From b534253a32b89136b486fbe1b15f645f549b89df Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Fri, 14 Mar 2025 01:00:57 +0100
Subject: x86: cpuid example
---
src/arch/x86/cpuid/cpuid.c | 47 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)
create mode 100644 src/arch/x86/cpuid/cpuid.c
(limited to 'src/arch/x86/cpuid/cpuid.c')
diff --git a/src/arch/x86/cpuid/cpuid.c b/src/arch/x86/cpuid/cpuid.c
new file mode 100644
index 0000000..ab4a7a4
--- /dev/null
+++ b/src/arch/x86/cpuid/cpuid.c
@@ -0,0 +1,47 @@
+#include <stdint.h>
+#include <stdio.h>
+
+typedef struct {
+ uint32_t eax, ebx, ecx, edx;
+} cpuid_t;
+
+// in: eax is the cpuid leaf number
+static inline cpuid_t cpuid(uint32_t eax) {
+ cpuid_t r;
+ asm volatile("cpuid"
+ : "=a"(r.eax), "=b"(r.ebx), "=c"(r.ecx), "=d"(r.edx)
+ : "a"(eax), "c"(0));
+ return r;
+};
+
+// in: eax is the cpuid leaf number
+// in: ecx is the cpuid sub-leaf number
+static inline cpuid_t cpuid_subleaf(uint32_t eax, uint32_t ecx) {
+ cpuid_t r;
+ asm volatile("cpuid"
+ : "=a"(r.eax), "=b"(r.ebx), "=c"(r.ecx), "=d"(r.edx)
+ : "a"(eax), "c"(ecx));
+ return r;
+};
+
+int main() {
+ cpuid_t r;
+ uint32_t leafs = 1;
+
+ for (uint32_t l = 0; l < leafs; ++l) {
+ r = cpuid(l);
+ if (l == 0) {
+ // leaf 0 returns the highest available cpuid leaf in eax.
+ leafs = r.eax;
+
+ // ebx, edx, ecx contain the vendor string
+ // clang-format off
+ printf("vendor: %c%c%c%c%c%c%c%c%c%c%c%c\n",
+ (r.ebx & 0xFF), (r.ebx >> 8) & 0xFF, (r.ebx >> 16) & 0xFF, (r.ebx >> 24) & 0xFF,
+ (r.edx & 0xFF), (r.edx >> 8) & 0xFF, (r.edx >> 16) & 0xFF, (r.edx >> 24) & 0xFF,
+ (r.ecx & 0xFF), (r.ecx >> 8) & 0xFF, (r.ecx >> 16) & 0xFF, (r.ecx >> 24) & 0xFF);
+ // clang-format on
+ }
+ printf("[0x%08x] eax=%08x ebx=%08x ecx=%08x edx=%08x\n", l, r.eax, r.ebx, r.ecx, r.edx);
+ }
+}
--
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