From: Jojo R <rjiejie@linux.alibaba.com>
To: rjiejie@linux.alibaba.com, binutils@sourceware.org
Subject: [PATCH] Support multiple .eh_frame sections
Date: Fri, 29 Jul 2022 15:48:37 +0800 [thread overview]
Message-ID: <20220729074837.82957-1-rjiejie@linux.alibaba.com> (raw)
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/dw2gencfi.c | 27 +++++++++++++++++++++++++--
gas/dw2gencfi.h | 7 ++++++-
5 files changed, 45 insertions(+), 3 deletions(-)
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index 65bd1128263..f9b64faa080 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 2b1450fa4e1..395718d72a6 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -10924,6 +10924,13 @@ 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 (bed->elf_backend_can_make_multiple_eh_frame
+ && strncmp (sec->name, ".eh_frame.", 10) == 0)
+ return 0;
+
if (sec->flags & SEC_DEBUGGING)
return PRETEND;
diff --git a/bfd/elfxx-target.h b/bfd/elfxx-target.h
index 0579f64d1a0..3927a377a0e 100644
--- a/bfd/elfxx-target.h
+++ b/bfd/elfxx-target.h
@@ -654,6 +654,9 @@
#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
@@ -887,6 +890,7 @@ 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/dw2gencfi.c b/gas/dw2gencfi.c
index 6be8cb50495..461ab601321 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, 0, frch->frch_root);;
+ 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 d570cdb8db3..0f5ae77d800 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
{
--
2.17.1
next reply other threads:[~2022-07-29 7:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-29 7:48 Jojo R [this message]
2022-08-01 11:10 ` Nick Clifton
2022-08-02 7:23 ` Jojo R
2022-11-02 8:01 ` [PATCH v2] " Jojo R
2022-11-02 12:21 ` Nick Clifton
2022-11-03 2:11 ` Jojo R
2022-11-03 2:04 ` [PATCH v3] " Jojo R
2022-11-03 10:26 ` Nick Clifton
2022-11-03 19:34 ` Fangrui Song
[not found] ` <DS7PR12MB57653A2E86C6779B24889E51CB389@DS7PR12MB5765.namprd12.prod.outlook.com>
2022-11-04 1:50 ` Jojo R
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