Fix userspace clone by clobbering all variables on clone

arch/x86_64/src/lib.rs

@@ -126,7 +126,16 @@ macro_rules! interrupt_error {
             }
 
             // Push scratch registers
-            asm!("push rax
+            asm!("xchg bx, bx
+                pop rax # Error
+                pop rbx # RIP
+                pop rcx # CS
+                pop rdx # RFLAGS
+                pop rsi # RSP
+                pop rdi # SS
+                cli
+                hlt
+                push rax
                 push rcx
                 push rdx
                 push rdi

bootloader/x86_64/vesa.asm

@@ -115,8 +115,8 @@ vesa:
 .minx dw 640
 .miny dw 480
 .required:
-.requiredx dw 0 ;1024    ;USE THESE WITH CAUTION
-.requiredy dw 0 ;768
+.requiredx dw 1024    ;USE THESE WITH CAUTION
+.requiredy dw 768
 .requiredmode dw 0
 
 .modeok db ": Is this OK?(y/n)",10,13,0

kernel/syscall/process.rs

@@ -82,10 +82,6 @@ pub fn clone(flags: usize, stack_base: usize) -> Result<usize> {
         pid = context.id;
     }
 
-    println!("Clone {}", pid);
-
-    unsafe { asm!("xchg bx, bx" : : : : "intel", "volatile"); }
-
     unsafe { context::switch(); }
 
     Ok(pid)

syscall/src/lib.rs

@@ -110,7 +110,7 @@ pub fn chdir(path: &str) -> Result<usize> {
 }
 
 pub unsafe fn clone(flags: usize) -> Result<usize> {
-    syscall1(SYS_CLONE, flags)
+    syscall1_clobber(SYS_CLONE, flags)
 }
 
 pub fn close(fd: usize) -> Result<usize> {

syscall/src/x86.rs

@@ -20,6 +20,17 @@ pub unsafe fn syscall1(mut a: usize, b: usize) -> Result<usize> {
     Error::demux(a)
 }
 
+// Clobbers all registers - special for clone
+pub unsafe fn syscall1_clobber(mut a: usize, b: usize) -> Result<usize> {
+    asm!("int 0x80"
+        : "={eax}"(a)
+        : "{eax}"(a), "{ebx}"(b)
+        : "memory", "ebx", "ecx", "edx", "esi", "edi"
+        : "intel", "volatile");
+
+    Error::demux(a)
+}
+
 pub unsafe fn syscall2(mut a: usize, b: usize, c: usize) -> Result<usize> {
     asm!("int 0x80"
         : "={eax}"(a)

syscall/src/x86_64.rs

@@ -20,6 +20,17 @@ pub unsafe fn syscall1(mut a: usize, b: usize) -> Result<usize> {
     Error::demux(a)
 }
 
+// Clobbers all registers - special for clone
+pub unsafe fn syscall1_clobber(mut a: usize, b: usize) -> Result<usize> {
+    asm!("int 0x80"
+        : "={rax}"(a)
+        : "{rax}"(a), "{rbx}"(b)
+        : "memory", "rbx", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
+        : "intel", "volatile");
+
+    Error::demux(a)
+}
+
 pub unsafe fn syscall2(mut a: usize, b: usize, c: usize) -> Result<usize> {
     asm!("int 0x80"
         : "={rax}"(a)