linux-kernel - Re: [PATCH 5/7] kcov: add ioctl(KCOV_UNIQUE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAG_fn=VfLhCNdU7Yu5D_nWuaxF7nU=YVirK2aTPM6h9o2wsy5A@mail.gmail.com>
Date: Wed, 23 Apr 2025 15:30:18 +0200
From: Alexander Potapenko <glider@...gle.com>
To: glider@...gle.com
Cc: quic_jiangenj@...cinc.com, linux-kernel@...r.kernel.org, 
	kasan-dev@...glegroups.com, Aleksandr Nogikh <nogikh@...gle.com>, 
	Andrey Konovalov <andreyknvl@...il.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Ingo Molnar <mingo@...hat.com>, Josh Poimboeuf <jpoimboe@...nel.org>, Marco Elver <elver@...gle.com>, 
	Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 5/7] kcov: add ioctl(KCOV_UNIQUE_ENABLE)

>  void notrace __sanitizer_cov_trace_pc_guard(u32 *guard)
>  {
> -       if (!check_kcov_mode(KCOV_MODE_TRACE_PC, current))
> -               return;
> +       u32 pc_index;
> +       enum kcov_mode mode = get_kcov_mode(current);
>
> -       sanitizer_cov_write_subsequent(current->kcov_state.s.trace,
> -                                      current->kcov_state.s.trace_size,
> -                                      canonicalize_ip(_RET_IP_));
> +       switch (mode) {
> +       case KCOV_MODE_TRACE_UNIQUE_PC:
> +               pc_index = READ_ONCE(*guard);
> +               if (unlikely(!pc_index))
> +                       pc_index = init_pc_guard(guard);
> +
> +               /*
> +                * Use the bitmap for coverage deduplication. We assume both
> +                * s.bitmap and s.trace are non-NULL.
> +                */
> +               if (likely(pc_index < current->kcov_state.s.bitmap_size))
> +                       if (test_and_set_bit(pc_index,

A promising improvement would be removing the LOCK prefix here by
changing test_and_set_bit() to __test_and_set_bit().

> +                                            current->kcov_state.s.bitmap))
> +                               return;
> +               /* If the PC is new, write it to the trace. */
> +               fallthrough;
> +       case KCOV_MODE_TRACE_PC:
> +               sanitizer_cov_write_subsequent(current->kcov_state.s.trace,
> +                                              current->kcov_state.s.trace_size,
> +                                              canonicalize_ip(_RET_IP_));
> +               break;
> +       default:
> +               return;
> +       }
>  }
>  EXPORT_SYMBOL(__sanitizer_cov_trace_pc_guard);