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ELF_GETDATA(3)             Library Functions Manual             ELF_GETDATA(3)

     elf_getdata, elf_newdata, elf_rawdata - iterate through or allocate
     section data

     ELF Access Library (libelf, -lelf)

     #include <libelf.h>

     Elf_Data *
     elf_getdata(Elf_Scn *scn, Elf_Data *data);

     Elf_Data *
     elf_newdata(Elf_Scn *scn);

     Elf_Data *
     elf_rawdata(Elf_Scn *scn, Elf_Data *data);

     These functions are used to access and manipulate data descriptors
     associated with section descriptors.  Data descriptors used by the ELF
     library are described in elf(3).

     Function elf_getdata() will return the next data descriptor associated
     with section descriptor scn.  The returned data descriptor will be setup
     to contain translated data.  Argument data may be NULL, in which case the
     function returns the first data descriptor associated with section scn.
     If argument data is not NULL, it must be a pointer to a data descriptor
     associated with section descriptor scn, and function elf_getdata() will
     return a pointer to the next data descriptor for the section, or NULL
     when the end of the section's descriptor list is reached.

     Function elf_newdata() will allocate a new data descriptor and append it
     to the list of data descriptors associated with section descriptor scn.
     The new data descriptor will be initialized as follows:
           d_align    Set to 1.
           d_buf      Initialized to NULL.
           d_off      Set to (off_t) -1.  This field is under application
                      control if the ELF_F_LAYOUT flag was set on the ELF
           d_size     Set to zero.
           d_type     Initialized to ELF_T_BYTE.
           d_version  Set to the current working version of the library, as
                      set by elf_version(3).
     The application must set these values as appropriate before calling
     elf_update(3).  Section scn must be associated with an ELF file opened
     for writing.  If the application has not requested full control of layout
     by setting the ELF_F_LAYOUT flag on descriptor elf, then the data
     referenced by the returned descriptor will be positioned after the
     existing content of the section, honoring the file alignment specified in
     member d_align.  On successful completion of a call to elf_newdata(), the
     ELF library will mark the section scn as "dirty".

     Function elf_rawdata() is used to step through the data descriptors
     associated with section scn.  In contrast to function elf_getdata(), this
     function returns untranslated data.  If argument data is NULL, the first
     data descriptor associated with section scn is returned.  If argument
     data is not NULL, is must be a data descriptor associated with section
     scn, and function elf_rawdata() will return the next data descriptor in
     the list, or NULL if no further descriptors are present.  Function
     elf_rawdata() always returns Elf_Data structures of type ELF_T_BYTE.

   Special handling of zero-sized and SHT_NOBITS sections
     For sections of type SHT_NOBITS, and for zero-sized sections, the
     functions elf_getdata() and elf_rawdata() return a pointer to a valid
     Elf_Data structure that has its d_buf member set to NULL and its d_size
     member set to the size of the section.

     If an application wishes to create a section of type SHT_NOBITS, it
     should add a data buffer to the section using function elf_newdata().  It
     should then set the d_buf and d_size members of the returned Elf_Data
     structure to NULL and the desired size of the section respectively.

     These functions return a valid pointer to a data descriptor if
     successful, or NULL if an error occurs.

     These functions may fail with the following errors:

     [ELF_E_ARGUMENT]  Either of the arguments scn or data was NULL.

     [ELF_E_ARGUMENT]  The data descriptor referenced by argument data is not
                       associated with section descriptor scn.

     [ELF_E_ARGUMENT]  The section denoted by argument scn had no data
                       associated with it.

     [ELF_E_DATA]      Retrieval of data from the underlying object failed.

     [ELF_E_RESOURCE]  An out of memory condition was detected.

     [ELF_E_SECTION]   Section scn had type SHT_NULL.

     [ELF_E_SECTION]   The type of the section scn was not recognized by the

     [ELF_E_SECTION]   The size of the section scn is not a multiple of the
                       file size for its section type.

     [ELF_E_SECTION]   The file offset for section scn is incorrect.

     [ELF_E_UNIMPL]    The section type associated with section scn is not

     [ELF_E_VERSION]   Section scn was associated with an ELF object with an
                       unsupported version.

     elf(3), elf_flagdata(3), elf_flagscn(3), elf_getscn(3), elf_getshdr(3),
     elf_newscn(3), elf_rawfile(3), elf_update(3), elf_version(3), gelf(3)

NetBSD 10.99                    April 22, 2019                    NetBSD 10.99