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diff --git a/static/netbsd/man5/elf.5 b/static/netbsd/man5/elf.5 new file mode 100644 index 00000000..0f316f8d --- /dev/null +++ b/static/netbsd/man5/elf.5 @@ -0,0 +1,528 @@ +.\" $NetBSD: elf.5,v 1.19 2025/12/09 22:21:28 uwe Exp $ +.\" +.\" Copyright (c) 2001, 2002 The NetBSD Foundation, Inc. +.\" All rights reserved. +.\" +.\" This document is derived from work contributed to The NetBSD Foundation +.\" by Antti Kantee. +.\" +.\" 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 THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS +.\" ``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 THE FOUNDATION OR CONTRIBUTORS 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. +.\" +.Dd December 9, 2025 +.Dt ELF 5 +.Os +.Sh NAME +.Nm ELF +.Nd executable and linking format +.Sh SYNOPSIS +.In elf.h +.Sh DESCRIPTION +Because of the flexible nature of ELF, the structures describing it are +available both as 32bit and 64bit versions. +This document uses the 32bit versions, refer to +.In elf.h +for the corresponding 64bit versions. +.Pp +The four main types of an ELF object file are: +. +.Bl -tag -offset indent -width ".Em relocatable" +. +.It Em executable +A file suitable for execution. +It contains the information required for creating a new process image. +. +.It Em shared +The shared object contains necessary information which can be used by +either the link editor +.Xr ld 1 +at link time or by the dynamic loader +.Xr ld.elf_so 1 +at run time. +. +.It Em relocatable +Contains the necessary information to be run through the link editor +.Xr ld 1 +to create an executable or a shared library. +. +.It Em core +A file which describes the virtual address space and register state of +a process. +Core files are typically used in conjunction with debuggers such as +.Xr gdb 1 . +.El +.Pp +ELF files have a dual nature. +The toolchain, including tools such as the +.Xr as 1 +and linker +.Xr ld 1 , +treats them as a set of +.Em sections +described by their section headers. +The system loader treats them as a set of +.Em segments +described by the program headers. +.Pp +The general format of an ELF file is the following: The file starts with an +ELF header. +This is followed by a table of program headers +.Pq optional for relocatable and shared files . +After this come the sections/segments. +The file ends with a table of section headers +.Pq optional for executable files . +.Pp +A segment can be considered to consist of several sections. +For example, all executable sections are typically packed into one +loadable segment which is read-only and executable +.Po +see +.Fa p_flags +in the program header +.Pc . +This enables the system to map the entire file with just a few +operations, one for each loadable segment, instead of doing numerous +map operations for each section separately. +. +. +.Ss ELF Header +. +Each file is described by the ELF header: +.Bd -literal -offset indent +typedef struct { + unsigned char e_ident[EI_NIDENT]; + Elf32_Half e_type; + Elf32_Half e_machine; + Elf32_Word e_version; + Elf32_Addr e_entry; + Elf32_Off e_phoff; + Elf32_Off e_shoff; + Elf32_Word e_flags; + Elf32_Half e_ehsize; + Elf32_Half e_phentsize; + Elf32_Half e_phnum; + Elf32_Half e_shentsize; + Elf32_Half e_shnum; + Elf32_Half e_shstrndx; +} Elf32_Ehdr; +.Ed +. +.Bl -tag -width Fa +. +.It Fa e_ident Ns Li [] +The array contains the following information in the indicated locations: +.Bl -tag -width Dv +. +.It Dv EI_MAG0 +The elements ranging from +.Dv EI_MAG0 +to +.Dv EI_MAG3 +contain the ELF magic number: +.Ql \e0177ELF . +. +.It Dv EI_CLASS +Contains the address size of the binary, either 32 or 64bit. +. +.It Dv EI_DATA +byte order. +. +.It Dv EI_VERSION +Contains the ELF header version. +This is currently always set to 1. +. +.It Dv EI_OSABI +Contains the operating system ABI identification. +Note that even though the definition +.Dv ELFOSABI_NETBSD +exists, +.Nx +uses +.Dv ELFOSABI_SYSV +here, since the +.Nx +ABI does not deviate from the standard. +. +.It Dv EI_ABIVERSION +ABI version. +.El +. +.It Fa e_type +Contains the file type identification. +It can be either +.Dv ET_REL , +.Dv ET_EXEC , +.Dv ET_DYN , +or +.Dv ET_CORE +for relocatable, executable, shared, or core, respectively. +. +.It Fa e_machine +Contains the machine type, e.g.\& +.Tn SPARC , +Alpha, +.Tn MIPS , +\&... +. +.It Fa e_entry +The program entry point if the file is executable. +. +.It Fa e_phoff +The position of the program header table in the file or 0 if it doesn't exist. +. +.It Fa e_shoff +The position of the section header table in the file or 0 if it doesn't exist. +. +.It Fa e_flags +Contains processor-specific flags. +For example, the +.Tn SPARC +port uses this space to specify what kind of memory store ordering is +required. +. +.It Fa e_ehsize +The size of the ELF header. +. +.It Fa e_phentsize +The size of an entry in the program header table. +All entries are the same size. +. +.It Fa e_phnum +The number of entries in the program header table, or 0 if none exists. +. +.It Fa e_shentsize +The size of an entry in the section header table. +All entries are the same size. +. +.It Fa e_shnum +The number of entries in the section header table, or 0 if none exists. +. +.It Fa e_shstrndx +Contains the index number of the section which contains the section +name strings. +.El +. +. +.Ss Section Headers +. +Each ELF section in turn is described by a section header: +.Bd -literal -offset indent +typedef struct { + Elf32_Word sh_name; + Elf32_Word sh_type; + Elf32_Word sh_flags; + Elf32_Addr sh_addr; + Elf32_Off sh_offset; + Elf32_Word sh_size; + Elf32_Word sh_link; + Elf32_Word sh_info; + Elf32_Word sh_addralign; + Elf32_Word sh_entsize; +} Elf32_Shdr; +.Ed +. +.Bl -tag -width Fa +. +.It Fa sh_name +Contains an index to the position in the section header string section +where the name of the current section can be found. +. +.It Fa sh_type +Contains the section type indicator. +The more important possible values are: +.Bl -tag -width Dv \" "SHT_PROGBITS" +. +.It Dv SHT_NULL +Section is inactive. +The other fields contain undefined values. +. +.It Dv SHT_PROGBITS +Section contains program information. +It can be for example code, data, or debugger information. +. +.It Dv SHT_SYMTAB +Section contains a symbol table. +This section usually contains all the symbols and is intended for the +regular link editor +.Xr ld 1 . +. +.It Dv SHT_STRTAB +Section contains a string table. +. +.It Dv SHT_RELA +Section contains relocation information with an explicit addend. +. +.It Dv SHT_HASH +Section contains a symbol hash table. +. +.It Dv SHT_DYNAMIC +Section contains dynamic linking information. +. +.It Dv SHT_NOTE +Section contains some special information. +The format can be e.g. vendor-specific. +. +.It Dv SHT_NOBITS +Sections contains information similar to +.Dv SHT_PROGBITS , +but takes up no space in the file. +This can be used for e.g. bss. +. +.It Dv SHT_REL +Section contains relocation information without an explicit addend. +. +.It Dv SHT_SHLIB +This section type is reserved but has unspecified semantics. +. +.It Dv SHT_DYNSYM +Section contains a symbol table. +This symbol table is intended for the dynamic linker, and is kept as +small as possible to conserve space, since it must be loaded to memory +at run time. +.El +. +.It Fa sh_flags +Contains the section flags, which can have the following values or any +combination of them: +.Bl -tag -width Dv +. +.It Dv SHF_WRITE +Section is writable after it has been loaded. +. +.It Dv SHF_ALLOC +Section will occupy memory at run time. +. +.It Dv SHF_EXECINSTR +Section contains executable machine instructions. +. +.El +. +.It Fa sh_addr +Address to where the section will be loaded, or 0 if this section does +not reside in memory at run time. +. +.It Fa sh_offset +The byte offset from the beginning of the file to the beginning of +this section. +If the section is of type +.Dv SHT_NOBITS , +this field specifies the conceptual placement in the file. +. +.It Fa sh_size +The size of the section in the file for all types except +.Dv SHT_NOBITS . +For that type the value may differ from zero, but the section will +still always take up no space from the file. +. +.It Fa sh_link +Contains an index to the section header table. +The interpretation depends on the section type as follows: +.Pp +.Bl -tag -compact -width SHT_DYNAMIC +. +.It Dv SHT_REL +.It Dv SHT_RELA +Section index of the associated symbol table. +. +.Pp +.It Dv SHT_SYMTAB +.It Dv SHT_DYNSYM +Section index of the associated string table. +. +.Pp +.It Dv SHT_HASH +Section index of the symbol table to which the hash table applies. +. +.Pp +.It Dv SHT_DYNAMIC +Section index of the string table by which entries in this section are used. +.El +. +.It Fa sh_info +Contains extra information. +The interpretation depends on the type as follows: +.Pp +.Bl -tag -compact -width SHT_DYNSYM +.It Dv SHT_REL +.It Dv SHT_RELA +Section index of the section to which the relocation information applies. +.Pp +.It Dv SHT_SYMTAB +.It Dv SHT_DYNSYM +Contains a value one greater that the last local symbol table index. +.El +. +.It Fa sh_addralign +Marks the section alignment requirement. +If, for example, the section contains a doubleword, +the entire section must be doubleword aligned to ensure proper alignment. +Only 0 and integral powers of two are allowed. +Values 0 and 1 denote that the section has no alignment. +. +.It Fa sh_entsize +Contains the entry size of an element for sections which are constructed +of a table of fixed-size entries. +If the section does not hold a table of fixed-size entries, this value +is 0. +.El +. +.Ss Program Headers +. +Every executable object must contain program headers. +Program headers contain information necessary in constructing a +process image. +.Bd -literal -offset indent +typedef struct { + Elf32_Word p_type; + Elf32_Off p_offset; + Elf32_Addr p_vaddr; + Elf32_Addr p_paddr; + Elf32_Word p_filesz; + Elf32_Word p_memsz; + Elf32_Word p_flags; + Elf32_Word p_align; +} Elf32_Phdr; +.Ed +. +.Bl -tag -width Fa +. +.It Fa p_type +Contains the segment type indicator. +The possible values are: +.Bl -tag -width Dv +. +.It Dv PT_NULL +Segment is inactive. +The other fields contain undefined values. +. +.It Dv PT_LOAD +Segment is loadable. +It is loaded to the address described by +.Fa p_vaddr . +If +.Fa p_memsz +is greater than +.Fa p_filesz , +the memory range from +.Po Fa p_vaddr ++ +.Fa p_filesz Pc +to +.Po Fa p_vaddr ++ +.Fa p_memsz Pc +is zero-filled when the segment is loaded. +.Fa p_filesz +can not be greater than +.Fa p_memsz . +Segments of this type are sorted in the header table by +.Fa p_vaddr +in ascending order. +. +.It Dv PT_DYNAMIC +Segment contains dynamic linking information. +. +.It Dv PT_INTERP +Segment contains a null-terminated path name to the interpreter. +This segment may be present only once in a file, and it must appear +before any loadable segments. +This field will most likely contain the ELF dynamic loader: +.Pa /libexec/ld.elf_so +. +.It Dv PT_NOTE +Segment contains some special information. +Format can be e.g. vendor-specific. +. +.It Dv PT_SHLIB +This segment type is reserved but has unspecified semantics. +Programs which contain a segment of this type do not conform to the +ABI, and must indicate this by setting the appropriate ABI in the ELF +header +.Dv EI_OSABI +field. +.It Dv PT_PHDR +The values in a program header of this type specify the characteristics +of the program header table itself. +For example, the +.Fa p_vaddr +field specifies the program header table location in memory once the +program is loaded. +This field may not occur more than once, may occur only if the program +header table is part of the file memory image, and must come before +any loadable segments. +.El +. +.It Fa p_offset +Contains the byte offset from the beginning of the file to the beginning +of this segment. +. +.It Fa p_vaddr +Contains the virtual memory address to which this segment is loaded. +. +.It Fa p_paddr +Contains the physical address to which this segment is loaded. +This value is usually ignored, but may be used while bootstrapping or +in embedded systems. +. +.It Fa p_filesz +Contains the number of bytes this segment occupies in the file image. +. +.It Fa p_memsz +Contains the number of bytes this segment occupies in the memory image. +. +.It Fa p_flags +Contains the segment flags, which specify the permissions for the segment +after it has been loaded. +The following values or any combination of them is acceptable: +.Pp +.Bl -tag -width Dv -compact +.It Dv PF_R +Segment can be read. +.It Dv PF_W +Segment can be written. +.It Dv PF_X +Segment is executable. +.El +. +.It Fa p_align +Contains the segment alignment. +Acceptable values are 0 and 1 for no alignment, and integral powers of two. +.Fa p_vaddr +should equal +.Fa p_offset +modulo +.Fa p_align . +.El +. +.Sh SEE ALSO +.Xr as 1 , +.Xr gdb 1 , +.Xr ld 1 , +.Xr ld.elf_so 1 , +.Xr execve 2 , +.Xr nlist 3 , +.Xr a.out 5 , +.Xr core 5 , +.Xr link 5 , +.Xr stab 5 +.Sh HISTORY +The ELF object file format first appeared in +.At V . |