feat: Improved SMP and added CPU-local contexts

.vscode/settings.json

@@ -21,7 +21,8 @@
         "kpanic.h": "c",
         "smp.h": "c",
         "string_view": "c",
-        "lapic.h": "c"
+        "lapic.h": "c",
+        "spinlock.h": "c"
     },
     "editor.formatOnPaste": true,
     "editor.formatOnSave": true,

GNUmakefile

@@ -2,7 +2,7 @@
 MAKEFLAGS += -rR
 .SUFFIXES:
 
-QEMUFLAGS := -m 2G -serial stdio -smp 4
+QEMUFLAGS := -serial stdio -smp 4
 USER_QEMUFLAGS ?=
 IMAGE_NAME := release/emk
 

kernel/src/arch/smp.c

@@ -1,44 +1,87 @@
 /* EMK 1.0 Copyright (c) 2025 Piraterna */
 #include <arch/smp.h>
+#include <arch/cpu.h>
 #include <boot/limine.h>
 #include <boot/emk.h>
 #include <util/log.h>
+#include <sys/kpanic.h>
+#include <stdatomic.h>
+#include <lib/string.h>
+#include <mm/heap.h>
+
+#define MAX_CPUS 256
+#define MSR_GS_BASE 0xC0000101
 
-uint32_t bootstrap_lapic_id = 0;
 uint32_t cpu_count = 0;
+uint32_t bootstrap_lapic_id = 0;
 
-uint32_t ctr = 0;
+atomic_uint started_cpus = 0;
+static cpu_local_t cpu_locals[MAX_CPUS];
+
+cpu_local_t *get_cpu_local(void)
+{
+    cpu_local_t *cpu = (cpu_local_t *)rdmsr(MSR_GS_BASE);
+    return cpu;
+}
+
+static inline void set_cpu_local(cpu_local_t *cpu)
+{
+    wrmsr(MSR_GS_BASE, (uint64_t)cpu);
+}
 
 void smp_entry(struct limine_mp_info *smp_info)
 {
+    uint32_t lapic_id = smp_info->lapic_id;
+    cpu_local_t *cpu = NULL;
 
-    log_early("CPU %d started", smp_info->processor_id);
-    __atomic_fetch_add(&ctr, 1, __ATOMIC_SEQ_CST);
+    for (uint32_t i = 0; i < cpu_count; i++)
+    {
+        if (cpu_locals[i].lapic_id == lapic_id)
+        {
+            cpu = &cpu_locals[i];
+            break;
+        }
+    }
+
+    if (!cpu)
+        kpanic(NULL, "CPU with LAPIC ID %u not found in cpu_locals!", lapic_id);
+
+    set_cpu_local(cpu);
+    atomic_fetch_add(&started_cpus, 1);
 
     while (1)
-        ;
+        __asm__ volatile("hlt");
 }
 
-void smp_init()
+void smp_init(void)
 {
     bootstrap_lapic_id = mp_response->bsp_lapic_id;
     cpu_count = mp_response->cpu_count;
 
-    for (uint64_t i = 0; i < cpu_count; i++)
+    log_early("%u CPUs detected", cpu_count);
+
+    for (uint32_t i = 0; i < cpu_count; i++)
     {
-        if (mp_response->cpus[i]->lapic_id != bootstrap_lapic_id)
+        struct limine_mp_info *info = mp_response->cpus[i];
+
+        memset(&cpu_locals[i], 0, sizeof(cpu_local_t));
+        cpu_locals[i].lapic_id = info->lapic_id;
+        cpu_locals[i].cpu_index = i;
+
+        if (info->lapic_id == bootstrap_lapic_id)
         {
-            uint32_t old_ctr = __atomic_load_n(&ctr, __ATOMIC_SEQ_CST);
-
-            __atomic_store_n(&mp_response->cpus[i]->goto_address, smp_entry,
-                             __ATOMIC_SEQ_CST);
-
-            while (__atomic_load_n(&ctr, __ATOMIC_SEQ_CST) == old_ctr)
-                ;
+            set_cpu_local(&cpu_locals[i]);
+            log_early("CPU %u (LAPIC %u) is the bootstrap processor", i, info->lapic_id);
+            atomic_fetch_add(&started_cpus, 1);
         }
         else
         {
-            log_early("CPU %d is the bootstrap processor", i);
+            atomic_store((_Atomic(void **))&info->goto_address, smp_entry);
+            while (atomic_load(&started_cpus) < (i + 1))
+                __asm__ volatile("pause");
         }
     }
-}
+
+    while (atomic_load(&started_cpus) < cpu_count)
+        __asm__ volatile("pause");
+}

kernel/src/arch/smp.h

@@ -5,6 +5,14 @@
 #include <stdint.h>
 
 extern uint32_t bootstrap_lapic_id;
+
+typedef struct
+{
+    uint32_t lapic_id;
+    uint32_t cpu_index;
+} cpu_local_t;
+
 void smp_init();
+cpu_local_t *get_cpu_local(void);
 
 #endif // SMP_H

kernel/src/emk.c

@@ -176,5 +176,7 @@ void emk_entry(void)
     smp_init();
     log_early("Initialized SMP");
 
+    __asm__ volatile("int $0x01");
+
     hlt();
 }

kernel/src/sys/kpanic.c

@@ -5,6 +5,7 @@
 #include <util/kprintf.h>
 #include <lib/string.h>
 #include <arch/cpu.h>
+#include <arch/smp.h>
 
 static const char *strings[32] = {
     "Division by Zero",
@@ -126,7 +127,11 @@ void kpanic(struct register_ctx *ctx, const char *fmt, ...)
         }
     }
 
-    log_panic("=== Kernel panic: '%s' @ 0x%.16llx ===", buf, regs.rip);
+    cpu_local_t *cpu = get_cpu_local();
+    if (cpu)
+        log_panic("=== Kernel panic: '%s' on CPU %d @ 0x%.16llx ===", buf, cpu->cpu_index, regs.rip);
+    else
+        log_panic("=== Kernel panic: '%s' on CPU ??? @ 0x%.16llx ===", buf, regs.rip);
     log_panic("Registers:");
     log_panic("  rax: 0x%.16llx  rbx:    0x%.16llx  rcx: 0x%.16llx  rdx: 0x%.16llx", regs.rax, regs.rbx, regs.rcx, regs.rdx);
     log_panic("  rsi: 0x%.16llx  rdi:    0x%.16llx  rbp: 0x%.16llx  rsp: 0x%.16llx", regs.rsi, regs.rdi, regs.rbp, regs.rsp);

kernel/src/util/kprintf.c

@@ -5,6 +5,7 @@
 #if FLANTERM_SUPPORT
 #include <flanterm/flanterm.h>
 #endif // FLANTERM_SUPPORT
+#include <sys/spinlock.h>
 
 #define NANOPRINTF_USE_FIELD_WIDTH_FORMAT_SPECIFIERS 1
 #define NANOPRINTF_USE_PRECISION_FORMAT_SPECIFIERS 1
@@ -16,8 +17,12 @@
 #define NANOPRINTF_IMPLEMENTATION
 #include <nanoprintf.h>
 
+static spinlock_t kprintf_lock = {0};
+
 int kprintf(const char *fmt, ...)
 {
+    spinlock_acquire(&kprintf_lock);
+
     va_list args;
     va_start(args, fmt);
     char buffer[1024];
@@ -33,6 +38,8 @@ int kprintf(const char *fmt, ...)
     }
 
     va_end(args);
+
+    spinlock_release(&kprintf_lock);
     return length;
 }