[PATCH 21/29] gdbstub: expose api to find registers

[Alex Bennée]

Expose an internal API to QEMU to find groups of registers. It returns
a 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>

---
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      | 59 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 105 insertions(+), 1 deletion(-)

diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
index da9ddfe54c..b201eb4b84 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_find_registers() - Return list of registers matching pattern
+ * @cpu: The CPU being searched
+ * @reg_pattern: the pattern being searched for
+ *
+ * Returns a GArray of GDBRegDesc, caller frees
+ */
+GArray *gdb_find_registers(CPUState *cpu, const char *reg_pattern);
+
 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 7d7d887817..45882d1a6f 100644
--- a/gdbstub/gdbstub.c
+++ b/gdbstub/gdbstub.c
@@ -490,7 +490,64 @@ 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_find_registers(CPUState *cpu, const char *reg_pattern)
+{
+    g_autoptr(GPatternSpec) pat = g_pattern_spec_new(reg_pattern);
+    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];
+            if (name && g_pattern_match_string(pat, name)) {
+                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