Re: [PULL 00/18] tcg plugins (deprecations, mem apis, contrib plugins)

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 18 Sept 2024 at 22:08, Alex Bennée <alex.bennee@linaro.org> wrote:
>
> The following changes since commit 2b81c046252fbfb375ad30632362fc16e6e22bd5:
>
>   Merge tag 'block-pull-request' of https://gitlab.com/stefanha/qemu into staging (2024-09-17 14:02:18 +0100)
>
> are available in the Git repository at:
>
>   https://gitlab.com/stsquad/qemu.git tags/pull-tcg-plugin-memory-180924-2
>
> for you to fetch changes up to a33f4871e0a0f4bf1cb037ab29fae7df7f2fc658:
>
>   contrib/plugins: avoid hanging program (2024-09-18 21:02:36 +0100)
>
> ----------------------------------------------------------------
> TCG plugin memory instrumentation updates
>
>   - deprecate plugins on 32 bit hosts
>   - deprecate plugins with TCI
>   - extend memory API to save value
>   - add check-tcg tests to exercise new memory API
>   - fix timer deadlock with non-changing timer
>   - add basic block vector plugin to contrib
>   - add cflow plugin to contrib
>   - extend syscall plugin to dump write memory
>   - validate ips plugin arguments meet minimum slice value
>
> ----------------------------------------------------------------

Fails to build on macos:
https://gitlab.com/qemu-project/qemu/-/jobs/7865151156

../tests/tcg/plugins/mem.c:12:10: fatal error: 'endian.h' file not found

endian.h is a Linuxism.

While I'm looking at the code, this caught my eye:

    case QEMU_PLUGIN_MEM_VALUE_U64:
    {
        uint64_t *p = (uint64_t *) &ri->data[offset];
        uint64_t val = be ? htobe64(value.data.u64) : htole64(value.data.u64);
        if (is_store) {
            *p = val;
        } else if (*p != val) {
            unseen_data = true;
        }
        break;
    }

Casting a random byte pointer to uint64_t* like that
and dereferencing it isn't valid -- it can fault if
it's not aligned correctly.

I suspect the plugin needs to define versions of at least some
of the functionality in qemu's include/qemu/bswap.h.

thanks
-- PMM