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soc:2008:stefanha:journal:week8 [2008/07/17 05:43]
stefanha
soc:2008:stefanha:journal:week8 [2009/03/07 09:20] (current)
stefanha
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 ====== Stefan Hajnoczi: GDB Remote Debugging ====== ====== Stefan Hajnoczi: GDB Remote Debugging ======
  
-===== Week =====+===== Week =====
  
 **Milestones:​** **Milestones:​**
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 I think the most general way to solve this dilemma is by allowing multiple I think the most general way to solve this dilemma is by allowing multiple
 embedded images and making gPXE //always// boot from an embedded image. ​ Even embedded images and making gPXE //always// boot from an embedded image. ​ Even
-when you build without explicit ''​EMBEDDED_IMAGE''​ settings, a **default gPXE +when you build without explicit ''​EMBEDDED_IMAGE''​ settings, a default gPXE 
-script** is built in.  The default ​script ​simply boots from DHCP:+script is built in
 + 
 +Anyway, I have created a ''​multiembed''​ branch with these features implemented. 
 +I think most of this solution has already been thought about by hpa, mcb30, and 
 +mdc.  I just wanted to code something last night; hope this is a step in the 
 +right direction. 
 + 
 +//Update: removed detailed description since the reworked patch changes things 
 +slightly//​. ​ See [[.:​week8#​sat_19_2008|newer entry]]. 
 + 
 +==== Fri 18 2008 ==== 
 +**Back to the b44 driver**, I have removed uhmalloc and am using malloc'​s allocator instead. ​ Once this reworking is complete, I can move up to the DMA mapping API to support DMA pools. ​ Then I will send these patches for review and merge before sending the actual b44 driver. 
 + 
 +**Sent cleaned up gpxelinux merge patch** for mainline review. 
 + 
 +==== Sat 19 2008 ==== 
 +Git commits: 
 +  * [[http://​git.etherboot.org/?​p=people/​stefanha/​gpxe.git;​a=commit;​h=26b0197cb63725a58f596bf279d4e37e6862b5c2|[image] Make dependencies for EMBEDDED_IMAGE]] 
 +  * [[http://​git.etherboot.org/?​p=people/​stefanha/​gpxe.git;​a=commit;​h=16dc7dddc05ef292dcda3f4c67632ef911eb984c|[image] Clean up embedded image support]] 
 + 
 +**Reworked multiembed patch**.  The following text documents the user-visible changes: 
 + 
 +=== Embedded images === 
 +gPXE normally fetches images over the network using TFTP, HTTP, iSCSI, or other network protocols. ​ It is also possible to //embed// an image file inside gPXE and make it available without fetching over the network. 
 + 
 +By embedding gPXE scripts, you can customize gPXE's behavior before its first network access. ​ For example, static network configuration can be done by embedding a gPXE script
 + 
 +Images are embedded when building gPXE with ''​make''​:
 <​code>​ <​code>​
-#!gpxe +$ make EMBEDDED_IMAGE=../​contrib/​scripts/​static.gpxe
-autoboot+
 </​code>​ </​code>​
  
-**Static network configuration** works just like you'd expect: you build with +This builds a gPXE image which executes the ''​static.gpxe'' ​script on startup.  ​The ''​static.gpxe'' ​sample script works with QEMU's user network stack:
-''​EMBEDDED_IMAGE=mystatic.gpxe''​.  ​This replaces the default script with our +
-custom script Here is a sample script ​that works with QEMU's user network +
-stack:+
 <​code>​ <​code>​
 #!gpxe #!gpxe
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 </​code>​ </​code>​
  
-**Embedding PXELINUX** is also pretty easythis time by using the multiple +Multiple images can be embedded: 
-embedded ​image feature.  ​We embed ''​pxelinux.0'' ​//and// a little ​script ​to do +<​code>​ 
-DHCP.  Once DHCP is complete, ​the little script boots ''​pxelinux.0'':​+$ make EMBEDDED_IMAGE=../​contrib/​scripts/​gpxelinux.gpxe,/​usr/​lib/​syslinux/​pxelinux.0 
 +</​code>​ 
 + 
 +This builds a gPXE image which executes the ''​gpxelinux.gpxe''​ script on startup.  ​The ''​gpxelinux.gpxe''​ script ​performs ​DHCP before loading ​the embedded ​''​pxelinux.0'' ​image and executing it:
 <​code>​ <​code>​
 #!gpxe #!gpxe
 dhcp net0 dhcp net0
 +imgload img1
 boot boot
 </​code>​ </​code>​
  
-Multiple embedded images theoretically allow embedding a ''​vmlinuz''​ and +Why did we write ''​imgload img1''​ and not ''​imgload pxelinux.0''​ Embedded images are automatically named ''​img#''​ starting from ''​img0''​. ​ They do not retain their original filenames. ​ For example: 
-''​initrd'' ​inside gPXE.  This isn't practical for space-constrained image types +<​code>​ 
-like floppy disk or ROM images.+$ make EMBEDDED_IMAGE=first.gpxe,​second.gpxe,​third.gpxe 
 +                      ^ img0     ^ img1      ^ img2 
 +</​code>​
  
-AnywayI have created a ''​multiembed'' ​branch with these features implemented+Alsonotice that we had to use ''​imgload''​ before doing ''​boot''​. ​ This is because embedded images are not automatically loaded for booting. ​ They are simply available as if they had been fetched using ''​imgfetch''​. 
-I think most of this solution has already been thought about by hpa, mcb30, and + 
-mdc.  ​I just wanted ​to code something last night; hope this is a step in the +The full behavior is described as follows. ​ When gPXE starts, it does the equivalent ​of ''​imgfetch''​ for every embedded image and assigns them names starting with ''​img0''​ for the first image. ​ Then it loads and boots the first image (''​img0''​). ​ If booting ''​img0''​ failsit <​del>​removes all embedded images ​and</​del>​ gives up. 
-right direction.+ 
 +**This paragraph does not apply to the multiembed code in gPXE mainline**.  ​It's interesting ​to note that gPXE //always// embeds an image, even if you do not give it one.  By specifying an embedded image, you are overriding the default embedded image. ​ The default embedded image is a script that tries DHCP booting from each network interface ​in turn: 
 +<​code>​ 
 +#!gpxe 
 +autoboot 
 +</​code>​
  
 **Limitations of my patch**: **Limitations of my patch**:
-  * The semantics of replacing ''​autoboot()''​ with embedded images are not 100% correct.  The autoboot process will bring up each network interface in turn using DHCP and attempt to run the embedded image or fetch a file from the network. ​ Now, embedded images ​are only once and without any network interface being up or configured.+  * The semantics of replacing ''​autoboot()''​ with embedded images are not 100% compatible with past gPXE behavior.  The autoboot process will bring up each network interface in turn using DHCP and attempt to run the embedded image or fetch a file from the network. ​ Now, embedded images ​run only once and without any network interface being up or configured.
  
-Next steps: +===== Next week ===== 
-  ​* ​[shutdown] Fine-grained shutdown including removing gPXE allocated memory and freeing up PXE+UNDI, if necessary. +On to [[.:week9|Week 9]].
-  * [uhmalloc] Kill this patch, use ''​malloc''​ allocator instead for DMA buffers. +
-  * [DMADMA pool API so drivers can reserve DMA buffers on ''​open()''​. +
-  * [b44] Cleanup, testing, performance. +
-  * [bzImage] Expand the heap size to the full 64K segment when loading a bzImage kernel with version 2.02 or higher. +
-  * [GDBReal-mode remote debugging.+

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