README_DEVELOPERS
outer/.../bin/valgrind --sim-hints=enable-outer --trace-children=yes
\
--smc-check=all-non-file \
--run-libc-freeres=no --tool=cachegrind -v \
inner/.../bin/valgrind --vgdb-prefix=./inner --tool=none -v prog
If you omit the --trace-children=yes, you’ll only monitor Inner’s launcher
program, not its stage2. Outer needs --run-libc-freeres=no, as otherwise
it will try to find and run __libc_freeres in the inner, while libc is not
used by the inner. Inner needs --vgdb-prefix=./inner to avoid inner
gdbserver colliding with outer gdbserver.
Currently, inner does *not* use the client request
VALGRIND_DISCARD_TRANSLATIONS for the JITted code or the code patched for
translation chaining. So the outer needs --smc-check=all-non-file to
detect the modified code.
Debugging the whole thing might imply to use up to 3 GDB:
* a GDB attached to the Outer valgrind, allowing
to examine the state of Outer.
* a GDB using Outer gdbserver, allowing to
examine the state of Inner.
* a GDB using Inner gdbserver, allowing to
examine the state of prog.
The whole thing is fragile, confusing and slow, but it does work well enough
for you to get some useful performance data.
Inner has most of
its output (ie. those lines beginning with "==<pid>==") prefixed with a ’>’,
which helps a lot. However, when running regression tests in an Outer/Inner
setup, this prefix causes the reg test diff to fail. Give
--sim-hints=no-inner-prefix to the Inner to disable the production
of the prefix in the stdout/stderr output of Inner.
The allocator (coregrind/m_mallocfree.c) is annotated with client requests
so Memcheck can be used to find leaks and use after free in an Inner
Valgrind.
The Valgrind "big lock" is annotated with helgrind client requests
so helgrind and drd can be used to find race conditions in an Inner
Valgrind.
All this has not been tested much, so don’t be surprised if you hit problems.
When using self-hosting with an outer Callgrind tool, use ’--pop-on-jump’
(on the outer). Otherwise, Callgrind has much higher memory requirements.
(B) Regression tests in an outer/inner setup:
To run all the regression tests with an outer memcheck, do :
perl tests/vg_regtest --outer-valgrind=../outer/.../bin/valgrind \
--all
To run a specific regression tests with an outer memcheck, do:
perl tests/vg_regtest --outer-valgrind=../outer/.../bin/valgrind \
none/tests/args.vgtest
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