backtrace

build.zig

@@ -32,10 +32,11 @@ const kernel_src = &[_][]const u8{
     "kernel/drivers/clock.c",
     "kernel/drivers/drivers.c",
     "kernel/drivers/pci.c",
-    "kernel/drivers/tty.c",
+    "kernel/drivers/term.c",
     "kernel/drivers/uart.c",
     "kernel/fs/fs.c",
     "kernel/lib/atox.c",
+    "kernel/lib/backtrace.c",
     "kernel/lib/bound.c",
     "kernel/lib/btoa.c",
     "kernel/lib/ctoi.c",

kernel/cpu/idt.c

@@ -1,3 +1,4 @@
+#include "lib/klib.h"
 #include <lib.h>
 #include <comus/memory.h>
 #include <comus/asm.h>
@@ -197,6 +198,8 @@ void idt_exception_handler(uint64_t exception, uint64_t code, regs_t *state)
 
 	kputs("\n");
 
+	log_backtrace_ex((void *)state->rip, (void *)state->rbp);
+
 	while (1) {
 		halt();
 	}

kernel/drivers/term.c

@@ -1,5 +1,5 @@
 #include <lib.h>
-#include <comus/drivers/tty.h>
+#include <comus/drivers/term.h>
 #include <comus/asm.h>
 #include <comus/memory.h>
 
@@ -18,7 +18,7 @@ static uint8_t fg = 15, bg = 0;
 // blank color
 const uint16_t blank = (uint16_t)0 | 0 << 12 | 15 << 8;
 
-static void term_clear_line(int line)
+void term_clear_line(int line)
 {
 	if (line < 0 || line >= height)
 		return;
@@ -28,13 +28,13 @@ static void term_clear_line(int line)
 	}
 }
 
-static void term_clear(void)
+void term_clear(void)
 {
 	for (uint8_t y = 0; y < height; y++)
 		term_clear_line(y);
 }
 
-static void term_scroll(int lines)
+void term_scroll(int lines)
 {
 	cli();
 	y -= lines;
@@ -52,7 +52,7 @@ static void term_scroll(int lines)
 	sti();
 }
 
-void tty_out(char c)
+void term_out(char c)
 {
 	if (buffer == NULL)
 		return;
@@ -98,8 +98,8 @@ void tty_out(char c)
 	outb(0x3D5, (uint8_t)((pos >> 8) & 0xFF));
 }
 
-void tty_out_str(const char *str)
+void term_out_str(const char *str)
 {
 	while (*str)
-		tty_out(*str++);
+		term_out(*str++);
 }

kernel/drivers/tty.c

@@ -1,105 +0,0 @@
-#include <lib.h>
-#include <comus/drivers/term.h>
-#include <comus/asm.h>
-#include <comus/memory.h>
-
-#define VGA_ADDR 0xB8000
-
-static const uint8_t width = 80;
-static const uint8_t height = 25;
-static volatile uint16_t *buffer = (uint16_t *)VGA_ADDR;
-
-// position
-static uint32_t x = 0, y = 0;
-
-// color
-static uint8_t fg = 15, bg = 0;
-
-// blank color
-const uint16_t blank = (uint16_t)0 | 0 << 12 | 15 << 8;
-
-void term_clear_line(int line)
-{
-	if (line < 0 || line >= height)
-		return;
-	for (uint8_t x = 0; x < width; x++) {
-		const size_t index = line * width + x;
-		buffer[index] = blank;
-	}
-}
-
-void term_clear(void)
-{
-	for (uint8_t y = 0; y < height; y++)
-		term_clear_line(y);
-}
-
-void term_scroll(int lines)
-{
-	cli();
-	y -= lines;
-	if (!lines)
-		return;
-	if (lines >= height || lines <= -height) {
-		term_clear();
-	} else if (lines > 0) {
-		memmovev(buffer, buffer + lines * width, 2 * (height - lines) * width);
-		term_clear_line(height - lines);
-	} else {
-		memmovev(buffer + lines * width, buffer + lines,
-				 (height + lines) * width);
-	}
-	sti();
-}
-
-void term_out(char c)
-{
-	if (buffer == NULL)
-		return;
-
-	// handle special chars
-	switch (c) {
-	case '\n':
-		x = 0;
-		y++;
-		break;
-	case '\t':
-		x += 4;
-		break;
-	case '\v':
-	case '\f':
-		y++;
-		break;
-	case '\r':
-		x = 0;
-		break;
-	default: {
-		const size_t index = y * width + x;
-		buffer[index] = c | bg << 12 | fg << 8;
-		x++;
-	}
-	}
-
-	// wrap cursor if needed
-	if (x >= width) {
-		x = 0;
-		y++;
-	}
-	if (y >= height) {
-		term_scroll(y - (height - 1));
-		y = height - 1;
-	}
-
-	// set cursor position on screen
-	const uint16_t pos = y * width + x;
-	outb(0x3D4, 0x0F);
-	outb(0x3D5, (uint8_t)(pos & 0xFF));
-	outb(0x3D4, 0x0E);
-	outb(0x3D5, (uint8_t)((pos >> 8) & 0xFF));
-}
-
-void term_out_str(const char *str)
-{
-	while (*str)
-		term_out(*str++);
-}

kernel/include/lib/klib.h

@@ -193,4 +193,30 @@ unsigned int bound(unsigned int min, unsigned int value, unsigned int max);
  */
 __attribute__((noreturn)) void panic(const char *format, ...);
 
+/**
+ * Fill dst with a stack trace consisting of return addresses in order
+ * from top to bottom
+ *
+ * @returns number of backtraces (at most len)
+ */
+size_t backtrace(void **dst, size_t len);
+
+/**
+ * Fill dst with a stack trace consisting of return addresses in order
+ * from top to bottom, starting at a provided ip/bp
+ *
+ * @returns number of backtraces (at most len)
+ */
+size_t backtrace_ex(void **dst, size_t len, void *ip, void *bp);
+
+/**
+ * Log a backtrace to output
+ */
+void log_backtrace(void);
+
+/**
+ * Log a backtrace to output starting at a provided ip/bp
+ */
+void log_backtrace_ex(void *ip, void *bp);
+
 #endif /* klib.h */

kernel/lib/backtrace.c

@@ -0,0 +1,46 @@
+#include <lib.h>
+
+struct stackframe {
+	struct stackframe *rbp;
+	void *rip;
+};
+
+size_t backtrace(void **dst, size_t len)
+{
+	struct stackframe *rbp;
+	__asm__("mov %%rbp, %0" : "=r"(rbp));
+	return backtrace_ex(dst, len, rbp->rip, rbp->rbp);
+}
+
+size_t backtrace_ex(void **dst, size_t len, void *ip, void *bp)
+{
+	struct stackframe *frame = bp;
+	__asm__("mov %%rbp, %0" : "=r"(frame));
+	if (len > 0) {
+		dst[0] = ip;
+	}
+	size_t i;
+	for (i = 1; frame && i < len; i++) {
+		dst[i] = frame->rip;
+		frame = frame->rbp;
+	}
+	return i;
+}
+
+void log_backtrace(void)
+{
+	struct stackframe *rbp;
+	__asm__("mov %%rbp, %0" : "=r"(rbp));
+	log_backtrace_ex(rbp->rip, rbp->rbp);
+}
+
+void log_backtrace_ex(void *ip, void *bp)
+{
+	struct stackframe *frame = bp;
+	kputs("Stack trace:\n");
+	kprintf("  %p\n", ip);
+	while (frame) {
+		kprintf("  %p\n", frame->rip);
+		frame = frame->rbp;
+	}
+}

kernel/lib/panic.c

@@ -1,3 +1,4 @@
+#include "lib/klib.h"
 #include <lib.h>
 #include <stdarg.h>
 #include <comus/asm.h>
@@ -10,6 +11,7 @@ __attribute__((noreturn)) void panic(const char *format, ...)
 	kprintf("\n\n!!! PANIC !!!\n");
 	kvprintf(format, list);
 	kprintf("\n\n");
+	log_backtrace();
 
 	while (1)
 		halt();