From 853ba67882805f415c9816ca13d738295cf54f48 Mon Sep 17 00:00:00 2001 From: Jojo R Date: Thu, 14 Jul 2022 00:28:09 +0800 Subject: Support multiple .eh_frame sections This patch is based on MULTIPLE_FRAME_SECTIONS and EH_FRAME_LINKONCE, it allows backend to enable this feature and use '--gc-sections' simply. * gas/dw2gencfi.h (TARGET_MULTIPLE_EH_FRAME_SECTIONS): New. (MULTIPLE_FRAME_SECTIONS): Add TARGET_MULTIPLE_EH_FRAME_SECTIONS. * gas/dw2gencfi.c (EH_FRAME_LINKONCE): Add TARGET_MULTIPLE_EH_FRAME_SECTIONS. (is_now_linkonce_segment): Likewise. (get_cfi_seg): Create relocation info between .eh_frame.* and .text.* section. * bfd/elf-bfd.h (elf_backend_can_make_multiple_eh_frame): New. * bfd/elfxx-target.h (elf_backend_can_make_multiple_eh_frame): Likewise. * bfd/elflink.c (_bfd_elf_default_action_discarded): Add checking for elf_backend_can_make_multiple_eh_frame. --- bfd/elf-bfd.h | 3 +++ bfd/elflink.c | 7 +++++++ bfd/elfxx-target.h | 4 ++++ gas/doc/internals.texi | 4 ++++ gas/dw2gencfi.c | 27 +++++++++++++++++++++++++-- gas/dw2gencfi.h | 7 ++++++- 6 files changed, 49 insertions(+), 3 deletions(-) diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h index f00f87b..fa4b9bc 100644 --- a/bfd/elf-bfd.h +++ b/bfd/elf-bfd.h @@ -1432,6 +1432,9 @@ struct elf_backend_data bool (*elf_backend_can_make_lsda_relative_eh_frame) (bfd *, struct bfd_link_info *, asection *); + /* Tell linker to support multiple eh_frame sections. */ + bool elf_backend_can_make_multiple_eh_frame; + /* This function returns an encoding after computing the encoded value (and storing it in ENCODED) for the given OFFSET into OSEC, to be stored in at LOC_OFFSET into the LOC_SEC input section. diff --git a/bfd/elflink.c b/bfd/elflink.c index 89dcf26..019ac30 100644 --- a/bfd/elflink.c +++ b/bfd/elflink.c @@ -10924,12 +10924,19 @@ elf_section_ignore_discarded_relocs (asection *sec) unsigned int _bfd_elf_default_action_discarded (asection *sec) { + const struct elf_backend_data *bed; + bed = get_elf_backend_data (sec->owner); + if (sec->flags & SEC_DEBUGGING) return PRETEND; if (strcmp (".eh_frame", sec->name) == 0) return 0; + if (bed->elf_backend_can_make_multiple_eh_frame + && strncmp (sec->name, ".eh_frame.", 10) == 0) + return 0; + if (strcmp (".gcc_except_table", sec->name) == 0) return 0; diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h index ca600bb..f39244e 100644 --- a/bfd/elfxx-target.h +++ b/bfd/elfxx-target.h @@ -658,6 +658,9 @@ #ifndef elf_backend_can_make_lsda_relative_eh_frame #define elf_backend_can_make_lsda_relative_eh_frame _bfd_elf_can_make_relative #endif +#ifndef elf_backend_can_make_multiple_eh_frame +#define elf_backend_can_make_multiple_eh_frame 0 +#endif #ifndef elf_backend_encode_eh_address #define elf_backend_encode_eh_address _bfd_elf_encode_eh_address #endif @@ -891,6 +894,7 @@ static const struct elf_backend_data elfNN_bed = elf_backend_eh_frame_address_size, elf_backend_can_make_relative_eh_frame, elf_backend_can_make_lsda_relative_eh_frame, + elf_backend_can_make_multiple_eh_frame, elf_backend_encode_eh_address, elf_backend_write_section, elf_backend_elfsym_local_is_section, diff --git a/gas/doc/internals.texi b/gas/doc/internals.texi index a91d2ab..f028874 100644 --- a/gas/doc/internals.texi +++ b/gas/doc/internals.texi @@ -1581,6 +1581,10 @@ If defined, GAS will check this macro before performing any optimizations on the DWARF call frame debug information that is emitted. Targets which implement link time relaxation may need to define this macro and set it to zero if it is possible to change the size of a function's prologue. + +@item TARGET_MULTIPLE_EH_FRAME_SECTIONS +If defined, GAS will create multiple .eh_frame.* sections according to +the name of owner's function sections. @end table @node Object format backend diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c index 6be8cb5..80b2628 100644 --- a/gas/dw2gencfi.c +++ b/gas/dw2gencfi.c @@ -75,7 +75,8 @@ # define tc_cfi_endproc(fde) ((void) (fde)) #endif -#define EH_FRAME_LINKONCE (SUPPORT_FRAME_LINKONCE || compact_eh) +#define EH_FRAME_LINKONCE (SUPPORT_FRAME_LINKONCE || compact_eh \ + || TARGET_MULTIPLE_EH_FRAME_SECTIONS) #ifndef DWARF2_FORMAT #define DWARF2_FORMAT(SEC) dwarf2_format_32bit @@ -277,6 +278,9 @@ is_now_linkonce_segment (void) if (compact_eh) return now_seg; + if (TARGET_MULTIPLE_EH_FRAME_SECTIONS) + return now_seg; + if ((bfd_section_flags (now_seg) & (SEC_LINK_ONCE | SEC_LINK_DUPLICATES_DISCARD | SEC_LINK_DUPLICATES_ONE_ONLY | SEC_LINK_DUPLICATES_SAME_SIZE @@ -1333,14 +1337,33 @@ static segT get_cfi_seg (segT cseg, const char *base, flagword flags, int align) { /* Exclude .debug_frame sections for Compact EH. */ - if (SUPPORT_FRAME_LINKONCE || ((flags & SEC_DEBUGGING) == 0 && compact_eh)) + if (SUPPORT_FRAME_LINKONCE || ((flags & SEC_DEBUGGING) == 0 && compact_eh) + || ((flags & SEC_DEBUGGING) == 0 && TARGET_MULTIPLE_EH_FRAME_SECTIONS)) { + segT iseg = cseg; struct dwcfi_seg_list *l; l = dwcfi_hash_find_or_make (cseg, base, flags); cseg = l->seg; subseg_set (cseg, l->subseg); + + if (TARGET_MULTIPLE_EH_FRAME_SECTIONS + && (flags & DWARF2_EH_FRAME_READ_ONLY)) + { + const frchainS *ifrch = seg_info (iseg)->frchainP; + const frchainS *frch = seg_info (cseg)->frchainP; + expressionS exp; + + exp.X_op = O_symbol; + exp.X_add_symbol = (symbolS *) local_symbol_make (cseg->name, cseg, frch->frch_root, 0); + exp.X_add_number = 0; + subseg_set (iseg, ifrch->frch_subseg); + fix_new_exp (ifrch->frch_root, 0, 0, &exp, 0, BFD_RELOC_NONE); + + /* Restore the original segment info. */ + subseg_set (cseg, l->subseg); + } } else { diff --git a/gas/dw2gencfi.h b/gas/dw2gencfi.h index d570cdb..0f5ae77 100644 --- a/gas/dw2gencfi.h +++ b/gas/dw2gencfi.h @@ -66,7 +66,12 @@ extern void cfi_add_CFA_restore_state (void); #define SUPPORT_COMPACT_EH 0 #endif -#define MULTIPLE_FRAME_SECTIONS (SUPPORT_FRAME_LINKONCE || SUPPORT_COMPACT_EH) +#ifndef TARGET_MULTIPLE_EH_FRAME_SECTIONS +#define TARGET_MULTIPLE_EH_FRAME_SECTIONS 0 +#endif + +#define MULTIPLE_FRAME_SECTIONS (SUPPORT_FRAME_LINKONCE || SUPPORT_COMPACT_EH \ + || TARGET_MULTIPLE_EH_FRAME_SECTIONS) struct cfi_insn_data { -- cgit v1.1