kernel: try some shit to get the compiler to put a backtrace

kernel/GNUmakefile

@@ -58,7 +58,9 @@ override CFLAGS += \
     -fno-stack-check \
     -fno-PIC \
     -ffunction-sections \
-    -fdata-sections
+    -fdata-sections \
+    -fno-omit-frame-pointer \
+    -fno-optimize-sibling-calls
 
 # Internal C preprocessor flags that should not be changed by the user.
 override CPPFLAGS := \

kernel/src/arch/x86_64/syscall.c

@@ -10,7 +10,7 @@ void __x86_64_syscall_init() {
   wrmsr(IA32_EFER, efer);
   uint64_t star = 0;
   star |= ((uint64_t)0x28 << 32); // kernel cs
-  star |= ((uint64_t)0x30 << 48); // user cs base (SYSCALL adds 16 for CS=0x38, 24 for SS=0x40)
+  star |= ((uint64_t)0x30 << 48); // user cs base (SYSCALL adds 16 for CS=0x40, 24 for SS=0x38)
   wrmsr(IA32_STAR, star);
   wrmsr(IA32_LSTAR, (uint64_t)syscall_entry);
   wrmsr(IA32_CSTAR, 0x0);

kernel/src/main.c

@@ -57,7 +57,11 @@ struct flanterm_context *ft_ctx;
 
 char kstack[8192];
 
-void kmain(void) {
+void test3() { *((uint8_t*)0x0) = (uint8_t)0xFF; }
+void test2() { test3();}
+void test1() { test2(); }
+
+void __kmain(void) {
   if (framebuffer_request.response != NULL) {
 
     struct limine_framebuffer *framebuffer =
@@ -97,6 +101,7 @@ void kmain(void) {
 
   syscall_init();
   sched_init();
+  test1();
 
   // vfs_init();
 
@@ -105,6 +110,7 @@ void kmain(void) {
 
   program_t *p = elf_load(module_request.response->modules[0]->address, 1);
 
+
   sched_process *proc =
       sched_create("Test", p->entry, p->pm, SCHED_USER_PROCESS);
 
@@ -112,6 +118,5 @@ void kmain(void) {
 
   pit_enable();
   while (1)
-    ;
-  ;
+    ;;
 }

kernel/src/premain.asm

@@ -0,0 +1,10 @@
+bits 64
+section .text
+    global kmain
+    extern __kmain
+    extern kstack
+
+kmain:
+    mov rsp, kstack+0x2000  ; supposons 16 KiB de stack
+    xor rbp, rbp       ; Set %ebp to NULL
+    call __kmain

kernel/src/sys/errhnd/panic.c

@@ -1,3 +1,4 @@
+#include "sys/errhnd/panic.h"
 #include "arch/x86_64/idt.h"
 #include "lib/spinlock.h"
 #include <mm/memop.h>
@@ -59,7 +60,9 @@ static void __panic_display_page_fault(registers_t *regs) {
   uint64_t cr2;
   asm volatile("mov %%cr2, %0" : "=r"(cr2));
 
-  log("Page Fault Details:\n");
+  log("-- PAGE FAULT DETAILS --\n");
+  log("This appears to be a page fault.\n");
+  log("\n");
   log("Faulting Address (CR2): 0x%lx\n", cr2);
   log("Error Code: %d\n", regs->err_code);
   log("Flags:\n");
@@ -83,6 +86,7 @@ static void __panic_display_page_fault(registers_t *regs) {
 
   if (regs->err_code & (1 << 4))
     log("  - Instruction Fetch\n");
+  log("\n");
 }
 
 static void __panic_display_regs(registers_t *regs) {
@@ -96,11 +100,60 @@ static void __panic_display_regs(registers_t *regs) {
       regs->rip, regs->cs, regs->ss, regs->rflags, regs->int_no,
       regs->err_code);
   log("RSP: %p\n", regs->rsp);
+  log("\n");
 
   if (regs->int_no == 14) // If it's a page fault
     __panic_display_page_fault(regs);
 }
 
+static void __panic_display_bt(registers_t *regs) {
+  if (regs->cs == 0x43 || regs->cs == 0x3B) {
+    log("The backtrace can't be dumped from a userspace process.\n");
+    return;  // Don't try to backtrace userspace
+  }
+
+  log("-- BACKTRACE --\n");
+
+  // First print the current instruction pointer from the interrupt frame
+  if (regs->rip) {
+    log("* %p (current)\n", regs->rip);
+  }
+
+  uint64_t *frame = (uint64_t*)regs->rbp;
+  if (!frame || (uint64_t)frame < 0xffffffff80000000) {
+    log("No further stack frames available\n");
+    return;
+  }
+
+  // Frame format in x86_64:
+  // [rbp] -> previous rbp
+  // [rbp+8] -> return address
+  int depth = 0;
+  while (frame && depth < 16) {  // Limit depth to avoid infinite loops
+    // Validate both frame and return address pointers
+    uint64_t *ret_addr_ptr = frame + 1;
+    if ((uint64_t)ret_addr_ptr < 0xffffffff80000000) {
+      break;
+    }
+
+    uint64_t ret_addr = *ret_addr_ptr;
+    if (ret_addr < 0xffffffff80000000 || ret_addr > 0xfffffffffffff000) {
+      break;
+    }
+
+    log("* %p\n", ret_addr);
+
+    uint64_t next_rbp = *frame;
+    if (next_rbp < 0xffffffff80000000 || next_rbp > 0xfffffffffffff000) {
+      break;
+    }
+    
+    frame = (uint64_t*)next_rbp;
+    depth++;
+  }
+  log("\n");
+}
+
 void __panic_display_ascii_art() {
   log(" _  __                 _   ___           _          \n");
   log("| |/ /___ _ _ _ _  ___| | | _ \\__ _ _ _ (_)__       \n");
@@ -145,6 +198,8 @@ void panic_ctx(char *msg, registers_t *regs) {
   else
     log("No register context provided.\n");
 
+  __panic_display_bt(regs);
+
   log("System halted: Please restart your computer manually.\n");
 
   asm("cli");

kernel/src/sys/errhnd/panic.h

@@ -1,5 +1,11 @@
 #pragma once
 
 #include "arch/x86_64/idt.h"
+
+typedef struct __panic_backtrace {
+    struct Idt_StackFrame* rbp;
+    uint64_t rip;
+} __attribute__((packed)) panic_backtrace_t;
+
 void panic(char *msg);
 void panic_ctx(char *msg, registers_t *regs);