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contrib/plugins: protect execlog's last_exec expansion

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We originally naively treated expansion as safe because we expected
each new CPU/thread to appear in order. However the -M raspi2 model
triggered a case where a new high cpu_index thread started executing
just before a smaller one.

Clean this up by converting the GArray into the simpler GPtrArray and
then holding a lock for the expansion.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Alexandre Iooss <erdnaxe@crans.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20221027183637.2772968-29-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2022-10-27 19:36:34 +01:00
parent a4cc0b7dd7
commit 14fd492b89
1 changed files with 30 additions and 8 deletions
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38
contrib/plugins/execlog.c
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@ -18,11 +18,30 @@
QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
/* Store last executed instruction on each vCPU as a GString */
GArray *last_exec;
static GPtrArray *last_exec;
static GMutex expand_array_lock;
static GPtrArray *imatches;
static GArray *amatches;
/*
* Expand last_exec array.
*
* As we could have multiple threads trying to do this we need to
* serialise the expansion under a lock. Threads accessing already
* created entries can continue without issue even if the ptr array
* gets reallocated during resize.
*/
static void expand_last_exec(int cpu_index)
{
g_mutex_lock(&expand_array_lock);
while (cpu_index >= last_exec->len) {
GString *s = g_string_new(NULL);
g_ptr_array_add(last_exec, s);
}
g_mutex_unlock(&expand_array_lock);
}
/**
* Add memory read or write information to current instruction log
*/
@ -33,7 +52,7 @@ static void vcpu_mem(unsigned int cpu_index, qemu_plugin_meminfo_t info,
/* Find vCPU in array */
g_assert(cpu_index < last_exec->len);
s = g_array_index(last_exec, GString *, cpu_index);
s = g_ptr_array_index(last_exec, cpu_index);
/* Indicate type of memory access */
if (qemu_plugin_mem_is_store(info)) {
@ -61,11 +80,10 @@ static void vcpu_insn_exec(unsigned int cpu_index, void *udata)
GString *s;
/* Find or create vCPU in array */
while (cpu_index >= last_exec->len) {
s = g_string_new(NULL);
g_array_append_val(last_exec, s);
if (cpu_index >= last_exec->len) {
expand_last_exec(cpu_index);
}
s = g_array_index(last_exec, GString *, cpu_index);
s = g_ptr_array_index(last_exec, cpu_index);
/* Print previous instruction in cache */
if (s->len) {
@ -163,7 +181,7 @@ static void plugin_exit(qemu_plugin_id_t id, void *p)
guint i;
GString *s;
for (i = 0; i < last_exec->len; i++) {
s = g_array_index(last_exec, GString *, i);
s = g_ptr_array_index(last_exec, i);
if (s->str) {
qemu_plugin_outs(s->str);
qemu_plugin_outs("\n");
@ -201,7 +219,11 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
* Initialize dynamic array to cache vCPU instruction. In user mode
* we don't know the size before emulation.
*/
last_exec = g_array_new(FALSE, FALSE, sizeof(GString *));
if (info->system_emulation) {
last_exec = g_ptr_array_sized_new(info->system.max_vcpus);
} else {
last_exec = g_ptr_array_new();
}
for (int i = 0; i < argc; i++) {
char *opt = argv[i];