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.\" $Id: elf_flagdata.3,v 1.3 2020/05/18 06:46:23 jsg Exp $
.\"
.Dd June 12, 2019
.Dt ELF_FLAGDATA 3
.Os
.Sh NAME
.Nm elf_flagarhdr ,
.Nm elf_flagdata ,
.Nm elf_flagehdr ,
.Nm elf_flagelf ,
.Nm elf_flagphdr ,
.Nm elf_flagscn ,
.Nm elf_flagshdr
.Nd manipulate flags associated with ELF data structures
.Sh LIBRARY
.Lb libelf
.Sh SYNOPSIS
.In libelf.h
.Ft "unsigned int"
.Fn elf_flagarhdr "Elf_Arhdr *arhdr" "Elf_Cmd cmd" "unsigned int flags"
.Ft "unsigned int"
.Fn elf_flagdata "Elf_Data *data" "Elf_Cmd cmd" "unsigned int flags"
.Ft "unsigned int"
.Fn elf_flagehdr "Elf *elf" "Elf_Cmd cmd" "unsigned int flags"
.Ft "unsigned int"
.Fn elf_flagelf "Elf *elf" "Elf_Cmd cmd" "unsigned int flags"
.Ft "unsigned int"
.Fn elf_flagphdr "Elf *elf" "Elf_Cmd cmd" "unsigned int flags"
.Ft "unsigned int"
.Fn elf_flagscn "Elf_Scn *scn" "Elf_Cmd cmd" "unsigned int flags"
.Ft "unsigned int"
.Fn elf_flagshdr "Elf_Scn *scn" "Elf_Cmd cmd" "unsigned int flags"
.Sh DESCRIPTION
These functions are used to query, set or reset flags on data
structures associated with an ELF file.
.Pp
Arguments
.Ar arhdr ,
.Ar data ,
.Ar elf
and
.Ar scn
denote the data structures whose flags need to be changed.
These values should have been returned by prior calls to
functions in the
.Xr elf 3
API set:
.Bl -bullet -compact
.It
Argument
.Ar arhdr
should have been returned by a prior call to
.Xr elf_getarhdr 3 .
.It
Argument
.Ar data
should have been returned by a prior call to one of
.Xr elf_newdata 3 ,
.Xr elf_getdata 3
or
.Xr elf_rawdata 3 .
.It
Argument
.Ar elf
should have been allocated by a prior call to one of
.Xr elf_begin 3
or
.Xr elf_memory 3 .
.It
Argument
.Ar scn
should have been returned by a prior call to one of
.Xr elf_getscn 3 ,
.Xr elf_newscn 3
or
.Xr elf_nextscn 3 .
.El
These values are allowed to be NULL to simplify error handling in
application code.
.Pp
Argument
.Ar cmd
may have the following values:
.Bl -tag -width ELF_C_SET
.It Dv ELF_C_CLR
The argument
.Ar flags
specifies the flags to be cleared.
.It Dv ELF_C_SET
The argument
.Ar flags
specifies the flags to be set.
.El
.Pp
The argument
.Ar flags
is allowed to have the following flags set:
.Bl -tag -width ELF_F_ARCHIVE_SYSV
.It Dv ELF_F_ARCHIVE
This flag is only valid with the
.Fn elf_flagelf
API.
It informs the library that the application desires to create an
.Xr ar 1
archive.
Argument
.Ar elf
should have been opened for writing using the
.Dv ELF_C_WRITE
command to function
.Fn elf_begin .
.It Dv ELF_F_ARCHIVE_SYSV
This flag is used in conjunction with the
.Dv ELF_F_ARCHIVE
flag to indicate that library should create archives that conform
to System V layout rules.
The default is to create BSD style archives.
.It Dv ELF_F_DIRTY
Mark the associated data structure as needing to be written back
to the underlying file.
A subsequent call to
.Xr elf_update 3
will resynchronize the library's internal data structures.
.It Dv ELF_F_LAYOUT
This flag is only valid with the
.Fn elf_flagelf
API.
It informs the library that the application will take
responsibility for the layout of the file and that the library is
not to insert any padding in between sections.
.El
.Pp
Marking a given data structure as
.Dq dirty
affects all of its contained elements.
Thus marking an ELF descriptor
.Ar elf
with
.Fn elf_flagelf "elf" "ELF_C_SET" "ELF_F_DIRTY"
means that the entire contents of the descriptor are
.Dq dirty .
.Pp
Using a value of zero for argument
.Ar flags
will return the current set of flags for the data structure being
queried.
.Sh RETURN VALUES
These functions return the updated flags if successful, or zero if
an error is detected.
.Sh COMPATIBILITY
The
.Fn elf_flagarhdr
function and the
.Dv ELF_F_ARCHIVE
and
.Dv ELF_F_ARCHIVE_SYSV
flags are an extension to the
.Xr elf 3
API.
.Sh ERRORS
These functions may fail with the following errors:
.Bl -tag -width "[ELF_E_RESOURCE]"
.It Bq Er ELF_E_ARGUMENT
An unsupported value was used for the
.Ar cmd
argument.
.It Bq Er ELF_E_ARGUMENT
Argument
.Ar flags
had unsupported flags set.
.It Bq Er ELF_E_ARGUMENT
The argument
.Ar elf
was not a descriptor for an ELF object.
.It Bq Er ELF_E_MODE
The
.Dv ELF_F_ARCHIVE
flag was used with an ELF descriptor that had not been opened for writing.
.It Bq Er ELF_E_SEQUENCE
Function
.Fn elf_flagehdr
was called without an executable header being allocated.
.It Bq Er ELF_E_SEQUENCE
Function
.Fn elf_flagphdr
was called without a program header being allocated.
.El
.Sh SEE ALSO
.Xr elf 3 ,
.Xr elf32_newehdr 3 ,
.Xr elf32_newphdr 3 ,
.Xr elf64_newehdr 3 ,
.Xr elf64_newphdr 3 ,
.Xr elf_newdata 3 ,
.Xr elf_update 3 ,
.Xr gelf 3 ,
.Xr gelf_newehdr 3 ,
.Xr gelf_newphdr 3 ,
.Xr gelf_update_dyn 3 ,
.Xr gelf_update_move 3 ,
.Xr gelf_update_rel 3 ,
.Xr gelf_update_rela 3 ,
.Xr gelf_update_sym 3 ,
.Xr gelf_update_syminfo 3