Re: [PATCH] plugins: fix qemu_plugin_reset

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

Sent a v2 to fix a leak issue with tcg_ctx->plugin_tb.

On 10/14/24 15:33, Pierrick Bouvier wrote:
> 34e5e1 refactored the plugin context initialization. After this change,
> tcg_ctx->plugin_insn is not reset inconditionnally anymore, but only if
> one plugin at least is active.
> 
> When uninstalling the last plugin active, we stopped reinitializing
> tcg_ctx->plugin_insn, which leads to memory callbacks being emitted.
> This results in an error as they don't appear in a plugin op sequence as
> expected.
> 
> The correct fix is to make sure we reset plugin translation variables
> after current block translation ends. This way, we can catch any
> potential misuse of those after a given block, in more than fixing the
> current bug.
> 
> Fixes: https://gitlab.com/qemu-project/qemu/-/issues/2570
> Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
> ---
>   accel/tcg/plugin-gen.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/accel/tcg/plugin-gen.c b/accel/tcg/plugin-gen.c
> index 2ee4c22befd..2a8c8b2ad14 100644
> --- a/accel/tcg/plugin-gen.c
> +++ b/accel/tcg/plugin-gen.c
> @@ -467,4 +467,9 @@ void plugin_gen_tb_end(CPUState *cpu, size_t num_insns)
>   
>       /* inject the instrumentation at the appropriate places */
>       plugin_gen_inject(ptb);
> +
> +    /* reset plugin translation state */
> +    tcg_ctx->plugin_db = NULL;
> +    tcg_ctx->plugin_insn = NULL;
> +    tcg_ctx->plugin_tb = NULL;
>   }