[PATCH 36/40] gdbstub: expose api to find registers

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

Expose an internal API to QEMU to return all the registers for a vCPU.
The list containing the details required to called gdb_read_register().

Based-on: <20231025093128.33116-15-akihiko.odaki@daynix.com>
Cc: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

---
v2
  - just make gdb_get_register_list return everything for a vCPU

vAJB:

This principle difference is the find registers is a single call which
can return a) multiple registers and b) is agnostic to the gdb
feature. This is because I haven't so far found any duplicate
registers in the system so I thing the regname by itself should be
enough. However I do expose the gdb feature name in case the caller
wants to do some additional filtering.
---
 include/exec/gdbstub.h | 47 +++++++++++++++++++++++++++++++++++
 gdbstub/gdbstub.c      | 56 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 102 insertions(+), 1 deletion(-)

diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
index da9ddfe54c5..7bddea8259e 100644
--- a/include/exec/gdbstub.h
+++ b/include/exec/gdbstub.h
@@ -111,6 +111,53 @@ void gdb_feature_builder_end(const GDBFeatureBuilder *builder);
  */
 const GDBFeature *gdb_find_static_feature(const char *xmlname);
 
+/**
+ * gdb_find_feature() - Find a feature associated with a CPU.
+ * @cpu: The CPU associated with the feature.
+ * @name: The feature's name.
+ *
+ * Return: The feature's number.
+ */
+int gdb_find_feature(CPUState *cpu, const char *name);
+
+/**
+ * gdb_find_feature_register() - Find a register associated with a CPU.
+ * @cpu: The CPU associated with the register.
+ * @feature: The feature's number returned by gdb_find_feature().
+ * @name: The register's name.
+ *
+ * Return: The register's number.
+ */
+int gdb_find_feature_register(CPUState *cpu, int feature, const char *name);
+
+/**
+ * gdb_read_register() - Read a register associated with a CPU.
+ * @cpu: The CPU associated with the register.
+ * @buf: The buffer that the read register will be appended to.
+ * @reg: The register's number returned by gdb_find_feature_register().
+ *
+ * Return: The number of read bytes.
+ */
+int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
+
+/**
+ * typedef GDBRegDesc - a register description from gdbstub
+ */
+typedef struct {
+    int gdb_reg;
+    const char *name;
+    const char *feature_name;
+} GDBRegDesc;
+
+/**
+ * gdb_get_register_list() - Return list of all registers for CPU
+ * @cpu: The CPU being searched
+ *
+ * Returns a GArray of GDBRegDesc, caller frees array but not the
+ * const strings.
+ */
+GArray *gdb_get_register_list(CPUState *cpu);
+
 void gdb_set_stop_cpu(CPUState *cpu);
 
 /* in gdbstub-xml.c, generated by scripts/feature_to_c.py */
diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
index 420ab2a3766..b0230138246 100644
--- a/gdbstub/gdbstub.c
+++ b/gdbstub/gdbstub.c
@@ -490,7 +490,61 @@ const GDBFeature *gdb_find_static_feature(const char *xmlname)
     g_assert_not_reached();
 }
 
-static int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg)
+int gdb_find_feature(CPUState *cpu, const char *name)
+{
+    GDBRegisterState *r;
+
+    for (guint i = 0; i < cpu->gdb_regs->len; i++) {
+        r = &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
+        if (!strcmp(name, r->feature->name)) {
+            return i;
+        }
+    }
+
+    return -1;
+}
+
+int gdb_find_feature_register(CPUState *cpu, int feature, const char *name)
+{
+    GDBRegisterState *r;
+
+    r = &g_array_index(cpu->gdb_regs, GDBRegisterState, feature);
+
+    for (int i = 0; i < r->feature->num_regs; i++) {
+        if (r->feature->regs[i] && !strcmp(name, r->feature->regs[i])) {
+            return r->base_reg + i;
+        }
+    }
+
+    return -1;
+}
+
+GArray *gdb_get_register_list(CPUState *cpu)
+{
+    GArray *results = g_array_new(true, true, sizeof(GDBRegDesc));
+
+    /* registers are only available once the CPU is initialised */
+    if (!cpu->gdb_regs) {
+        return results;
+    }
+
+    for (int f = 0; f < cpu->gdb_regs->len; f++) {
+        GDBRegisterState *r = &g_array_index(cpu->gdb_regs, GDBRegisterState, f);
+        for (int i = 0; i < r->feature->num_regs; i++) {
+            const char *name = r->feature->regs[i];
+            GDBRegDesc desc = {
+                r->base_reg + i,
+                name,
+                r->feature->name
+            };
+            g_array_append_val(results, desc);
+        }
+    }
+
+    return results;
+}
+
+int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg)
 {
     CPUClass *cc = CPU_GET_CLASS(cpu);
     GDBRegisterState *r;
-- 
2.39.2