Compilation Unit name
Hello guys,
I work for Dyninst, and I am moving from libdwarf to libdw. I am trying to get
the compilation unit name calling dwarf_nextcu, dwarf_offdie and
dwarf_diename, but it won't work as it works with libdwarf. I got NULL as
return from dwarf_diename. When I print the error messages after each of these
three function calls, I get no errors for the first two and an "invalid dwarf"
for the third one. Can you help me with it?
Below I present the snippet where I am doing the calls, both with libdwarf and
libdw.
Sasha Nicolas
//Using libdwarf
bool Object::fix_global_symbol_modules_static_dwarf()
{
/* Initialize libdwarf. */
::Dwarf **dbg_ptr = dwarf->type_dbg();
if (!dbg_ptr)
return false;
::Dwarf *dbg = *dbg_ptr;
std::set dies_seen;
dwarf_parse_aranges(dbg, dies_seen);
/* Iterate over the compilation-unit headers. */
size_t cu_header_size;
for(Dwarf_Off cu_off = 0, next_cu_off;
dwarf_nextcu(dbg, cu_off, &next_cu_off, &cu_header_size,
NULL, NULL, NULL) == 0;
cu_off = next_cu_off)
{
cerr << "Error message:" << dwarf_errmsg(-1) << endl;
Dwarf_Die cu_die, *cu_die_p;
cu_die_p = dwarf_offdie(dbg, next_cu_off /*cu_die_off*/, &cu_die);
cerr << "Error message:" << dwarf_errmsg(-1) << endl;
if(cu_die_p == NULL) continue;
if(dies_seen.find(next_cu_off/* cu_die_off*/) != dies_seen.end())
continue;
std::string modname;
auto diename = dwarf_diename(&cu_die);
cerr << "Error message:" << dwarf_errmsg(-1) << endl;
if(diename == NULL)
{
modname = associated_symtab->file(); // default module
}
else
{
modname = diename;
}
...
//Using libdwarf
bool Object::fix_global_symbol_modules_static_dwarf()
{
/* Initialize libdwarf. */
Dwarf_Debug *dbg_ptr = dwarf->type_dbg();
if (!dbg_ptr)
return false;
Dwarf_Debug dbg = *dbg_ptr;
std::set dies_seen;
Dwarf_Off cu_die_off;
Dwarf_Die cu_die;
dwarf_parse_aranges(dbg, dies_seen);
/* Iterate over the compilation-unit headers. */
while (dwarf_next_cu_header_c(dbg, Dwarf_Bool(true),
NULL,NULL,NULL,NULL,NULL,NULL,NULL,
&cu_die_off, NULL) == DW_DLV_OK )
{
int status = dwarf_siblingof_b(dbg, NULL, Dwarf_Bool(true), &cu_die,
NULL);
assert(status == DW_DLV_OK);
if(dies_seen.find(cu_die_off) != dies_seen.end()) continue;
std::string modname;
if(!DwarfWalker::findDieName(dbg, cu_die, modname))
{
modname = associated_symtab->file(); // default module
}
Re: Compilation Unit name
[no HTML]
I had that before, and it didn't work, then I empirically changed to
next_cu_off because it contained the same offset I was supposed to get when I
compared to the libdwarf execution.
We already discarded the option of using dwarf_offdie_types since previously,
with libdwarf, it was passed true to:
dwarf_next_cu_header_c(dbg, Dwarf_Bool(true),
NULL,NULL,NULL,NULL,NULL,NULL,NULL,
&cu_die_off, NULL) == DW_DLV_OK )
and to:
int status = dwarf_siblingof_b(dbg, NULL, Dwarf_Bool(true), &cu_die, NULL);
De: Josh Stone
Enviado: quinta-feira, 16 de março de 2017 17:06
Para: SASHA NICOLAS DA ROCHA PINHEIRO; elfutils-devel@sourceware.org
Assunto: Re: Compilation Unit name
On 03/16/2017 03:03 PM, SASHA NICOLAS DA ROCHA PINHEIRO wrote:
> /* Iterate over the compilation-unit headers. */
> size_t cu_header_size;
> for(Dwarf_Off cu_off = 0, next_cu_off;
> dwarf_nextcu(dbg, cu_off, &next_cu_off, &cu_header_size,
> NULL, NULL, NULL) == 0;
> cu_off = next_cu_off)
> {
> cerr << "Error message:" << dwarf_errmsg(-1) << endl;
> Dwarf_Die cu_die, *cu_die_p;
> cu_die_p = dwarf_offdie(dbg, next_cu_off /*cu_die_off*/, &cu_die);
I don't understand why you're using next_cu_off here.
The die offset is cu_off + cu_header_size.
Also, when you get around to it, note there's a different
dwarf_offdie_types when you're parsing .debug_types.
Re: Compilation Unit name
I did not find the reference about the argument named next_cu_header_offset (below I pasted the respective functions signatures). Anyway, name orthography apart, what is being used in Dyninst with libdwarf is exactly the value of what we called next_cu_off, which corresponds to the third parameter of dwarf_nextcu(), named in libdw as next_off. Do you have any other thoughts why the sequence of function calls is not working, instead it is giving invalid dwarf? // libdw /* Read the header for the DWARF CU. */ extern int dwarf_nextcu (Dwarf *dwarf, Dwarf_Off off, Dwarf_Off *next_off, size_t *header_sizep, Dwarf_Off *abbrev_offsetp, uint8_t *address_sizep, uint8_t *offset_sizep) __nonnull_attribute__ (3); // libdwarf int dwarf_next_cu_header_c(Dwarf_Debug dbg, Dwarf_Bool is_info, Dwarf_Unsigned *cu_length, Dwarf_Half *cu_version, Dwarf_Off *cu_abbrev_offset, Dwarf_Half *cu_pointer_size, Dwarf_Half *cu_offset_size, Dwarf_Half *cu_extension_size, Dwarf_Sig8 *type_signature, Dwarf_Unsigned *type_offset, Dwarf_Unsigned *cu_next_offset, Dwarf_Error *err); De: Josh Stone Enviado: quinta-feira, 16 de março de 2017 19:29:12 Para: SASHA NICOLAS DA ROCHA PINHEIRO; elfutils-devel@sourceware.org Assunto: Re: Compilation Unit name Stick to plain text, not HTML, if you want to reach the list. On 03/16/2017 03:44 PM, SASHA NICOLAS DA ROCHA PINHEIRO wrote: > I had that before, and it didn't work, then I empirically changed to > next_cu_off because it contained the same offset I was supposed to get > when I compared to the libdwarf execution. What you have called cu_die_off is *not* a die offset! In libdwarf.h that argument is called next_cu_header_offset, which is why it has the same value as the next_cu_off you're getting from libdw. > We already discarded the option of using dwarf_offdie_types since > previously, with libdwarf, it was passed true to: That's fine and correct. You shouldn't use dwarf_offdie_types now, I was trying to preempt a future problem. Sorry for adding confusion.
Group section
Hi Josh
I am getting error on the following code, and it looks like to be related to
group sections.
As you can see I changed the dwarf_elf_init to dwarf_begin_elf, but passed NULL
on the third parameter.
Do you know how should I actually deal with it?
91 bool DwarfHandle::init_dbg()
92 {
93 //int status;
94 //Dwarf_Error err;
95 if (init_dwarf_status == dwarf_status_ok) {
96 return true;
97 }
98
99 if (init_dwarf_status == dwarf_status_error) {
100 return false;
101 }
102
103 //status = dwarf_elf_init(file->e_elfp(), DW_DLC_READ,
104 // err_func, &file_data, &file_data, &err);
105
106 file_data = dwarf_begin_elf(file->e_elfp(), DWARF_C_READ, NULL);
107 cerr << "Error message:" << dwarf_errmsg(-1) << endl;
108 if (!file_data) {
109 init_dwarf_status = dwarf_status_error;
110 return false;
111 }
Re: Group section
That's the problem. It says "no error" once, in another call it says "no
reference value", and in another call "no DWARF information".
De: Josh Stone
Enviado: terça-feira, 21 de março de 2017 14:53:12
Para: SASHA NICOLAS DA ROCHA PINHEIRO; elfutils-devel@sourceware.org
Assunto: Re: Group section
On 03/21/2017 12:38 PM, SASHA NICOLAS DA ROCHA PINHEIRO wrote:
>
> Hi Josh
> I am getting error on the following code, and it looks like to be related to
> group sections.
What is the error?
> As you can see I changed the dwarf_elf_init to dwarf_begin_elf, but passed
> NULL on the third parameter.
> Do you know how should I actually deal with it?
>
> 91 bool DwarfHandle::init_dbg()
>
> 92 {
>
> 93 //int status;
>
> 94 //Dwarf_Error err;
>
> 95 if (init_dwarf_status == dwarf_status_ok) {
>
> 96 return true;
>
> 97 }
>
> 98
>
> 99 if (init_dwarf_status == dwarf_status_error) {
>
> 100 return false;
>
> 101 }
>
> 102
>
> 103 //status = dwarf_elf_init(file->e_elfp(), DW_DLC_READ,
>
> 104 // err_func, &file_data, &file_data, &err);
>
> 105
>
> 106 file_data = dwarf_begin_elf(file->e_elfp(), DWARF_C_READ, NULL);
>
> 107 cerr << "Error message:" << dwarf_errmsg(-1) << endl;
>
> 108 if (!file_data) {
>
> 109 init_dwarf_status = dwarf_status_error;
>
> 110 return false;
>
> 111 }
>
dwarf_line_srcfileno
Hey all, what is the equivalent function to dwarf_line_srcfileno in lbdw?? Sasha
