futex.cxx

// cosmos
#include <cosmos/formatting.hxx>
 
// clues
#include <clues/items/futex.hxx>
#include <clues/macros.h>
#include <clues/private/utils.hxx>
 
namespace clues::item {
 
std::string FutexOperation::str() const {
        /*
         * there are a number of undocumented constants and some flags can be
         * or'd in like FUTEX_PRIVATE_FLAG. Without exactly understanding that
         * we can't sensibly trace this ...
         * it seems the man page doesn't tell the complete story, strace
         * understands all the "private" stuff that can also be found in the
         * header.
         */
        auto format_op = [](int val) -> std::string {
                switch (val & FUTEX_CMD_MASK) {
                        CASE_ENUM_TO_STR(FUTEX_CMP_REQUEUE);
                        CASE_ENUM_TO_STR(FUTEX_CMP_REQUEUE_PI);
                        CASE_ENUM_TO_STR(FUTEX_FD);
                        CASE_ENUM_TO_STR(FUTEX_LOCK_PI);
                        CASE_ENUM_TO_STR(FUTEX_LOCK_PI2);
                        CASE_ENUM_TO_STR(FUTEX_REQUEUE);
                        CASE_ENUM_TO_STR(FUTEX_TRYLOCK_PI);
                        CASE_ENUM_TO_STR(FUTEX_UNLOCK_PI);
                        CASE_ENUM_TO_STR(FUTEX_WAIT);
                        CASE_ENUM_TO_STR(FUTEX_WAIT_BITSET);
                        CASE_ENUM_TO_STR(FUTEX_WAIT_REQUEUE_PI);
                        CASE_ENUM_TO_STR(FUTEX_WAKE);
                        CASE_ENUM_TO_STR(FUTEX_WAKE_BITSET);
                        CASE_ENUM_TO_STR(FUTEX_WAKE_OP);
                        default: return cosmos::sprintf("unknown (%d)", val);
                }
        };
 
        const auto val = valueAs<int>();
        BITFLAGS_FORMAT_START_COMBINED(m_flags, val);
 
        BITFLAGS_STREAM() << format_op(val);
 
        if (!m_flags.none()) {
                BITFLAGS_STREAM() << '|';
                BITFLAGS_ADD(FUTEX_PRIVATE_FLAG);
                BITFLAGS_ADD(FUTEX_CLOCK_REALTIME);
        }
 
        return BITFLAGS_STR();
}
 
void FutexOperation::processValue(const Tracee &) {
        m_cmd = Command{valueAs<int>() & FUTEX_CMD_MASK};
        m_flags = Flags{valueAs<int>() xor cosmos::to_integral(m_cmd)};
}
 
namespace {
 
std::string get_label(const FutexWakeOperation::Operation op) {
        switch (cosmos::to_integral(op)) {
                CASE_ENUM_TO_STR(FUTEX_OP_SET);
                CASE_ENUM_TO_STR(FUTEX_OP_ADD);
                CASE_ENUM_TO_STR(FUTEX_OP_OR);
                CASE_ENUM_TO_STR(FUTEX_OP_ANDN);
                CASE_ENUM_TO_STR(FUTEX_OP_XOR);
                default: return cosmos::sprintf("unknown (%d)", cosmos::to_integral(op));
        }
}
 
std::string get_label(const FutexWakeOperation::Comparator cmp) {
        switch (cosmos::to_integral(cmp)) {
                CASE_ENUM_TO_STR(FUTEX_OP_CMP_EQ);
                CASE_ENUM_TO_STR(FUTEX_OP_CMP_NE);
                CASE_ENUM_TO_STR(FUTEX_OP_CMP_LT);
                CASE_ENUM_TO_STR(FUTEX_OP_CMP_LE);
                CASE_ENUM_TO_STR(FUTEX_OP_CMP_GT);
                CASE_ENUM_TO_STR(FUTEX_OP_CMP_GE);
                default: return cosmos::sprintf("unknown (%d)", cosmos::to_integral(cmp));
        }
}
 
}
 
void FutexWakeOperation::processValue(const Tracee &) {
        const auto raw = valueAs<uint32_t>();
        /*
         * the integer is structured like this:
         *
         * <4 bits Operation><4 bits Comparator><12 bits oparg><12 bits cmparg>
         *
         * where the upper bit of the operation is the optional "shift arg"
         * flag.
         */
 
        const auto op_bits = raw >> 28;
        /*
         * NOTE: there's a bug in man futex(2), which names FUTEX_OP_ARG_SHIFT
         * here instead.
         */
        m_op = Operation{op_bits & (~FUTEX_OP_OPARG_SHIFT)};
        m_shift_arg = op_bits & FUTEX_OP_OPARG_SHIFT;
        m_comp = Comparator{(raw >> 24) & 0xF};
        m_oparg = (raw >> 12) & 0xFFF;
        m_cmparg = raw & 0xFFF;
 
}
 
std::string FutexWakeOperation::str() const {
        return cosmos::sprintf("{op=%s%s, cmp=%s, oparg=%u, cmparg=%u}",
                get_label(m_op).c_str(),
                m_shift_arg ? "|FUTEX_OP_OPARG_SHIFT" : "",
                get_label(m_comp).c_str(),
                m_oparg,
                m_cmparg);
}
 
} // end ns