operator use to describe tls
> location in debug information. Please see the reference 3 below.
>
> References:
> - https://github.com/llvm/llvm-project/pull/146572
> [AArch64] Support TLS variables in debug info
> - https://github.com/llvm/llvm-project/pull/183962
> [LLD][AArch64] Handle R_AARCH64_TLS_DTPREL64 in non-alloc sections
> - https://github.com/ARM-software/abi-aa/pull/330
> [AAELF64] Allow R_AARCH64_TLS_DTPREL to be used statically.
>
> bfd/
> * elfnn-aarch64.c (elfNN_aarch64_final_link_relocate): Handle
> BFD_RELOC_AARCH64_TLS_DTPREL.
>
> gas/
> * config/tc-aarch64.c (s_aarch64_cons): Parse %dtprel(var) syntax.
> * testsuite/gas/aarch64/tls-debug.s: New test.
> * testsuite/gas/aarch64/tls-debug.d: Run the test.
>
> ld/
> * testsuite/ld-aarch64/tls-debug.s: New test.
> * testsuite/ld-aarch64/tls-debug.d: Run the test.
>
> Bug: https://sourceware.org/PR28351
>
> Signed-off-by: Shivam Gupta <shivam98.tkg@gmail.com>
>
> ---
>
> Notes :
> Changes in v3:
> - Combine multiple %dtprel relocations into a single line in test
> - Simplify %dtprel parsing logic
> - Simplify unknown relocation operator error message
Thanks - I've committed this for you.
Alice
>
> bfd/elfnn-aarch64.c | 11 ++++++++
> gas/config/tc-aarch64.c | 37 +++++++++++++++++++++++++
> gas/testsuite/gas/aarch64/tls-debug.d | 10 +++++++
> gas/testsuite/gas/aarch64/tls-debug.s | 8 ++++++
> ld/testsuite/ld-aarch64/aarch64-elf.exp | 1 +
> ld/testsuite/ld-aarch64/tls-debug.d | 9 ++++++
> ld/testsuite/ld-aarch64/tls-debug.s | 9 ++++++
> 7 files changed, 85 insertions(+)
> create mode 100644 gas/testsuite/gas/aarch64/tls-debug.d
> create mode 100644 gas/testsuite/gas/aarch64/tls-debug.s
> create mode 100644 ld/testsuite/ld-aarch64/tls-debug.d
> create mode 100644 ld/testsuite/ld-aarch64/tls-debug.s
>
> diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
> index 66049c81..117e1498 100644
> --- a/bfd/elfnn-aarch64.c
> +++ b/bfd/elfnn-aarch64.c
> @@ -6496,6 +6496,17 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
> *unresolved_reloc_p = false;
> break;
>
> + case BFD_RELOC_AARCH64_TLS_DTPREL:
> + if (input_section->flags & SEC_ALLOC)
> + return bfd_reloc_notsupported;
> + value -= dtpoff_base (info);
> + value += rel->r_addend;
> +
> + bfd_put_64 (output_bfd, value, contents + rel->r_offset);
> +
> + *unresolved_reloc_p = false;
> + break;
> +
> case BFD_RELOC_AARCH64_TLSDESC_OFF_G0_NC:
> case BFD_RELOC_AARCH64_TLSDESC_OFF_G1:
> if (globals->root.sgot == NULL)
> diff --git a/gas/config/tc-aarch64.c b/gas/config/tc-aarch64.c
> index cd761634..73b549a1 100644
> --- a/gas/config/tc-aarch64.c
> +++ b/gas/config/tc-aarch64.c
> @@ -2229,6 +2229,42 @@ s_aarch64_cons (int nbytes)
> {
> struct reloc_table_entry *reloc;
>
> + /* Check for %dtprel(var) syntax */
> + if (*input_line_pointer == '%')
> + {
> + if (strncmp (input_line_pointer, "%dtprel(", 8) == 0)
> + {
> + input_line_pointer += 8;
> +
> + expression (&exp);
> +
> + /* Ensure we have a closing parenthesis */
> + if (*input_line_pointer == ')')
> + input_line_pointer++;
> + else
> + {
> + as_bad (_("missing ')' after %%dtprel"));
> + ignore_rest_of_line ();
> + return;
> + }
> +
> + addressT where = frag_now_fix ();
> + fix_new_exp (frag_now, where, nbytes, &exp, 0,
> + BFD_RELOC_AARCH64_TLS_DTPREL);
> +
> + char *dest = frag_more (nbytes);
> + memset (dest, 0, nbytes);
> + continue;
> + }
> +
> + else
> + {
> + as_bad (_("unknown relocation operator"));
> + ignore_rest_of_line ();
> + return;
> + }
> + }
> +
> expression (&exp);
>
> if (exp.X_op != O_symbol)
> @@ -10114,6 +10150,7 @@ md_apply_fix (fixS * fixP, valueT * valP, segT seg)
> case BFD_RELOC_AARCH64_TLSLE_MOVW_TPREL_G1:
> case BFD_RELOC_AARCH64_TLSLE_MOVW_TPREL_G1_NC:
> case BFD_RELOC_AARCH64_TLSLE_MOVW_TPREL_G2:
> + case BFD_RELOC_AARCH64_TLS_DTPREL:
> S_SET_THREAD_LOCAL (fixP->fx_addsy);
> /* Should always be exported to object file, see
> aarch64_force_relocation(). */
> diff --git a/gas/testsuite/gas/aarch64/tls-debug.d b/gas/testsuite/gas/aarch64/tls-debug.d
> new file mode 100644
> index 00000000..1dd4df17
> --- /dev/null
> +++ b/gas/testsuite/gas/aarch64/tls-debug.d
> @@ -0,0 +1,10 @@
> +#as:
> +#objdump: -r
> +#target: aarch64*-*-*
> +
> +#...
> +RELOCATION RECORDS FOR \[\.debug_info\]:
> +OFFSET +TYPE +VALUE
> +0*0 R_AARCH64_TLS_DTPREL64 +var
> +0*8 R_AARCH64_TLS_DTPREL64 +var\+0x0+1
> +#...
> diff --git a/gas/testsuite/gas/aarch64/tls-debug.s b/gas/testsuite/gas/aarch64/tls-debug.s
> new file mode 100644
> index 00000000..c45507ed
> --- /dev/null
> +++ b/gas/testsuite/gas/aarch64/tls-debug.s
> @@ -0,0 +1,8 @@
> +.section .tdata,"awT",@progbits
> +.skip 8 // Force var to have an offset of 8
> +.globl var
> +var:
> + .word 0
> +
> +.section .debug_info,"",@progbits
> + .xword %dtprel(var), %dtprel(var+1)
> diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
> index 24c73d53..fa802105 100644
> --- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
> +++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
> @@ -261,6 +261,7 @@ run_dump_test "tls-relax-ld-le-small"
> run_dump_test "tls-relax-ld-le-small-ilp32"
> run_dump_test "tls-relax-ld-le-tiny"
> run_dump_test "tls-relax-ld-le-tiny-ilp32"
> +run_dump_test "tls-debug"
> run_dump_test "tls-desc-ie"
> run_dump_test "tls-desc-ie-ilp32"
> run_dump_test "tls-relax-gdesc-le-2"
> diff --git a/ld/testsuite/ld-aarch64/tls-debug.d b/ld/testsuite/ld-aarch64/tls-debug.d
> new file mode 100644
> index 00000000..4344b02e
> --- /dev/null
> +++ b/ld/testsuite/ld-aarch64/tls-debug.d
> @@ -0,0 +1,9 @@
> +#source: tls-debug.s
> +#ld: -shared -T relocs.ld -e0
> +#objdump: -s -j .debug_info
> +
> +#...
> +Contents of section .debug_info:
> +#...
> + [0-9a-f]+ 08000000 00000000 09000000 00000000 .*
> +#...
> diff --git a/ld/testsuite/ld-aarch64/tls-debug.s b/ld/testsuite/ld-aarch64/tls-debug.s
> new file mode 100644
> index 00000000..9590ad40
> --- /dev/null
> +++ b/ld/testsuite/ld-aarch64/tls-debug.s
> @@ -0,0 +1,9 @@
> +.section .tdata,"awT",@progbits
> +.skip 8 // Force var to have an offset of 8
> +.globl var
> +var:
> + .word 0
> +
> +.section .debug_info,"",@progbits
> + .xword %dtprel(var)
> + .xword %dtprel(var+1)
> --
> 2.34.1
>
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