misc(kernel): use load fence before swapgs

sigsegv7 · Andy-Python-Programmer · commit 85c7cbdffb2f · 2024-07-05T16:43:50.000+10:00
Avoid potential speculative execution issues with swapgs, such as swapgs
being speculatively missed.

Signed-off-by: Ian Moffett &lt;ian@osmora.org&gt;
diff --git a/src/aero_kernel/src/arch/x86_64/interrupts/handlers.asm b/src/aero_kernel/src/arch/x86_64/interrupts/handlers.asm
@@ -39,6 +39,7 @@ interrupt_handler_%1:
     test qword [rsp + 16], 0x3
     ; skip the SWAPGS instruction if CS & 0b11 == 0b00.
     jz .dont_swapgs
+    lfence
     swapgs
     .dont_swapgs:
 
@@ -70,6 +71,7 @@ interrupt_handler_%1:
     test qword [rsp + 8], 0x3
     ; skip the SWAPGS instruction if CS & 0b11 == 0b00.
     jz .dont_swapgs_again
+    lfence
     swapgs
     .dont_swapgs_again:
     
