sysenter: save the registers into _sysexit_regs, makes the code cleaner (imo)

2 files changed, 21 insertions, 25 deletions

diff --git a/src/kernel/arch/i386/sysenter.c b/src/kernel/arch/i386/sysenter.c
index a7c7123..a2810b2 100644
--- a/src/kernel/arch/i386/sysenter.c
+++ b/src/kernel/arch/i386/sysenter.c
@@ -22,26 +22,16 @@ void sysexit(struct registers regs) {
 	_sysexit_real();
 }
 
-void sysenter_stage2(int edi, int esi, void *ebp, void *esp,
-                     int ebx, int edx, int   ecx, int   eax)
-{
+_Noreturn void sysenter_stage2() {
 	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,
-	};
+	struct registers *regs = &process_current->regs;
+
+	*regs = _sysexit_regs; // save the registers
+	regs->esp = regs->ecx; // fix them up
+	regs->eip = regs->edx;
 
-	val = syscall_handler(eax, ebx, esi, edi);
+	val = syscall_handler(regs->eax, regs->ebx,
+	                      regs->esi, regs->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 24cbc89..db65a8c 100644
--- a/src/kernel/arch/i386/sysenter.s
+++ b/src/kernel/arch/i386/sysenter.s
@@ -24,7 +24,7 @@ _sysexit_real:
 
 	// restore the registers
 	mov $_sysexit_regs, %esp
-	popal // probably a bad idea
+	popal
 	sysexit
 
 
@@ -48,11 +48,17 @@ sysenter_setup:
 	ret
 
 sysenter_stage1:
-	pushal // register dump
+	//   disable paging
+	// I don't want to damage any of the registers passed in by the user,
+	// so i'm using ESP as a temporary register. At this point there's nothing
+	// useful in it, it's == _bss_end.
+	mov %cr0, %esp
+	and $0x7FFFFFFF, %esp  // disable paging
+	mov %esp, %cr0
 
-	mov %cr0, %eax
-	and $0x7FFFFFFF, %eax  // disable paging
-	mov %eax, %cr0
+	// save the registers
+	mov $(_sysexit_regs + 32), %esp
+	pushal
 
-	call sysenter_stage2
-	jmp halt_cpu
+	mov $_bss_end, %esp
+	jmp sysenter_stage2