>>>> Would pairing one rseq_start with two rseq_finish do the trick >>>> there ? >>> >>> Yes, two rseq_finish works, as long as the extra rseq management overhead >>> is not substantial. >> >> I've added a commit implementing rseq_finish2() in my rseq volatile >> dev branch. You can fetch it at: >> >> https://github.com/compudj/linux-percpu-dev/tree/rseq-fallback >> >> I also have a separate test and benchmark tree in addition to the >> kernel selftests here: >> >> https://github.com/compudj/rseq-test >> >> I named the first write a "speculative" write, and the second write >> the "final" write. >> >> Would you like to extend the test cases to cover your intended use-case ? >> > >Hi Dave! > >I just pushed a rseq_finish2() test in my rseq-fallback branch. It implements >a per-cpu buffer holding pointers, and pushes/pops items to/from it. > >To use it: > >cd tools/testing/selftests/rseq >./param_test -T b > >(see -h for advanced usage) > >Let me know if I got it right! Hi Mathieu, Thanks, you beat me to it. I commented on the github, that's pretty much it. > In the kernel, if rather than testing for: > > if ((void __user *)instruction_pointer(regs) < post_commit_ip) { > > we could test for both start_ip and post_commit_ip: > > if ((void __user *)instruction_pointer(regs) < post_commit_ip > && (void __user *)instruction_pointer(regs) >= start_ip) { > > We could perform the failure path (storing NULL into the rseq_cs > field of struct rseq) in C rather than being required to do it in > assembly at addresses >= to post_commit_ip, all because the kernel > would test whether we are within the assembly block address range > using both the lower and upper bounds (start_ip and post_commit_ip). Sounds reasonable to me. I agree it would be best to move the failure path out of the asm if possible.-- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
