dwarf_get_relocation_info —
retrieve generated relocation arrays
DWARF Access Library (libdwarf, -ldwarf)
#include
<libdwarf.h>
int
dwarf_get_relocation_info(
Dwarf_P_Debug
dbg,
Dwarf_Signed *elf_section_index,
Dwarf_Signed *elf_section_link,
Dwarf_Unsigned *reloc_entry_count,
Dwarf_Relocation_Data *reloc_buf,
Dwarf_Error *err);
The function
dwarf_get_relocation_info() is used to
retrieve the relocation arrays generated by a prior call to
dwarf_transform_to_disk_form(3).
Each call to this function retrieves the next available relocation array.
Application code should call this function repeatly to retrieve all the
relocation arrays. The total number of generated relocation arrays retrievable
by this function may be obtained by calling function
dwarf_get_relocation_info_count(3).
Argument
dbg should reference a DWARF producer
instance allocated using
dwarf_producer_init(3)
in sequence. or
dwarf_producer_init_b(3).
The
DW_DLC_SYMBOLIC_RELOCATIONS
flag should
have been set on the DWARF producer instance.
Argument
elf_section_index should point to a
location which will be set to the ELF section index of the relocation section
to which the retrieved relocation array belongs.
Argument
elf_section_link should point to a
location which will be set to the section index of the ELF section to which
the retrieved relocation array applies.
Argument
reloc_entry_count should point to a
location which will be set to the total number of relocation entries contained
in the relocation array.
Argument
reloc_buf should point to a location
which will be set to a pointer to the retrieved array of relocation entries.
If argument
err is not NULL, it will be used to
store error information in case of an error.
The retrieved relocation entries are described using structure
Dwarf_Relocation_Data_s, defined in the
header file
<libdwarf.h>:
typedef struct Dwarf_Relocation_Data_s {
unsigned char drd_type;
unsigned char drd_length;
Dwarf_Unsigned drd_offset;
Dwarf_Unsigned drd_symbol_index;
} *Dwarf_Relocation_Data;
Struct
Dwarf_Relocation_Data_s consists of
following fields:
- drd_type
- The type code of the relocation entry. The
Dwarf_Rel_Type enumeration defined in the
header file
<libdwarf.h>
specifies legal values for this field.
- drd_length
- The size in bytes of the field to be relocated.
- drd_offset
- The section-relative offset of the field to be
relocated.
- drd_symbol_index
- The symbol index associated with the relocation entry.
The memory area used for the relocation arrays is managed by the
DWARF Access Library (libdwarf, -ldwarf).
The function
dwarf_producer_finish() may be used
to release it, along with other resources associated with the producer
instance.
On success, function
dwarf_get_relocation_info()
returns
DW_DLV_OK
. It returns
DW_DLV_NO_ENTRY
if there were no more
relocation arrays to retrieve, or if the flag
DW_DLC_SYMBOLIC_RELOCATIONS
was not set on
the producer instance. In case of an error, function
dwarf_get_relocation_info() returns
DW_DLV_ERROR
and sets the argument
err.
To generate relocation entries and retrieve them, use:
Dwarf_P_Debug dbg;
Dwarf_Relocation_Data buf;
Dwarf_Signed count, index, link;
Dwarf_Unsigned reloc_cnt, entry_cnt;
Dwarf_Error de;
int version, i, j;
/*
* Assume that dbg refers to a DWARF producer instance created
* created with DW_DLC_SYMBOLIC_RELOCATIONS flag set and that
* application code has added DWARF debugging information
* to the producer instance.
*/
if ((count = dwarf_transform_to_disk_form(dbg, &de)) ==
DW_DLV_NOCOUNT) {
warnx("dwarf_transform_to_disk_form failed: %s",
dwarf_errmsg(-1));
return;
}
/* ... process generated section byte streams ... */
if (dwarf_get_relocation_info_count(dbg, &reloc_cnt, &version, &de) !=
DW_DLV_OK) {
warnx("dwarf_get_relocation_info_count failed: %s",
dwarf_errmsg(-1));
return;
}
for (i = 0; (Dwarf_Unsigned) i < reloc_cnt; i++) {
if (dwarf_get_relocation_info(dbg, &index, &link, &entry_cnt,
&buf, &de) != DW_DLV_OK) {
warnx("dwarf_get_relocation_info failed: %s",
dwarf_errmsg(-1));
continue;
}
for (j = 0; (Dwarf_Unsigned) j < entry_cnt; j++) {
/* ...use each reloc data in buf[j]... */
}
}
dwarf_producer_finish(dbg, &de);
Function
dwarf_get_relocation_info() can fail with:
-
-
- [
DW_DLE_ARGUMENT
]
- One of the arguments dbg,
elf_section_index,
elf_section_link,
reloc_entry_count or
reloc_buf was NULL.
-
-
- [
DW_DLE_NO_ENTRY
]
- There were no more ELF relocation arrays to retrieve.
-
-
- [
DW_DLE_NO_ENTRY
]
- The flag
DW_DLC_SYMBOLIC_RELOCATIONS
was not set
on the producer instance.
-
-
- [
DW_DLE_NO_ENTRY
]
- Function
dwarf_transform_to_disk_form(3)
was not called prior to calling function
dwarf_get_relocation_info().
dwarf(3),
dwarf_get_relocation_info_count(3),
dwarf_producer_finish(3),
dwarf_producer_init(3),
dwarf_producer_init_b(3),
dwarf_reset_section_bytes(3),
dwarf_transform_to_disk_form(3)