[RFC PATCH] plugins/api: expose symbol lookup to plugins

["Alex Bennée" <alex.bennee@linaro.org>]

This is a quality of life helper for plugins so they don't need to
re-implement symbol lookup when dumping an address. The strings are
constant so don't need to be duplicated. One minor tweak is to return
NULL instead of a zero length string to show lookup failed.

Based-on: 20210530063712.6832-4-ma.mandourr@gmail.com
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 include/qemu/qemu-plugin.h |  9 +++++++++
 contrib/plugins/cache.c    | 10 ++++++++--
 plugins/api.c              |  6 ++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/include/qemu/qemu-plugin.h b/include/qemu/qemu-plugin.h
index 97cdfd7761..dc3496f36c 100644
--- a/include/qemu/qemu-plugin.h
+++ b/include/qemu/qemu-plugin.h
@@ -525,6 +525,15 @@ qemu_plugin_register_vcpu_syscall_ret_cb(qemu_plugin_id_t id,
 
 char *qemu_plugin_insn_disas(const struct qemu_plugin_insn *insn);
 
+/**
+ * qemu_plugin_insn_symbol() - best effort symbol lookup
+ * @insn: instruction reference
+ *
+ * Return a static string referring to the symbol. This is dependent
+ * on the binary QEMU is running having provided a symbol table.
+ */
+const char *qemu_plugin_insn_symbol(const struct qemu_plugin_insn *insn);
+
 /**
  * qemu_plugin_vcpu_for_each() - iterate over the existing vCPU
  * @id: plugin ID
diff --git a/contrib/plugins/cache.c b/contrib/plugins/cache.c
index 1e323494bf..afaa3d9db5 100644
--- a/contrib/plugins/cache.c
+++ b/contrib/plugins/cache.c
@@ -46,6 +46,7 @@ enum AccessResult {
 
 struct InsnData {
     char *disas_str;
+    const char *symbol;
     uint64_t addr;
     uint64_t misses;
 };
@@ -377,10 +378,12 @@ static void vcpu_tb_trans(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
         struct InsnData *idata = g_new(struct InsnData, 1);
 
         ddata->disas_str = qemu_plugin_insn_disas(insn);
+        ddata->symbol = qemu_plugin_insn_symbol(insn);
         ddata->misses = 0;
         ddata->addr = effective_addr;
 
         idata->disas_str = g_strdup(ddata->disas_str);
+        idata->symbol = qemu_plugin_insn_symbol(insn);
         idata->misses = 0;
         idata->addr = effective_addr;
 
@@ -397,8 +400,11 @@ static void print_entry(gpointer data)
 {
     struct InsnData *insn = (struct InsnData *) data;
     g_autoptr(GString) xx = g_string_new("");
-    g_string_append_printf(xx, "0x%" PRIx64 ": %s - misses: %lu\n",
-            insn->addr, insn->disas_str, insn->misses);
+    g_string_append_printf(xx, "0x%" PRIx64, insn->addr);
+    if (insn->symbol) {
+        g_string_append_printf(xx, " (%s)", insn->symbol);
+    }
+    g_string_append_printf(xx, ", %lu, %s\n", insn->misses, insn->disas_str);
     qemu_plugin_outs(xx->str);
 }
 
diff --git a/plugins/api.c b/plugins/api.c
index 817c9b6b69..332e2c60e2 100644
--- a/plugins/api.c
+++ b/plugins/api.c
@@ -233,6 +233,12 @@ char *qemu_plugin_insn_disas(const struct qemu_plugin_insn *insn)
     return plugin_disas(cpu, insn->vaddr, insn->data->len);
 }
 
+const char *qemu_plugin_insn_symbol(const struct qemu_plugin_insn *insn)
+{
+    const char *sym = lookup_symbol(insn->vaddr);
+    return sym[0] != 0 ? sym : NULL;
+}
+
 /*
  * The memory queries allow the plugin to query information about a
  * memory access.
-- 
2.20.1