X-Git-Url: http://git.joshuawise.com/netwatch.git/blobdiff_plain/3116da4b2f512f121bfc7b89e948de25a7daf2cc..33e49b2e6d599bc56326841b5b373b9f76adc5f7:/netwatch/traps.c

diff --git a/netwatch/traps.c b/netwatch/traps.c
new file mode 100644
index 0000000..1fc0977
--- /dev/null
+++ b/netwatch/traps.c
@@ -0,0 +1,105 @@
+#include <output.h>
+#include <io.h>
+#include <paging.h>
+
+#include "traps.h"
+
+#define CS_SEGSEL	0x10
+
+#define FAULT_WRAPPER(func_name)        asm (           \
+        ".global " #func_name "_wrapper\n"              \
+        #func_name "_wrapper:\n"                        \
+        "mov %cr2, %eax\n"                              \
+        "push %eax\n"                                   \
+        "push %esp\n"                                   \
+        "call " #func_name "\n"                         \
+); void func_name##_wrapper(void);
+
+#define WRAPPER_INSTALL(idt, idt4_value, func_name, int_number) {	\
+	*(int *)((void *)idt + (8 * int_number)) =	\
+		((int)func_name##_wrapper & 0xFFFF) |	\
+		(CS_SEGSEL << 16);		\
+	*(int *)((void *)idt + (8 * int_number) + 4) =	\
+		((int)func_name##_wrapper & 0xFFFF0000) | idt4_value; \
+}
+
+/* The 16 bits at offset 4 from the start of an interrupt gate are a
+ * bitfield, according to the Intel spec:
+ * 15           P - Segment Present - set to 1
+ * 14-13        DPL - Descriptor privilege level - set to 11 for trap/int, 00 for IPI
+ * 12-8         01111 for 32-bit trap gates, 01110 for 32-bit interrupt gates
+ * 7-0          Set to 0
+ * Trap:      binary 11101111 0000000, hex EF00.
+ * Interrupt: binary 11101110 0000000, hex EE00.
+ */
+#define TRAP		0xEF00
+#define INTERRUPT	0xEE00
+
+typedef struct trap_t {
+	int cr2;
+        int error_code;
+        int eip;
+        int cs;
+        int eflags;
+        int esp;
+        int ss;
+} trap_t;
+
+void die(struct trap_t * trap) {
+	outputf("Error %08x %%eip %08x", trap->error_code, trap->eip);
+	outputf("%%esp %08x %%eflags %08x", trap->esp, trap->eflags);
+	while(1) asm("hlt");
+}
+
+void fault_gp(struct trap_t * trap) {
+	outputf("GENERAL PROTECTION FAULT");
+	die(trap);
+}
+
+void fault_page(struct trap_t * trap) {
+	outputf("PAGE FAULT: %08x", trap->cr2);
+	die(trap);
+}
+void fault_divide(struct trap_t * trap) {
+	outputf("DIVISION FAULT");
+	die(trap);
+}
+void double_fault(struct trap_t * trap) {
+	outputf("DOUBLE FAULT");
+	die(trap);
+}
+
+FAULT_WRAPPER(fault_gp);
+FAULT_WRAPPER(fault_page);
+FAULT_WRAPPER(fault_divide);
+FAULT_WRAPPER(double_fault);
+
+/* pseudo_descriptor and x86_gate structs from 15-410 basis code. */
+
+struct x86_gate {
+unsigned int filler[2]; //64 bits; or 8 bytes.
+};
+
+static struct x86_gate idt[64];
+
+struct pseudo_descriptor {
+        short pad;
+        unsigned short limit;
+        unsigned long linear_base;
+} __attribute__((packed));
+
+void traps_install(void) {
+
+        struct pseudo_descriptor pdesc;
+	pdesc.limit = sizeof(idt) - 1;
+	pdesc.linear_base = v2p(&idt);
+
+	WRAPPER_INSTALL(idt, TRAP, fault_divide, T_DIVIDE_ERROR);
+	WRAPPER_INSTALL(idt, TRAP, fault_gp, T_GENERAL_PROTECTION);
+	WRAPPER_INSTALL(idt, TRAP, fault_page, T_PAGE_FAULT);
+	WRAPPER_INSTALL(idt, TRAP, double_fault, T_DOUBLE_FAULT);
+
+        outb(0x80, 0xCC);
+	asm volatile("lidt %0" : : "m" (pdesc.limit));
+        outb(0x80, 0xCD);
+}