Cirrus Logic CS485 Manual de usuario descargar pdf (Pagina 36)

CS485G Spring 2015 36

(d) Windows calls shared object ﬁles Dynamic Link Libraries (DLLs).

7. Lecture 21, 3/23/2015

8. Relocation

(a) The linker combines the object ﬁles into a single ﬁle.

(b) All text segments are placed together; similarly for other seg-

ment types.

ject ﬁle to account for the space occupied by the identiﬁers in

previous object ﬁles in its list.

(d) The linker updates all references to relocated global identiﬁers.

38 Format for object ﬁles

1. Since about 1990, Unix variants have standardized to a single format

for object ﬁles: Executable and Linkable Format (ELF).

2. ELF format applies to relocatable object ﬁles, executable object ﬁles,

and shared object ﬁles; together, we call them ELF binaries.

3. Sections of an ELF ﬁle.

(a) header: word size, byte ordering, object-ﬁle type, architecture

(b) segment header table page size, segment sizes.

(d) read-only data, such as jump tables (.rodata section)

(e) initialized global variables (.data section)

(f) uninitialized global variables (.bss section): only length, no

content. “bss” stands for “block started by symbol”.

(g) symbol table (.symtab section), including procedures and static

variables, section names, each with location.

(h) text relocation table (.rel.text section): addresses in .text

that need to be modiﬁed for relocation and how to relocate them.

(i) data relocation table (.rel.data section): addresses in .data

that need to be modiﬁed for relocation and how to relocate them.

(j) debugging information (.debug section), produced, for instance,

with gcc -g.

(k) section header table: offsets and sizes of each section

1 2 ... 31 32 33 34 35 36 37 38 39 40 41 ... 66 67

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Cirrus Logic CS485 Manual de usuario Pagina 36