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Re: Breakpoint problem when running on gdb-4.18 arm/thumb simulator target
- To: karuottu at freenet dot hut dot fi
- Subject: Re: Breakpoint problem when running on gdb-4.18 arm/thumb simulator target
- From: Scott Bambrough <scottb at netwinder dot org>
- Date: Thu, 13 Jan 2000 09:39:34 -0500
- CC: "Lim, Sung-taek" <totohero at poppy dot snu dot ac dot kr>, crossgcc mailinglist <crossgcc at sourceware dot cygnus dot com>, gdb at sourceware dot cygnus dot com
- Organization: Rebel.com
- References: <001401bf5db1$10157720$8f742e93@snu.ac.kr> <387DB7E5.E479256B@freenet.hut.fi>
Kai Ruottu wrote:
>
> "Lim, Sung-taek" wrote:
> >
> Generally for the ARM-target it would be better to try the GDB snapshots. I don't
> remember this phenomen from my gdb-4.18.x's, but perhaps I had updated some ARM-stuff
> from the snapshots before building my first GDB for arm-elf...
This is true. After the merge of the ARM Linux code, the number of testsuite
failures has fallen according to the last reports I got from Stan.
> Some targets had their 'opcodes' changed for the simulated 'breakpoint' instruction,
> perhaps ARM was one of these. Anyway the synchronization between the binutils, GCC and
> GDB hasn't been the best, and one must try more than one release before getting the
> toolset to work. For arm-elf the '991130' and newer binutils seem to be broken. The
> linked executables will not load into older or current GDBs (like Insight).
ARM CPU's currently have no hardware support for breakpoints that I know of.
GDB uses two approaches for breakpoints on ARM systems. On systems such as ARM
Linux the OS has support for breakpoints in the kernel via a software
interrupt. The instruction where the breakpoint occurs is replaced by a
software interrupt call into the kernel. In embedded systems, with no such
kernel support, an undefined instruction is used and GDB provides a handler for
the undefined instruction trap. See the comments in tm-arm.h in the latest
snapshot for more detail.
> > the patch can be found at:
> > http://poppy.snu.ac.kr/~totohero/arm-linux/gdb-4.18-dal-patch
The current snapshot should build and work fine for most things from what I
understand.
Scott
--
Scott Bambrough - Software Engineer
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