Stack Smashing Protection

Makefile

@@ -6,7 +6,7 @@ SOURCES := $(shell find src -name '*.c')
 OBJFILES := $(patsubst $(SRC)/%.c, $(BUILDDIR)/%.o, $(SOURCES))
 
 CC := x86_64-elf-gcc
-CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fno-stack-protector -fno-omit-frame-pointer -fno-stack-check -fno-PIC -ffunction-sections -fdata-sections -mcmodel=kernel
+CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fstack-protector -fno-omit-frame-pointer -fno-stack-check -fno-PIC -ffunction-sections -fdata-sections -mcmodel=kernel
 CC_PROBLEMATIC_FLAGS=-Wno-unused-parameter -Wno-unused-variable
 
 LD := x86_64-elf-ld

include/config.h

@@ -55,4 +55,7 @@
 /* time */
 #define TIMER_FREQUENCY 1000
 
+/* ssp */
+#define STACK_CHK_GUARD 0x7ABA5C007ABA5C00
+
 #endif

src/kapps/kshell.c

@@ -12,6 +12,15 @@
 #include <kernel.h>
 #include <time/date.h>
 
+__attribute__((noinline))
+void smash_it()
+{
+    char buf[16]; (void)buf;
+    for (size_t i=0; i<256; i++) {
+        buf[i] = (char)i;
+    }
+}
+
 /*
  * pedicel_main - Kernel shell main function
  * @arg: argument (optional)
@@ -38,7 +47,8 @@ void pedicel_main(void* arg)
                             "panic   - trigger a test panic\r\n"
                             "syscall - trigger int 0x80\r\n"
                             "pf      - trigger a page fault\r\n"
-                            "now     - get current date\r\n");
+                            "now     - get current date\r\n"
+                            "smash   - smash the stack\r\n");
             continue;
         }
 
@@ -64,6 +74,11 @@ void pedicel_main(void* arg)
             continue;
         }
 
+        if (strncmp(input_buf, "smash", 5) == 0) {
+            smash_it();
+            continue;
+        }
+
         printf("%s: command not found\r\n", input_buf);
     }
 }

src/kmain.c

@@ -85,6 +85,15 @@ void thing_main(void* arg)
 
 extern uintptr_t kheap_start;
 
+/* Stack Smashing Protection */
+
+uint64_t __stack_chk_guard = STACK_CHK_GUARD;
+
+void __stack_chk_fail(void)
+{
+	panic(NULL, "SSP: Stask Smashing Detected!!! (very spicy)");
+}
+
 /*
  * kmain - Kernel entry point
  *