From 23b28e59e8a4922252415f0a44497d7471fce942 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 12 Oct 2025 15:25:51 -0400
Subject: kern/amd64: Identify processor vendor in mdcore

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/sys/arch/amd64/cpu/cpu_conf.c | 74 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

(limited to 'src/sys/arch/amd64')

diff --git a/src/sys/arch/amd64/cpu/cpu_conf.c b/src/sys/arch/amd64/cpu/cpu_conf.c
index 20a2cec..16bd57d 100644
--- a/src/sys/arch/amd64/cpu/cpu_conf.c
+++ b/src/sys/arch/amd64/cpu/cpu_conf.c
@@ -35,8 +35,14 @@
 #include <machine/lapic.h>
 #include <machine/gdt.h>
 #include <machine/mdcpu.h>
+#include <machine/cpuid.h>
 #include <string.h>
 
+/* Valid vendor strings */
+#define VENDSTR_INTEL "GenuineIntel"
+#define VENDSTR_INTEL1 "GenuineIotel"
+#define VENDSTR_AMD    "AuthenticAMD"
+
 extern void syscall_isr(void);
 extern void core_halt_isr(void);
 void core_halt_handler(void);
@@ -71,6 +77,73 @@ init_vectors(void)
     idt_set_desc(HALT_VECTOR, IDT_USER_GATE, ISR(core_halt_isr), 0);
 }
 
+/*
+ * Identify the CPU vendor - used by cpu_identify()
+ */
+static void
+cpu_vendor(struct mdcore *mdcore)
+{
+    uint32_t ebx, edx, ecx, dmmy;
+    char vendstr[13];
+
+    if (mdcore == NULL) {
+        return;
+    }
+
+    CPUID(0x00, dmmy, ebx, ecx, edx);
+
+    /* DWORD 0 */
+    vendstr[0] = (ebx & 0xFF);
+    vendstr[1] = (ebx >> 8) & 0xFF;
+    vendstr[2] = (ebx >> 16) & 0xFF;
+    vendstr[3] = (ebx >> 24) & 0xFF;
+
+    /* DWORD 1 */
+    vendstr[4] = (edx & 0xFF);
+    vendstr[5] = (edx >> 8) & 0xFF;
+    vendstr[6] = (edx >> 16) & 0xFF;
+    vendstr[7] = (edx >> 24) & 0xFF;
+
+    /* DWORD 2 */
+    vendstr[8] = (ecx & 0xFF);
+    vendstr[9] = (ecx >> 8) & 0xFF;
+    vendstr[10] = (ecx >> 16) & 0xFF;
+    vendstr[11] = (ecx >> 24) & 0xFF;
+    vendstr[12] = '\0';
+
+    if (strcmp(vendstr, VENDSTR_INTEL) == 0) {
+        mdcore->vendor = CPU_VENDOR_INTEL;
+        return;
+    }
+
+    /* Some buggy Intel CPUs have this rare one */
+    if (strcmp(vendstr, VENDSTR_INTEL1) == 0) {
+        mdcore->vendor = CPU_VENDOR_INTEL;
+        return;
+    }
+
+    if (strcmp(vendstr, VENDSTR_AMD) == 0) {
+        mdcore->vendor = CPU_VENDOR_AMD;
+        return;
+    }
+
+    /* Unknown CPU vendor */
+    mdcore->vendor = CPU_VENDOR_OTHER;
+}
+
+/*
+ * Identify the CPU via a CPUID
+ */
+static void
+cpu_identify(struct mdcore *mdcore)
+{
+    if (mdcore == NULL) {
+        return;
+    }
+
+    cpu_vendor(mdcore);
+}
+
 void
 cpu_conf(struct pcore *pcore)
 {
@@ -93,6 +166,7 @@ cpu_conf(struct pcore *pcore)
 
     init_vectors();
     idt_load();
+    cpu_identify(mdcore);
     __ASMV("sti");
 }
 
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