mirror of https://github.com/torvalds/linux.git
05924717ac
This patch introduces a new algorithm for multiplication of tristate numbers (tnums) that is provably sound. It is faster and more precise when compared to the existing method. Like the existing method, this new algorithm follows the long multiplication algorithm. The idea is to generate partial products by multiplying each bit in the multiplier (tnum a) with the multiplicand (tnum b), and adding the partial products after appropriately bit-shifting them. The new algorithm, however, uses just a single loop over the bits of the multiplier (tnum a) and accumulates only the uncertain components of the multiplicand (tnum b) into a mask-only tnum. The following paper explains the algorithm in more detail: https://arxiv.org/abs/2105.05398. A natural way to construct the tnum product is by performing a tnum addition on all the partial products. This algorithm presents another method of doing this: decompose each partial product into two tnums, consisting of the values and the masks separately. The mask-sum is accumulated within the loop in acc_m. The value-sum tnum is generated using a.value * b.value. The tnum constructed by tnum addition of the value-sum and the mask-sum contains all possible summations of concrete values drawn from the partial product tnums pairwise. We prove this result in the paper. Our evaluations show that the new algorithm is overall more precise (producing tnums with less uncertain components) than the existing method. As an illustrative example, consider the input tnums A and B. The numbers in the parenthesis correspond to (value;mask). A = 000000x1 (1;2) B = 0010011x (38;1) A * B (existing) = xxxxxxxx (0;255) A * B (new) = 0x1xxxxx (32;95) Importantly, we present a proof of soundness of the new algorithm in the aforementioned paper. Additionally, we show that this new algorithm is empirically faster than the existing method. Co-developed-by: Matan Shachnai <m.shachnai@rutgers.edu> Co-developed-by: Srinivas Narayana <srinivas.narayana@rutgers.edu> Co-developed-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu> Signed-off-by: Matan Shachnai <m.shachnai@rutgers.edu> Signed-off-by: Srinivas Narayana <srinivas.narayana@rutgers.edu> Signed-off-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu> Signed-off-by: Harishankar Vishwanathan <harishankar.vishwanathan@rutgers.edu> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Edward Cree <ecree.xilinx@gmail.com> Link: https://arxiv.org/abs/2105.05398 Link: https://lore.kernel.org/bpf/20210531020157.7386-1-harishankar.vishwanathan@rutgers.edu |
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| .. | ||
| bpf | ||
| cgroup | ||
| configs | ||
| debug | ||
| dma | ||
| entry | ||
| events | ||
| gcov | ||
| irq | ||
| kcsan | ||
| livepatch | ||
| locking | ||
| power | ||
| printk | ||
| rcu | ||
| sched | ||
| time | ||
| trace | ||
| .gitignore | ||
| Kconfig.freezer | ||
| Kconfig.hz | ||
| Kconfig.locks | ||
| Kconfig.preempt | ||
| Makefile | ||
| acct.c | ||
| async.c | ||
| audit.c | ||
| audit.h | ||
| audit_fsnotify.c | ||
| audit_tree.c | ||
| audit_watch.c | ||
| auditfilter.c | ||
| auditsc.c | ||
| backtracetest.c | ||
| bounds.c | ||
| capability.c | ||
| cfi.c | ||
| compat.c | ||
| configs.c | ||
| context_tracking.c | ||
| cpu.c | ||
| cpu_pm.c | ||
| crash_core.c | ||
| crash_dump.c | ||
| cred.c | ||
| delayacct.c | ||
| dma.c | ||
| exec_domain.c | ||
| exit.c | ||
| extable.c | ||
| fail_function.c | ||
| fork.c | ||
| freezer.c | ||
| futex.c | ||
| gen_kheaders.sh | ||
| groups.c | ||
| hung_task.c | ||
| iomem.c | ||
| irq_work.c | ||
| jump_label.c | ||
| kallsyms.c | ||
| kcmp.c | ||
| kcov.c | ||
| kexec.c | ||
| kexec_core.c | ||
| kexec_elf.c | ||
| kexec_file.c | ||
| kexec_internal.h | ||
| kheaders.c | ||
| kmod.c | ||
| kprobes.c | ||
| ksysfs.c | ||
| kthread.c | ||
| latencytop.c | ||
| module-internal.h | ||
| module.c | ||
| module_signature.c | ||
| module_signing.c | ||
| notifier.c | ||
| nsproxy.c | ||
| padata.c | ||
| panic.c | ||
| params.c | ||
| pid.c | ||
| pid_namespace.c | ||
| profile.c | ||
| ptrace.c | ||
| range.c | ||
| reboot.c | ||
| regset.c | ||
| relay.c | ||
| resource.c | ||
| resource_kunit.c | ||
| rseq.c | ||
| scftorture.c | ||
| scs.c | ||
| seccomp.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| smpboot.h | ||
| softirq.c | ||
| stackleak.c | ||
| stacktrace.c | ||
| static_call.c | ||
| stop_machine.c | ||
| sys.c | ||
| sys_ni.c | ||
| sysctl-test.c | ||
| sysctl.c | ||
| task_work.c | ||
| taskstats.c | ||
| test_kprobes.c | ||
| torture.c | ||
| tracepoint.c | ||
| tsacct.c | ||
| ucount.c | ||
| uid16.c | ||
| uid16.h | ||
| umh.c | ||
| up.c | ||
| user-return-notifier.c | ||
| user.c | ||
| user_namespace.c | ||
| usermode_driver.c | ||
| utsname.c | ||
| utsname_sysctl.c | ||
| watch_queue.c | ||
| watchdog.c | ||
| watchdog_hld.c | ||
| workqueue.c | ||
| workqueue_internal.h | ||