feat(mm): implemented on-demand paging support for lazy stack growth (user faults only)

kernel/arch/aarch64/trap/trap.cpp

@@ -13,6 +13,7 @@
 #include "timer/timer.h"
 #include "sched/sched.h"
 #include "sched/task.h"
+#include "mm/mm.h"
 
 // Forward declaration of syscall dispatch
 extern "C" void stlx_aarch64_syscall_dispatch(aarch64::trap_frame* tf);
@@ -79,6 +80,35 @@ void stlx_aarch64_el0_sync_handler(aarch64::trap_frame* tf) {
         return;
     }
 
+    // If it's a page fault, attempt to handle it for on-demand paging
+    if (in_user_code && (
+        ec == aarch64::EC_DATA_ABORT_LOWER ||
+        ec == aarch64::EC_INST_ABORT_LOWER)
+    ) {
+        uintptr_t fault_addr = aarch64::get_far(tf);
+        uint32_t pf_flags = 0;
+
+        // DFSC[5:0] is in ESR.ISS bits [5:0] for data/instruction aborts.
+        uint32_t dfsc = esr & 0x3F;
+        uint32_t fault_class = dfsc >> 2; // top 4 bits identify the class
+        if (fault_class == 0b0011) pf_flags |= mm::PF_FLAG_PRESENT; // permission fault
+
+        // ESR.ISS bit 6 = WnR (Write not Read) for data aborts.
+        if (ec == aarch64::EC_DATA_ABORT_LOWER && (esr & (1u << 6))) {
+            pf_flags |= mm::PF_FLAG_WRITE;
+        }
+
+        if (ec == aarch64::EC_INST_ABORT_LOWER) {
+            pf_flags |= mm::PF_FLAG_INSTRUCTION;
+        }
+
+        if (mm::handle_user_pf(guard.task_core->mm_ctx, fault_addr, pf_flags)) {
+            // Fault has been handled successfully, restart instruction
+            restore_post_trap_elevation_state();
+            return;
+        }
+    }
+
     if (in_user_code && (
         ec == aarch64::EC_DATA_ABORT_LOWER ||
         ec == aarch64::EC_INST_ABORT_LOWER ||

kernel/arch/x86_64/trap/trap.cpp

@@ -1,4 +1,4 @@
-#include "trap_frame.h"
+#include "trap/trap_frame.h"
 #include "defs/vectors.h"
 #include "irq/irq.h"
 #include "io/serial.h"
@@ -10,6 +10,7 @@
 #include "msi/msi.h"
 #include "sched/sched.h"
 #include "sched/task.h"
+#include "mm/mm.h"
 
 namespace sched {
 __PRIVILEGED_CODE void on_yield(x86::trap_frame* tf);
@@ -90,6 +91,23 @@ extern "C" __PRIVILEGED_CODE void stlx_x86_64_trap_handler(x86::trap_frame* tf)
         return;
     }
 
+    // If it's a page fault, attempt to handle it for on-demand paging
+    if (in_user_code && tf->vector == x86::EXC_PAGE_FAULT) {
+        uintptr_t fault_addr = x86::read_cr2();
+        uint64_t ec = tf->error_code;
+        uint32_t pf_flags = 0;
+        if (ec & 0x1)  pf_flags |= mm::PF_FLAG_PRESENT;
+        if (ec & 0x2)  pf_flags |= mm::PF_FLAG_WRITE;
+        if (ec & 0x10) pf_flags |= mm::PF_FLAG_INSTRUCTION;
+
+        if (mm::handle_user_pf(irq_task_core->mm_ctx, fault_addr, pf_flags)) {
+            // Fault has been handled successfully, restart instruction
+            irq_task_core->flags &= ~sched::TASK_FLAG_IN_IRQ;
+            restore_post_trap_elevation_state();
+            return;
+        }
+    }
+
     if (in_user_code && (
         tf->vector == x86::EXC_PAGE_FAULT ||
         tf->vector == x86::EXC_GENERAL_PROTECTION ||

kernel/drivers/graphics/gfxfb.cpp

@@ -6,6 +6,7 @@
 #include "fs/fs.h"
 #include "fs/node.h"
 #include "mm/heap.h"
+#include "mm/mm.h"
 #include "mm/paging_types.h"
 #include "mm/pmm_types.h"
 #include "mm/uaccess.h"

kernel/exec/elf.cpp

@@ -5,6 +5,7 @@
 #include "mm/heap.h"
 #include "mm/paging.h"
 #include "mm/pmm.h"
+#include "mm/mm.h"
 #include "mm/vma.h"
 #include "dynpriv/dynpriv.h"
 #include "common/string.h"