Messages in this thread | | | Date | Mon, 23 Nov 2009 19:09:39 -0200 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 4/4] perf tools: Add support for breakpoint events in perf tools |
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Em Mon, Nov 23, 2009 at 09:25:28PM +0100, Frederic Weisbecker escreveu: > On Mon, Nov 23, 2009 at 11:06:01PM +0530, K.Prasad wrote: > > With kernel symbols as input it would be possible to derive the bkpt > > length based on the symbol-size, say using kallsyms_lookup_size_offset() > > (although the corresponding length may not be available on the host > > processor such requests can be failed or over-ridden by the user using > > a smaller length), but for addresses I think it is vital to know what > > breakpoint length is desired by the user.
> Yeah. I guess we first need a way to manually add this length, may be:
> mem:addr/len:access
> And as you said, finding it automatically for symbols. But still, > passing symbols to perf attr leads to confusion and complexity if we > want to profile in userspace.
> I think we should find this symbol length from userspace. I'm not sure > how yet, probably using Dwarf. Arnaldo, do you have an idea about that?
DWARF has the type for each variable or struct member, getting its size is straightforward.
Using just /proc/kallsyms all we can do is find the size of a variable by looking at its address and the address of the next one.
- Arnaldo
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