✎ soc:2010:cooldavid:notes:gpxememlayout

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==== gPXE memory layout ====

Currently the linker script for each arch is locate at:
  * ''src/arch/x86/scripts/efi.lds''
  * ''src/arch/i386/scripts/i386-kir.lds''
  * ''src/arch/i386/scripts/i386.lds''

We can reference ''src/arch/i386/README.i386'' for the difference
between ''i386-kir.lds'' and ''i386.lds'', the ''efi.lds'' should
be obvious as its file name that is for Extensible Firmware Interface
(EFI). In this note we take the binary linked against
''src/arch/i386/scripts/i386.lds'' linker script for instance.

\\

To see the memory layout of an target image, for instance ''gpxe.pxe'',
the all driver PXE loadable image. Use one of the following command:
  * objdump -h bin/gpxe.pxe.tmp
  * readelf -S bin/gpxe.pxe.tmp
It can tell you each section's size and where it will put in the memory
while execution(VMA).
== objdump -h bin/gpxe.pxe.tmp ==
<file>
bin/gpxe.pxe.tmp:     file format elf32-i386

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .prefix       0000081a  00000000  00000000  00000160  2**4
                  CONTENTS, ALLOC, LOAD, CODE
  1 .text16       00000854  00000000  00000820  00000980  2**4
                  CONTENTS, ALLOC, LOAD, CODE
  2 .data16       000004a2  00000000  00001080  000011e0  2**4
                  CONTENTS, ALLOC, LOAD, DATA
  3 .bss.data16   000029a0  000004a8  000963f0  00096540  2**3
                  ALLOC
  4 .textdata     00094e7c  00000000  00001530  00001684  2**2
                  CONTENTS, ALLOC, LOAD, CODE
  5 .bss.textdata 00058b68  00094e80  000963f0  00096580  2**7
                  ALLOC
  6 .zinfo        00000040  00000000  000963b0  00096500  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  7 .debug_abbrev 000346c3  00000000  00000000  00096540  2**0
                  CONTENTS, READONLY, DEBUGGING
  8 .debug_info   002274b7  00000000  00000000  000cac03  2**0
                  CONTENTS, READONLY, DEBUGGING
  9 .debug_line   000384b6  00000000  00000000  002f20ba  2**0
                  CONTENTS, READONLY, DEBUGGING
 10 .debug_frame  0001953c  00000000  00000000  0032a570  2**2
                  CONTENTS, READONLY, DEBUGGING
 11 .debug_loc    00091542  00000000  00000000  00343aac  2**0
                  CONTENTS, READONLY, DEBUGGING
 12 .debug_pubnames 0000fffd  00000000  00000000  003d4fee  2**0
                  CONTENTS, READONLY, DEBUGGING
 13 .debug_aranges 00002460  00000000  00000000  003e4feb  2**0
                  CONTENTS, READONLY, DEBUGGING
 14 .debug_ranges 00006f58  00000000  00000000  003e744b  2**0
                  CONTENTS, READONLY, DEBUGGING
 15 .debug_str    0003c4ef  00000000  00000000  003ee3a3  2**0
                  CONTENTS, READONLY, DEBUGGING
</file>

\\

To see each symbol's memory location, use one of the following command:
  * objdump -t bin/gpxe.pxe.tmp
  * readelf -s bin/gpxe.pxe.tmp
== objdump -t bin/gpxe.pxe.tmp | sort -k1 | tail -n 30 ==
<file>
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_dhcppkt
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_eapol
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_editstring
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_hmac
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_ib_mcast
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_ib_pathrec
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_icmp
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_iwmgmt
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_iwmgmt_cmd
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_job
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_linebuf
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_monojob
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_readline
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_sec80211
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_sha1
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_sha1extra
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_smbios
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_tcp
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_wep
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_wpa
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_wpa_ccmp
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_wpa_psk
000ec9e4 g     O .bss.textdata  00000000 .hidden obj_wpa_tkip
000ec9e8 g       .bss.textdata  00000000 _stack
000ed9e8 g       *ABS*  00000000 _textdata_memsz
000ed9e8 g       .bss.textdata  00000000 _estack
000ed9e8 g       .bss.textdata  00000000 .hidden _etextdata
00400000 g       *ABS*  00000000 HIGHMEM_LOADPOINT
bin/gpxe.pxe.tmp:     file format elf32-i386
SYMBOL TABLE:
</file>

==== Current memory usage ====
Trace: • qemupxe • week9 • weekb4 • week9 • week4 • debian_and_ubuntu
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