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Implement CPUID support check and CPU info printing

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Added functions to check CPUID support and print CPU details.
This commit is contained in:
Gregory Kenneth Bowne
2026-01-05 00:42:05 -08:00
committed by GitHub
parent 9eae2e1005
commit cc2e967a4d
1 changed files with 77 additions and 15 deletions
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90
kernel/cpu.c
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@@ -2,36 +2,98 @@
#include "serial.h"
#include "terminal.h"
#include "utils.h"
#include "print.h"
void cpuid(uint32_t function, uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx) {
__asm__(
"cpuid"
: "=a"(*eax), "=b"(*ebx), "=c"(*ecx), "=d"(*edx)
: "a"(function)
);
// Helper to print a labeled decimal value
void print_val(const char* label, uint32_t val) {
char buf[12];
utoa(val, buf, 10);
terminal_write(label);
terminal_write(buf);
terminal_write(" ");
}
// Safely check if CPUID is supported by attempting to flip bit 21 of EFLAGS
int check_cpuid_supported() {
uint32_t f1, f2;
__asm__ volatile (
"pushfl\n\t"
"pushfl\n\t"
"popl %0\n\t"
"movl %0, %1\n\t"
"xorl $0x200000, %0\n\t"
"pushl %0\n\t"
"popfl\n\t"
"pushfl\n\t"
"popl %0\n\t"
"popfl\n\t"
: "=&r" (f1), "=&r" (f2));
return ((f1 ^ f2) & 0x200000) != 0;
}
void identify_cpu() {
if (!check_cpuid_supported()) {
terminal_write("CPUID not supported. Likely a 386 or early 486.\n");
return;
}
uint32_t eax, ebx, ecx, edx;
char vendor[13];
// Leaf 0: Vendor String & Max Leaf
cpuid(0, &eax, &ebx, &ecx, &edx);
uint32_t max_leaf = eax;
*(uint32_t *)&vendor[0] = ebx;
*(uint32_t *)&vendor[4] = edx;
*(uint32_t *)&vendor[8] = ecx;
vendor[12] = '\0';
terminal_write("CPU Vendor: ");
terminal_write("Vendor: ");
terminal_write(vendor);
terminal_write("\n");
serial_write("CPU Vendor: ");
serial_write(vendor);
serial_write("\n");
// Leaf 1: Family, Model, Stepping
if (max_leaf >= 1) {
cpuid(1, &eax, &ebx, &ecx, &edx);
terminal_write("CPUID max leaf: ");
print_hex(eax, false, false); // You must implement this (see below)
uint32_t stepping = eax & 0xF;
uint32_t model = (eax >> 4) & 0xF;
uint32_t family = (eax >> 8) & 0xF;
uint32_t type = (eax >> 12) & 0x3;
// Handle Extended Family/Model (Required for Pentium 4 and newer)
if (family == 0xF) {
family += (eax >> 20) & 0xFF;
model += ((eax >> 16) & 0xF) << 4;
}
print_val("Family:", family);
print_val("Model:", model);
print_val("Step:", stepping);
terminal_write("\n");
}
// Leaf 2: Cache Descriptors
if (max_leaf >= 2) {
cpuid(2, &eax, &ebx, &ecx, &edx);
terminal_write("Cache Descriptors: ");
// Note: Leaf 2 returns a list of 1-byte descriptors in the registers.
// We look for common Intel ones:
uint32_t regs[4] = {eax, ebx, ecx, edx};
for (int i = 0; i < 4; i++) {
if (regs[i] & 0x80000000) continue; // Reserved bit
for (int j = 0; j < 4; j++) {
uint8_t desc = (regs[i] >> (j * 8)) & 0xFF;
if (desc == 0) continue;
// Example decoding for specific chips you mentioned:
if (desc == 0x06) terminal_write("8KB L1 I-Cache ");
if (desc == 0x0A) terminal_write("8KB L1 D-Cache ");
if (desc == 0x41) terminal_write("128KB L2 ");
if (desc == 0x43) terminal_write("512KB L2 ");
if (desc == 0x2C) terminal_write("32KB L1 D-Cache ");
}
}
terminal_write("\n");
}
}