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binutils-gdb/gdb/elfread.c
Pedro Alves 7022349d5c Stop assuming no-debug-info functions return int 
The fact that GDB defaults to assuming that functions return int, when
it has no debug info for the function has been a recurring source of
user confusion.  Recently this came up on the errno pretty printer
discussions.  Shortly after, it came up again on IRC, with someone
wondering why does getenv() in GDB return a negative int:

  (gdb) p getenv("PATH")
  $1 = -6185

This question (with s/getenv/random-other-C-runtime-function) is a FAQ
on IRC.

The reason for the above is:

 (gdb) p getenv
 $2 = {<text variable, no debug info>} 0x7ffff7751d80 <getenv>
 (gdb) ptype getenv
 type = int ()

... which means that GDB truncated the 64-bit pointer that is actually
returned from getent to 32-bit, and then sign-extended it:

 (gdb) p /x -6185
 $6 = 0xffffe7d7

The workaround is to cast the function to the right type, like:

 (gdb) p ((char *(*) (const char *)) getenv) ("PATH")
 $3 = 0x7fffffffe7d7 "/usr/local/bin:/"...

IMO, we should do better than this.

I see the "assume-int" issue the same way I see printing bogus values
for optimized-out variables instead of "<optimized out>" -- I'd much
rather that the debugger tells me "I don't know" and tells me how to
fix it than showing me bogus misleading results, making me go around
tilting at windmills.

If GDB prints a signed integer when you're expecting a pointer or
aggregate, you at least have some sense that something is off, but
consider the case of the function actually returning a 64-bit integer.
For example, compile this without debug info:

 unsigned long long
 function ()
 {
   return 0x7fffffffffffffff;
 }

Currently, with pristine GDB, you get:

 (gdb) p function ()
 $1 = -1                      # incorrect
 (gdb) p /x function ()
 $2 = 0xffffffff              # incorrect

maybe after spending a few hours debugging you suspect something is
wrong with that -1, and do:

 (gdb) ptype function
 type = int ()

and maybe, just maybe, you realize that the function actually returns
unsigned long long.  And you try to fix it with:

(gdb) p /x (unsigned long long) function ()
 $3 = 0xffffffffffffffff      # incorrect

... which still produces the wrong result, because GDB simply applied
int to unsigned long long conversion.  Meaning, it sign-extended the
integer that it extracted from the return of the function, to 64-bits.

and then maybe, after asking around on IRC, you realize you have to
cast the function to a pointer of the right type, and call that.  It
won't be easy, but after a few missteps, you'll get to it:

.....  (gdb) p /x ((unsigned long long(*) ()) function) ()
 $666 = 0x7fffffffffffffff             # finally! :-)


So to improve on the user experience, this patch does the following
(interrelated) things:

 - makes no-debug-info functions no longer default to "int" as return
   type.  Instead, they're left with NULL/"<unknown return type>"
   return type.

    (gdb) ptype getenv
    type = <unknown return type> ()

 - makes calling a function with unknown return type an error.

    (gdb) p getenv ("PATH")
    'getenv' has unknown return type; cast the call to its declared return type

 - and then to make it easier to call the function, makes it possible
   to _only_ cast the return of the function to the right type,
   instead of having to cast the function to a function pointer:

    (gdb) p (char *) getenv ("PATH")                      # now Just Works
    $3 = 0x7fffffffe7d7 "/usr/local/bin:/"...

    (gdb) p ((char *(*) (const char *)) getenv) ("PATH")  # continues working
    $4 = 0x7fffffffe7d7 "/usr/local/bin:/"...

   I.e., it makes GDB default the function's return type to the type
   of the cast, and the function's parameters to the type of the
   arguments passed down.

After this patch, here's what you'll get for the "unsigned long long"
example above:

 (gdb) p function ()
 'function' has unknown return type; cast the call to its declared return type
 (gdb) p /x (unsigned long long) function ()
 $4 = 0x7fffffffffffffff     # correct!

Note that while with "print" GDB shows the name of the function that
has the problem:

  (gdb) p getenv ("PATH")
  'getenv' has unknown return type; cast the call to its declared return type

which can by handy in more complicated expressions, "ptype" does not:

  (gdb) ptype getenv ("PATH")
  function has unknown return type; cast the call to its declared return type

This will be fixed in the next patch.

gdb/ChangeLog:
2017-09-04  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_evaluate_subexp) <TYPE_CODE_FUNC>: Don't handle
	TYPE_GNU_IFUNC specially here.  Throw error if return type is
	unknown.
	* ada-typeprint.c (print_func_type): Handle functions with unknown
	return type.
	* c-typeprint.c (c_type_print_base): Handle functions and methods
	with unknown return type.
	* compile/compile-c-symbols.c (convert_symbol_bmsym)
	<mst_text_gnu_ifunc>: Use nodebug_text_gnu_ifunc_symbol.
	* compile/compile-c-types.c: Include "objfiles.h".
	(convert_func): For functions with unknown return type, warn and
	default to int.
	* compile/compile-object-run.c (compile_object_run): Adjust call
	to call_function_by_hand_dummy.
	* elfread.c (elf_gnu_ifunc_resolve_addr): Adjust call to
	call_function_by_hand.
	* eval.c (evaluate_subexp_standard): Adjust calls to
	call_function_by_hand.  Handle functions and methods with unknown
	return type.  Pass expect_type to call_function_by_hand.
	* f-typeprint.c (f_type_print_base): Handle functions with unknown
	return type.
	* gcore.c (call_target_sbrk): Adjust call to
	call_function_by_hand.
	* gdbtypes.c (objfile_type): Leave nodebug text symbol with NULL
	return type instead of int.  Make nodebug_text_gnu_ifunc_symbol be
	an integer address type instead of nodebug.
	* guile/scm-value.c (gdbscm_value_call): Adjust call to
	call_function_by_hand.
	* infcall.c (error_call_unknown_return_type): New function.
	(call_function_by_hand): New "default_return_type" parameter.
	Pass it down.
	(call_function_by_hand_dummy): New "default_return_type"
	parameter.  Use it instead of defaulting to int.  If there's no
	default and the return type is unknown, throw an error.  If
	there's a default return type, and the called function has no
	debug info, then assume the function is prototyped.
	* infcall.h (call_function_by_hand, call_function_by_hand_dummy):
	New "default_return_type" parameter.
	(error_call_unknown_return_type): New declaration.
	* linux-fork.c (call_lseek): Cast return type of lseek.
	(inferior_call_waitpid, checkpoint_command): Adjust calls to
	call_function_by_hand.
	* linux-tdep.c (linux_infcall_mmap, linux_infcall_munmap): Adjust
	calls to call_function_by_hand.
	* m2-typeprint.c (m2_procedure): Handle functions with unknown
	return type.
	* objc-lang.c (lookup_objc_class, lookup_child_selector)
	(value_nsstring, print_object_command): Adjust calls to
	call_function_by_hand.
	* p-typeprint.c (pascal_type_print_varspec_prefix): Handle
	functions with unknown return type.
	(pascal_type_print_func_varspec_suffix): New function.
	(pascal_type_print_varspec_suffix) <TYPE_CODE_FUNC,
	TYPE_CODE_METHOD>: Use it.
	* python/py-value.c (valpy_call): Adjust call to
	call_function_by_hand.
	* rust-lang.c (rust_evaluate_funcall): Adjust call to
	call_function_by_hand.
	* valarith.c (value_x_binop, value_x_unop): Adjust calls to
	call_function_by_hand.
	* valops.c (value_allocate_space_in_inferior): Adjust call to
	call_function_by_hand.
	* typeprint.c (type_print_unknown_return_type): New function.
	* typeprint.h (type_print_unknown_return_type): New declaration.

gdb/testsuite/ChangeLog:
2017-09-04  Pedro Alves  <palves@redhat.com>

	* gdb.base/break-main-file-remove-fail.exp (test_remove_bp): Cast
	return type of munmap in infcall.
	* gdb.base/break-probes.exp: Cast return type of foo in infcall.
	* gdb.base/checkpoint.exp: Simplify using for loop.  Cast return
	type of ftell in infcall.
	* gdb.base/dprintf-detach.exp (dprintf_detach_test): Cast return
	type of getpid in infcall.
	* gdb.base/infcall-exec.exp: Cast return type of execlp in
	infcall.
	* gdb.base/info-os.exp: Cast return type of getpid in infcall.
	Bail on failure to extract the pid.
	* gdb.base/nodebug.c: #include <stdint.h>.
	(multf, multf_noproto, mult, mult_noproto, add8, add8_noproto):
	New functions.
	* gdb.base/nodebug.exp (test_call_promotion): New procedure.
	Change expected output of print/whatis/ptype with functions with
	no debug info.  Test all supported languages.  Call
	test_call_promotion.
	* gdb.compile/compile.exp: Adjust expected output to expect
	warning.
	* gdb.threads/siginfo-threads.exp: Likewise.
2017-09-04 20:21:13 +01:00

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/* Read ELF (Executable and Linking Format) object files for GDB.
Copyright (C) 1991-2017 Free Software Foundation, Inc.
Written by Fred Fish at Cygnus Support.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "bfd.h"
#include "elf-bfd.h"
#include "elf/common.h"
#include "elf/internal.h"
#include "elf/mips.h"
#include "symtab.h"
#include "symfile.h"
#include "objfiles.h"
#include "buildsym.h"
#include "stabsread.h"
#include "gdb-stabs.h"
#include "complaints.h"
#include "demangle.h"
#include "psympriv.h"
#include "filenames.h"
#include "probe.h"
#include "arch-utils.h"
#include "gdbtypes.h"
#include "value.h"
#include "infcall.h"
#include "gdbthread.h"
#include "regcache.h"
#include "bcache.h"
#include "gdb_bfd.h"
#include "build-id.h"
#include "location.h"
#include "auxv.h"
extern void _initialize_elfread (void);
/* Forward declarations. */
extern const struct sym_fns elf_sym_fns_gdb_index;
extern const struct sym_fns elf_sym_fns_lazy_psyms;
/* The struct elfinfo is available only during ELF symbol table and
psymtab reading. It is destroyed at the completion of psymtab-reading.
It's local to elf_symfile_read. */
struct elfinfo
{
asection *stabsect; /* Section pointer for .stab section */
asection *mdebugsect; /* Section pointer for .mdebug section */
};
/* Per-BFD data for probe info. */
static const struct bfd_data *probe_key = NULL;
/* Minimal symbols located at the GOT entries for .plt - that is the real
pointer where the given entry will jump to. It gets updated by the real
function address during lazy ld.so resolving in the inferior. These
minimal symbols are indexed for <tab>-completion. */
#define SYMBOL_GOT_PLT_SUFFIX "@got.plt"
/* Locate the segments in ABFD. */
static struct symfile_segment_data *
elf_symfile_segments (bfd *abfd)
{
Elf_Internal_Phdr *phdrs, **segments;
long phdrs_size;
int num_phdrs, num_segments, num_sections, i;
asection *sect;
struct symfile_segment_data *data;
phdrs_size = bfd_get_elf_phdr_upper_bound (abfd);
if (phdrs_size == -1)
return NULL;
phdrs = (Elf_Internal_Phdr *) alloca (phdrs_size);
num_phdrs = bfd_get_elf_phdrs (abfd, phdrs);
if (num_phdrs == -1)
return NULL;
num_segments = 0;
segments = XALLOCAVEC (Elf_Internal_Phdr *, num_phdrs);
for (i = 0; i < num_phdrs; i++)
if (phdrs[i].p_type == PT_LOAD)
segments[num_segments++] = &phdrs[i];
if (num_segments == 0)
return NULL;
data = XCNEW (struct symfile_segment_data);
data->num_segments = num_segments;
data->segment_bases = XCNEWVEC (CORE_ADDR, num_segments);
data->segment_sizes = XCNEWVEC (CORE_ADDR, num_segments);
for (i = 0; i < num_segments; i++)
{
data->segment_bases[i] = segments[i]->p_vaddr;
data->segment_sizes[i] = segments[i]->p_memsz;
}
num_sections = bfd_count_sections (abfd);
data->segment_info = XCNEWVEC (int, num_sections);
for (i = 0, sect = abfd->sections; sect != NULL; i++, sect = sect->next)
{
int j;
CORE_ADDR vma;
if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)
continue;
vma = bfd_get_section_vma (abfd, sect);
for (j = 0; j < num_segments; j++)
if (segments[j]->p_memsz > 0
&& vma >= segments[j]->p_vaddr
&& (vma - segments[j]->p_vaddr) < segments[j]->p_memsz)
{
data->segment_info[i] = j + 1;
break;
}
/* We should have found a segment for every non-empty section.
If we haven't, we will not relocate this section by any
offsets we apply to the segments. As an exception, do not
warn about SHT_NOBITS sections; in normal ELF execution
environments, SHT_NOBITS means zero-initialized and belongs
in a segment, but in no-OS environments some tools (e.g. ARM
RealView) use SHT_NOBITS for uninitialized data. Since it is
uninitialized, it doesn't need a program header. Such
binaries are not relocatable. */
if (bfd_get_section_size (sect) > 0 && j == num_segments
&& (bfd_get_section_flags (abfd, sect) & SEC_LOAD) != 0)
warning (_("Loadable section \"%s\" outside of ELF segments"),
bfd_section_name (abfd, sect));
}
return data;
}
/* We are called once per section from elf_symfile_read. We
need to examine each section we are passed, check to see
if it is something we are interested in processing, and
if so, stash away some access information for the section.
For now we recognize the dwarf debug information sections and
line number sections from matching their section names. The
ELF definition is no real help here since it has no direct
knowledge of DWARF (by design, so any debugging format can be
used).
We also recognize the ".stab" sections used by the Sun compilers
released with Solaris 2.
FIXME: The section names should not be hardwired strings (what
should they be? I don't think most object file formats have enough
section flags to specify what kind of debug section it is.
-kingdon). */
static void
elf_locate_sections (bfd *ignore_abfd, asection *sectp, void *eip)
{
struct elfinfo *ei;
ei = (struct elfinfo *) eip;
if (strcmp (sectp->name, ".stab") == 0)
{
ei->stabsect = sectp;
}
else if (strcmp (sectp->name, ".mdebug") == 0)
{
ei->mdebugsect = sectp;
}
}
static struct minimal_symbol *
record_minimal_symbol (minimal_symbol_reader &reader,
const char *name, int name_len, bool copy_name,
CORE_ADDR address,
enum minimal_symbol_type ms_type,
asection *bfd_section, struct objfile *objfile)
{
struct gdbarch *gdbarch = get_objfile_arch (objfile);
if (ms_type == mst_text || ms_type == mst_file_text
|| ms_type == mst_text_gnu_ifunc)
address = gdbarch_addr_bits_remove (gdbarch, address);
return reader.record_full (name, name_len, copy_name, address,
ms_type,
gdb_bfd_section_index (objfile->obfd,
bfd_section));
}
/* Read the symbol table of an ELF file.
Given an objfile, a symbol table, and a flag indicating whether the
symbol table contains regular, dynamic, or synthetic symbols, add all
the global function and data symbols to the minimal symbol table.
In stabs-in-ELF, as implemented by Sun, there are some local symbols
defined in the ELF symbol table, which can be used to locate
the beginnings of sections from each ".o" file that was linked to
form the executable objfile. We gather any such info and record it
in data structures hung off the objfile's private data. */
#define ST_REGULAR 0
#define ST_DYNAMIC 1
#define ST_SYNTHETIC 2
static void
elf_symtab_read (minimal_symbol_reader &reader,
struct objfile *objfile, int type,
long number_of_symbols, asymbol **symbol_table,
bool copy_names)
{
struct gdbarch *gdbarch = get_objfile_arch (objfile);
asymbol *sym;
long i;
CORE_ADDR symaddr;
enum minimal_symbol_type ms_type;
/* Name of the last file symbol. This is either a constant string or is
saved on the objfile's filename cache. */
const char *filesymname = "";
struct dbx_symfile_info *dbx = DBX_SYMFILE_INFO (objfile);
int stripped = (bfd_get_symcount (objfile->obfd) == 0);
int elf_make_msymbol_special_p
= gdbarch_elf_make_msymbol_special_p (gdbarch);
for (i = 0; i < number_of_symbols; i++)
{
sym = symbol_table[i];
if (sym->name == NULL || *sym->name == '\0')
{
/* Skip names that don't exist (shouldn't happen), or names
that are null strings (may happen). */
continue;
}
/* Skip "special" symbols, e.g. ARM mapping symbols. These are
symbols which do not correspond to objects in the symbol table,
but have some other target-specific meaning. */
if (bfd_is_target_special_symbol (objfile->obfd, sym))
{
if (gdbarch_record_special_symbol_p (gdbarch))
gdbarch_record_special_symbol (gdbarch, objfile, sym);
continue;
}
if (type == ST_DYNAMIC
&& sym->section == bfd_und_section_ptr
&& (sym->flags & BSF_FUNCTION))
{
struct minimal_symbol *msym;
bfd *abfd = objfile->obfd;
asection *sect;
/* Symbol is a reference to a function defined in
a shared library.
If its value is non zero then it is usually the address
of the corresponding entry in the procedure linkage table,
plus the desired section offset.
If its value is zero then the dynamic linker has to resolve
the symbol. We are unable to find any meaningful address
for this symbol in the executable file, so we skip it. */
symaddr = sym->value;
if (symaddr == 0)
continue;
/* sym->section is the undefined section. However, we want to
record the section where the PLT stub resides with the
minimal symbol. Search the section table for the one that
covers the stub's address. */
for (sect = abfd->sections; sect != NULL; sect = sect->next)
{
if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)
continue;
if (symaddr >= bfd_get_section_vma (abfd, sect)
&& symaddr < bfd_get_section_vma (abfd, sect)
+ bfd_get_section_size (sect))
break;
}
if (!sect)
continue;
/* On ia64-hpux, we have discovered that the system linker
adds undefined symbols with nonzero addresses that cannot
be right (their address points inside the code of another
function in the .text section). This creates problems
when trying to determine which symbol corresponds to
a given address.
We try to detect those buggy symbols by checking which
section we think they correspond to. Normally, PLT symbols
are stored inside their own section, and the typical name
for that section is ".plt". So, if there is a ".plt"
section, and yet the section name of our symbol does not
start with ".plt", we ignore that symbol. */
if (!startswith (sect->name, ".plt")
&& bfd_get_section_by_name (abfd, ".plt") != NULL)
continue;
msym = record_minimal_symbol
(reader, sym->name, strlen (sym->name), copy_names,
symaddr, mst_solib_trampoline, sect, objfile);
if (msym != NULL)
{
msym->filename = filesymname;
if (elf_make_msymbol_special_p)
gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
}
continue;
}
/* If it is a nonstripped executable, do not enter dynamic
symbols, as the dynamic symbol table is usually a subset
of the main symbol table. */
if (type == ST_DYNAMIC && !stripped)
continue;
if (sym->flags & BSF_FILE)
{
filesymname
= (const char *) bcache (sym->name, strlen (sym->name) + 1,
objfile->per_bfd->filename_cache);
}
else if (sym->flags & BSF_SECTION_SYM)
continue;
else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK
| BSF_GNU_UNIQUE))
{
struct minimal_symbol *msym;
/* Select global/local/weak symbols. Note that bfd puts abs
symbols in their own section, so all symbols we are
interested in will have a section. */
/* Bfd symbols are section relative. */
symaddr = sym->value + sym->section->vma;
/* For non-absolute symbols, use the type of the section
they are relative to, to intuit text/data. Bfd provides
no way of figuring this out for absolute symbols. */
if (sym->section == bfd_abs_section_ptr)
{
/* This is a hack to get the minimal symbol type
right for Irix 5, which has absolute addresses
with special section indices for dynamic symbols.
NOTE: uweigand-20071112: Synthetic symbols do not
have an ELF-private part, so do not touch those. */
unsigned int shndx = type == ST_SYNTHETIC ? 0 :
((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
switch (shndx)
{
case SHN_MIPS_TEXT:
ms_type = mst_text;
break;
case SHN_MIPS_DATA:
ms_type = mst_data;
break;
case SHN_MIPS_ACOMMON:
ms_type = mst_bss;
break;
default:
ms_type = mst_abs;
}
/* If it is an Irix dynamic symbol, skip section name
symbols, relocate all others by section offset. */
if (ms_type != mst_abs)
{
if (sym->name[0] == '.')
continue;
}
}
else if (sym->section->flags & SEC_CODE)
{
if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
{
if (sym->flags & BSF_GNU_INDIRECT_FUNCTION)
ms_type = mst_text_gnu_ifunc;
else
ms_type = mst_text;
}
/* The BSF_SYNTHETIC check is there to omit ppc64 function
descriptors mistaken for static functions starting with 'L'.
*/
else if ((sym->name[0] == '.' && sym->name[1] == 'L'
&& (sym->flags & BSF_SYNTHETIC) == 0)
|| ((sym->flags & BSF_LOCAL)
&& sym->name[0] == '$'
&& sym->name[1] == 'L'))
/* Looks like a compiler-generated label. Skip
it. The assembler should be skipping these (to
keep executables small), but apparently with
gcc on the (deleted) delta m88k SVR4, it loses.
So to have us check too should be harmless (but
I encourage people to fix this in the assembler
instead of adding checks here). */
continue;
else
{
ms_type = mst_file_text;
}
}
else if (sym->section->flags & SEC_ALLOC)
{
if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
{
if (sym->section->flags & SEC_LOAD)
{
ms_type = mst_data;
}
else
{
ms_type = mst_bss;
}
}
else if (sym->flags & BSF_LOCAL)
{
if (sym->section->flags & SEC_LOAD)
{
ms_type = mst_file_data;
}
else
{
ms_type = mst_file_bss;
}
}
else
{
ms_type = mst_unknown;
}
}
else
{
/* FIXME: Solaris2 shared libraries include lots of
odd "absolute" and "undefined" symbols, that play
hob with actions like finding what function the PC
is in. Ignore them if they aren't text, data, or bss. */
/* ms_type = mst_unknown; */
continue; /* Skip this symbol. */
}
msym = record_minimal_symbol
(reader, sym->name, strlen (sym->name), copy_names, symaddr,
ms_type, sym->section, objfile);
if (msym)
{
/* NOTE: uweigand-20071112: A synthetic symbol does not have an
ELF-private part. */
if (type != ST_SYNTHETIC)
{
/* Pass symbol size field in via BFD. FIXME!!! */
elf_symbol_type *elf_sym = (elf_symbol_type *) sym;
SET_MSYMBOL_SIZE (msym, elf_sym->internal_elf_sym.st_size);
}
msym->filename = filesymname;
if (elf_make_msymbol_special_p)
gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
}
/* If we see a default versioned symbol, install it under
its version-less name. */
if (msym != NULL)
{
const char *atsign = strchr (sym->name, '@');
if (atsign != NULL && atsign[1] == '@' && atsign > sym->name)
{
int len = atsign - sym->name;
record_minimal_symbol (reader, sym->name, len, true, symaddr,
ms_type, sym->section, objfile);
}
}
/* For @plt symbols, also record a trampoline to the
destination symbol. The @plt symbol will be used in
disassembly, and the trampoline will be used when we are
trying to find the target. */
if (msym && ms_type == mst_text && type == ST_SYNTHETIC)
{
int len = strlen (sym->name);
if (len > 4 && strcmp (sym->name + len - 4, "@plt") == 0)
{
struct minimal_symbol *mtramp;
mtramp = record_minimal_symbol (reader, sym->name, len - 4,
true, symaddr,
mst_solib_trampoline,
sym->section, objfile);
if (mtramp)
{
SET_MSYMBOL_SIZE (mtramp, MSYMBOL_SIZE (msym));
mtramp->created_by_gdb = 1;
mtramp->filename = filesymname;
if (elf_make_msymbol_special_p)
gdbarch_elf_make_msymbol_special (gdbarch,
sym, mtramp);
}
}
}
}
}
}
/* Build minimal symbols named `function@got.plt' (see SYMBOL_GOT_PLT_SUFFIX)
for later look ups of which function to call when user requests
a STT_GNU_IFUNC function. As the STT_GNU_IFUNC type is found at the target
library defining `function' we cannot yet know while reading OBJFILE which
of the SYMBOL_GOT_PLT_SUFFIX entries will be needed and later
DYN_SYMBOL_TABLE is no longer easily available for OBJFILE. */
static void
elf_rel_plt_read (minimal_symbol_reader &reader,
struct objfile *objfile, asymbol **dyn_symbol_table)
{
bfd *obfd = objfile->obfd;
const struct elf_backend_data *bed = get_elf_backend_data (obfd);
asection *plt, *relplt, *got_plt;
int plt_elf_idx;
bfd_size_type reloc_count, reloc;
struct gdbarch *gdbarch = get_objfile_arch (objfile);
struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
size_t ptr_size = TYPE_LENGTH (ptr_type);
if (objfile->separate_debug_objfile_backlink)
return;
plt = bfd_get_section_by_name (obfd, ".plt");
if (plt == NULL)
return;
plt_elf_idx = elf_section_data (plt)->this_idx;
got_plt = bfd_get_section_by_name (obfd, ".got.plt");
if (got_plt == NULL)
{
/* For platforms where there is no separate .got.plt. */
got_plt = bfd_get_section_by_name (obfd, ".got");
if (got_plt == NULL)
return;
}
/* This search algorithm is from _bfd_elf_canonicalize_dynamic_reloc. */
for (relplt = obfd->sections; relplt != NULL; relplt = relplt->next)
if (elf_section_data (relplt)->this_hdr.sh_info == plt_elf_idx
&& (elf_section_data (relplt)->this_hdr.sh_type == SHT_REL
|| elf_section_data (relplt)->this_hdr.sh_type == SHT_RELA))
break;
if (relplt == NULL)
return;
if (! bed->s->slurp_reloc_table (obfd, relplt, dyn_symbol_table, TRUE))
return;
std::string string_buffer;
reloc_count = relplt->size / elf_section_data (relplt)->this_hdr.sh_entsize;
for (reloc = 0; reloc < reloc_count; reloc++)
{
const char *name;
struct minimal_symbol *msym;
CORE_ADDR address;
const char *got_suffix = SYMBOL_GOT_PLT_SUFFIX;
const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
name = bfd_asymbol_name (*relplt->relocation[reloc].sym_ptr_ptr);
address = relplt->relocation[reloc].address;
/* Does the pointer reside in the .got.plt section? */
if (!(bfd_get_section_vma (obfd, got_plt) <= address
&& address < bfd_get_section_vma (obfd, got_plt)
+ bfd_get_section_size (got_plt)))
continue;
/* We cannot check if NAME is a reference to mst_text_gnu_ifunc as in
OBJFILE the symbol is undefined and the objfile having NAME defined
may not yet have been loaded. */
string_buffer.assign (name);
string_buffer.append (got_suffix, got_suffix + got_suffix_len);
msym = record_minimal_symbol (reader, string_buffer.c_str (),
string_buffer.size (),
true, address, mst_slot_got_plt, got_plt,
objfile);
if (msym)
SET_MSYMBOL_SIZE (msym, ptr_size);
}
}
/* The data pointer is htab_t for gnu_ifunc_record_cache_unchecked. */
static const struct objfile_data *elf_objfile_gnu_ifunc_cache_data;
/* Map function names to CORE_ADDR in elf_objfile_gnu_ifunc_cache_data. */
struct elf_gnu_ifunc_cache
{
/* This is always a function entry address, not a function descriptor. */
CORE_ADDR addr;
char name[1];
};
/* htab_hash for elf_objfile_gnu_ifunc_cache_data. */
static hashval_t
elf_gnu_ifunc_cache_hash (const void *a_voidp)
{
const struct elf_gnu_ifunc_cache *a
= (const struct elf_gnu_ifunc_cache *) a_voidp;
return htab_hash_string (a->name);
}
/* htab_eq for elf_objfile_gnu_ifunc_cache_data. */
static int
elf_gnu_ifunc_cache_eq (const void *a_voidp, const void *b_voidp)
{
const struct elf_gnu_ifunc_cache *a
= (const struct elf_gnu_ifunc_cache *) a_voidp;
const struct elf_gnu_ifunc_cache *b
= (const struct elf_gnu_ifunc_cache *) b_voidp;
return strcmp (a->name, b->name) == 0;
}
/* Record the target function address of a STT_GNU_IFUNC function NAME is the
function entry address ADDR. Return 1 if NAME and ADDR are considered as
valid and therefore they were successfully recorded, return 0 otherwise.
Function does not expect a duplicate entry. Use
elf_gnu_ifunc_resolve_by_cache first to check if the entry for NAME already
exists. */
static int
elf_gnu_ifunc_record_cache (const char *name, CORE_ADDR addr)
{
struct bound_minimal_symbol msym;
asection *sect;
struct objfile *objfile;
htab_t htab;
struct elf_gnu_ifunc_cache entry_local, *entry_p;
void **slot;
msym = lookup_minimal_symbol_by_pc (addr);
if (msym.minsym == NULL)
return 0;
if (BMSYMBOL_VALUE_ADDRESS (msym) != addr)
return 0;
/* minimal symbols have always SYMBOL_OBJ_SECTION non-NULL. */
sect = MSYMBOL_OBJ_SECTION (msym.objfile, msym.minsym)->the_bfd_section;
objfile = msym.objfile;
/* If .plt jumps back to .plt the symbol is still deferred for later
resolution and it has no use for GDB. Besides ".text" this symbol can
reside also in ".opd" for ppc64 function descriptor. */
if (strcmp (bfd_get_section_name (objfile->obfd, sect), ".plt") == 0)
return 0;
htab = (htab_t) objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data);
if (htab == NULL)
{
htab = htab_create_alloc_ex (1, elf_gnu_ifunc_cache_hash,
elf_gnu_ifunc_cache_eq,
NULL, &objfile->objfile_obstack,
hashtab_obstack_allocate,
dummy_obstack_deallocate);
set_objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data, htab);
}
entry_local.addr = addr;
obstack_grow (&objfile->objfile_obstack, &entry_local,
offsetof (struct elf_gnu_ifunc_cache, name));
obstack_grow_str0 (&objfile->objfile_obstack, name);
entry_p
= (struct elf_gnu_ifunc_cache *) obstack_finish (&objfile->objfile_obstack);
slot = htab_find_slot (htab, entry_p, INSERT);
if (*slot != NULL)
{
struct elf_gnu_ifunc_cache *entry_found_p
= (struct elf_gnu_ifunc_cache *) *slot;
struct gdbarch *gdbarch = get_objfile_arch (objfile);
if (entry_found_p->addr != addr)
{
/* This case indicates buggy inferior program, the resolved address
should never change. */
warning (_("gnu-indirect-function \"%s\" has changed its resolved "
"function_address from %s to %s"),
name, paddress (gdbarch, entry_found_p->addr),
paddress (gdbarch, addr));
}
/* New ENTRY_P is here leaked/duplicate in the OBJFILE obstack. */
}
*slot = entry_p;
return 1;
}
/* Try to find the target resolved function entry address of a STT_GNU_IFUNC
function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
is not NULL) and the function returns 1. It returns 0 otherwise.
Only the elf_objfile_gnu_ifunc_cache_data hash table is searched by this
function. */
static int
elf_gnu_ifunc_resolve_by_cache (const char *name, CORE_ADDR *addr_p)
{
struct objfile *objfile;
ALL_PSPACE_OBJFILES (current_program_space, objfile)
{
htab_t htab;
struct elf_gnu_ifunc_cache *entry_p;
void **slot;
htab = (htab_t) objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data);
if (htab == NULL)
continue;
entry_p = ((struct elf_gnu_ifunc_cache *)
alloca (sizeof (*entry_p) + strlen (name)));
strcpy (entry_p->name, name);
slot = htab_find_slot (htab, entry_p, NO_INSERT);
if (slot == NULL)
continue;
entry_p = (struct elf_gnu_ifunc_cache *) *slot;
gdb_assert (entry_p != NULL);
if (addr_p)
*addr_p = entry_p->addr;
return 1;
}
return 0;
}
/* Try to find the target resolved function entry address of a STT_GNU_IFUNC
function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
is not NULL) and the function returns 1. It returns 0 otherwise.
Only the SYMBOL_GOT_PLT_SUFFIX locations are searched by this function.
elf_gnu_ifunc_resolve_by_cache must have been already called for NAME to
prevent cache entries duplicates. */
static int
elf_gnu_ifunc_resolve_by_got (const char *name, CORE_ADDR *addr_p)
{
char *name_got_plt;
struct objfile *objfile;
const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
name_got_plt = (char *) alloca (strlen (name) + got_suffix_len + 1);
sprintf (name_got_plt, "%s" SYMBOL_GOT_PLT_SUFFIX, name);
ALL_PSPACE_OBJFILES (current_program_space, objfile)
{
bfd *obfd = objfile->obfd;
struct gdbarch *gdbarch = get_objfile_arch (objfile);
struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
size_t ptr_size = TYPE_LENGTH (ptr_type);
CORE_ADDR pointer_address, addr;
asection *plt;
gdb_byte *buf = (gdb_byte *) alloca (ptr_size);
struct bound_minimal_symbol msym;
msym = lookup_minimal_symbol (name_got_plt, NULL, objfile);
if (msym.minsym == NULL)
continue;
if (MSYMBOL_TYPE (msym.minsym) != mst_slot_got_plt)
continue;
pointer_address = BMSYMBOL_VALUE_ADDRESS (msym);
plt = bfd_get_section_by_name (obfd, ".plt");
if (plt == NULL)
continue;
if (MSYMBOL_SIZE (msym.minsym) != ptr_size)
continue;
if (target_read_memory (pointer_address, buf, ptr_size) != 0)
continue;
addr = extract_typed_address (buf, ptr_type);
addr = gdbarch_convert_from_func_ptr_addr (gdbarch, addr,
&current_target);
addr = gdbarch_addr_bits_remove (gdbarch, addr);
if (addr_p)
*addr_p = addr;
if (elf_gnu_ifunc_record_cache (name, addr))
return 1;
}
return 0;
}
/* Try to find the target resolved function entry address of a STT_GNU_IFUNC
function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
is not NULL) and the function returns 1. It returns 0 otherwise.
Both the elf_objfile_gnu_ifunc_cache_data hash table and
SYMBOL_GOT_PLT_SUFFIX locations are searched by this function. */
static int
elf_gnu_ifunc_resolve_name (const char *name, CORE_ADDR *addr_p)
{
if (elf_gnu_ifunc_resolve_by_cache (name, addr_p))
return 1;
if (elf_gnu_ifunc_resolve_by_got (name, addr_p))
return 1;
return 0;
}
/* Call STT_GNU_IFUNC - a function returning addresss of a real function to
call. PC is theSTT_GNU_IFUNC resolving function entry. The value returned
is the entry point of the resolved STT_GNU_IFUNC target function to call.
*/
static CORE_ADDR
elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc)
{
const char *name_at_pc;
CORE_ADDR start_at_pc, address;
struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
struct value *function, *address_val;
CORE_ADDR hwcap = 0;
struct value *hwcap_val;
/* Try first any non-intrusive methods without an inferior call. */
if (find_pc_partial_function (pc, &name_at_pc, &start_at_pc, NULL)
&& start_at_pc == pc)
{
if (elf_gnu_ifunc_resolve_name (name_at_pc, &address))
return address;
}
else
name_at_pc = NULL;
function = allocate_value (func_func_type);
VALUE_LVAL (function) = lval_memory;
set_value_address (function, pc);
/* STT_GNU_IFUNC resolver functions usually receive the HWCAP vector as
parameter. FUNCTION is the function entry address. ADDRESS may be a
function descriptor. */
target_auxv_search (&current_target, AT_HWCAP, &hwcap);
hwcap_val = value_from_longest (builtin_type (gdbarch)
->builtin_unsigned_long, hwcap);
address_val = call_function_by_hand (function, NULL, 1, &hwcap_val);
address = value_as_address (address_val);
address = gdbarch_convert_from_func_ptr_addr (gdbarch, address,
&current_target);
address = gdbarch_addr_bits_remove (gdbarch, address);
if (name_at_pc)
elf_gnu_ifunc_record_cache (name_at_pc, address);
return address;
}
/* Handle inferior hit of bp_gnu_ifunc_resolver, see its definition. */
static void
elf_gnu_ifunc_resolver_stop (struct breakpoint *b)
{
struct breakpoint *b_return;
struct frame_info *prev_frame = get_prev_frame (get_current_frame ());
struct frame_id prev_frame_id = get_stack_frame_id (prev_frame);
CORE_ADDR prev_pc = get_frame_pc (prev_frame);
int thread_id = ptid_to_global_thread_id (inferior_ptid);
gdb_assert (b->type == bp_gnu_ifunc_resolver);
for (b_return = b->related_breakpoint; b_return != b;
b_return = b_return->related_breakpoint)
{
gdb_assert (b_return->type == bp_gnu_ifunc_resolver_return);
gdb_assert (b_return->loc != NULL && b_return->loc->next == NULL);
gdb_assert (frame_id_p (b_return->frame_id));
if (b_return->thread == thread_id
&& b_return->loc->requested_address == prev_pc
&& frame_id_eq (b_return->frame_id, prev_frame_id))
break;
}
if (b_return == b)
{
/* No need to call find_pc_line for symbols resolving as this is only
a helper breakpointer never shown to the user. */
symtab_and_line sal;
sal.pspace = current_inferior ()->pspace;
sal.pc = prev_pc;
sal.section = find_pc_overlay (sal.pc);
sal.explicit_pc = 1;
b_return = set_momentary_breakpoint (get_frame_arch (prev_frame), sal,
prev_frame_id,
bp_gnu_ifunc_resolver_return);
/* set_momentary_breakpoint invalidates PREV_FRAME. */
prev_frame = NULL;
/* Add new b_return to the ring list b->related_breakpoint. */
gdb_assert (b_return->related_breakpoint == b_return);
b_return->related_breakpoint = b->related_breakpoint;
b->related_breakpoint = b_return;
}
}
/* Handle inferior hit of bp_gnu_ifunc_resolver_return, see its definition. */
static void
elf_gnu_ifunc_resolver_return_stop (struct breakpoint *b)
{
struct gdbarch *gdbarch = get_frame_arch (get_current_frame ());
struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
struct type *value_type = TYPE_TARGET_TYPE (func_func_type);
struct regcache *regcache = get_thread_regcache (inferior_ptid);
struct value *func_func;
struct value *value;
CORE_ADDR resolved_address, resolved_pc;
gdb_assert (b->type == bp_gnu_ifunc_resolver_return);
while (b->related_breakpoint != b)
{
struct breakpoint *b_next = b->related_breakpoint;
switch (b->type)
{
case bp_gnu_ifunc_resolver:
break;
case bp_gnu_ifunc_resolver_return:
delete_breakpoint (b);
break;
default:
internal_error (__FILE__, __LINE__,
_("handle_inferior_event: Invalid "
"gnu-indirect-function breakpoint type %d"),
(int) b->type);
}
b = b_next;
}
gdb_assert (b->type == bp_gnu_ifunc_resolver);
gdb_assert (b->loc->next == NULL);
func_func = allocate_value (func_func_type);
VALUE_LVAL (func_func) = lval_memory;
set_value_address (func_func, b->loc->related_address);
value = allocate_value (value_type);
gdbarch_return_value (gdbarch, func_func, value_type, regcache,
value_contents_raw (value), NULL);
resolved_address = value_as_address (value);
resolved_pc = gdbarch_convert_from_func_ptr_addr (gdbarch,
resolved_address,
&current_target);
resolved_pc = gdbarch_addr_bits_remove (gdbarch, resolved_pc);
gdb_assert (current_program_space == b->pspace || b->pspace == NULL);
elf_gnu_ifunc_record_cache (event_location_to_string (b->location.get ()),
resolved_pc);
b->type = bp_breakpoint;
update_breakpoint_locations (b, current_program_space,
find_pc_line (resolved_pc, 0), {});
}
/* A helper function for elf_symfile_read that reads the minimal
symbols. */
static void
elf_read_minimal_symbols (struct objfile *objfile, int symfile_flags,
const struct elfinfo *ei)
{
bfd *synth_abfd, *abfd = objfile->obfd;
long symcount = 0, dynsymcount = 0, synthcount, storage_needed;
asymbol **symbol_table = NULL, **dyn_symbol_table = NULL;
asymbol *synthsyms;
struct dbx_symfile_info *dbx;
if (symtab_create_debug)
{
fprintf_unfiltered (gdb_stdlog,
"Reading minimal symbols of objfile %s ...\n",
objfile_name (objfile));
}
/* If we already have minsyms, then we can skip some work here.
However, if there were stabs or mdebug sections, we go ahead and
redo all the work anyway, because the psym readers for those
kinds of debuginfo need extra information found here. This can
go away once all types of symbols are in the per-BFD object. */
if (objfile->per_bfd->minsyms_read
&& ei->stabsect == NULL
&& ei->mdebugsect == NULL)
{
if (symtab_create_debug)
fprintf_unfiltered (gdb_stdlog,
"... minimal symbols previously read\n");
return;
}
minimal_symbol_reader reader (objfile);
/* Allocate struct to keep track of the symfile. */
dbx = XCNEW (struct dbx_symfile_info);
set_objfile_data (objfile, dbx_objfile_data_key, dbx);
/* Process the normal ELF symbol table first. */
storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);
if (storage_needed < 0)
error (_("Can't read symbols from %s: %s"),
bfd_get_filename (objfile->obfd),
bfd_errmsg (bfd_get_error ()));
if (storage_needed > 0)
{
/* Memory gets permanently referenced from ABFD after
bfd_canonicalize_symtab so it must not get freed before ABFD gets. */
symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
symcount = bfd_canonicalize_symtab (objfile->obfd, symbol_table);
if (symcount < 0)
error (_("Can't read symbols from %s: %s"),
bfd_get_filename (objfile->obfd),
bfd_errmsg (bfd_get_error ()));
elf_symtab_read (reader, objfile, ST_REGULAR, symcount, symbol_table,
false);
}
/* Add the dynamic symbols. */
storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);
if (storage_needed > 0)
{
/* Memory gets permanently referenced from ABFD after
bfd_get_synthetic_symtab so it must not get freed before ABFD gets.
It happens only in the case when elf_slurp_reloc_table sees
asection->relocation NULL. Determining which section is asection is
done by _bfd_elf_get_synthetic_symtab which is all a bfd
implementation detail, though. */
dyn_symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
dynsymcount = bfd_canonicalize_dynamic_symtab (objfile->obfd,
dyn_symbol_table);
if (dynsymcount < 0)
error (_("Can't read symbols from %s: %s"),
bfd_get_filename (objfile->obfd),
bfd_errmsg (bfd_get_error ()));
elf_symtab_read (reader, objfile, ST_DYNAMIC, dynsymcount,
dyn_symbol_table, false);
elf_rel_plt_read (reader, objfile, dyn_symbol_table);
}
/* Contrary to binutils --strip-debug/--only-keep-debug the strip command from
elfutils (eu-strip) moves even the .symtab section into the .debug file.
bfd_get_synthetic_symtab on ppc64 for each function descriptor ELF symbol
'name' creates a new BSF_SYNTHETIC ELF symbol '.name' with its code
address. But with eu-strip files bfd_get_synthetic_symtab would fail to
read the code address from .opd while it reads the .symtab section from
a separate debug info file as the .opd section is SHT_NOBITS there.
With SYNTH_ABFD the .opd section will be read from the original
backlinked binary where it is valid. */
if (objfile->separate_debug_objfile_backlink)
synth_abfd = objfile->separate_debug_objfile_backlink->obfd;
else
synth_abfd = abfd;
/* Add synthetic symbols - for instance, names for any PLT entries. */
synthcount = bfd_get_synthetic_symtab (synth_abfd, symcount, symbol_table,
dynsymcount, dyn_symbol_table,
&synthsyms);
if (synthcount > 0)
{
long i;
std::unique_ptr<asymbol *[]>
synth_symbol_table (new asymbol *[synthcount]);
for (i = 0; i < synthcount; i++)
synth_symbol_table[i] = synthsyms + i;
elf_symtab_read (reader, objfile, ST_SYNTHETIC, synthcount,
synth_symbol_table.get (), true);
xfree (synthsyms);
synthsyms = NULL;
}
/* Install any minimal symbols that have been collected as the current
minimal symbols for this objfile. The debug readers below this point
should not generate new minimal symbols; if they do it's their
responsibility to install them. "mdebug" appears to be the only one
which will do this. */
reader.install ();
if (symtab_create_debug)
fprintf_unfiltered (gdb_stdlog, "Done reading minimal symbols.\n");
}
/* Scan and build partial symbols for a symbol file.
We have been initialized by a call to elf_symfile_init, which
currently does nothing.
This function only does the minimum work necessary for letting the
user "name" things symbolically; it does not read the entire symtab.
Instead, it reads the external and static symbols and puts them in partial
symbol tables. When more extensive information is requested of a
file, the corresponding partial symbol table is mutated into a full
fledged symbol table by going back and reading the symbols
for real.
We look for sections with specific names, to tell us what debug
format to look for: FIXME!!!
elfstab_build_psymtabs() handles STABS symbols;
mdebug_build_psymtabs() handles ECOFF debugging information.
Note that ELF files have a "minimal" symbol table, which looks a lot
like a COFF symbol table, but has only the minimal information necessary
for linking. We process this also, and use the information to
build gdb's minimal symbol table. This gives us some minimal debugging
capability even for files compiled without -g. */
static void
elf_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
{
bfd *abfd = objfile->obfd;
struct elfinfo ei;
memset ((char *) &ei, 0, sizeof (ei));
bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei);
elf_read_minimal_symbols (objfile, symfile_flags, &ei);
/* ELF debugging information is inserted into the psymtab in the
order of least informative first - most informative last. Since
the psymtab table is searched `most recent insertion first' this
increases the probability that more detailed debug information
for a section is found.
For instance, an object file might contain both .mdebug (XCOFF)
and .debug_info (DWARF2) sections then .mdebug is inserted first
(searched last) and DWARF2 is inserted last (searched first). If
we don't do this then the XCOFF info is found first - for code in
an included file XCOFF info is useless. */
if (ei.mdebugsect)
{
const struct ecoff_debug_swap *swap;
/* .mdebug section, presumably holding ECOFF debugging
information. */
swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;
if (swap)
elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);
}
if (ei.stabsect)
{
asection *str_sect;
/* Stab sections have an associated string table that looks like
a separate section. */
str_sect = bfd_get_section_by_name (abfd, ".stabstr");
/* FIXME should probably warn about a stab section without a stabstr. */
if (str_sect)
elfstab_build_psymtabs (objfile,
ei.stabsect,
str_sect->filepos,
bfd_section_size (abfd, str_sect));
}
if (dwarf2_has_info (objfile, NULL))
{
/* elf_sym_fns_gdb_index cannot handle simultaneous non-DWARF debug
information present in OBJFILE. If there is such debug info present
never use .gdb_index. */
if (!objfile_has_partial_symbols (objfile)
&& dwarf2_initialize_objfile (objfile))
objfile_set_sym_fns (objfile, &elf_sym_fns_gdb_index);
else
{
/* It is ok to do this even if the stabs reader made some
partial symbols, because OBJF_PSYMTABS_READ has not been
set, and so our lazy reader function will still be called
when needed. */
objfile_set_sym_fns (objfile, &elf_sym_fns_lazy_psyms);
}
}
/* If the file has its own symbol tables it has no separate debug
info. `.dynsym'/`.symtab' go to MSYMBOLS, `.debug_info' goes to
SYMTABS/PSYMTABS. `.gnu_debuglink' may no longer be present with
`.note.gnu.build-id'.
.gnu_debugdata is !objfile_has_partial_symbols because it contains only
.symtab, not .debug_* section. But if we already added .gnu_debugdata as
an objfile via find_separate_debug_file_in_section there was no separate
debug info available. Therefore do not attempt to search for another one,
objfile->separate_debug_objfile->separate_debug_objfile GDB guarantees to
be NULL and we would possibly violate it. */
else if (!objfile_has_partial_symbols (objfile)
&& objfile->separate_debug_objfile == NULL
&& objfile->separate_debug_objfile_backlink == NULL)
{
gdb::unique_xmalloc_ptr<char> debugfile
(find_separate_debug_file_by_buildid (objfile));
if (debugfile == NULL)
debugfile.reset (find_separate_debug_file_by_debuglink (objfile));
if (debugfile != NULL)
{
gdb_bfd_ref_ptr abfd (symfile_bfd_open (debugfile.get ()));
symbol_file_add_separate (abfd.get (), debugfile.get (),
symfile_flags, objfile);
}
}
}
/* Callback to lazily read psymtabs. */
static void
read_psyms (struct objfile *objfile)
{
if (dwarf2_has_info (objfile, NULL))
dwarf2_build_psymtabs (objfile);
}
/* Initialize anything that needs initializing when a completely new symbol
file is specified (not just adding some symbols from another file, e.g. a
shared library).
We reinitialize buildsym, since we may be reading stabs from an ELF
file. */
static void
elf_new_init (struct objfile *ignore)
{
stabsread_new_init ();
buildsym_new_init ();
}
/* Perform any local cleanups required when we are done with a particular
objfile. I.E, we are in the process of discarding all symbol information
for an objfile, freeing up all memory held for it, and unlinking the
objfile struct from the global list of known objfiles. */
static void
elf_symfile_finish (struct objfile *objfile)
{
dwarf2_free_objfile (objfile);
}
/* ELF specific initialization routine for reading symbols. */
static void
elf_symfile_init (struct objfile *objfile)
{
/* ELF objects may be reordered, so set OBJF_REORDERED. If we
find this causes a significant slowdown in gdb then we could
set it in the debug symbol readers only when necessary. */
objfile->flags |= OBJF_REORDERED;
}
/* Implementation of `sym_get_probes', as documented in symfile.h. */
static VEC (probe_p) *
elf_get_probes (struct objfile *objfile)
{
VEC (probe_p) *probes_per_bfd;
/* Have we parsed this objfile's probes already? */
probes_per_bfd = (VEC (probe_p) *) bfd_data (objfile->obfd, probe_key);
if (!probes_per_bfd)
{
int ix;
const struct probe_ops *probe_ops;
/* Here we try to gather information about all types of probes from the
objfile. */
for (ix = 0; VEC_iterate (probe_ops_cp, all_probe_ops, ix, probe_ops);
ix++)
probe_ops->get_probes (&probes_per_bfd, objfile);
if (probes_per_bfd == NULL)
{
VEC_reserve (probe_p, probes_per_bfd, 1);
gdb_assert (probes_per_bfd != NULL);
}
set_bfd_data (objfile->obfd, probe_key, probes_per_bfd);
}
return probes_per_bfd;
}
/* Helper function used to free the space allocated for storing SystemTap
probe information. */
static void
probe_key_free (bfd *abfd, void *d)
{
int ix;
VEC (probe_p) *probes = (VEC (probe_p) *) d;
struct probe *probe;
for (ix = 0; VEC_iterate (probe_p, probes, ix, probe); ix++)
probe->pops->destroy (probe);
VEC_free (probe_p, probes);
}
/* Implementation `sym_probe_fns', as documented in symfile.h. */
static const struct sym_probe_fns elf_probe_fns =
{
elf_get_probes, /* sym_get_probes */
};
/* Register that we are able to handle ELF object file formats. */
static const struct sym_fns elf_sym_fns =
{
elf_new_init, /* init anything gbl to entire symtab */
elf_symfile_init, /* read initial info, setup for sym_read() */
elf_symfile_read, /* read a symbol file into symtab */
NULL, /* sym_read_psymbols */
elf_symfile_finish, /* finished with file, cleanup */
default_symfile_offsets, /* Translate ext. to int. relocation */
elf_symfile_segments, /* Get segment information from a file. */
NULL,
default_symfile_relocate, /* Relocate a debug section. */
&elf_probe_fns, /* sym_probe_fns */
&psym_functions
};
/* The same as elf_sym_fns, but not registered and lazily reads
psymbols. */
const struct sym_fns elf_sym_fns_lazy_psyms =
{
elf_new_init, /* init anything gbl to entire symtab */
elf_symfile_init, /* read initial info, setup for sym_read() */
elf_symfile_read, /* read a symbol file into symtab */
read_psyms, /* sym_read_psymbols */
elf_symfile_finish, /* finished with file, cleanup */
default_symfile_offsets, /* Translate ext. to int. relocation */
elf_symfile_segments, /* Get segment information from a file. */
NULL,
default_symfile_relocate, /* Relocate a debug section. */
&elf_probe_fns, /* sym_probe_fns */
&psym_functions
};
/* The same as elf_sym_fns, but not registered and uses the
DWARF-specific GNU index rather than psymtab. */
const struct sym_fns elf_sym_fns_gdb_index =
{
elf_new_init, /* init anything gbl to entire symab */
elf_symfile_init, /* read initial info, setup for sym_red() */
elf_symfile_read, /* read a symbol file into symtab */
NULL, /* sym_read_psymbols */
elf_symfile_finish, /* finished with file, cleanup */
default_symfile_offsets, /* Translate ext. to int. relocatin */
elf_symfile_segments, /* Get segment information from a file. */
NULL,
default_symfile_relocate, /* Relocate a debug section. */
&elf_probe_fns, /* sym_probe_fns */
&dwarf2_gdb_index_functions
};
/* STT_GNU_IFUNC resolver vector to be installed to gnu_ifunc_fns_p. */
static const struct gnu_ifunc_fns elf_gnu_ifunc_fns =
{
elf_gnu_ifunc_resolve_addr,
elf_gnu_ifunc_resolve_name,
elf_gnu_ifunc_resolver_stop,
elf_gnu_ifunc_resolver_return_stop
};
void
_initialize_elfread (void)
{
probe_key = register_bfd_data_with_cleanup (NULL, probe_key_free);
add_symtab_fns (bfd_target_elf_flavour, &elf_sym_fns);
elf_objfile_gnu_ifunc_cache_data = register_objfile_data ();
gnu_ifunc_fns_p = &elf_gnu_ifunc_fns;
}
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