Re: the "load" command and the .bss section

[Daniel Jacobowitz <drow@false.org>]

On Sun, Apr 27, 2008 at 05:09:31AM -0400, Mike Frysinger wrote:
> i was doing a new board port using jtag and so was leveraging the "load" 
> command to setup the initial ELF in the relevant memory regions.  things kept 
> crashing on me and then i realized that the loading process wasnt actually 
> zeroing out the bss.  is there a reason for this ?  i googled and flipped 
> through the manual, but the details on what exactly the "load" command is 
> supposed to do is a bit on sketchy side.  from what i can tell from the gdb 
> source code and the actual output from running the command, it walks the 
> section headers (rather than the program headers ?) and loads up everything 
> that is in the file.  since the bss section doesnt actually exist in the file 
> and is only allocated, that is why it gets skipped ?

Load puts things at their LMA rather than their VMA.  So it assumes
that whatever sets up load -> virtual also handles bss; it's more like
flash programming than like the Linux kernel's loader.  Heck,
sometimes it is flash programming...

IIRC we have a couple of old requests for a version of load which
drops things at their VMA.  That one would have to clear the BSS.

-- 
Daniel Jacobowitz
CodeSourcery