Re: [RFC PATCH v2 3/7] contrib/plugins: add plugin showcasing new trap related API

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

On 10/19/24 09:39, Julian Ganz wrote:
> We recently introduced new plugin API for registration of trap related
> callbacks. This change introduces a minimal plugin showcasing the new
> API. It simply counts the occurances of interrupts, exceptions and
> semihosting events per CPU and reports the counts when exitting.
> 
> Signed-off-by: Julian Ganz <neither@nut.email>
> ---
>   contrib/plugins/Makefile |  1 +
>   contrib/plugins/traps.c  | 89 ++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 90 insertions(+)
>   create mode 100644 contrib/plugins/traps.c
> 
> diff --git a/contrib/plugins/Makefile b/contrib/plugins/Makefile
> index bbddd4800f..6085fd701f 100644
> --- a/contrib/plugins/Makefile
> +++ b/contrib/plugins/Makefile
> @@ -31,6 +31,7 @@ NAMES += drcov
>   NAMES += ips
>   NAMES += stoptrigger
>   NAMES += cflow
> +NAMES += traps
>   
>   ifeq ($(CONFIG_WIN32),y)
>   SO_SUFFIX := .dll
> diff --git a/contrib/plugins/traps.c b/contrib/plugins/traps.c
> new file mode 100644
> index 0000000000..2a38dbb8b3
> --- /dev/null
> +++ b/contrib/plugins/traps.c
> @@ -0,0 +1,89 @@
> +/*
> + * Copyright (C) 2024, Julian Ganz <neither@nut.email>
> + *
> + * Traps - count traps
> + *
> + * License: GNU GPL, version 2 or later.
> + *   See the COPYING file in the top-level directory.
> + */
> +
> +#include <stdio.h>
> +
> +#include <qemu-plugin.h>
> +
> +QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
> +
> +typedef struct {
> +    uint64_t interrupts;
> +    uint64_t exceptions;
> +    uint64_t semihosting;
> +    bool active;
> +} TrapCounters;
> +
> +static TrapCounters *traps;
> +size_t max_vcpus;
> +
> +static void vcpu_init(qemu_plugin_id_t id, unsigned int vcpu_index)
> +{
> +    traps[vcpu_index].active = true;
> +}
> +
> +static void vcpu_interrupt(qemu_plugin_id_t id, unsigned int vcpu_index)
> +{
> +    traps[vcpu_index].interrupts++;
> +}
> +
> +static void vcpu_exception(qemu_plugin_id_t id, unsigned int vcpu_index)
> +{
> +    traps[vcpu_index].exceptions++;
> +}
> +
> +static void vcpu_semihosting(qemu_plugin_id_t id, unsigned int vcpu_index)
> +{
> +    traps[vcpu_index].semihosting++;
> +}
> +
> +static void plugin_exit(qemu_plugin_id_t id, void *p)
> +{
> +    g_autoptr(GString) report;
> +    report = g_string_new("VCPU, interrupts, exceptions, semihosting\n");
> +    int vcpu;
> +
> +    for (vcpu = 0; vcpu < max_vcpus; vcpu++) {
> +        TrapCounters *rec = &traps[vcpu];
> +        if (rec->active) {
> +            g_string_append_printf(report,
> +                                   "% 4d, % 10"PRId64", % 10"PRId64", % 10"
> +                                   PRId64"\n",
> +                                   vcpu,
> +                                   rec->interrupts, rec->exceptions,
> +                                   rec->semihosting);
> +        }
> +    }
> +
> +    qemu_plugin_outs(report->str);
> +}
> +
> +QEMU_PLUGIN_EXPORT
> +int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
> +                        int argc, char **argv)
> +{
> +    if (!info->system_emulation) {
> +        fputs("trap plugin can only be used in system emulation mode.\n",
> +              stderr);
> +        return -1;
> +    }
> +
> +    max_vcpus = info->system.max_vcpus;
> +    traps = calloc(max_vcpus, sizeof(TrapCounters));


> +    qemu_plugin_register_vcpu_init_cb(id, vcpu_init);
> +    qemu_plugin_vcpu_for_each(id, vcpu_init);
> +
> +    qemu_plugin_register_vcpu_interrupt_cb(id, vcpu_interrupt);
> +    qemu_plugin_register_vcpu_exception_cb(id, vcpu_exception);
> +    qemu_plugin_register_vcpu_semihosting_cb(id, vcpu_semihosting);
> +
> +    qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
> +
> +    return 0;
> +