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ABSOLUTE(exp)
ADDR(section)
symbol_1
and symbol_2
are assigned
identical values:
SECTIONS { ... .output1 : { start_of_output_1 = ABSOLUTE(.); ... } .output : { symbol_1 = ADDR(.output1); symbol_2 = start_of_output_1; } ... } |
ALIGN(exp)
.
) aligned to the next exp
boundary.
ALIGN
doesn't change the value of the location counter--it just
does arithmetic on it. Here is an example which aligns the output
.data
section to the next 0x2000
byte boundary after the
preceding section and sets a variable within the section to the next
0x8000
boundary after the input sections:
SECTIONS { ... .data ALIGN(0x2000): { *(.data) variable = ALIGN(0x8000); } ... } |
ALIGN
in this example specifies the location of
a section because it is used as the optional address attribute of
a section definition (see section 3.6.3 Output section address). The second use
of ALIGN
is used to defines the value of a symbol.
The builtin function NEXT
is closely related to ALIGN
.
BLOCK(exp)
ALIGN
, for compatibility with older linker
scripts. It is most often seen when setting the address of an output
section.
DATA_SEGMENT_ALIGN(maxpagesize, commonpagesize)
(ALIGN(maxpagesize) + (. & (maxpagesize - 1))) |
(ALIGN(maxpagesize) + (. & (maxpagesize - commonpagesize))) |
DATA_SEGMENT_END
) than the former or not.
If the latter form is used, it means commonpagesize bytes of runtime
memory will be saved at the expense of up to commonpagesize wasted
bytes in the on-disk file.
This expression can only be used directly in SECTIONS
commands, not in
any output section descriptions and only once in the linker script.
commonpagesize should be less or equal to maxpagesize and should
be the system page size the object wants to be optimized for (while still
working on system page sizes up to maxpagesize).
Example:
. = DATA_SEGMENT_ALIGN(0x10000, 0x2000); |
DATA_SEGMENT_END(exp)
DATA_SEGMENT_ALIGN
evaluation purposes.
. = DATA_SEGMENT_END(.); |
DEFINED(symbol)
SECTIONS { ... .text : { begin = DEFINED(begin) ? begin : . ; ... } ... } |
LOADADDR(section)
ADDR
, but it may be different if the AT
attribute is used in the output section definition (see section 3.6.8.2 Output section LMA).
MAX(exp1, exp2)
MIN(exp1, exp2)
NEXT(exp)
ALIGN(exp)
; unless you
use the MEMORY
command to define discontinuous memory for the
output file, the two functions are equivalent.
SIZEOF(section)
symbol_1
and symbol_2
are assigned identical values:
SECTIONS{ ... .output { .start = . ; ... .end = . ; } symbol_1 = .end - .start ; symbol_2 = SIZEOF(.output); ... } |
SIZEOF_HEADERS
sizeof_headers
When producing an ELF output file, if the linker script uses the
SIZEOF_HEADERS
builtin function, the linker must compute the
number of program headers before it has determined all the section
addresses and sizes. If the linker later discovers that it needs
additional program headers, it will report an error `not enough
room for program headers'. To avoid this error, you must avoid using
the SIZEOF_HEADERS
function, or you must rework your linker
script to avoid forcing the linker to use additional program headers, or
you must define the program headers yourself using the PHDRS
command (see section 3.8 PHDRS Command).
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