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ELF_FLAGELF

Section: Libelf Programmer's Manual (3)
Updated: 202-0-23
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NAME

elf_flagelf, elf_flagdata, elf_flagehdr, elf_flagphdr, elf_flagscn, elf_flagshdr - set or clear flags on ELF descriptors and components

SYNOPSIS

#include <libelf.h>

unsigned int elf_flagelf(Elf * elf, Elf_Cmd cmd, unsigned int flags);
unsigned int elf_flagehdr(Elf * elf, Elf_Cmd cmd, unsigned int flags);
unsigned int elf_flagphdr(Elf * elf, Elf_Cmd cmd, unsigned int flags);
unsigned int elf_flagscn(Elf_Scn * scn, Elf_Cmd cmd, unsigned int flags);
unsigned int elf_flagshdr(Elf_Scn * scn, Elf_Cmd cmd, unsigned int flags);
unsigned int elf_flagdata(Elf_Data * data, Elf_Cmd cmd, unsigned int flags);

DESCRIPTION

These functions allow the caller to set or clear flags on various ELF components managed by libelf . They are typically used to indicate that a component has been modified (dirty), or to control layout behavior during output.

elf_flagelf() modifies flags on the to-level Elf descriptor.

elf_flagdata() modifies flags on an Elf_Data descriptor, typically retrieved using elf_getdata(3) or created with elf_newdata(3).

elf_flagehdr() modifies flags on the ELF header for a ELF descriptor (e.g., the result of gelf_getehdr(3)).

elf_flagphdr() modifies flags on the program header table of an ELF descriptor.

elf_flagscn() modifies flags on an Elf_Scn (section) descriptor.

elf_flagshdr() modifies flags on the section header of a given Elf_Scn .

The cmd argument determines whether the given flags should be set ( ELF_C_SET ) or cleared ( ELF_C_CLR ).

The following flag values may be passed via the flags parameter:

ELF_F_DIRTY: Marks the object as modified. This ensures changes to the component is written out during elf_update(3).
ELF_F_LAYOUT: Indicates that the layout of the ELF component is managed manually. Offsets and sizes will be preserved as provided. This flag is only used with elf_flagelf() and is ignored when used with other functions. If this flag is set the user must set Ehdr e_phoff, e_shoff, as well as Elf_Data d_off and Shdr sh_offset. If not set, then these offsets will be recalculated when elf_update is called. If ELF_F_LAYOUT is set then changes to phdr offsets will prevent elf_update from automatically adjusting shdr offsets.
ELF_F_PERMISSIVE: Enables relaxed validation of object structure. This flag permits nonstandard layouts without strict checks. Specifically this removes a check in elf_update() that the section sh_size is a multiple of the section sh_entsize (if not zero). This flag is only used with elf_flagelf() and is ignored when used with other functions. ELF_F_PERMISSIVE is an elfutils libelf extention and may not be available in other libelf implementations.

PARAMETERS

obj

The object to be modified: For elf_flagelf, elf_flagehdr, elf_flagphdr, this is an Elf * descriptor. For elf_flagscn and elf_flagshdr , this is an Elf_Scn * descriptor. For elf_flagdata , an Elf_Data * buffer.

cmd

Must be either: ELF_C_SET to set the given flags, or ELF_C_CLR to clear them.

flags

Bitmask of flags to modify. May include any combination of ELF_F_DIRTY , ELF_F_LAYOUT , and ELF_F_PERMISSIVE .

Note that ELF_F_LAYOUT and ELF_F_PERMISSIVE are only used with elf_flagelf() and are ignored for other functions.

RETURN VALUE

Returns the new value of the flags after the set/clear operation.

Returns 0 on error, and sets an error code retrievable via elf_errmsg(3). If the first argument is NULL then 0 is return and no error code is set.

If the last flag is cleared, 0 will be returned as the new flag value. In this case 0 is not an error indicator and no error code is set.

ATTRIBUTES

Interface	Attribute	Value
elf_flagelf(),~elf_flagehdr(),~elf_flagphdr(),~elf_flagscn(),~elf_flagshdr(),~elf_flagdata()	Thread safety	M-Unsafe race

REPORTING BUGS

Report bugs to <elfutil-devel@sourceware.org> or https://sourceware.org/bugzilla/.