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All memory dereferences during leak search are checked either with aspacemgr or using the VA-bits. So, in theory, no memory fault should occur. However, the leak search is done so as to resist to e.g. - desynchronisation between the real pages mapped and the aspacemgr state. - client pages mprotected against reading - any other reason why dereferencing a client address would fail. So, the function lc_scan_memory installs a fault catcher that is called if a memory fault signal is raised during memory scan. However, memory dereference is also done in the function heuristic_reachedness. So, this function must also resist to memory fault. This patch also installs a fault catcher for the function heuristic_reachedness. More in details, the following changes are done: * pub_tool_signal.h and m_signals.c : VG_(set_fault_catcher) now returns the previously set fault catcher. This is needed so that heuristic_reachedness/lc_scan_memory can save and restore the previous fault catcher. * mc_leakcheck.c: Addition of leak_search_fault_catcher that contains the common code for the (currently 2) fault catchers used during leak search. * Modification of heuristic_reachedness and lc_scan_memory: Add 2 (small) specific fault catcher that are calling the common leak_search_fault_catcher. * The way sigprocmask is handled has been changed: Before this patch, lc_scan_memory was saving/restoring the procsigmask for each scanned block (and was restoring it when the fault catcher was longjmp-ing back to lc_scan_memory in case of SEGV or BUS. This was causing 2 system calls for each block scanned. Now, lc_scan_memory and heuristic_reachedness are not saving/restoring the procmask: the work to reset the sigprocmask is only done in leak_search_fault_catcher. This is more efficient as no syscall anymore is done during leak search, except for (normally) unfrequent SIGSEGV/BUS. It is also simpler as signal handling is now done at a single place. It is ok to reset the procmask (in fact, just remove the caught signal from the process sigmask) as during leak search, no other activity than the leak search is on-going, and so no other SEGV/BUS can be received while the handler runs. This gives moderate speed improvements for applications allocating a lot of blocks (about 10% improvement when leak searching in 1 million small blocks). Test case (slightly modified) by Matthias Schwarzott. git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15716