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Diffstat (limited to 'linkers/elftoolchain/libelf/elf_update.3')
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diff --git a/linkers/elftoolchain/libelf/elf_update.3 b/linkers/elftoolchain/libelf/elf_update.3 new file mode 100644 index 0000000..40a1e40 --- /dev/null +++ b/linkers/elftoolchain/libelf/elf_update.3 @@ -0,0 +1,378 @@ +.\" Copyright (c) 2006-2011 Joseph Koshy. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" This software is provided by Joseph Koshy ``as is'' and +.\" any express or implied warranties, including, but not limited to, the +.\" implied warranties of merchantability and fitness for a particular purpose +.\" are disclaimed. in no event shall Joseph Koshy be liable +.\" for any direct, indirect, incidental, special, exemplary, or consequential +.\" damages (including, but not limited to, procurement of substitute goods +.\" or services; loss of use, data, or profits; or business interruption) +.\" however caused and on any theory of liability, whether in contract, strict +.\" liability, or tort (including negligence or otherwise) arising in any way +.\" out of the use of this software, even if advised of the possibility of +.\" such damage. +.\" +.\" $Id: elf_update.3 1729 2011-08-14 09:13:00Z jkoshy $ +.\" +.Dd August 14, 2011 +.Os +.Dt ELF_UPDATE 3 +.Sh NAME +.Nm elf_update +.Nd update an ELF descriptor +.Sh LIBRARY +.Lb libelf +.Sh SYNOPSIS +.In libelf.h +.Ft off_t +.Fn elf_update "Elf *elf" "Elf_Cmd cmd" +.Sh DESCRIPTION +Function +.Fn elf_update +causes the library to recalculate the structure of an ELF +object and optionally write out the image of the object +to file. +.Pp +Argument +.Ar elf +should reference a valid ELF descriptor. +.Pp +Argument +.Ar cmd +can be one of the following values: +.Bl -tag -width "Dv ELF_C_WRITE" +.It Dv ELF_C_NULL +The library will recalculate structural information flagging +modified structures with the +.Dv ELF_F_DIRTY +flag, but will not write data to the underlying file image. +.It Dv ELF_C_WRITE +The library will recalculate structural information and will +also write the new image to the underlying file. +The ELF descriptor referenced by argument +.Ar elf +should permit the underlying ELF object to be written or updated +(see +.Xr elf_begin 3 ) . +.El +.Pp +All pointers to +.Vt Elf_Scn +and +.Vt Elf_Data +descriptors associated with descriptor +.Ar elf +should be considered invalid after a call to +.Fn elf_update . +.Ss Specifying Object Layout +The +.Lb libelf +supports two layout modes. +.Bl -tag -width indent +.It "Library Layout" +If the +.Dv ELF_F_LAYOUT +flag is not set on the ELF descriptor, the ELF library will lay out +the ELF object according to the following scheme: +.Bl -tag -compact -width "Section Data" +.It Em EHDR +The ELF executable header will be placed at the start of the object. +.It Em PHDR +If the ELF descriptor contains a program header table, it will be +placed after the Executable Header. +.It Em Section Data +ELF section data, if any, will be placed next, keeping each section's +alignment requirements in mind. +.It Em SHDR +The ELF section header table, if any, will be placed last. +.El +.It "Application Controlled Layout" +The application can take full control of the layout of the ELF object +by setting the +.Dv ELF_F_LAYOUT +flag on the ELF descriptor (see +.Xr elf_flagelf 3 ) . +In this case the library will lay out the ELF object using +application-supplied information as below: +.Pp +.Bl -tag -compact -width "Section Data" +.It Em EHDR +The ELF executable header will be placed at the start of the object. +.It Em PHDR +The ELF program header table, if any, it will be placed at the offset +specified in the +.Va e_phoff +field of the ELF executable header. +.It Em Section Data +The data for each ELF section will be placed at the offset specified +by the +.Va sh_offset +field of the section's header. +The size of the section will be taken from the +.Va sh_size +field of the section header. +.It Em SHDR +The ELF section header table, if any, will be placed at the offset +specified by the +.Va e_shoff +field of the executable header. +.El +.El +.Pp +Gaps in the coverage of the file's contents will be set to the fill value +specified by +.Xr elf_fill 3 . +.Ss Application Supplied Information +The application needs to set the following fields in the data +structures associated with the ELF descriptor prior to calling +.Fn elf_update . +.Bl -tag -width indent +.It "Executable Header" +The fields of the ELF executable header that need to be set by the +application are: +.Pp +.Bl -tag -width "e_ident[EI_OSABI]" -compact +.It Va e_entry +To be set to the desired entry address for executables. +.It Va e_flags +To be set to the desired processor specific flags. +.It Va "e_ident[EI_DATA]" +Must be set to one of +.Dv ELFDATA2LSB +or +.Dv ELFDATA2MSB . +.It Va "e_ident[EI_OSABI]" +To be set to the OS ABI desired. +For example, for +.Fx +executables, this field should be set to +.Dv ELFOSABI_FREEBSD . +.It Va e_machine +To be set to the desired machine architecture, one of the +.Dv EM_* +values in the header file +.In elfdefinitions.h . +.It Va e_phoff +If the application is managing the object's layout, it must +set this field to the file offset of the ELF program header table. +.It Va e_shoff +If the application is managing the object's layout, it must +set this field to the file offset of the ELF section header table. +.It Va e_shstrndx +To be set to the index of the string table containing +section names. +.It Va e_type +To be set to the type of the ELF object, one of the +.Dv ET_* +values in the header file +.In elfdefinitions.h . +.It Va e_version +To be set to the desired version of the ELF object. +.El +.It "Program Header" +All fields of the entries in the program header table need to be +set by the application. +.It "Section Header" +The fields of ELF section headers that need to be set by the +application are: +.Pp +.Bl -tag -width "sh_addralign" -compact +.It Va sh_addr +To be set to the memory address where the section should reside. +.It Va sh_addralign +If the application is managing the file layout, it must set this +field to the desired alignment for the section's contents. +This value must be a power of two and must be at least as large as the +largest alignment needed by any +.Vt Elf_Data +descriptor associated with the section. +.It Va sh_entsize +To be set to the size of each entry, for sections containing fixed size +elements, or set to zero for sections without fixed size elements. +If the application is not managing file layout, it may leave this +field as zero for those sections whose types are known to the library. +.It Va sh_flags +To be set to the desired section flags. +.It Va sh_info +To be set as described in +.Xr elf 5 . +.It Va sh_link +To be set as described in +.Xr elf 5 . +.It Va sh_name +To be set to the index of the section's name in the string table +containing section names. +.It Va sh_offset +If the application is managing the file layout, it must set this +field to the file offset of the section's contents. +.It Va sh_size +If the application is managing the file layout, it must set this +field to the file size of the section's contents. +.It Va sh_type +To be set to the type of the section. +.El +.It "Section Data" +The +.Vt Elf_Data +descriptors associated with each section specify its contents +(see +.Xr elf_getdata 3 ) . +While all the fields in these descriptors are under application +control, the following fields influence object layout: +.Bl -tag -width "Va d_align" -compact +.It Va d_align +To be set to the desired alignment, within the containing section, of +the descriptor's data. +.It Va d_off +If the application is managing object layout, it must set this field +to the file offset, within the section, at which the descriptor's data +should be placed. +.It Va d_size +To be set to the size in bytes of the memory representation of the +descriptor's data. +.El +.El +.Sh RETURN VALUES +Function +.Fn elf_update +returns the total size of the file image if successful, or -1 if an +error occurred. +.Sh ERRORS +This function may fail with the following errors: +.Bl -tag -width "[ELF_E_RESOURCE]" +.It Bq Er ELF_E_ARGUMENT +Argument +.Ar elf +was null. +.It Bq Er ELF_E_ARGUMENT +Argument +.Ar cmd +was not recognized. +.It Bq Er ELF_E_ARGUMENT +The argument +.Ar elf +was not a descriptor for an ELF object. +.It Bq Er ELF_E_CLASS +The +.Va e_ident[EI_CLASS] +field of the executable header of argument +.Ar elf +did not match the class of the file. +.It Bq Er ELF_E_DATA +An +.Vt Elf_Data +descriptor contained in argument +.Ar elf +specified an unsupported type. +.It Bq Er ELF_E_DATA +An +.Vt Elf_Data +descriptor specified an alignment that was zero or was not a power of +two. +.It Bq Er ELF_E_HEADER +The ELF header in argument +.Ar elf +requested a different byte order from the byte order already +associated with the file. +.It Bq Er ELF_E_IO +An I/O error was encountered. +.It Bq Er ELF_E_LAYOUT +An +.Vt Elf_Data +descriptor contained in argument +.Ar elf +specified an alignment incompatible with its containing section. +.It Bq Er ELF_E_LAYOUT +Argument +.Ar elf +contained section descriptors that overlapped in extent. +.It Bq Er ELF_E_LAYOUT +Argument +.Ar elf +contained section descriptors that were incorrectly aligned or were +too small for their data. +.It Bq Er ELF_E_LAYOUT +The flag +.Dv ELF_F_LAYOUT +was set on the Elf descriptor and the executable header overlapped +with the program header table. +.It Bq Er ELF_E_LAYOUT +The flag +.Dv ELF_F_LAYOUT +was set on the Elf descriptor and the program header table was placed +at a misaligned file offset. +.It Bq Er ELF_E_LAYOUT +The flag +.Dv ELF_F_LAYOUT +was set on the Elf descriptor and the section header table overlapped +an extent mapped by a section descriptor. +.It Bq Er ELF_E_LAYOUT +The +.Dv ELF_F_LAYOUT +flag was set on the Elf descriptor, and the +.Va d_offset +field in an +.Vt Elf_Data +descriptor contained a value that was not a multiple of the +descriptor's specified alignment. +.It Bq Er ELF_E_MODE +An +.Dv ELF_C_WRITE +operation was requested with an ELF descriptor that was not opened for +writing or updating. +.It Bq Er ELF_E_SECTION +Argument +.Ar elf +contained a section with an unrecognized type. +.It Bq Er ELF_E_SECTION +The section header at index +.Dv SHN_UNDEF +had an illegal section type. +.It Bq Er ELF_E_SEQUENCE +An +.Dv ELF_C_WRITE +operation was requested after a prior call to +.Fn elf_cntl elf ELF_C_FDDONE +disassociated the ELF descriptor +.Ar elf +from its underlying file. +.It Bq Er ELF_E_VERSION +Argument +.Ar elf +had an unsupported version or contained an +.Vt Elf_Data +descriptor with an unsupported version. +.El +.Sh SEE ALSO +.Xr elf 3 , +.Xr elf32_getehdr 3 , +.Xr elf32_getphdr 3 , +.Xr elf32_newehdr 3 , +.Xr elf32_newphdr 3 , +.Xr elf64_getehdr 3 , +.Xr elf64_getphdr 3 , +.Xr elf64_newehdr 3 , +.Xr elf64_newphdr 3 , +.Xr elf_begin 3 , +.Xr elf_cntl 3 , +.Xr elf_fill 3 , +.Xr elf_flagehdr 3 , +.Xr elf_flagelf 3 , +.Xr elf_getdata 3 , +.Xr elf_getscn 3 , +.Xr elf_newdata 3 , +.Xr elf_newscn 3 , +.Xr elf_rawdata 3 , +.Xr gelf 3 , +.Xr gelf_newehdr 3 , +.Xr gelf_newphdr 3 , +.Xr elf 5 |