save all registers on syscalls

8 files changed, 52 insertions, 33 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
diff --git a/src/kernel/main.c b/src/kernel/main.c
index 004be15..ce69bc2 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -14,7 +14,7 @@ static void run_init(struct kmain_info *info) {
 	for (uintptr_t off = 0; off < info->init.size; off += PAGE_SIZE)
 		pagedir_map(proc->pages, init_base + off, info->init.at + off,
 		            true, true);
-	proc->eip = init_base;
+	proc->regs.eip = init_base;
 
 	log_const("switching...");
 	process_switch(proc);
diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index a3adf41..a64d5ee 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -11,7 +11,7 @@ struct process *process_new() {
 
 	// map the stack to the last page in memory
 	pagedir_map(proc->pages, (void*)~PAGE_MASK, page_alloc(1), true, true);
-	proc->stack_top = proc->esp = (void*) ~0xF;
+	proc->stack_top = proc->regs.esp = (void*) ~0xF;
 
 	// map the kernel
 	//   yup, .text is writeable too. the plan is to not map the kernel
@@ -26,5 +26,5 @@ struct process *process_new() {
 void process_switch(struct process *proc) {
 	process_current = proc;
 	pagedir_switch(proc->pages);
-	sysexit(proc->eip, proc->esp);
+	sysexit(proc->regs.eip, proc->regs.esp);
 }
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 745db8d..a40d3ca 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -3,10 +3,8 @@
 
 struct process {
 	void *stack_top;
-	void *esp;
-	void *eip;
-
 	struct pagedir *pages;
+	struct registers regs;
 };
 
 extern struct process *process_current;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 1bc1a44..27e835d 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -25,10 +25,7 @@ int sc_debuglog(const char *msg, size_t len) {
 	return len;
 }
 
-int syscall_handler(int num, int a, int b, int c, void *stack, void *eip) {
-	process_current->esp = stack;
-	process_current->eip = eip;
-
+int syscall_handler(int num, int a, int b, int c) {
 	switch (num) {
 		case SC_EXIT:
 			sc_exit((void*)a, b);