sched: Implement basic scheduling and signal handling system

Note: this is probably 25% broken, but it works right now as written, so I hope it all works.

- Added a new scheduler header file (scheduler.h) defining task structures, scheduling policies, and signal handling mechanisms.
- Integrated scheduling functions into the syscall interface, including SYS_GETPID, SYS_GETPPID, SYS_EXIT, SYS_SCHED_YIELD, SYS_NICE, SYS_KILL, SYS_SIGACTION, SYS_SIGPROCMASK, SYS_SCHED_GETSCHEDULER, and SYS_SCHED_SETSCHEDULER.
- Updated syscall handler to manage new scheduling-related syscalls and signal actions.

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

src/fs/elf.c

@@ -7,16 +7,13 @@
 #include "fs/ext2.h"
 
 extern uintptr_t g_hhdm_offset;
-extern struct pagemap *kernel_pagemap;
 
 #define ELF_BUFFER_SIZE (1024 * 1024)
 
 
-#define PTE_PRESENT  (1ULL << 0)
-#define PTE_WRITABLE (1ULL << 1)
-#define PTE_USER     (1ULL << 2)
 
-bool ELF_Read(const char* path, void** entryPoint)
+
+bool ELF_Read(const char* path, void** entryPoint, struct pagemap *target_pagemap)
 {
     uint32_t size;
 
@@ -41,6 +38,15 @@ bool ELF_Read(const char* path, void** entryPoint)
 
     ELFHeader* header = (ELFHeader*)elf_buffer;
 
+    printf("=== ELF DEBUG ===\n");
+    printf("Entry point VA      = 0x%lx\n", header->ProgramEntryPosition);
+    printf("PHDR offset         = 0x%lx\n", header->ProgramHeaderTablePosition);
+    printf("PHDR count          = %u\n", header->ProgramHeaderTableEntryCount);
+
+
+
+    printf("=== END ELF DEBUG ===\n");
+
     // ── validate ELF ──────────────────────────────────
     if (memcmp(header->Magic, ELF_MAGIC, 4) != 0) {
         printf("ELF: bad magic\n");
@@ -82,8 +88,11 @@ bool ELF_Read(const char* path, void** entryPoint)
         ELFProgramHeader* ph = (ELFProgramHeader*)(ph_table +
             i * header->ProgramHeaderTableEntrySize);
 
-        if (ph->Type != ELF_PROGRAM_TYPE_LOAD)
+        if (ph->Type != ELF_PROGRAM_TYPE_LOAD) {
+            printf("LOAD segment: VA=0x%lx  FileSz=0x%lx  MemSz=0x%lx\n",
+                ph->VirtualAddress, ph->FileSize, ph->MemorySize);
             continue;
+        }
 
         uint64_t virt   = ph->VirtualAddress;
         uint64_t offset = ph->Offset;
@@ -114,7 +123,7 @@ bool ELF_Read(const char* path, void** entryPoint)
             uint64_t phys_addr = phys_base + p * PAGE_SIZE;
 
             bool success = vmm_map_page(
-                kernel_pagemap,
+                target_pagemap,
                 virt_addr,
                 phys_addr,
                 PAGE_READ | PAGE_WRITE | PAGE_USER,   // RW + User mode