Jan Kiszka wrote:
> Philippe Gerum wrote:
>>>> (*) You could avoid passing the function name in the systrace calls, by
>>>> relying on the value of __FUNCTION__, with a small hack to trimm the
>>>> __wrap_ prefix when needed. Making tracepoints less hairy would ease my
>>>> pain reading this stuff.
>>> OK, but let's not spend brain cycles on this until we know if and how we
>>> can separate the entry/exit tracing from the traced service. If we could
>>> leave existing lib code untouched, I would be happier as well.
>>>
>> It does matter because it reduce visual clutter, and that's a
>> prerequisite for merging, that's why I'm suggesting it.
>> We already have an automated instrumentation tool for the simulator, but
>> I'm not sure automatically inserted tracepoints would always be relevant
>> in all cases.
>
> Doesn't it rely on a patched gcc? Here is a suggestion for an
> instrumentation procedure based on standard tools:
>
>
> lib.h:
> ------
> int my_lib_func(int arg1, const char *arg2);
>
> lib.c:
> ------
> int my_lib_func(int arg1, const char *arg2)
> {
> return 13;
> }
>
> main.c:
> -------
> #include <stdio.h>
> #include "lib.h"
> main()
> {
> printf("my_lib_func = %d\n",
> my_lib_func(1, "hello"));
> }
>
>
> So far, so ordinary. Now we add entry/exit tracing for my_lib_func:
>
>
> trace.c
> -------
> #include <stdio.h>
> #include "lib.h"
> int __trace_my_lib_func(int arg1, const char *arg2)
> {
> int ret;
> printf("entry: arg1 = %d, arg2 = %s\n", arg1, arg2);
> ret = my_lib_func(arg1, arg2);
> printf("exit: ret = %d\n", ret);
> return ret;
> }
>
> Makefile:
> ---------
> ifneq (,$(TRACE))
> TRACELIB=trace.o
> endif
>
> main: main.c lib.o
>
> lib.o: lib.c $(TRACELIB)
> gcc -c -o $@ $<
> ifneq (,$(TRACE))
> ld -r -o [EMAIL PROTECTED] $@ $(TRACELIB)
> objcopy --redefine-sym my_lib_func=__orig_my_lib_func \
> --redefine-sym __trace_my_lib_func=my_lib_func [EMAIL
> PROTECTED] $@We could even build this symbol list dynamically by looking for everything that starts with "__trace_". That way, no one would have to maintain lists of traced functions in separated files or so. > rm -f [EMAIL PROTECTED] > endif > > clean: > rm -f *.o main > > > Build with "make TRACE=1" to get the traced variant, or call "make" for > non-traced mode. > > This means we have a switch in the build process, we don't need to touch > the library sources. We only have to add a __trace_xxx() version for > every xxx() that can even use original headers to call into the original > service. Converting the Makefile stuff into something more handy for > autotools shouldn't be tricky. > > There is just one no-go: functions with variable argument lists. > Fortunately, the only one that comes into my mind right now, > [rtdm_]ioctl(), has a single well-known "unknown" argument and needs to > be unrolled unconditionally anyway. > > What do you think? > > Jan >
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