Re: [ECOS] MIPS GDB Problems

[Jonathan Larmour <jlarmour at cygnus dot co dot uk>]

Colin Spier wrote:
> 
> If I set up the stub code as you suggest, gdb does not communicate with the
> target unless I rebuild it (gdb) for mips64-elf.  Unfortunately, this still
> doesn't help...

Sorry I assumed that's what you had been doing already. We've found it
certainly makes it easier to use the mips3 opcodes in the assembler, and
for gdb to grok that assembler. Although you can use .set mips3 directives
for that. But your way can work too.

> I tried rebuilding the entire mips gnu toolchain for mips64-elf, and then
> built eCos and my source file (which contains a very simple 'main' that just
> switches an LED on and calls 'breakpoint()') with no -mcpu= or -mips
> directives, and gdb still thinks that the address of main is 0x0.
> 
> I've looked at the assembly code produced by gcc for the source file
> containing my 'main' function, and it definitely contains stabs information.

Try compiling with -ggdb or -gdwarf or -gdwarf-2. Sometimes that helps
although we've never needed it for mips targets in the past. Also if you've
written your own linker script, try discarding the .mdebug section. We've
found that helps.

Also try building without -ffunction-sections -fdata-sections in the
cflags, and -Wl,--gc-sections in the ldflags, as section garbage collection
has been known to interfere with debugging.

> However, 'mips-elf-objdump --debugging' states that the executable file
> contains "no recognized debugging information".  Despite this, when in
> graphical mode, gdb does appear to realise which lines of my 'main' function
> are actually executable code, and those are the only lines at which it will
> attempt to instantiate a breakpoint...
> 
> Has anyone successfully used this toolchain (binutils 2.10.1, gcc 2.95.2,
> insight 5.0) to provide a debugging capability on mips?  Should I have
> applied any patches?

I've done it with versions very close to the above, but not those very
versions other than gcc 2.95.2.

Jifl
-- 
Red Hat, 35 Cambridge Place, Cambridge, UK. CB2 1NS  Tel: +44 (1223) 728762
"Plan to be spontaneous tomorrow."  ||  These opinions are all my own fault