Change the way the kernel entry point is called to honor alignement ABI (#81)

GuillaumeDIDIER · phil-opp · commit 4e3b456182e0 · 2019-10-08T18:47:46.000+02:00
Compilers expect functions to be called with the stack containing the return address making the rsp be 8 mod 16. jmp caused rsp to be 0 mod 16 (aka 16 bytes aligned), which then caused compiler to meke the stack misaligned everywhere.
diff --git a/src/main.rs b/src/main.rs
@@ -44,7 +44,7 @@ global_asm!(include_str!("video_mode/vga_320x200.s"));
 global_asm!(include_str!("video_mode/vga_text_80x25.s"));
 
 unsafe fn context_switch(boot_info: VirtAddr, entry_point: VirtAddr, stack_pointer: VirtAddr) -> ! {
-    asm!("jmp $1; ${:private}.spin.${:uid}: jmp ${:private}.spin.${:uid}" ::
+    asm!("call $1; ${:private}.spin.${:uid}: jmp ${:private}.spin.${:uid}" ::
          "{rsp}"(stack_pointer), "r"(entry_point), "{rdi}"(boot_info) :: "intel");
     ::core::hint::unreachable_unchecked()
 }

Original file line number	Diff line number	Diff line change
`@@ -44,7 +44,7 @@ global_asm!(include_str!("video_mode/vga_320x200.s"));`
`44`	`44`	`global_asm!(include_str!("video_mode/vga_text_80x25.s"));`
`45`	`45`
`46`	`46`	`unsafe fn context_switch(boot_info: VirtAddr, entry_point: VirtAddr, stack_pointer: VirtAddr) -> ! {`
`47`		`- asm!("jmp $1; ${:private}.spin.${:uid}: jmp ${:private}.spin.${:uid}" ::`
	`47`	`+ asm!("call $1; ${:private}.spin.${:uid}: jmp ${:private}.spin.${:uid}" ::`
`48`	`48`	`"{rsp}"(stack_pointer), "r"(entry_point), "{rdi}"(boot_info) :: "intel");`
`49`	`49`	`::core::hint::unreachable_unchecked()`
`50`	`50`	`}`