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tcg: exclude non-memory effecting helpers from instrumentation 

There are actually a whole bunch of helpers that don't affect memory
that we shouldn't instrument. They are helpfully identified by the
TCG_CALL_NO_SIDE_EFFECTS flag which marks out lookup_tb_ptr as well as
a lot of the maths helpers. To avoid the string compare we introduce a
new flag for plugin internals so we skip that too.

Related: #1381
Signed-off-by: Emilio Cota <cota@braap.org>
Message-Id: <20230108164731.61469-4-cota@braap.org>
[AJB: updated to skip all no SE plugins, add flag for plugin helper]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230124180127.1881110-34-alex.bennee@linaro.org>
This commit is contained in:
Emilio Cota 2023-01-24 18:01:25 +00:00 committed by Alex Bennée
parent 0f92d94ae3
commit 17083f6fa6
3 changed files with 8 additions and 4 deletions
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4
accel/tcg/plugin-helpers.h
View File

@ -1,4 +1,4 @@
#ifdef CONFIG_PLUGIN
DEF_HELPER_FLAGS_2(plugin_vcpu_udata_cb, TCG_CALL_NO_RWG, void, i32, ptr)
DEF_HELPER_FLAGS_4(plugin_vcpu_mem_cb, TCG_CALL_NO_RWG, void, i32, i32, i64, ptr)
DEF_HELPER_FLAGS_2(plugin_vcpu_udata_cb, TCG_CALL_NO_RWG | TCG_CALL_PLUGIN, void, i32, ptr)
DEF_HELPER_FLAGS_4(plugin_vcpu_mem_cb, TCG_CALL_NO_RWG | TCG_CALL_PLUGIN, void, i32, i32, i64, ptr)
#endif

2
include/tcg/tcg.h
View File

@ -405,6 +405,8 @@ typedef TCGv_ptr TCGv_env;
#define TCG_CALL_NO_SIDE_EFFECTS 0x0004
/* Helper is G_NORETURN. */
#define TCG_CALL_NO_RETURN 0x0008
/* Helper is part of Plugins. */
#define TCG_CALL_PLUGIN 0x0010
/* convenience version of most used call flags */
#define TCG_CALL_NO_RWG TCG_CALL_NO_READ_GLOBALS

6
tcg/tcg.c
View File

@ -1674,8 +1674,10 @@ void tcg_gen_callN(void *func, TCGTemp *ret, int nargs, TCGTemp **args)
op = tcg_op_alloc(INDEX_op_call, total_args);
#ifdef CONFIG_PLUGIN
/* detect non-plugin helpers */
if (tcg_ctx->plugin_insn && unlikely(strncmp(info->name, "plugin_", 7))) {
/* Flag helpers that may affect guest state */
if (tcg_ctx->plugin_insn &&
!(info->flags & TCG_CALL_PLUGIN) &&
!(info->flags & TCG_CALL_NO_SIDE_EFFECTS)) {
tcg_ctx->plugin_insn->calls_helpers = true;
}
#endif