From: Tulio A M Mendes <tadryanom@hotmail.com>
Date: Thu, 12 Feb 2026 04:18:08 +0000 (-0300)
Subject: feat: vDSO shared page — kernel-updated tick_count mapped read-only into user address... 
X-Git-Url: https://projects.tadryanom.me/docs/static/gitweb.css?a=commitdiff_plain;h=72d2f05b6cf5f845cce1138b15211b44d925d5f2;p=AdrOS.git

feat: vDSO shared page — kernel-updated tick_count mapped read-only into user address space at 0x007FE000
---

diff --git a/include/vdso.h b/include/vdso.h
new file mode 100644
index 0000000..9048ef1
--- /dev/null
+++ b/include/vdso.h
@@ -0,0 +1,20 @@
+#ifndef VDSO_H
+#define VDSO_H
+
+#include <stdint.h>
+
+/* Shared page layout — mapped read-only at VDSO_USER_ADDR in every process */
+#define VDSO_USER_ADDR 0x007FE000U  /* one page below stack guard */
+
+struct vdso_data {
+    volatile uint32_t tick_count;   /* updated by kernel timer ISR */
+    uint32_t tick_hz;               /* ticks per second (e.g. 50) */
+};
+
+void vdso_init(void);
+void vdso_update_tick(uint32_t tick);
+
+/* Returns the physical address of the vDSO page (for mapping into user AS) */
+uintptr_t vdso_get_phys(void);
+
+#endif
diff --git a/src/arch/x86/elf.c b/src/arch/x86/elf.c
index ebe9fa2..9eacc64 100644
--- a/src/arch/x86/elf.c
+++ b/src/arch/x86/elf.c
@@ -292,6 +292,16 @@ int elf32_load_user_from_initrd(const char* filename, uintptr_t* entry_out, uint
         return src2;
     }
 
+    /* Map vDSO shared page read-only into user address space */
+    {
+        extern uintptr_t vdso_get_phys(void);
+        uintptr_t vp = vdso_get_phys();
+        if (vp) {
+            vmm_map_page((uint64_t)vp, (uint64_t)0x007FE000U,
+                         VMM_FLAG_PRESENT | VMM_FLAG_USER);
+        }
+    }
+
     *entry_out = real_entry;
     *user_stack_top_out = user_stack_base + user_stack_size;
     *addr_space_out = new_as;
diff --git a/src/drivers/timer.c b/src/drivers/timer.c
index be453eb..d6bd59b 100644
--- a/src/drivers/timer.c
+++ b/src/drivers/timer.c
@@ -1,6 +1,7 @@
 #include "timer.h"
 #include "uart_console.h"
 #include "process.h" 
+#include "vdso.h"
 
 #include "hal/timer.h"
 
@@ -12,6 +13,7 @@ uint32_t get_tick_count(void) {
 
 static void hal_tick_bridge(void) {
     tick++;
+    vdso_update_tick(tick);
     process_wake_check(tick);
     schedule();
 }
diff --git a/src/kernel/main.c b/src/kernel/main.c
index bab32ee..b0f5dd0 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -63,6 +63,12 @@ void kernel_main(const struct boot_info* bi) {
     kprintf("[AdrOS] Initializing Scheduler...\n");
     process_init();
     
+    // 7b. Initialize vDSO shared page
+    {
+        extern void vdso_init(void);
+        vdso_init();
+    }
+
     // 8. Start Timer (Preemption!) - 50Hz
     timer_init(50);
 
diff --git a/src/kernel/vdso.c b/src/kernel/vdso.c
new file mode 100644
index 0000000..5c09a33
--- /dev/null
+++ b/src/kernel/vdso.c
@@ -0,0 +1,48 @@
+#include "vdso.h"
+#include "pmm.h"
+#include "vmm.h"
+#include "utils.h"
+#include "uart_console.h"
+
+static uintptr_t vdso_phys = 0;
+static volatile struct vdso_data* vdso_kptr = 0;
+
+void vdso_init(void) {
+    void* page = pmm_alloc_page();
+    if (!page) {
+        uart_print("[VDSO] OOM\n");
+        return;
+    }
+    vdso_phys = (uintptr_t)page;
+
+    /* Map into kernel space at a fixed VA so we can write to it.
+     * Use 0xC0230000 (above ATA DMA bounce at 0xC0221000). */
+    uintptr_t kva = 0xC0230000U;
+    vmm_map_page((uint64_t)vdso_phys, (uint64_t)kva,
+                 VMM_FLAG_PRESENT | VMM_FLAG_RW);
+
+    vdso_kptr = (volatile struct vdso_data*)kva;
+    memset((void*)vdso_kptr, 0, PAGE_SIZE);
+    vdso_kptr->tick_hz = 50;
+
+    uart_print("[VDSO] Initialized at phys=0x");
+    /* Simple hex print */
+    char hex[9];
+    for (int i = 7; i >= 0; i--) {
+        uint8_t nib = (uint8_t)((vdso_phys >> (i * 4)) & 0xF);
+        hex[7 - i] = (char)(nib < 10 ? '0' + nib : 'a' + nib - 10);
+    }
+    hex[8] = '\0';
+    uart_print(hex);
+    uart_print("\n");
+}
+
+void vdso_update_tick(uint32_t tick) {
+    if (vdso_kptr) {
+        vdso_kptr->tick_count = tick;
+    }
+}
+
+uintptr_t vdso_get_phys(void) {
+    return vdso_phys;
+}