With the new plugin register API we can now track changes to register
values. Currently the implementation is fairly dumb which will slow
down if a large number of register values are being tracked. This
could be improved by only instrumenting instructions which mention
registers we are interested in tracking.
Example usage:
./qemu-aarch64 -D plugin.log -d plugin \
-cpu max,sve256=on \
-plugin contrib/plugins/libexeclog.so,reg=sp,reg=z\* \
./tests/tcg/aarch64-linux-user/sha512-sve
will display in the execlog any changes to the stack pointer (sp) and
the SVE Z registers.
Message-Id: <20240103173349.398526-41-alex.bennee@xxxxxxxxxx>
Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx>
Cc: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
Based-On: <20231025093128.33116-19-akihiko.odaki@xxxxxxxxxx>
---
v3
- just use a GArray for the CPU array
- drop duplicate of cpu_index
---
docs/devel/tcg-plugins.rst | 17 +-
contrib/plugins/execlog.c | 317 +++++++++++++++++++++++++++++++------
2 files changed, 282 insertions(+), 52 deletions(-)
diff --git a/docs/devel/tcg-plugins.rst b/docs/devel/tcg-plugins.rst
index 81dcd43a612..fa7421279f5 100644
--- a/docs/devel/tcg-plugins.rst
+++ b/docs/devel/tcg-plugins.rst
@@ -497,6 +497,22 @@ arguments if required::
$ qemu-system-arm $(QEMU_ARGS) \
-plugin ./contrib/plugins/libexeclog.so,ifilter=st1w,afilter=0x40001808 -d plugin
+This plugin can also dump registers when they change value. Specify the name of the
+registers with multiple ``reg`` options. You can also use glob style matching if you wish::
+
+ $ qemu-system-arm $(QEMU_ARGS) \
+ -plugin ./contrib/plugins/libexeclog.so,reg=\*_el2,reg=sp -d plugin
+
+Be aware that each additional register to check will slow down
+execution quite considerably. You can optimise the number of register
+checks done by using the rdisas option. This will only instrument
+instructions that mention the registers in question in disassembly.
+This is not foolproof as some instructions implicitly change
+instructions. You can use the ifilter to catch these cases:
+
+ $ qemu-system-arm $(QEMU_ARGS) \
+ -plugin ./contrib/plugins/libexeclog.so,ifilter=msr,ifilter=blr,reg=x30,reg=\*_el1,rdisas=on
+
- contrib/plugins/cache.c
Cache modelling plugin that measures the performance of a given L1 cache
@@ -583,4 +599,3 @@ The following API is generated from the inline documentation in
include the full kernel-doc annotations.
.. kernel-doc:: include/qemu/qemu-plugin.h
-
diff --git a/contrib/plugins/execlog.c b/contrib/plugins/execlog.c
index f262e5555eb..c26664c0ab3 100644
--- a/contrib/plugins/execlog.c
+++ b/contrib/plugins/execlog.c
@@ -1,7 +1,7 @@
/*
* Copyright (C) 2021, Alexandre Iooss <erdnaxe@xxxxxxxxx>
*
- * Log instruction execution with memory access.
+ * Log instruction execution with memory access and register changes
*
* License: GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
@@ -15,29 +15,40 @@
#include <qemu-plugin.h>
+typedef struct {
+ struct qemu_plugin_register *handle;
+ GByteArray *last;
+ GByteArray *new;
+ const char *name;
+} Register;
+
+typedef struct CPU {
+ /* Store last executed instruction on each vCPU as a GString */
+ GString *last_exec;
+ /* Ptr array of Register */
+ GPtrArray *registers;
+} CPU;
+
QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
-/* Store last executed instruction on each vCPU as a GString */
-static GPtrArray *last_exec;
+static GArray *cpus;
static GRWLock expand_array_lock;
static GPtrArray *imatches;
static GArray *amatches;
+static GPtrArray *rmatches;
+static bool disas_assist;
+static GMutex add_reg_name_lock;
+static GPtrArray *all_reg_names;
-/*
- * Expand last_exec array.
- *
- * As we could have multiple threads trying to do this we need to
- * serialise the expansion under a lock.
- */
-static void expand_last_exec(int cpu_index)
+static CPU *get_cpu(int vcpu_index)
{
- g_rw_lock_writer_lock(&expand_array_lock);
- while (cpu_index >= last_exec->len) {
- GString *s = g_string_new(NULL);
- g_ptr_array_add(last_exec, s);
- }
- g_rw_lock_writer_unlock(&expand_array_lock);
+ CPU *c;
+ g_rw_lock_reader_lock(&expand_array_lock);
+ c = &g_array_index(cpus, CPU, vcpu_index);
+ g_rw_lock_reader_unlock(&expand_array_lock);
+
+ return c;
}
/**
@@ -46,13 +57,10 @@ static void expand_last_exec(int cpu_index)
static void vcpu_mem(unsigned int cpu_index, qemu_plugin_meminfo_t info,
uint64_t vaddr, void *udata)
{
- GString *s;
+ CPU *c = get_cpu(cpu_index);
+ GString *s = c->last_exec;
/* Find vCPU in array */
- g_rw_lock_reader_lock(&expand_array_lock);
- g_assert(cpu_index < last_exec->len);
- s = g_ptr_array_index(last_exec, cpu_index);
- g_rw_lock_reader_unlock(&expand_array_lock);
/* Indicate type of memory access */
if (qemu_plugin_mem_is_store(info)) {
@@ -73,32 +81,91 @@ static void vcpu_mem(unsigned int cpu_index, qemu_plugin_meminfo_t info,
}
/**
- * Log instruction execution
+ * Log instruction execution, outputting the last one.
+ *
+ * vcpu_insn_exec() is a copy and paste of vcpu_insn_exec_with_regs()
+ * without the checking of register values when we've attempted to
+ * optimise with disas_assist.
*/
-static void vcpu_insn_exec(unsigned int cpu_index, void *udata)
+static void insn_check_regs(int vcpu_index, CPU *cpu)
{
- GString *s;
+ for (int n = 0; n < cpu->registers->len; n++) {
+ Register *reg = cpu->registers->pdata[n];
+ int sz;
- /* Find or create vCPU in array */
- g_rw_lock_reader_lock(&expand_array_lock);
- if (cpu_index >= last_exec->len) {
- g_rw_lock_reader_unlock(&expand_array_lock);
- expand_last_exec(cpu_index);
- g_rw_lock_reader_lock(&expand_array_lock);
+ g_byte_array_set_size(reg->new, 0);
+ sz = qemu_plugin_read_register(vcpu_index, reg->handle, reg->new);
+ g_assert(sz == reg->last->len);
+
+ if (memcmp(reg->last->data, reg->new->data, sz)) {
+ GByteArray *temp = reg->last;
+ g_string_append_printf(cpu->last_exec, ", %s -> 0x", reg->name);
+ /* TODO: handle BE properly */
+ for (int i = sz; i >= 0; i--) {
+ g_string_append_printf(cpu->last_exec, "%02x",
+ reg->new->data[i]);
+ }
+ reg->last = reg->new;
+ reg->new = temp;
+ }
+ }
+}
+
+/* Log last instruction while checking registers */
+static void vcpu_insn_exec_with_regs(unsigned int cpu_index, void *udata)
+{
+ CPU *cpu = get_cpu(cpu_index);
+
+ /* Print previous instruction in cache */
+ if (cpu->last_exec->len) {
+ if (cpu->registers) {
+ insn_check_regs(cpu_index, cpu);
+ }
+
+ qemu_plugin_outs(cpu->last_exec->str);
+ qemu_plugin_outs("\n");
+ }
+
+ /* Store new instruction in cache */
+ /* vcpu_mem will add memory access information to last_exec */
+ g_string_printf(cpu->last_exec, "%u, ", cpu_index);
+ g_string_append(cpu->last_exec, (char *)udata);
+}
+
+/* Log last instruction while checking registers, ignore next */
+static void vcpu_insn_exec_only_regs(unsigned int cpu_index, void *udata)
+{
+ CPU *cpu = get_cpu(cpu_index);
+
+ /* Print previous instruction in cache */
+ if (cpu->last_exec->len) {
+ if (cpu->registers) {
+ insn_check_regs(cpu_index, cpu);
+ }
+
+ qemu_plugin_outs(cpu->last_exec->str);
+ qemu_plugin_outs("\n");
}
- s = g_ptr_array_index(last_exec, cpu_index);
- g_rw_lock_reader_unlock(&expand_array_lock);
+
+ /* reset */
+ cpu->last_exec->len = 0;
+}
+
+/* Log last instruction without checking regs, setup next */
+static void vcpu_insn_exec(unsigned int cpu_index, void *udata)
+{
+ CPU *cpu = get_cpu(cpu_index);
/* Print previous instruction in cache */
- if (s->len) {
- qemu_plugin_outs(s->str);
+ if (cpu->last_exec->len) {
+ qemu_plugin_outs(cpu->last_exec->str);
qemu_plugin_outs("\n");
}
/* Store new instruction in cache */
/* vcpu_mem will add memory access information to last_exec */
- g_string_printf(s, "%u, ", cpu_index);
- g_string_append(s, (char *)udata);
+ g_string_printf(cpu->last_exec, "%u, ", cpu_index);
+ g_string_append(cpu->last_exec, (char *)udata);
}
/**
@@ -111,6 +178,8 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
{
struct qemu_plugin_insn *insn;
bool skip = (imatches || amatches);
+ bool check_regs_this = rmatches;
+ bool check_regs_next = false;
size_t n = qemu_plugin_tb_n_insns(tb);
for (size_t i = 0; i < n; i++) {
@@ -131,7 +200,8 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
/*
* If we are filtering we better check out if we have any
* hits. The skip "latches" so we can track memory accesses
- * after the instruction we care about.
+ * after the instruction we care about. Also enable register
+ * checking on the next instruction.
*/
if (skip && imatches) {
int j;
@@ -139,6 +209,7 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
char *m = g_ptr_array_index(imatches, j);
if (g_str_has_prefix(insn_disas, m)) {
skip = false;
+ check_regs_next = rmatches;
}
}
}
@@ -153,8 +224,39 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
}
}
+ /*
+ * Check the disassembly to see if a register we care about
+ * will be affected by this instruction. This relies on the
+ * dissembler doing something sensible for the registers we
+ * care about.
+ */
+ if (disas_assist && rmatches) {
+ check_regs_next = false;
+ gchar *args = g_strstr_len(insn_disas, -1, " ");
+ for (int n = 0; n < all_reg_names->len; n++) {
+ gchar *reg = g_ptr_array_index(all_reg_names, n);
+ if (g_strrstr(args, reg)) {
+ check_regs_next = true;
+ skip = false;
+ }
+ }
+ }
+
+ /*
+ * We now have 3 choices:
+ *
+ * - Log insn
+ * - Log insn while checking registers
+ * - Don't log this insn but check if last insn changed registers
+ */
+
if (skip) {
- g_free(insn_disas);
+ if (check_regs_this) {
+ qemu_plugin_register_vcpu_insn_exec_cb(insn,
+ vcpu_insn_exec_only_regs,
+ QEMU_PLUGIN_CB_R_REGS,
+ NULL);
+ }
} else {
uint32_t insn_opcode;
insn_opcode = *((uint32_t *)qemu_plugin_insn_data(insn));
@@ -167,30 +269,125 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
QEMU_PLUGIN_MEM_RW, NULL);
/* Register callback on instruction */
- qemu_plugin_register_vcpu_insn_exec_cb(insn, vcpu_insn_exec,
- QEMU_PLUGIN_CB_NO_REGS, output);
+ if (check_regs_this) {
+ qemu_plugin_register_vcpu_insn_exec_cb(
+ insn, vcpu_insn_exec_with_regs,
+ QEMU_PLUGIN_CB_R_REGS,
+ output);
+ } else {
+ qemu_plugin_register_vcpu_insn_exec_cb(
+ insn, vcpu_insn_exec,
+ QEMU_PLUGIN_CB_NO_REGS,
+ output);
+ }
/* reset skip */
skip = (imatches || amatches);
}
+ /* set regs for next */
+ if (disas_assist && rmatches) {
+ check_regs_this = check_regs_next;
+ }
+
+ g_free(insn_disas);
}
}
+static Register *init_vcpu_register(int vcpu_index,
+ qemu_plugin_reg_descriptor *desc)
+{
+ Register *reg = g_new0(Register, 1);
+ g_autofree gchar *lower = g_utf8_strdown(desc->name, -1);
+ int r;
+
+ reg->handle = desc->handle;
+ reg->name = g_intern_string(lower);
+ reg->last = g_byte_array_new();
+ reg->new = g_byte_array_new();
+
+ /* read the initial value */
+ r = qemu_plugin_read_register(vcpu_index, reg->handle, reg->last);
+ g_assert(r > 0);
+ return reg;
+}
+
+static GPtrArray *registers_init(int vcpu_index)
+{
+ g_autoptr(GPtrArray) registers = g_ptr_array_new();
+ g_autoptr(GArray) reg_list = qemu_plugin_get_registers(vcpu_index);
+
+ if (rmatches && reg_list && reg_list->len) {
+ /*
+ * Go through each register in the complete list and
+ * see if we want to track it.
+ */
+ for (int r = 0; r < reg_list->len; r++) {
+ qemu_plugin_reg_descriptor *rd = &g_array_index(
+ reg_list, qemu_plugin_reg_descriptor, r);
+ for (int p = 0; p < rmatches->len; p++) {
+ g_autoptr(GPatternSpec) pat = g_pattern_spec_new(rmatches->pdata[p]);
+ g_autofree gchar *rd_lower = g_utf8_strdown(rd->name, -1);
+ if (g_pattern_match_string(pat, rd->name) ||
+ g_pattern_match_string(pat, rd_lower)) {
+ Register *reg = init_vcpu_register(vcpu_index, rd);
+ g_ptr_array_add(registers, reg);
+
+ /* we need a list of regnames at TB translation time */
+ if (disas_assist) {
+ g_mutex_lock(&add_reg_name_lock);
+ if (!g_ptr_array_find(all_reg_names, reg->name, NULL)) {
+ g_ptr_array_add(all_reg_names, reg->name);
+ }
+ g_mutex_unlock(&add_reg_name_lock);
+ }
+ }
+ }
+ }
+ }
+
+ return registers->len ? g_steal_pointer(®isters) : NULL;
+}
+
+/*
+ * Initialise a new vcpu/thread with:
+ * - last_exec tracking data
+ * - list of tracked registers
+ * - initial value of registers
+ *
+ * As we could have multiple threads trying to do this we need to
+ * serialise the expansion under a lock.
+ */
+static void vcpu_init(qemu_plugin_id_t id, unsigned int vcpu_index)
+{
+ CPU *c;
+
+ g_rw_lock_writer_lock(&expand_array_lock);
+ if (vcpu_index >= cpus->len) {
+ g_array_set_size(cpus, vcpu_index + 1);
+ }
+ g_rw_lock_writer_unlock(&expand_array_lock);
+
+ c = get_cpu(vcpu_index);
+ c->last_exec = g_string_new(NULL);
+ c->registers = registers_init(vcpu_index);
+}
+
/**
* On plugin exit, print last instruction in cache
*/
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_ptr_array_index(last_exec, i);
- if (s->str) {
- qemu_plugin_outs(s->str);
+ g_rw_lock_reader_lock(&expand_array_lock);
+ for (i = 0; i < cpus->len; i++) {
+ CPU *c = get_cpu(i);
+ if (c->last_exec && c->last_exec->str) {
+ qemu_plugin_outs(c->last_exec->str);
qemu_plugin_outs("\n");
}
}
+ g_rw_lock_reader_unlock(&expand_array_lock);
}
/* Add a match to the array of matches */
@@ -212,6 +409,18 @@ static void parse_vaddr_match(char *match)
g_array_append_val(amatches, v);
}
+/*
+ * We have to wait until vCPUs are started before we can check the
+ * patterns find anything.
+ */
+static void add_regpat(char *regpat)
+{
+ if (!rmatches) {
+ rmatches = g_ptr_array_new();
+ }
+ g_ptr_array_add(rmatches, g_strdup(regpat));
+}
+
/**
* Install the plugin
*/
@@ -223,11 +432,8 @@ 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.
*/
- if (info->system_emulation) {
- last_exec = g_ptr_array_sized_new(info->system.max_vcpus);
- } else {
- last_exec = g_ptr_array_new();
- }
+ cpus = g_array_sized_new(true, true, sizeof(CPU),
+ info->system_emulation ? info->system.max_vcpus : 1);
for (int i = 0; i < argc; i++) {
char *opt = argv[i];
@@ -236,13 +442,22 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
parse_insn_match(tokens[1]);
} else if (g_strcmp0(tokens[0], "afilter") == 0) {
parse_vaddr_match(tokens[1]);
+ } else if (g_strcmp0(tokens[0], "reg") == 0) {
+ add_regpat(tokens[1]);
+ } else if (g_strcmp0(tokens[0], "rdisas") == 0) {
+ if (!qemu_plugin_bool_parse(tokens[0], tokens[1], &disas_assist)) {
+ fprintf(stderr, "boolean argument parsing failed: %s\n", opt);
+ return -1;
+ }
+ all_reg_names = g_ptr_array_new();
} else {
fprintf(stderr, "option parsing failed: %s\n", opt);
return -1;
}
}
- /* Register translation block and exit callbacks */
+ /* Register init, translation block and exit callbacks */
+ qemu_plugin_register_vcpu_init_cb(id, vcpu_init);
qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans);
qemu_plugin_register_atexit_cb(id, plugin_exit, NULL);
--
2.39.2
