[PATCH 04/17] tools/arch/x86/pmtctl: Add libpmtctl metric definition database

[David E. Box]

Add a growable container for PMT metric definitions to support loading and
querying hardware metric descriptors at runtime.

PMT metrics vary by platform and are discovered dynamically from sysfs. A
block-based database allows metric definitions to be appended as they are
parsed, without requiring the final size to be known in advance, while
bounding individual memory allocations.

Assisted-by: GitHub-Copilot:claude-sonnet-4.6
Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx>
---
 .../arch/x86/pmtctl/include/lib/metrics_db.h  | 69 +++++++++++++++++++
 tools/arch/x86/pmtctl/lib/metrics_db.c        | 62 +++++++++++++++++
 2 files changed, 131 insertions(+)
 create mode 100644 tools/arch/x86/pmtctl/include/lib/metrics_db.h
 create mode 100644 tools/arch/x86/pmtctl/lib/metrics_db.c

diff --git a/tools/arch/x86/pmtctl/include/lib/metrics_db.h b/tools/arch/x86/pmtctl/include/lib/metrics_db.h
new file mode 100644
index 000000000000..9dff27d8785a
--- /dev/null
+++ b/tools/arch/x86/pmtctl/include/lib/metrics_db.h
@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef PMTCTL_METRICS_DB_H
+#define PMTCTL_METRICS_DB_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "lib/pmt_guid.h"
+
+/* Metric definition from builtin or JSON */
+struct pmt_metric_def {
+	const char *event_name;
+	const char *description;
+	const char *group;
+	const char *platform_group;
+
+	const struct pmt_guid *guid;
+	uint32_t sample_id;
+	uint8_t  lsb;
+	uint8_t  msb;
+};
+
+struct pmt_metrics_block {
+	const struct pmt_metric_def *defs;
+	int count;
+	bool is_builtin;
+};
+
+struct pmt_metrics_db {
+	struct pmt_metrics_block *blocks;
+	int nblocks;
+	int total;   /* sum of all block->count */
+};
+
+/* Treat DB as a flat array [0..total-1] */
+static inline const struct pmt_metric_def *pmt_metrics_at(const struct pmt_metrics_db *db, int idx)
+{
+	if (!db || idx < 0 || idx >= db->total)
+		return NULL;
+
+	for (int i = 0; i < db->nblocks; i++) {
+		if (idx < db->blocks[i].count)
+			return &db->blocks[i].defs[idx];
+		idx -= db->blocks[i].count;
+	}
+	return NULL;
+}
+
+static inline const struct pmt_metrics_block *
+pmt_metrics_block_for(const struct pmt_metrics_db *db, int idx)
+{
+	if (!db || idx < 0 || idx >= db->total)
+		return NULL;
+
+	for (int i = 0; i < db->nblocks; i++) {
+		if (idx < db->blocks[i].count)
+			return &db->blocks[i];
+		idx -= db->blocks[i].count;
+	}
+
+	return NULL;
+}
+
+int pmt_metrics_add_block(struct pmt_metrics_db *db, const struct pmt_metric_def *defs,
+			  int count, bool is_builtin);
+void pmt_metrics_free(struct pmt_metrics_db *db);
+
+#endif
diff --git a/tools/arch/x86/pmtctl/lib/metrics_db.c b/tools/arch/x86/pmtctl/lib/metrics_db.c
new file mode 100644
index 000000000000..82e8121a1b98
--- /dev/null
+++ b/tools/arch/x86/pmtctl/lib/metrics_db.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lib/metrics_db.h"
+
+int pmt_metrics_add_block(struct pmt_metrics_db *db, const struct pmt_metric_def *defs,
+			  int count, bool is_builtin)
+{
+	struct pmt_metrics_block *blocks;
+	size_t alloc_size;
+	int new_cap;
+
+	if (!db || !defs || count <= 0)
+		return -EINVAL;
+
+	if (db->nblocks > INT_MAX - 1)
+		return -EOVERFLOW;
+
+	if (db->total > INT_MAX - count)
+		return -EOVERFLOW;
+
+	new_cap = db->nblocks + 1;
+
+	if ((size_t)new_cap > SIZE_MAX / sizeof(*blocks))
+		return -EOVERFLOW;
+
+	alloc_size = (size_t)new_cap * sizeof(*blocks);
+
+	blocks = realloc(db->blocks, alloc_size);
+	if (!blocks)
+		return -ENOMEM;
+
+	db->blocks = blocks;
+
+	db->blocks[db->nblocks].defs       = defs;
+	db->blocks[db->nblocks].count      = count;
+	db->blocks[db->nblocks].is_builtin = is_builtin;
+
+	db->nblocks++;
+	db->total += count;
+
+	return 0;
+}
+
+void pmt_metrics_free(struct pmt_metrics_db *db)
+{
+	if (!db)
+		return;
+
+	if (db->blocks) {
+		for (int i = 0; i < db->nblocks; i++) {
+			if (!db->blocks[i].is_builtin && db->blocks[i].defs)
+				free((void *)db->blocks[i].defs);
+		}
+		free(db->blocks);
+	}
+
+	memset(db, 0, sizeof(*db));
+}
-- 
2.43.0