From b6983be0368bb39e3a8cbd919235b14504f1d995 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 17 Sep 2025 01:06:27 -0400
Subject: kern/amd64: mp: Add cpu_get() routine

This commit introduces a new cpu_get() function to acquire a specific
CPU by using a logical ID as an index.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/sys/arch/amd64/cpu/cpu_mp.c | 17 +++++++++++++++++
 src/sys/include/sys/cpuvar.h    | 11 +++++++++++
 2 files changed, 28 insertions(+)

(limited to 'src')

diff --git a/src/sys/arch/amd64/cpu/cpu_mp.c b/src/sys/arch/amd64/cpu/cpu_mp.c
index 8d84b1f..3483e4a 100644
--- a/src/sys/arch/amd64/cpu/cpu_mp.c
+++ b/src/sys/arch/amd64/cpu/cpu_mp.c
@@ -79,6 +79,23 @@ ap_entry(struct limine_smp_info *)
     for (;;);
 }
 
+/*
+ * Get a specific core descriptor
+ */
+struct pcore *
+cpu_get(uint16_t index)
+{
+    if (index == 0) {
+        return &g_bsp;
+    }
+
+    if ((index - 1) >= ncores_up) {
+        index %= (ncores_up - 1);
+    }
+
+    return corelist[index - 1];
+}
+
 void
 bsp_ap_startup(void)
 {
diff --git a/src/sys/include/sys/cpuvar.h b/src/sys/include/sys/cpuvar.h
index 9a2dc4d..5820646 100644
--- a/src/sys/include/sys/cpuvar.h
+++ b/src/sys/include/sys/cpuvar.h
@@ -79,6 +79,17 @@ void cpu_conf(struct pcore *pcore);
  */
 void cpu_init(struct pcore *pcore);
 
+/*
+ * Get a specific CPU descriptor using a logical
+ * ID number (`index') as a key
+ *
+ * @index: Index / logical ID of desired processor
+ *
+ * Returns a pointer to the core descriptor on success,
+ * otherwise NULL to represent failure.
+ */
+struct pcore *cpu_get(uint16_t index);
+
 /*
  * Get the current processing element (core) as
  * a 'pcore' descriptor.
-- 
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