Imagelibrary/binutils-gdb
1
0
Fork 1
mirror of https://github.com/bminor/binutils-gdb.git synced 2025-12-26 09:08:59 +00:00
Code Issues Packages Projects Releases Wiki Activity

s390: Generate .eh_frame unwind information for .plt section

Browse Source 
Enable unwinding using .eh_frame information through PLT entries.  Based
on x86-64.

This enhances stack traces if the instruction pointer is in a PLT entry.
For instance perf call graphs, when using --call-graph=dwarf, and Glibc
backtraces, when using backtrace() e.g. from a signal handler.
Note that GDB could already unwind through PLT entries using its s390-
specific prologue unwinder.

Furthermore this lays the foundation to generate SFrame information for
the PLT section in the future.

bfd/
	* elf64-s390.c: Include dwarf2.h.
	(PLT_CIE_SIZE, PLT_FDE_SIZE,
	PLT_FDE_START_OFFSET, PLT_FDE_LEN_OFFSET,
	elf_s390x_eh_frame_plt): New .eh_frame template for .plt
	section.
	(elf_s390_link_hash_table): Add plt_eh_frame field.
	(elf_s390_create_dynamic_sections): New s390-specific wrapper
	around _bfd_elf_create_dynamic_sections.  Create .eh_frame
	section for .plt section.
	(elf_backend_create_dynamic_sections): Register s390-specific
	elf_s390_create_dynamic_sections.
	(elf_s390_late_size_sections): Fill in .eh_frame section for
	.plt section.  Write .plt section size into .eh_frame FDE
	covering .plt section.
	(elf_s390_finish_dynamic_sections): Write .plt section start
	into .eh_frame FDE covering .plt section.  Call
	_bfd_elf_write_section_eh_frame on on htab->plt_eh_frame
	section.

ld/
	* NEWS: Add news entry.
	* emulparams/elf64_s390.sh: Include plt_unwind.sh.

ld/testsuite/
	* ld-s390/plt_64-1_eh.wf: New PLT .eh_frame generation test.
	* ld-s390/s390.exp: Link some existing test cases with
	--no-ld-generated-unwind-info so that they do not fail.  Run
	new PLT .eh_frame generation test.

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
This commit is contained in:
Jens Remus
2025-01-27 16:47:10 +01:00
parent 6dbc8a3ef4
commit 98d9fe6cb6
5 changed files with 171 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

126
bfd/elf64-s390.c
View File

@@ -26,6 +26,7 @@
#include "elf-bfd.h"
#include "elf/s390.h"
#include "elf-s390.h"
#include "dwarf2.h"
#include <stdarg.h>
/* In case we're on a 32-bit machine, construct a 64-bit "-1" value
@@ -564,6 +565,35 @@ static const bfd_byte elf_s390x_first_plt_entry[PLT_FIRST_ENTRY_SIZE] =
0x07, 0x00 /* nopr %r0 */
};
/* .eh_frame covering the .plt section. */
#define PLT_CIE_SIZE 24
#define PLT_FDE_SIZE 20
#define PLT_FDE_START_OFFSET (PLT_CIE_SIZE + 8)
#define PLT_FDE_LEN_OFFSET (PLT_CIE_SIZE + 12)
static const bfd_byte elf_s390x_eh_frame_plt[] =
{
0, 0, 0, PLT_CIE_SIZE - 4, /* CIE length */
0, 0, 0, 0, /* CIE ID */
1, /* CIE version */
'z', 'R', 0, /* Augmentation string */
1, /* Code alignment factor */
0x78, /* Data alignment factor */
14, /* Return address column */
1, /* Augmentation size */
DW_EH_PE_pcrel | DW_EH_PE_sdata4, /* FDE encoding */
DW_CFA_def_cfa, 15, 0xa0, 0x01, /* DW_CFA_def_cfa: r15 ofs 160 */
DW_CFA_nop, DW_CFA_nop, DW_CFA_nop,
0, 0, 0, PLT_FDE_SIZE - 4, /* FDE length */
0, 0, 0, PLT_CIE_SIZE + 4, /* CIE pointer */
0, 0, 0, 0, /* R_S390_PC32 .plt goes here */
0, 0, 0, 0, /* .plt size goes here */
0, /* Augmentation size */
DW_CFA_nop, DW_CFA_nop, DW_CFA_nop
};
/* s390 ELF linker hash entry. */
@@ -656,6 +686,7 @@ struct elf_s390_link_hash_table
/* Short-cuts to get to dynamic linker sections. */
asection *irelifunc;
asection *plt_eh_frame;
union {
bfd_signed_vma refcount;
@@ -1852,6 +1883,15 @@ elf_s390_late_size_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
sym dynamic relocs. */
elf_link_hash_traverse (&htab->elf, allocate_dynrelocs, info);
if (_bfd_elf_eh_frame_present (info))
{
if (htab->plt_eh_frame != NULL
&& htab->elf.splt != NULL
&& htab->elf.splt->size != 0
&& !bfd_is_abs_section (htab->elf.splt->output_section))
htab->plt_eh_frame->size = sizeof (elf_s390x_eh_frame_plt);
}
/* We now have determined the sizes of the various dynamic sections.
Allocate memory for them. */
relocs = false;
@@ -1863,6 +1903,7 @@ elf_s390_late_size_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
if (s == htab->elf.splt
|| s == htab->elf.sgot
|| s == htab->elf.sgotplt
|| s == htab->plt_eh_frame
|| s == htab->elf.sdynbss
|| s == htab->elf.sdynrelro
|| s == htab->elf.iplt
@@ -1930,6 +1971,16 @@ elf_s390_late_size_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
s->alloced = 1;
}
if (htab->plt_eh_frame != NULL
&& htab->plt_eh_frame->contents != NULL)
{
memcpy (htab->plt_eh_frame->contents,
elf_s390x_eh_frame_plt,
htab->plt_eh_frame->size);
bfd_put_32 (dynobj, htab->elf.splt->size,
htab->plt_eh_frame->contents + PLT_FDE_LEN_OFFSET);
}
return _bfd_elf_add_dynamic_tags (output_bfd, info, relocs);
}
@@ -3703,6 +3754,38 @@ elf_s390_finish_dynamic_sections (bfd *output_bfd,
}
}
/* Adjust .eh_frame for .plt section. */
if (htab->plt_eh_frame != NULL
&& htab->plt_eh_frame->contents != NULL)
{
if (htab->elf.splt != NULL
&& htab->elf.splt->size != 0
&& (htab->elf.splt->flags & SEC_EXCLUDE) == 0
&& htab->elf.splt->output_section != NULL
&& htab->plt_eh_frame->output_section != NULL)
{
bfd_vma plt_start = htab->elf.splt->output_section->vma;
bfd_vma eh_frame_start = htab->plt_eh_frame->output_section->vma
+ htab->plt_eh_frame->output_offset
+ PLT_FDE_START_OFFSET;
/* Note: Linker may have discarded the FDE, so that store may
be beyond current htab->plt_eh_frame->size. Can be ignored,
as htab->plt_eh_frame->contents got allocated with
sizeof (elf_s390x_eh_frame_plt). See PR 12570. */
bfd_put_signed_32 (dynobj, plt_start - eh_frame_start,
htab->plt_eh_frame->contents
+ PLT_FDE_START_OFFSET);
}
if (htab->plt_eh_frame->sec_info_type == SEC_INFO_TYPE_EH_FRAME)
{
if (! _bfd_elf_write_section_eh_frame (output_bfd, info,
htab->plt_eh_frame,
htab->plt_eh_frame->contents))
return NULL;
}
}
return true;
}
@@ -3926,6 +4009,47 @@ bfd_elf_s390_set_options (struct bfd_link_info *info,
return true;
}
/* Create .plt, .rela.plt, .got, .got.plt, .rela.got, .dynbss, and
.rela.bss sections in DYNOBJ, and set up shortcuts to them in our
hash table. */
static bool
elf_s390_create_dynamic_sections (bfd *dynobj,
struct bfd_link_info *info)
{
struct elf_s390_link_hash_table *htab;
if (!_bfd_elf_create_dynamic_sections (dynobj, info))
return false;
htab = elf_s390_hash_table (info);
if (htab == NULL)
return false;
if (htab->elf.splt != NULL)
{
/* Create .eh_frame section for .plt section. */
if (!info->no_ld_generated_unwind_info)
{
flagword flags = (SEC_ALLOC | SEC_LOAD | SEC_READONLY
| SEC_HAS_CONTENTS | SEC_IN_MEMORY
| SEC_LINKER_CREATED);
if (htab->plt_eh_frame == NULL)
{
htab->plt_eh_frame
= bfd_make_section_anyway_with_flags (dynobj,
".eh_frame",
flags);
if (htab->plt_eh_frame == NULL
|| !bfd_set_section_alignment (htab->plt_eh_frame, 3))
return false;
}
}
}
return true;
}
/* Why was the hash table entry size definition changed from
ARCH_SIZE/8 to 4? This breaks the 64 bit dynamic linker and
@@ -3992,7 +4116,7 @@ const struct elf_size_info s390_elf64_size_info =
#define elf_backend_adjust_dynamic_symbol elf_s390_adjust_dynamic_symbol
#define elf_backend_check_relocs elf_s390_check_relocs
#define elf_backend_copy_indirect_symbol elf_s390_copy_indirect_symbol
#define elf_backend_create_dynamic_sections _bfd_elf_create_dynamic_sections
#define elf_backend_create_dynamic_sections elf_s390_create_dynamic_sections
#define elf_backend_finish_dynamic_sections elf_s390_finish_dynamic_sections
#define elf_backend_finish_dynamic_symbol elf_s390_finish_dynamic_symbol
#define elf_backend_gc_mark_hook elf_s390_gc_mark_hook

6
ld/NEWS
View File

@@ -1,5 +1,11 @@
-*- text -*-
* On s390, generate ".eh_frame" unwind information for the linker generated
.plt section. Enabled by default. Can be disabled using linker option
--no-ld-generated-unwind-info.
* On s390, add support for linker option --[no-]ld-generated-unwind-info.
Changes in 2.44:
* Support for Nios II target has been removed, as this architecture has been

1
ld/emulparams/elf64_s390.sh
View File

@@ -1,3 +1,4 @@
source_sh ${srcdir}/emulparams/plt_unwind.sh
SCRIPT_NAME=elf
ELFSIZE=64
OUTPUT_FORMAT="elf64-s390"

31
ld/testsuite/ld-s390/plt_64-1_eh.wf Normal file
View File

@@ -0,0 +1,31 @@
#source: plt_64-1.s
#as: -m64
#ld: -m elf64_s390
#readelf: -wf
#target: s390x-*-*
Contents of the .eh_frame section:
00000000 0000000000000014 00000000 CIE
Version: 1
Augmentation: "zR"
Code alignment factor: 1
Data alignment factor: -8
Return address column: 14
Augmentation data: 1b
DW_CFA_def_cfa: r15 ofs 160
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
00000018 0000000000000014 0000001c FDE cie=00000000 pc=0000000001000258..00000000010002b8
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
#...

12
ld/testsuite/ld-s390/s390.exp
View File

@@ -74,7 +74,7 @@ set s390tests {
}
set s390xtests {
{"TLS -fpic -shared transitions" "-shared -melf64_s390 --hash-style=sysv" ""
{"TLS -fpic -shared transitions" "-shared -melf64_s390 --hash-style=sysv --no-ld-generated-unwind-info" ""
"-m64 -Aesame" {tlspic1_64.s tlspic2_64.s}
{{readelf -WSsrl tlspic_64.rd} {objdump -dzrj.text tlspic_64.dd}
{objdump -sj.got tlspic_64.sd} {objdump -sj.tdata tlspic_64.td}}
@@ -82,7 +82,7 @@ set s390xtests {
{"Helper shared library" "-shared -melf64_s390" ""
"-m64 -Aesame" {tlslib_64.s} {} "libtlslib_64.so"}
{"TLS -fpic and -fno-pic exec transitions"
"-melf64_s390 tmpdir/libtlslib_64.so --hash-style=sysv" ""
"-melf64_s390 tmpdir/libtlslib_64.so --hash-style=sysv --no-ld-generated-unwind-info" ""
"-m64 -Aesame" {tlsbinpic_64.s tlsbin_64.s}
{{readelf -WSsrl tlsbin_64.rd} {objdump -dzrj.text tlsbin_64.dd}
{objdump -sj.got tlsbin_64.sd} {objdump -sj.tdata tlsbin_64.td}}
@@ -117,10 +117,14 @@ set s390xtests {
"-shared -m elf64_s390" "" "-m64" {pltlib.s}
{}
"libpltlib_64.so"}
{"PLT: PLT generation"
"-m elf64_s390 tmpdir/libpltlib_64.so" "" "-m64" {plt_64-1.s}
{"PLT: PLT generation without .eh_frame unwind info"
"-m elf64_s390 tmpdir/libpltlib_64.so --no-ld-generated-unwind-info" "" "-m64" {plt_64-1.s}
{{objdump "-dzrj.plt" plt_64-1.pd} {readelf "-wf" plt_64-1.wf}}
"plt_64-1"}
{"PLT: PLT generation with .eh_frame unwind info"
"-m elf64_s390 tmpdir/libpltlib_64.so" "" "-m64" {plt_64-1.s}
{{objdump "-dzrj.plt" plt_64-1.pd} {readelf "-wf" plt_64-1_eh.wf}}
"plt_64-1_eh"}
}
if [istarget "s390-*-*"] {