Hi David.
> [Changed from v1: Adjust to account for file renaming so patch applies.]
>
> BPF CO-RE relocations contain offsets to strings buffered in the BTF
> string table. These BTF-specific strings are stored in memory in the
> CTF auxilliary strtab, which at output time is concatenated onto the end
> of the standard strtab.
>
> Previously, these string offsets were computed at the time the
> relocations were created. But strings could be added to the standard
> strtab after this point, causing the offsets to no longer be correct.
>
> Compute the offsets just before output instead, when they are sure to no
> longer change.
>
> Tested for bpf-unknown-none. OK to install?
> Thanks.
OK.
Thanks.
>
> gcc/ChangeLog:
>
> * config/bpf/coreout.cc (bpf_core_reloc_add): Do not account
> for base strtab offset yet as it may change.
> (output_asm_btfext_core_reloc): Do so here instead.
> (output_btfext_core_sections): Likewise.
> ---
> gcc/config/bpf/coreout.cc | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/config/bpf/coreout.cc b/gcc/config/bpf/coreout.cc
> index 4ec12ecd305..cceaaa969cc 100644
> --- a/gcc/config/bpf/coreout.cc
> +++ b/gcc/config/bpf/coreout.cc
> @@ -168,11 +168,8 @@ bpf_core_reloc_add (const tree type, const char *
> section_name,
> bpf_core_reloc_ref bpfcr = ggc_cleared_alloc<bpf_core_reloc_t> ();
> ctf_container_ref ctfc = ctf_get_tu_ctfc ();
>
> - /* Buffer the access string in the auxiliary strtab. Since the two string
> - tables are concatenated, add the length of the first to the offset. */
> - size_t strtab_len = ctfc_get_strtab_len (ctfc, CTF_STRTAB);
> + /* Buffer the access string in the auxiliary strtab. */
> ctf_add_string (ctfc, buf, &(bpfcr->bpfcr_astr_off), CTF_AUX_STRTAB);
> - bpfcr->bpfcr_astr_off += strtab_len;
>
> bpfcr->bpfcr_type = get_btf_id (ctf_lookup_tree_type (ctfc, type));
> bpfcr->bpfcr_insn_label = label;
> @@ -191,7 +188,6 @@ bpf_core_reloc_add (const tree type, const char *
> section_name,
> sec = ggc_cleared_alloc<bpf_core_section_t> ();
>
> ctf_add_string (ctfc, section_name, &sec->name_offset, CTF_AUX_STRTAB);
> - sec->name_offset += strtab_len;
> if (strcmp (section_name, ""))
> ctfc->ctfc_aux_strlen += strlen (section_name) + 1;
>
> @@ -287,6 +283,9 @@ output_btfext_header (void)
> static void
> output_asm_btfext_core_reloc (bpf_core_reloc_ref bpfcr)
> {
> + bpfcr->bpfcr_astr_off += ctfc_get_strtab_len (ctf_get_tu_ctfc (),
> + CTF_STRTAB);
> +
> dw2_assemble_integer (4, gen_rtx_LABEL_REF (Pmode,
> bpfcr->bpfcr_insn_label));
> fprintf (asm_out_file, "\t%s bpfcr_insn\n", ASM_COMMENT_START);
>
> @@ -323,6 +322,11 @@ output_btfext_core_sections (void)
> /* Section name offset, refers to the offset of a string with the name
> of
> the section to which these CORE relocations refer, e.g. '.text'.
> The string is buffered in the BTF strings table. */
> +
> + /* BTF specific strings are in CTF_AUX_STRTAB, which is concatenated
> + after CTF_STRTAB. Add the length of STRTAB to the final offset. */
> + sec->name_offset += ctfc_get_strtab_len (ctf_get_tu_ctfc (),
> CTF_STRTAB);
> +
> dw2_asm_output_data (4, sec->name_offset,
> "btfext_secinfo_sec_name_off");
> dw2_asm_output_data (4, vec_safe_length (sec->relocs),
> "btfext_secinfo_num_recs");
