Re: [RFC PATCH v3 11/11] tests: add plugin asserting correctness of discon event's to_pc

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 12/2/24 11:41, Julian Ganz wrote:
> We recently introduced plugin API for the registration of callbacks for
> discontinuity events, specifically for interrupts, exceptions and host
> call events. The callback receives, among other information, the VCPU
> index and the PC after the event. This change introduces a test plugin
> asserting that particular behaviour.
> ---
>   tests/tcg/plugins/discons.c   | 95 +++++++++++++++++++++++++++++++++++
>   tests/tcg/plugins/meson.build |  2 +-
>   2 files changed, 96 insertions(+), 1 deletion(-)
>   create mode 100644 tests/tcg/plugins/discons.c
> 
> diff --git a/tests/tcg/plugins/discons.c b/tests/tcg/plugins/discons.c
> new file mode 100644
> index 0000000000..54e52f563a
> --- /dev/null
> +++ b/tests/tcg/plugins/discons.c
> @@ -0,0 +1,95 @@
> +/*
> + * Copyright (C) 2024, Julian Ganz <neither@nut.email>
> + *
> + * License: GNU GPL, version 2 or later.
> + *   See the COPYING file in the top-level directory.
> + */

Would be nice to include a description of the plugin here.

> +#include <stdio.h>
> +
> +#include <qemu-plugin.h>
> +
> +QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
> +
> +struct cpu_state {
> +    uint64_t next_pc;
> +    bool has_next;
> +};
> +
> +static struct qemu_plugin_scoreboard *states;
> +
> +static bool abort_on_mismatch;
> +
> +static void vcpu_discon(qemu_plugin_id_t id, unsigned int vcpu_index,
> +                        enum qemu_plugin_discon_type type, uint64_t from_pc,
> +                        uint64_t to_pc)
> +{
> +    struct cpu_state *state = qemu_plugin_scoreboard_find(states, vcpu_index);
> +    state->next_pc = to_pc;
> +    state->has_next = true;
> +}
> +
> +static void insn_exec(unsigned int vcpu_index, void *userdata)
> +{
> +    struct cpu_state *state = qemu_plugin_scoreboard_find(states, vcpu_index);
> +    uint64_t pc = (uint64_t) userdata;
> +    GString* report;
> +
> +    if (state->has_next) {
> +        if (state->next_pc != pc) {
> +            report = g_string_new("Trap target PC mismatch\n");
> +            g_string_append_printf(report,
> +                                   "Expected:    %"PRIx64"\nEncountered: %"
> +                                   PRIx64"\n",
> +                                   state->next_pc, pc);
> +            qemu_plugin_outs(report->str);
> +            if (abort_on_mismatch) {
> +                g_abort();
> +            }
> +            g_string_free(report, true);
> +        }
> +        state->has_next = false;
> +    }
> +}

When booting an arm64 vm, I get this message:
Trap target PC mismatch
Expected:    23faf3a80
Encountered: 23faf3a84

 From what I understand, it means that the next_pc we have is incorrect.

> +
> +static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
> +{
> +    size_t i;
> +    size_t n_insns = qemu_plugin_tb_n_insns(tb);
> +
> +    for (i = 0; i < n_insns; i++) {
> +        struct qemu_plugin_insn * insn = qemu_plugin_tb_get_insn(tb, i);
> +        uint64_t pc = qemu_plugin_insn_vaddr(insn);
> +        qemu_plugin_register_vcpu_insn_exec_cb(insn, insn_exec,
> +                                               QEMU_PLUGIN_CB_NO_REGS,
> +                                               (void*) pc);
> +    }
 > +}> +
> +QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
> +                                           const qemu_info_t *info,
> +                                           int argc, char **argv)
> +{
> +    int i;
> +
> +    for (i = 0; i < argc; i++) {
> +        char *opt = argv[i];
> +        g_auto(GStrv) tokens = g_strsplit(opt, "=", 2);
> +        if (g_strcmp0(tokens[0], "abort") == 0) {
> +            if (!qemu_plugin_bool_parse(tokens[0], tokens[1], &abort_on_mismatch)) {
> +                fprintf(stderr, "boolean argument parsing failed: %s\n", opt);
> +                return -1;
> +            }
> +        } else {
> +            fprintf(stderr, "option parsing failed: %s\n", opt);
> +            return -1;
> +        }
> +    }
> +
> +    states = qemu_plugin_scoreboard_new(sizeof(struct cpu_state));
> +
> +    qemu_plugin_register_vcpu_discon_cb(id, QEMU_PLUGIN_DISCON_ALL,
> +                                        vcpu_discon);
> +    qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
> +
> +    return 0;
> +}
> diff --git a/tests/tcg/plugins/meson.build b/tests/tcg/plugins/meson.build
> index f847849b1b..f057238da1 100644
> --- a/tests/tcg/plugins/meson.build
> +++ b/tests/tcg/plugins/meson.build
> @@ -1,6 +1,6 @@
>   t = []
>   if get_option('plugins')
> -  foreach i : ['bb', 'empty', 'inline', 'insn', 'mem', 'syscall']
> +  foreach i : ['bb', 'discons', 'empty', 'inline', 'insn', 'mem', 'syscall']
>       if host_os == 'windows'
>         t += shared_module(i, files(i + '.c') + '../../../contrib/plugins/win32_linker.c',
>                           include_directories: '../../../include/qemu',