s390: Generate .eh_frame unwind information for .plt section
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>
diff --git a/bfd/elf64-s390.c b/bfd/elf64-s390.c
index 27836b8..259ad13 100644
--- a/bfd/elf64-s390.c
+++ b/bfd/elf64-s390.c
@@ -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 @@
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 @@
/* Short-cuts to get to dynamic linker sections. */
asection *irelifunc;
+ asection *plt_eh_frame;
union {
bfd_signed_vma refcount;
@@ -1852,6 +1883,15 @@
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 @@
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 @@
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 @@
}
}
+ /* 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 @@
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 @@
#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
diff --git a/ld/NEWS b/ld/NEWS
index 17fb20a..acb3263 100644
--- a/ld/NEWS
+++ b/ld/NEWS
@@ -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
diff --git a/ld/emulparams/elf64_s390.sh b/ld/emulparams/elf64_s390.sh
index d0a2a59..b583148 100644
--- a/ld/emulparams/elf64_s390.sh
+++ b/ld/emulparams/elf64_s390.sh
@@ -1,3 +1,4 @@
+source_sh ${srcdir}/emulparams/plt_unwind.sh
SCRIPT_NAME=elf
ELFSIZE=64
OUTPUT_FORMAT="elf64-s390"
diff --git a/ld/testsuite/ld-s390/plt_64-1_eh.wf b/ld/testsuite/ld-s390/plt_64-1_eh.wf
new file mode 100644
index 0000000..717e7a7
--- /dev/null
+++ b/ld/testsuite/ld-s390/plt_64-1_eh.wf
@@ -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
+
+#...
diff --git a/ld/testsuite/ld-s390/s390.exp b/ld/testsuite/ld-s390/s390.exp
index 26dab72..d91eeac 100644
--- a/ld/testsuite/ld-s390/s390.exp
+++ b/ld/testsuite/ld-s390/s390.exp
@@ -74,7 +74,7 @@
}
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 @@
{"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 @@
"-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-*-*"] {
