save all registers on syscalls

4 files changed, 47 insertions, 23 deletions

diff --git a/src/kernel/arch/generic.h b/src/kernel/arch/generic.h
index 8db079c..f816c71 100644
--- a/src/kernel/arch/generic.h
+++ b/src/kernel/arch/generic.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <kernel/arch/i386/registers.h>
 #include <kernel/arch/log.h>
 #include <stdbool.h>
 
@@ -17,7 +18,7 @@ void halt_cpu();
 // src/arch/i386/sysenter.s
 void sysexit(void (*fun)(), void *stack_top);
 void sysenter_setup();
-int syscall_handler(int, int, int, int, void *stack, void *eip);
+int syscall_handler(int, int, int, int);
 
 // all of those can allocate memory
 struct pagedir *pagedir_new();
diff --git a/src/kernel/arch/i386/registers.h b/src/kernel/arch/i386/registers.h
new file mode 100644
index 0000000..feba157
--- /dev/null
+++ b/src/kernel/arch/i386/registers.h
@@ -0,0 +1,13 @@
+#pragma once
+#include <stdint.h>
+
+struct registers {
+	uint32_t eax, ebx, ecx, edx, esi, edi;
+	void *ebp, *esp, *eip;
+};
+
+// saves a return value according to the SysV ABI
+inline void regs_savereturn(struct registers *regs, uint64_t value) {
+	regs->eax = value;
+	regs->edx = value >> 32;
+}
diff --git a/src/kernel/arch/i386/sysenter.c b/src/kernel/arch/i386/sysenter.c
new file mode 100644
index 0000000..91dac2e
--- /dev/null
+++ b/src/kernel/arch/i386/sysenter.c
@@ -0,0 +1,27 @@
+#include <kernel/arch/generic.h>
+#include <kernel/proc.h>
+
+void sysenter_stage2(int edi, int esi, void *ebp, void *esp,
+                     int ebx, int edx, int   ecx, int   eax)
+{
+	uint64_t val;
+	process_current->regs = (struct registers) {
+		// EAX and EDX will get overriden with the return value later on
+
+		.eax = eax,
+		.ecx = ecx,
+		.edx = edx,
+		.ebx = ebx,
+		.esi = esi,
+		.edi = edi,
+
+		.esp = (void*) ecx, // not a typo, part of my calling convention
+		.eip = (void*) edx, // ^
+		.ebp = ebp,
+	};
+
+	val = syscall_handler(eax, ebx, esi, edi);
+	regs_savereturn(&process_current->regs, val);
+
+	process_switch(process_current); // TODO process_resume
+}
diff --git a/src/kernel/arch/i386/sysenter.s b/src/kernel/arch/i386/sysenter.s
index 64b7d01..a982dd8 100644
--- a/src/kernel/arch/i386/sysenter.s
+++ b/src/kernel/arch/i386/sysenter.s
@@ -42,34 +42,17 @@ sysenter_setup:
 	wrmsr
 
 	mov $IA32_SYSENTER_EIP, %ecx
-	mov $sysenter_handler, %eax
+	mov $sysenter_stage1, %eax
 	wrmsr
 
 	ret
 
-sysenter_handler:
-	pushal
-	push %edx
-	push %ecx
-	push %edi
-	push %esi
-	push %ebx
-	push %eax
+sysenter_stage1:
+	pushal // register dump
 
 	mov %cr0, %eax
 	and $0x7FFFFFFF, %eax  // disable paging
 	mov %eax, %cr0
 
-	call syscall_handler
-
-	// save the return value
-	mov %eax, 52(%esp) // 24 [top of eflags] + 7*4 [skip until EAX]
-	mov %edx, 40(%esp) // 24                 + 4*4 [skip until EBX]
-
-	mov %cr0, %eax
-	or  $0x80000000, %eax  // enable paging
-	mov %eax, %cr0
-
-	add $24, %esp
-	popal
-	sysexit
+	call sysenter_stage2
+	jmp halt_cpu