I was reading about sections and segments. Seems you could list the mapping between sections and segments as below.
$ readelf -l test
Elf file type is EXEC (Executable file)
Entry point 0x8048330
There are 9 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
PHDR 0x000034 0x08048034 0x08048034 0x00120 0x00120 R E 0x4
INTERP 0x000154 0x08048154 0x08048154 0x00013 0x00013 R 0x1
[Requesting program interpreter: /lib/ld-linux.so.2]
LOAD 0x000000 0x08048000 0x08048000 0x0065c 0x0065c R E 0x1000
LOAD 0x000f14 0x08049f14 0x08049f14 0x00104 0x00110 RW 0x1000
DYNAMIC 0x000f28 0x08049f28 0x08049f28 0x000c8 0x000c8 RW 0x4
NOTE 0x000168 0x08048168 0x08048168 0x00044 0x00044 R 0x4
GNU_EH_FRAME 0x000564 0x08048564 0x08048564 0x00034 0x00034 R 0x4
GNU_STACK 0x000000 0x00000000 0x00000000 0x00000 0x00000 RW 0x4
GNU_RELRO 0x000f14 0x08049f14 0x08049f14 0x000ec 0x000ec R 0x1
Section to Segment mapping:
Segment Sections...
00
01 .interp
02 .interp .note.ABI-tag .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rel.dyn .rel.plt .init .plt .text .fini .rodata .eh_frame_hdr .eh_frame
03 .ctors .dtors .jcr .dynamic .got .got.plt .data .bss
04 .dynamic
05 .note.ABI-tag .note.gnu.build-id
06 .eh_frame_hdr
07
08 .ctors .dtors .jcr .dynamic .got
My questions,
To understand the output of readelf
it will help for you to understand the format of an ELF
file. Please reference this document.
As far as understanding how to interpret the output of readelf
this link may be of help.
As to your question 2, this link describes the segments. In that document search for "Various sections hold program and control information:" to find the area where the segment names are described.
That document describes the segments as follows:
Various sections hold program and control information:
.bss This section holds uninitialized data that contributes to the
program's memory image. By definition, the system initializes the
data with zeros when the program begins to run. This section is of
type SHT_NOBITS. The attribute types are SHF_ALLOC and SHF_WRITE.
.comment This section holds version control information. This section is of
type SHT_PROGBITS. No attribute types are used.
.ctors This section holds initialized pointers to the C++ constructor
functions. This section is of type SHT_PROGBITS. The attribute
types are SHF_ALLOC and SHF_WRITE.
.data This section holds initialized data that contribute to the program's
memory image. This section is of type SHT_PROGBITS. The attribute
types are SHF_ALLOC and SHF_WRITE.
.data1 This section holds initialized data that contribute to the program's
memory image. This section is of type SHT_PROGBITS. The attribute
types are SHF_ALLOC and SHF_WRITE.
.debug This section holds information for symbolic debugging. The contents
are unspecified. This section is of type SHT_PROGBITS. No
attribute types are used.
.dtors This section holds initialized pointers to the C++ destructor
functions. This section is of type SHT_PROGBITS. The attribute
types are SHF_ALLOC and SHF_WRITE.
.dynamic This section holds dynamic linking information. The section's
attributes will include the SHF_ALLOC bit. Whether the SHF_WRITE
bit is set is processor-specific. This section is of type
SHT_DYNAMIC. See the attributes above.
.dynstr This section holds strings needed for dynamic linking, most commonly
the strings that represent the names associated with symbol table
entries. This section is of type SHT_STRTAB. The attribute type
used is SHF_ALLOC.
.dynsym This section holds the dynamic linking symbol table. This section
is of type SHT_DYNSYM. The attribute used is SHF_ALLOC.
.fini This section holds executable instructions that contribute to the
process termination code. When a program exits normally the system
arranges to execute the code in this section. This section is of
type SHT_PROGBITS. The attributes used are SHF_ALLOC and
SHF_EXECINSTR.
.gnu.version
This section holds the version symbol table, an array of ElfN_Half
elements. This section is of type SHT_GNU_versym. The attribute
type used is SHF_ALLOC.
.gnu.version_d
This section holds the version symbol definitions, a table of
ElfN_Verdef structures. This section is of type SHT_GNU_verdef.
The attribute type used is SHF_ALLOC.
.gnu.version_r
This section holds the version symbol needed elements, a table of
ElfN_Verneed structures. This section is of type SHT_GNU_versym.
The attribute type used is SHF_ALLOC.
.got This section holds the global offset table. This section is of type
SHT_PROGBITS. The attributes are processor specific.
.hash This section holds a symbol hash table. This section is of type
SHT_HASH. The attribute used is SHF_ALLOC.
.init This section holds executable instructions that contribute to the
process initialization code. When a program starts to run the
system arranges to execute the code in this section before calling
the main program entry point. This section is of type SHT_PROGBITS.
The attributes used are SHF_ALLOC and SHF_EXECINSTR.
.interp This section holds the pathname of a program interpreter. If the
file has a loadable segment that includes the section, the section's
attributes will include the SHF_ALLOC bit. Otherwise, that bit will
be off. This section is of type SHT_PROGBITS.
.line This section holds line number information for symbolic debugging,
which describes the correspondence between the program source and
the machine code. The contents are unspecified. This section is of
type SHT_PROGBITS. No attribute types are used.
.note This section holds information in the "Note Section" format. This
section is of type SHT_NOTE. No attribute types are used. OpenBSD
native executables usually contain a .note.openbsd.ident section to
identify themselves, for the kernel to bypass any compatibility ELF
binary emulation tests when loading the file.
.note.GNU-stack
This section is used in Linux object files for declaring stack
attributes. This section is of type SHT_PROGBITS. The only
attribute used is SHF_EXECINSTR. This indicates to the GNU linker
that the object file requires an executable stack.
.plt This section holds the procedure linkage table. This section is of
type SHT_PROGBITS. The attributes are processor specific.
.relNAME This section holds relocation information as described below. If
the file has a loadable segment that includes relocation, the
section's attributes will include the SHF_ALLOC bit. Otherwise the
bit will be off. By convention, "NAME" is supplied by the section
to which the relocations apply. Thus a relocation section for .text
normally would have the name .rel.text. This section is of type
SHT_REL.
.relaNAME This section holds relocation information as described below. If
the file has a loadable segment that includes relocation, the
section's attributes will include the SHF_ALLOC bit. Otherwise the
bit will be off. By convention, "NAME" is supplied by the section
to which the relocations apply. Thus a relocation section for .text
normally would have the name .rela.text. This section is of type
SHT_RELA.
.rodata This section holds read-only data that typically contributes to a
nonwritable segment in the process image. This section is of type
SHT_PROGBITS. The attribute used is SHF_ALLOC.
.rodata1 This section holds read-only data that typically contributes to a
nonwritable segment in the process image. This section is of type
SHT_PROGBITS. The attribute used is SHF_ALLOC.
.shstrtab This section holds section names. This section is of type
SHT_STRTAB. No attribute types are used.
.strtab This section holds strings, most commonly the strings that represent
the names associated with symbol table entries. If the file has a
loadable segment that includes the symbol string table, the
section's attributes will include the SHF_ALLOC bit. Otherwise the
bit will be off. This section is of type SHT_STRTAB.
.symtab This section holds a symbol table. If the file has a loadable
segment that includes the symbol table, the section's attributes
will include the SHF_ALLOC bit. Otherwise the bit will be off.
This section is of type SHT_SYMTAB.
.text This section holds the "text", or executable instructions, of a
program. This section is of type SHT_PROGBITS. The attributes used
are SHF_ALLOC and SHF_EXECINSTR.