[RFC] [PATCH 0/4] ARM: kprobes: Infrastructure to support probes in Thumb code

[Nicolas Pitre]

On Mon, 21 Mar 2011, Tixy wrote:

> On Mon, 2011-03-21 at 12:01 -0400, Nicolas Pitre wrote:
> > Why not always using a 16-bit Thumb breakpoint instruction even in place 
> > of a 32-bit Thumb instruction?  This way you sidestep all the issues 
> > about atomically updating the instruction across two words.  The 
> > instruction to emulate might still be 32-bit and therefore pc would be 
> > advanced appropriately.
> 
> If the breakpoint is in an IT block and its execution condition is false
> then the breakpoint may not cause an exception and the CPU will go on
> and try and execute the other half of the instruction.

yeah... bummer.

In this case this might be a worthwhile optimization to not do the heavy 
dance when the instruction is word aligned.


Nicolas