added rule to compile .S files; page fault ISR and skeleton handler are present

7 files changed, 96 insertions, 7 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 1e6ce69..da4591d 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -19,7 +19,7 @@ LOADLIBES := -lgcc
 
 SOBJS := 
 GOBJS := entry_efi.o kprint.o serial.o port.o main.o memory.o \
-	 memset.o memcpy.o memmove.o memcmp.o cpu.o 
+	 memset.o memcpy.o memmove.o memcmp.o cpu.o exceptions.o 
 IOBJS :=
 
 $(SOBJS): CFLAGS += -fPIC
diff --git a/kernel/cpu.c b/kernel/cpu.c
index db4108f..ed1a04e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1,4 +1,5 @@
 #include "cpu.h"
+#include "exceptions.h"
 
 #include <stdint.h>
 
@@ -140,6 +141,7 @@ static void gdt_init(void)
         "mov %w2, %%es\n"
         "mov %w2, %%fs\n"
         "mov %w2, %%gs\n"
+        "mov %w2, %%ss\n"
         // make a far return frame on the stack
         // [ss] @rsp+8
         // [rip] @rsp
@@ -183,11 +185,24 @@ void cpu_init(void)
 {
     gdt_init();
     idt_init();
+    exceptions_init();
 }
 
-void isr_install(int vec, void *isr, int ist)
+void exceptions_init(void)
 {
-    set_idt(vec, CODE_SEG_INDEX << 3, (uint64_t)isr, INT64_GATE);
+    isr_install(PAGE_FAULT_VECTOR, &page_fault_isr, 0, 0);
+}
+
+void isr_install(int vec, void (*isr)(void), int trap, int ist)
+{
+    enum gate_descriptor_type type = INT64_GATE;
+    
+    if (trap)
+    {
+        type = TRAP64_GATE;
+    }
+    
+    set_idt(vec, CODE_SEG_INDEX << 3, (uint64_t)isr, type);
     if (ist)
     {
         set_ist(vec, ist);
diff --git a/kernel/cpu.h b/kernel/cpu.h
index 15cf44a..56a4073 100644
--- a/kernel/cpu.h
+++ b/kernel/cpu.h
@@ -2,7 +2,7 @@
 
 void cpu_init(void);
 
-void isr_install(int vec, void *isr, int ist);
+void isr_install(int vec, void (*isr)(void), int ist, int trap);
 void ist_install(int ist, void *stack);
 
 void int_enable(void);
diff --git a/kernel/exceptions.S b/kernel/exceptions.S
new file mode 100644
index 0000000..03402f2
--- /dev/null
+++ b/kernel/exceptions.S
@@ -0,0 +1,55 @@
+.extern page_fault_handler
+
+.global page_fault_isr
+.type page_fault_isr, @function
+page_fault_isr:
+    /* just in case something tried to be clever before */
+    cld
+    /* push param registers */
+    push %rdi
+    push %rsi
+    push %rdx
+    push %rcx
+    push %r8
+    push %r9
+    /* collect parameters for page fault handler */
+    mov 48(%rsp), %rdi /* error code is first parameter */
+    mov %cr2, %rsi /* PFLA is next parameter */
+    /* caller-saved registers */
+    push %rax
+    push %r10
+    push %r11
+    /* callee-saved registers */
+    push %rbx
+    push %rbp
+    push %r12
+    push %r13
+    push %r14
+    push %r15
+    /* stack has to be aligned */
+    mov %rsp, %rbp
+    and $-16, %rsp
+    call page_fault_handler
+    mov %rbp, %rsp
+    /* TODO: test for error code here and panic() */
+    pop %r15
+    pop %r14
+    pop %r13
+    pop %r12
+    pop %rbp
+    pop %rbx
+    pop %r11
+    pop %r10
+    pop %rax
+    pop %r9
+    pop %r8
+    pop %rcx
+    pop %rdx
+    pop %rsi
+    pop %rdi
+    /* unwind the error code from the stack */
+    add $8, %rsp
+    /* leave the isr */
+    iretq
+.size page_fault_isr, . - page_fault_isr
+    
diff --git a/kernel/exceptions.h b/kernel/exceptions.h
new file mode 100644
index 0000000..5d22284
--- /dev/null
+++ b/kernel/exceptions.h
@@ -0,0 +1,7 @@
+#pragma once
+
+extern void page_fault_isr(void);
+
+#define PAGE_FAULT_VECTOR 0xe
+
+void exceptions_init(void);
diff --git a/kernel/memory.c b/kernel/memory.c
index d9bc8c3..f233b85 100644
--- a/kernel/memory.c
+++ b/kernel/memory.c
@@ -1,4 +1,5 @@
 #include "memory.h"
+#include "kprint.h"
 
 #include <kernel/memory/paging.h>
 
@@ -326,11 +327,10 @@ void kernel_unmap_page(void *vaddr)
 
 phys_addr_t page_alloc(void)
 {
-    int index;
+    int index = first_free_page_index;
     
-    if (first_free_page_index > 0)
+    if (index > 0)
     {
-        index = first_free_page_index;
         page_array[index].used = 1;
         first_free_page_index = page_array[index].next;
     }
@@ -361,3 +361,11 @@ static uint64_t *get_kernel_pm2e(void *vaddr)
 {
     return &kernel_pm2[kpm2_index(vaddr)];
 }
+
+int page_fault_handler(uint32_t code, void *address)
+{
+    (void)code;
+    (void)address;
+    kputs("page faulmt\n");
+    return 0;
+}
diff --git a/rules.mk b/rules.mk
index 4ac15a4..2115028 100644
--- a/rules.mk
+++ b/rules.mk
@@ -29,6 +29,10 @@ COMPILE.info = $(info $$(CC) $@)
 	$(COMPILE.info)
 	@$(COMPILE.cpp) -MMD -MP
 
+%.o: %.S
+	$(COMPILE.info)
+	@$(COMPILE.S) -MMD -MP
+
 clean:
 	$(info $$(RM) $(CLEANLIST))
 	-@$(RM) $(CLEANLIST)